Spatial Ecology and Diet of the Argentine Black and White Tegu (Salvator Merianae) in Central Florida

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Spatial Ecology and Diet of the Argentine Black and White Tegu (Salvator Merianae) in Central Florida
Offner, Marietherese
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[Gainesville, Fla.]
University of Florida
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Master's ( M.S.)
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University of Florida
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Wildlife Ecology and Conservation
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diet -- habitat -- invasive -- scrub -- tegu
Wildlife Ecology and Conservation -- Dissertations, Academic -- UF
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Wildlife Ecology and Conservation thesis, M.S.


Populations of a large-bodied lizard, the Argentine black and white tegu (Salvator merianae) have become established in two distinct regions of Florida: one in the south near Everglades National Park and one in the west-central region near Riverview, Florida. Tegus are highly adaptable opportunistic omnivores, and invasions such as this can have devastating and long lasting impacts on native ecosystems. To date, a number of preliminary investigations have been conducted on tegus in the west central region, however only superficial data have been collected on impacts on local wildlife and spatial ecology of tegus. The goals of my research were to: 1) identify habitats selected by tegus and their frequency of use; 2) identify winter refugia; and 3) describe diet of tegus in Central Florida. I conducted first and second order habitat selection of tegus in Central Florida at two study sites. Tegus were found to select for scrub habitat at second and third order at both sites but showed no overall species or seasonal trend in habitat selection. In addition I collected 105 samples of tegu diets and found tegus ate plant, invertebrate and vertebrate prey at multiple trophic levels. I also found the remains of gopher tortoise hatchlings in five tegus. My results indicate that tegus are habitat and dietary generalists and should be considered a significant threat to Florida's native wildlife. ( en )
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Thesis (M.S.)--University of Florida, 2017.
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by Marietherese Offner.

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2017 Marie Therese Offner


To my parents, for putting me in touch with nature


4 ACKNOWLEDGEMENTS I would like to express my deepest gratitude for the people who made it possible for me to fulfil my dreams, from the beginning of my work with tegus to the culmination of my thes is submission. My committee members each spent their time and talents shaping me to become a better biologist. Dr. Todd Campbell put me on the path. Dr. Steve Johnson accepted me under his tutelage and his continuous support ensured I was able to reach my goals. invaluable and Dr. Christina Romagosa always knew how to keep up spirits. Much of my work would not have happened without my colleagues and friends past and present a t Florida Fish and Wildlife Conservation Commission, Hillsborough County Conservation and Environmental Lands Management and RVR Horse Rescue (where I began removing tegus in 2012) including Sarah Funck, Jenny Eckles, Liz Barraco, Jake Edwards, Angeline Sc otten, Bernie Kaiser, Ross Dickerson, and everyone else who work s to defend Florida from the threat of invasives while conserving I may not have survived without my volunte ers and interns Kayla Williams, Haley Hanson, Christin Meilink, Nick Espinosa, Jesse Goodyear and others who worked alongside me collecting data in the field, nor my family and friends who supported me through the years, especially my husband Gabriel Rogas ner. Thank you for believing in and supporting my research.


5 TABLE OF CONTENTS page ACKNOWLEDGEMENTS ................................ ................................ ............................... 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ..................... 9 CHAPTER 1 BACKGROUND ON SALVATOR MERIANAE INVASION ................................ ...... 11 Ecosystems and Invasive Species ................................ ................................ .......... 11 Florida Scrub Habitat ................................ ................................ ........................ 12 Tegu Ecology and History of Invasion ................................ .............................. 13 Research Objectives ................................ ................................ ............................... 16 2 HABITAT SELECTION OF INVASIVE ARGENTINE BLACK AND WHITE TEGUS IN CENTRAL FLORIDA ................................ ................................ ............. 18 Introduction ................................ ................................ ................................ ............. 18 Methods ................................ ................................ ................................ .................. 23 Study Site ................................ ................................ ................................ ......... 23 Data Collection ................................ ................................ ................................ 24 Data Analysi s ................................ ................................ ................................ ... 26 Results ................................ ................................ ................................ .................... 29 Tegu Tracking ................................ ................................ ................................ .. 29 Home Range ................................ ................................ ................................ .... 30 Habitat Selection ................................ ................................ .............................. 31 Winter Refugia ................................ ................................ ................................ .. 33 Discussion ................................ ................................ ................................ .............. 34 3 DIET OF ARGENTINE BLACK AND WHITE TEGUS IN CENTRAL FLORIDA ...... 50 Introduction ................................ ................................ ................................ ............. 50 Materials and Methods ................................ ................................ ............................ 53 Study Site ................................ ................................ ................................ ......... 53 Tegu Acquisition ................................ ................................ ............................... 54 Diet Analysis ................................ ................................ ................................ ..... 54 Results ................................ ................................ ................................ .................... 56 Diet Composition ................................ ................................ .............................. 56 Niche Overlap ................................ ................................ ................................ ... 59 Discussion ................................ ................................ ................................ .............. 59


6 4 CONSERVATION IMP LICATIONS AND CONCLUSIONS ................................ ..... 70 APPENDIX LIST OF ITEMS CONSUMED BY TEGUS ................................ ............... 73 LIST OF REFERENCES ................................ ................................ ............................... 78 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 85


7 LIST OF TABLES Table page 2 1 Tegu identification number; study site in Hillsborough County, Florida from which they were collected: Balm Boyette Scrub (BBS) or Rhodine Scrub (RS), sex of tegu and size at capt ure. ................................ ................................ 40 2 2 Number of locations recorded for each tegu each season. ................................ 41 2 3 Bi weekly mean temperatures in Riverview, Florida near tegu study sites from October 4 th 2015 through the week of February 21 st 2016. Temperature data obtained from web/. ............ 41 2 4 Total tegu home range size in hectares (100% minimum convex polygon) for each season, total hectares of each habitat wit number of relocations in each habitat type ................................ ......................... 42 3 1 Identified Food items consumed by 93 argentine black a nd white tegus and frequency of occurrence (FO) ................................ ................................ ............. 65 A 1 Items consumed by tegus organized by taxa ................................ ...................... 73


8 LIST OF FIGURES Figure page 1 1 Argentine black and white tegu ( Salvator merianae ) wearing a telemetry harness around the pelvic girdle. Photo by Marie Therese Offner. ..................... 17 2 1 Location of study sites in Hillsborough County, Florida including Rhodine Scrub in the north (A) and Balm Boyette Scrub in the south (B). Map data: 2017 Google Maps. ................................ ................................ ............................ 39 2 2 Odds ratio s (OR) with Bonferroni confidence intervals calculated for tegu second order habitat selection at Rhodine Scrub, Hillsborough County, FL.. ..... 44 2 3 Odds ratios (OR) with Bonferroni confidence intervals calculated for tegu second order habitat selection at Balm Boyette Scrub, Hillsborough County, FL. ................................ ................................ ................................ ...................... 45 2 4 Results of Eigenanalysis for tegus within the Rhodine Scrub study site. Factor loading for habitat variables along the first two axes can be seen at the top. ................................ ................................ ................................ ............... 46 2 5 Results of Eigenanalysis for tegus within the Balm Boyette Scrub study site. Factor loading for habitat variables along the first two axes can be seen a t the top. ................................ ................................ ................................ ............... 47 2 6 Odds ratios (OR) with Bonferroni confidence intervals calculated for tegu third order habitat selection at Rho dine Scrub, Hillsborough County, FL.. ......... 48 2 7 Odds ratios (OR) with Bonferroni confidence intervals calculated for tegu third or der habitat selection at Balm Boyette Scrub, Hillsborough County, FL. .. 49 3 1 Location of Central Florida invasive Argentine black and white tegus ( Salvator merianae ) within Hillsborough County ................................ ................ 64 3 2 Number of tegus collected by month (n = 96) ................................ ..................... 6 7 3 3 Seasonal Frequency of Occurrence (FO) of fruits, invertebrates and vertebrates in invasive Salvator merianae in central Florid a, expressed as percent (%) of tegus found to have consumed food from each group. ............... 68 3 4 Comparison of Frequency of Occurrence (FO) of plants, invertebrates and vertebrates in diets of invasive central Florida Salvator merianae to native (A) and introduced (B) populations of S. merianae. ................................ .................. 69


9 Abstract of Thesis Presented t o the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science SPATIAL ECOLOGY AND DIET OF THE ARGENTINE BLACK AND WHITE TEGU ( SALVATOR MERIANAE ) IN CENTRAL FLORIDA By Marie Therese Offner December 2017 Chair: Steven A. Johnson Major: Wildlife Ecology and Conservation Populations of a large bodied lizard, the Argentine black and white tegu ( Salvator merianae ) have become established in two distinct regions of Florida: one in the south near Everglades National Park and one in the west central region near Riverview, Florida. Tegus are highly adaptable opportunistic omnivo res, and invasions such as this can have devastating and long lasting impacts on native ecosystems. To date, a number of preliminary investigations have been conducted on tegus in the west central region, however only superficial data have been collected o n impacts on local wildlife and spatial ecology of tegus. The goals of my research were to: 1) identify habitats selected by tegus and their frequency of use; 2) identify winter refugia; and 3) describe diet of tegus in Central Florida. I fitted nine tegus from two study sites in Central Florida with very high frequency (VHF) radio transmitters to gather location data. I used a hierarchical approach to assess habitat selection. I evaluated landscape level habitat use within study areas (second order) and ha bitat used within home ranges (third order). Tegus were found to select for scrub habitat at second and third order at both sites but showed no overall species or seasonal trend in habitat selection. I located four winter refugia used by


10 tegus for brumatio n, all characterized as pre dug burrows in 100% vegetative cover. In addition I collected 105 samples of tegu diets and found tegus ate plant, invertebrate and vertebrate prey at multiple trophic levels. I also found the remains of gopher tortoise hatchlin gs in five tegus. My results indicate that tegus are habitat generalists that readily consume vertebrate prey along with invertebrates and fruit and should be considered a


11 CHAPTER 1 BACKGROUND ON SALVATOR MERIANAE INVASION Ecosystems and Invasive Species Humans have facilitated introductions of non native species across the globe. These introductions threaten human health, agricultural yields, wildlife populations and ecosystem productivity. Along with these impacts, management of invasive species is an economic burden. It is estimated that control of invasive species, and the losses they create, costs the United States up to $120 billion dollars a year (Pimentel 2005). Newly established species may not immediately have a noticeable impact on their invaded ecosystem. In fact, impacts may not be apparent for decades or longer, giving the invaders time to establish and spread (Strayer et al. 2006, Simberloff 2013). As a population of invasive species r eproduces and begins to disperse, eradication becomes increasingly unlikely. As a result, long term management and resource protection become the only viable options, which is an economic burden (Strayer et al. 2006, Simberloff 2013). As of 2016, 180 speci es of herpetofauna (reptiles and amphibians) had been introduced to the state of Florida, more than any state in the US (Krysko et al. 2016). With a mild climate and diverse ecosystems, Florida often has suitable conditions for introduced species to surviv e. Climate matching has been shown to be a reliable predictor of species establishment success, and many introduced herpetofauna hail from regions with a similar climate as Florida (Fujasaki et al. 2010, Mahoney et al. 2015, Krysko et al. 2016). Introduce d species may out compete native species for position within a niche or benefit from the presence of humans or other introduced species (Simberloff and Van Holle 1999, Kamath et al. 2013). Islands are particularly vulnerable to effects of non


12 native specie s introduction (Lockwood et al. 2013, Simberloff 2013); one explanation is high endemism and low biodiversity on islands compared to mainlands (Kier et al. 2009), which gives rise to vacant niches (Lekevicius 2009) that could be filled by introduced specie s. Although islands are geographically isolated by water, terrestrial invaders such as cats or rats may be introduced repeatedly by human activities, putting endemic island species at risk (Courchamp et al. 2002, Hulme 2009). Along with habitat destruction invasive species are considered to be one of the leading causes of biodiversity loss ( Vitousek et al. 1997 ) and island endemics have accounted for the majority of extinctions in the past forty years, leading to an increased need for conservation (Whittak er and Fernndez Palacios 2007). Florida Scrub Habitat True islands are separated from mainlands by bodies of water, causing varying of terrestrial habitats that can b ecome similarly isolated within a landscape of human dominated areas. In Florida, dry upland xeric habitat is being rapidly lost to development and agriculture (Abrahamson et al. 1990, Scott 2004, FNAI 2010) and over 80% of has been destroyed (Scott 2004). The Lake Wales R idge n of scrub habitat. West of the ridge in central Florida, highly fragmented peninsular coastal scrub is found throughout Hillsborough County (Abrahamson et al. 1990). Here, wildlife are underway to maintain and restore remaining scrub patches through county initiatives such as the Envir onmental Lands Acquisition and Protection Program, or ELAPP (Hillsborough County Parks, Recreation and Conservation Program 2011).


13 Fragmentation of scrub lands by development leads to isolation of wildlife from other populations, putting them at greater ri sk of extirpation and local extinction, and over 60 percent of scrub has been lost due to anthropogenic causes (Kautz 1993, Gilbert et al. 1998, Gonzalez & Chaneton 2002, Liebold et al. 2004). Like true islands, the scrub ecosystem has a high number of end concentrations of threatened and endangered species (Christman 1988, Scott 2004). Natural resources, such as plants and wildlife, define the unique character of a habitat, and the goal of conservation is to maint ain natural resources in perpetuity. Florida scrub and surrounding xeric habitats include a variety of unique mammals, birds, invertebrates and many terrestrial herpetofauna of particular conservation concern because they are rare, endemic to scrub habitat or ecosystem engineers (Christman 1988, Campbell 1992, Humphery 1992, Deyrup 1994, Kinlaw and Grasmueck 2012). Due to naturally limited geographic range of scrub, continued fragmentation through habitat loss, and small percentage of remaining habitat lef t in the state, it is critical to quickly identify and address threats to this habitat, including management of invasive species. Tegu Ecology and History of Invasion In Florida there have been several introductions of predatory lizards including the Nile monitor ( Varanus niloticus iguana ( Ctenosaurua similus ) in Sarasota and Fort Lauderdale and smaller species such as the northern curly tailed lizard ( Leiocephalus carinatus ), knight anole ( Anolis e questris ) and tokay gecko ( Gekko gecko ). These species exist primarily below the frost front in southern peninsular Florida. All species are known to eat small mammals, insects and smaller lizards, with the Nile monitor and spiny tail iguana posing an


14 addi tional threat to medium sized mammals, reptiles and birds (Campbell 2005, Krysko 2009). The Argentine black and white tegu (Figure 1 1), Salvator merianae hereafter referred to as ABWT, a large predatory lizard, was introduced to Florida in the early 200 0s (Enge 2006), likely a consequence of demand for tegus as pets. The ABWT is native to Argentina, Uruguay, Paraguay and Brazil and can be found in a variety of habitats including savannas, forest clearings and human dominated landscapes (Presch 1973, Fitz gerald et al 1991). Two separate populations occur in the state, one in south Florida in the Miami Dade region and another in Hillsborough County in and around scrub habitat. In their native range ABWTs are known to inhabit a wide variety of landscapes, fr om urban parks to grasslands to forest edges and clearings (Presch 1973, Fitzgerald 1993, Juri et al. 2015, Lopez et al. 2015). They are a large bodied lizard, growing to 145 cm in total length and weighing up to 8 kg (Lopes and Abe 1999). True omnivores, ABWTs eat a variety of foods including insects, mollusks, arachnids and other invertebrates, small mammals, amphibians, reptiles (including adult snakes and small turtles), birds, eggs and a variety of fruits (Mercolli and Yanosky 1994, Colli et al. 1998, Silva et al. 2004, Baracco 2014). Tegus are not adept climbers and forage mainly from the ground during the day. However, they are opportunistic and enter burrows to capture prey and are occasionally able to seize unsuspecting birds from the ground. Tegus are capable of preying upon rare and endangered wildlife in xeric communities including the gopher tortoise ( Gopherus polyphemus ), indigo snake ( Drymarchon couperi ), short tailed snake ( Lampropeltis extenuate ), Florida pine snake ( Pituophis melanoleucus ), sand skink ( Neoseps reynoldsi ), gopher frog ( Rana capito ),


15 scrub jay ( Aphelocoma coerulescens ) and the endemic Florida mouse ( Podomys floridanus ) (Campbell 1992, Humphery 1992). Additionally, tegus retreat to burrows at night and during the winter months t o escape cold temperatures, brumating (a form of hibernation in herpetofauna) for four months underground (Sanders et al. 2015). Tegus their ultimate impacts are still unknown. Tegus in South Florida are known to inhabit elevated canal embankments adjacent to wetlands and the surrounding human dominated landscape (Klug et al 2014). Although impacts are not well understood, tegus in South Florida eat a wide variety of ver tebrates, invertebrates and fruits and may be a seed disperser for nonnative plants (Baracco 2014) and have been documented raiding alligator nests for eggs (Mazzotti et al. 2014). Although research has assessed habitat use and potential impacts of souther n populations associated with wetland and coastal habitat in Florida (Klug et al. 2014, Mazzotti et al. 2014, Barraco 2014), few studies have been conducted to asses ABWT in the dissimilar central Florida xeric uplands (Enge 2006). Reports from invaded reg ions in west central Hillsborough County suggest that ABWT persist primarily along edges of human dominated landscapes bordering public lands consisting of scrub and other upland habitat (Enge 2006, ). Knowledge from the southern tegu population is of limited use for making management decisions in central Florida because tegus persist in novel habitats here and thus may behave or impact wildlife differently. Little formal research has been conducted on Hillsborough County tegu populations. One unpublished study in 2010 made use of wildlife cameras to document tegu presence at gopher tortoise burrows on Balm


16 Boyette Scrub Preserve (BBSP; Kaiser 2016). Tegus were documented visiting burrows and burrow aprons but behavior in the burrows was not well documented. It was theorized tegus were frequenting burrows as a forag ing site and possibly preying on gopher tortoise burrow associates. Additional research was conducted in 2013 on private land north of BBSP to trap and remove tegus for diet analysis (Offner and Campbell 2013, unpublished). The outcome of this study was no t published and neither study addressed spatial ecology, which is a vital tool for invasive species management that can identify range extent, pinpoint movement corridors and highlight habitats disproportionately occupied in the landscape. Research Object ives In order to appropriately plan conservation efforts and manage lands in which Argentine black and white tegus occur it is important to identify areas that this species is likely to impact. Therefore, investigating habitat selection across different ha bitat types will aid efforts for trapping and removal of tegus and, complimented by diet analysis, highlight species vulnerable to predation and competition from tegus. One goal of my study was to examine spatial ecology of tegus in Central Florida in orde r to identify habitats occupied and frequently used by tegus and to estimate home range (Chapter 2). A second goal was to describe tegu diet based on data from prior studies and additional data I collected (Chapter 3). In Chapter 4, I propose best practice s for continued monitoring and removal of tegus from public lands, future research goals for tegus in Central Florida and argue for statewide restrictions of this species in the pet trade.


17 Figure 1 1. Argentine black and white tegu ( Salvator meriana e ) wearing a telemetry harness around the pelvic girdle. Photo by Marie Therese Offner


18 CHAPTER 2 HABITAT SELECTION OF INVASIVE ARGENTINE BLACK AND WHITE TEGUS IN CENTRAL FLORIDA Introduction Invasive species cause negative impacts to native ecosystems, harm wild and domestic animals, threaten human health and burden the economy of countries around the world (Pimentel et al. 2004, Simberloff 2013). Invaders frequently reach new habitats with th e aid of humans who facilitate introductions either intentionally or accidentally (Hulme 2009; Lockwood et al. 2013). Once established, nonnative wildlife may have deleterious effects on native species through direct or indirect competition and predation. Impacts caused by an invasive species are sometimes not apparent for many years after initial introduction (Pimentel et al. 2004, Simberloff 2013). This time lag gives invaders time to adapt to their niche within the new environment, reproduce and disperse It is necessary to identify the resources and habitats that may be impacted by the presence of an introduced species. Natural resources define the unique character of a habitat, and habitats can be altered by the introduction of invasive species. The go al of conservation is to maintain natural resources in perpetuity. Direct intervention through land stewardship is routinely required to prevent degradation of natural areas by human growth and development and from the introduction of invasive species (Loc kwood et al. 2013, Simberloff 2013). Prevention, early detection and rapid response are the best solutions to limiting the establishment and spread of introduced species (Burnett and Kaiser 2010, Maxwell et al. 2007). As time passes, established invaders c an become widespread and eradication and control costs increase. Understanding where to look for an


19 inconspicuous invader can direct early detection initiatives and facilitate removal. al for impacts during risk assessments (Mehta et al. 2006). Salvator merianae commonly known as the Argentine black and white tegu, is a terrestrial, omnivorous lizard native to South America (Presch 1973). Argentine black and white tegus (ABWT) can grow to be as large as 145 cm total length and weigh up to 8 kg (Lopez and Abe 1999). The species ranges widely throughout Brazil, Argentina, Paraguay and Uruguay, from the Amazon basin near the equator to east central e is similar to climate within the native range of ABWT, with a mild cold season where temperatures rarely drop below freezing. In the winter, when temperatures are insufficient for thermoregulation, ABWTs brumate for up to four months (Milstead 1961, McEa chern et al. 2014, Sanders 2015). In the spring, males emerge first, followed by females, and mating occurs (Fitzgerald 1993). Females lay a clutch of 10 45 eggs that hatch during the late summer (South America) and early fall (Florida) (Fitzgerald 1993, P ernas et al. 2012, Naretto et al. 2015). Juveniles feed primarily on arthropods, but begin adding vertebrate prey and fruits to their diet as they age (Colli et al. 1998, Mercolli and Yanosky 1994). Tegus have been introduced to the state of Florida multi ple times and two confirmed breeding populations of ABWT, established since the early 2000s, now exist in the state ( Pernas et al. 2012, Barraco 2014). The population i n South Florida has received much attention in recent years (Pernas et al. 2012, Mazzotti et al. 2014, MaEachern et al. 2014, Barraco 2014, Klug et al. 2015). However, comparatively little is known about the tegu population in Central Florida (Hillsborough County).


20 Trapping efforts by the Florida Fish and Wildlife Conservation Commission (FWC) targeting this population from 2013 2016 indicate the population is less dense and not as widespread as in the south. Individual ABWT in South Florida are frequently found in and around wetlands and disturbed habitat (Mazzotti et al. 2014, Klug et al. 2015). In contrast tegus in Central Florida are often reported from regions in and around scrub and xeric uplands ( personal observation). The presence of congeners and climate match between the native range and introduced range have been implicated in the likelihood of successful establishment of an invader (Ferrira et al. 2002, Bomfor d et al. 2009, Mahoney et al. 2014). Hillsborough County and the native South American range of ABWTs have similar proximity to the equator, with invaded regions as far north of the equator as the middle southern extent of tegu native range is south ( ). Tegus are large diurnal, terrestrial, opportunistic omnivores, and no other ecologically similar species exi sts in the introduced range in central Florida. H owever another smaller ins ectivorous Teiid, the six lined race runner ( Aspidoscelis sexlineata ) is common to scrubby habitat in the region. Although not a congener, the presence of this Teiid could indicate ABWTs may indeed do well in scrubby upland habitats. Scrub is a vulnerable ecosystem in decline primarily due to habitat loss from development (Scott 2004). The scrub ecosystem has numerous endemic biota and also 2004). Protection of scrub is a priority in Hillsborough County, Florida. Here, scrub is found sporadically throughout the county and natural corridors between patches are limited, ill defined or interrupted by urbanization (Abrahamson 1990). This habitat


21 fragmentation increases risk of species extirpation in local scrub communities and emphasizes the need for protection (Gilbert et al. 1998, Gonzalez & Chaneton 2002, Liebold et al. 2004). Although ABWT are reported in and around scrub habitat, a mosaic of heterogeneous landscape exists within Hillsborough County and includes wetlands, forested uplands, urban areas, pasture and cropland. No formal studies of ABWT resource use or habitat selection have been conducted here. Resource use is the amount that a resource within a habitat is expl oited by an animal within a fixed period of time. Habitat selection is the intentional, preferential use of some habitats over others by an organism. It is a hierarchical process that drives establishment of wildlife within a new environment (Johnson 1980, Mayor et. al. 2009). Habitat selection studies are interested in estimating the probability that a defined habitat is selected (or avoided) over other habitats. The theoretical framework for habitat selection is organized into four levels of increasing sp ecificity (Johnson 1980). First order selection is the geographical range of the species, second order selection is the home range of individuals within the population, third order selection identifies habitat within the home range from which resources are obtained and fourth order selection identifies the specific location among many where the resource is acquired (Johnson 1980). Resource availability may change through time, and this may influence what habitats are used by animals. After emerging from bru mation (a period of inactivity similar to hibernation), adult tegus show a seasonal burst of activity in the spring followed by declining activity in the summer and fall until tegus enter brumation to seek shelter during cold winter months (Fitzgerald et a l. 1993, Lopes and Abe 1999, Juri et al. 2015, McEachern et al. 2015). During months


22 of activity tegus may seek mates, food, and water and disperse to new habitat. Survival and reproduction depend on access to biotic and abiotic resources. Adaptations may aid (or prevent) resource acquisition within the environment. Tegus within Hillsborough County have historically been reported from multiple habitats including disturbed and natural areas ( ), d emonstrating little evidence of a population level consensus in habitat use. Private properties utilized by tegu s are a challenge to sampling efforts for population level habitat selection studies. For this reason radio telemetry wa s used to understand habitats selected by individual tegus. The location of individual tegus outfitted with transmitters can be triangulated at a distance from areas accessible by researchers and overlaid on satellite imagery to identify utilized habitat w ithout needing to access restricted areas. Wildlife and habitat are linked. Impacts on seed dispersers such as rodents, or ecosystem engineers such as the gopher tortoise may alter a habitat in time. Without intervention it is likely ABWTs will continue t o thrive in Florida and could have long term impacts on species diversity and abundance on local wildlife in Central Florida habitat. Understanding habitat use of the Argentine black and white tegu in central Florida will aid in identifying natural resourc es that could be affected by their presence. The goals of my study were to determine 1) habitat selection at landscape level and within home ranges by ABWTs and 2) location of winter refugia, where tegus seek thermal insulation during cold months when they enter a seasonal period of inactivity known as brumation. Further, because tegu behavior changes by season, with inactivity throughout the winter followed by a burst of activity in the spring and declining activity in the summer and fall (Fitzgerald 1993, Sanders 2015), I wanted to determine if habi tat


23 selection differed among seasons. To achieve these goals, I outfitted tegus with transmitters on a harness and utilized radio telemetry to monitor the location of individual tegus throughout the study. When observed at regular intervals, patterns of ha bitat use will begin to emerge. If tegus in Central Florida are primarily procuring resources from dry upland habitat, scrub and other xeric habitat will make up the majority of tegu home r anges and tegus will be loc ated in this habitat more frequently tha n in others. In addition, tegus will have larger home ranges in spring after emerging from brumation (and thus have a larger home range) and that no activity would occur during winter brumation. Methods Study Site My study areas were portions of two prese rves located in Hillsborough County (Figure 2 1). Balm Boyette Scrub Preserve (BBS) and Rhodine Scrub Preserve (RS) are located 7km east of Apollo Beach, Florida with RS located 4km north of BBS. I selected these preserves because of their rich history of tegu reports and prior agency lead investigations. Both Hillsborough County and the FWC have conducted tegu related fieldwork on these sites. Although the first records of tegus from this population were approximately 16km to the east, most tegus are now r eported from the rural and urban areas surrounding BBS and RS ( ). Both sites have a history of tegu presence starting in the early 2000s, and both are bound by a mosaic o f public roads, houses, agriculture fields and ruderal lands. My primary habitat of interest on BBS and RS was scrub, however both preserves contain a mixture of xeric and hydric soils and nearby habitats included pine flatwoods, xeric hammock, ephemeral ponds and wetlands adjacent to steams. The


24 dominant vegetation in the study area on both sites was saw palmetto ( Serenoa repens ), which grew so thick as to be impenetrable on foot in some areas. In RS live oak ( Quercus virginiana ) and pine ( Pinus spp ) formed a closed canopy on portions of the property. In BBS tall pines and live oak formed an open canopy with dense stands of scrub oak ( Q. ilicifolia ) growing in some burn units. Both BBS and RS are fire managed lands. Land within the preserves i s section ed by fire lanes, which are mowed at regular intervals to maintain a 3m wide path of either bare sand or herbaceous plants. The southern edge of BBS is bordered by a 70m wide electrical utilities right of way operated by TECO (Tampa Electric Company). The right of way was used daily during the course of the study by heavy machinery and construction crews installing updated utilities. Pallets of equipment and supplies lined the eastern southern edge of this corridor. Prior to the study, the right of way had been maintained and periodically grazed by cattle. The vegetation consisted of grasses and short herbaceous plants with clumps of palmetto along the perimeter fence. Similarly, the private properties to the south of this right of way featured well mowed g rassy fields intermittently grazed by cattle. A clump of palmettos and live oak remained on the east end of one property. A 150ha commercial tomato farm shared a border with this private property and the utility right of way. This agricultural field was pl anted, harvested, cleared and planted again during the course of the study. The agricultural field featured bare sandy soils with rows of tomato crops, bordered by thick clumps of palmetto along the perimeter fence. Data Collection To acquire study specim where tegus were known to visit as demonstrated in previous investigations by


25 Hillsborough County and FWC, such as along fences or near gopher tortoise burrows. I placed traps in bushes in the shade o r partially covered to provide shade and airflow. I baited traps with a whole, raw chicken egg and replaced it every week if the egg had not been consumed. Water was provided and traps were checked daily in accordance with my UF IACUC protocol (# 201508846 ). Trapping occurred in two phases, the first from Mar Sept 2015 and the second from Mar Sept 2016. I did not trap during months where tegus exhibit reduced activity from late October through mid February, although radio tracking was conducted year round. I assembled transmitter harnesses by attaching radio transmitters (Holohil PD 2 or SI 2) to stainless steel ball chain. Transmitters emitted pulses between frequencies 164 MHz and 168 MHz. As I caught tegus they were weighed and measured, fitted with radio transmitter harnesses around the pelvic girdle and released at the site of capture. All captured tegus weighing over 1000g were outfitted with harnesses. To find tegus once released, I used triangulation methods instead of close approach so as not to dist urb the tegus and influence their movement. Three times a week I triangulated tegu positions by standing at predetermined stations and taking an azimuth bearing in the direction of the strongest radio signal. I recorded GPS coordinates of stations along wi th the average azimuth bearing, temperature, humidity, and weather conditions. If tegus remained in the same location for more than three sessions, I found exact locations using telemetry to confirm disposition of tegus or retrieve dropped harnesses. If te gus were tracked to burrows, as in winter months, I recorded the location of the burrow and monitored it regularly until tegu emergence. Additionally, I matched burrows to likely burrow architects (gopher tortoise, armadillo, rabbit, or tegu). I caught tel emetered tegus


26 periodically to adjust harness fit, measure, and weigh. I retrieved and removed tegus at the end of the study where possible. Data Analysis To analyze movement patterns and habitat use of tegus I used the R software packages sigloc (Berg 201 4) and adehabitat (Calenge 2006) which is subdivided into adehabitatHR for home range analysis and adehabitatHS for habitat selection analysis. Of the eleven tegus fitted for harnesses, data were insufficient for two individuals. This resulted in nine teg us (five females, four males) ultimately used for spatial ecology analysis. I entered azimuth reading stations and bearings into the sigloc program to extract triangulat ed positions for accuracy utilizing ellipse errors generated within the program and removed locations if they were recorded at a distance further than was possible for a tegu to move within the time between the previous and next locations. I compiled trian gulated positions for each tegu and combined them with known exact locations (e.g. tegus in winter burrows) to produce a list of GPS coordinates, hereafter called relocations. I fed all relocations into a data frame and used them to calculate tegu home ra nges using Minimum Convex Polygon (MCP) methods in the software package adehabitatHR (Calenge 2006). To understand habitat selection I chose the 100% MCP over kernel analysis for two reasons. First, recent research indicates MCP is a more accurate represen tation of herpetofauna home range, especially when smoothing values for kernel analysis cannot be reliably determined (Row and Blouin Demers 2006, Kay et al. 2017). Second, due to the limitations of the data and the challenges this


27 created for reliably est imating home range size, 100% MCP was more appropriate for understanding habitat selection, including regions that tegus may move through but not spend much time. Finally, the focus of my study was on habitat selection and not home range estimation methods and using a hierarchical approach to understand resource use diminishes the importance of home range methods. I grouped location data by tegu and by season. I define d seasons as the four sets of three month intervals that primarily coincide with the spr ing (Mar May), summer (June Aug), fall (Sep Nov) and winter (Dec Feb) in the northern hemisphere and which reflect patterns of seasonal tegu activity. Although fewer tegus are active in November and tegus in in my study entered brumation as early as mid Oc tober, I chose to include November with the fall months to ensure time periods were consistent across analyses. I exported the 100% MCP for each tegu in each season as a GIS layer in UTM 17 N coordinate reference system. Using QGIS, I overlaid the home ran ge polygon with an existing layer of statewide land use land cover compiled from 2004 2016 by regional Florida Water Management Districts. I cut a new layer the same size and shape of the 100% MCP including the associated habitat within that home range. Al ong with the study area, I exported these polygons to R where area was calculated for each MCP and habitat polygons therein and tegu relocations were plotted on top of the image. Using this technique I was able to count the number of relocations of a tegu in a defined habitat for third order habitat selection analysis, and to calculate the area of each habitat available to a tegu for both second and third order habitat selection analysis. e the proportion of available habitat to the proportion used (Johnson 1980, Manly et al. 2002).


28 Three study designs are considered, which are hierarchical in nature. Design I studies measure use and availability at population level and individual animals a re not identified, design II studies measure habitat use (as home range) of identified animals against habitat available for all animals in the population and corresponds to second order habitat selection, and design III studies measure both use and availa bility for individually identified animals and correlates with third order habitat selection (Johnson 1980, Manly et al. 2002). I carried out design II and design III habitat selection analysis in the software package adehabitatHS (Calenge 2006). For desig n II analysis, the boundaries of the study sites (either RS or BBS) defined the habitat to which every tegu within that site had access. I compared habitat within home range polygons to habitat within the study site to determine if habitat was selected in proportion to availability. For design III analysis I compared number of relocations within each habitat to habitat square analysis to determine if strong habitat selection was occurring and if habitat use was dictated by individual tegus or at the species level. Manly Selection Ratios are drawn from a unimodal distribution and it is assumed that on average all animals within a population prefer to select the same habitat to acquire resou rces (Manly et al. 2002). Seasonal cycles and tegu age or sex may influence habitat selection (Fitzgerald et al. 1993, Juri et al. 2015, McEachern et al. 2015). To control for variation among age classes I used only adult tegus during the course of the stu dy. I used eigenanalysis to visually explore sex and seasonal trends in tegu selection for (or avoidance of) habitat types. Eigenanalysis of selection ratios is an exploratory method that can expose variation in resource selection among individuals. It


29 uti lizes an additive linear partitioning of the White and Garrott statistic (White and Garrott 1990). Variation in odds ratios (OR) of selection are maximized to examine selection patterns between individuals. Greatest variation occurs along the first axis if the majority of tegus select the same type of habitat, however if multiple habitats are select ed the n those habitats will be distributed along multiple axes, thus exposing patterns in habitat selection, if any exist, among seasons and between sexes. I eva luated tegu habitat selection in both the design II and design III study and made conclusions based on the resulting factor loading for habitat variables along the factorial plane. Results Tegu Tracking I captured nine adult tegus (five females, four males ) in the BBS study area. However one female was too small (790g) so I did not fit her with a transmitter harness. As seen in Table 2 1, tegus outfitted with transmitter harnesses varied in total length (mean = 93.44cm 8.64, range = 81.1cm 106.36cm) and m ass (mean = 1686g 379, range 1100g 2300g). Two tegus (one male, one female) dropped transmitters within a week of deployment with only two and one relocation point collected respectively and so were removed from the analyses. Four tegus lost their harnes ses; two after deterioration of the ball chain attachment (tegus TL3, TL5) and two after becoming entangled in vegetation (TL8, TL12). This resulted in considerable variation between the minimum number of relocations (n = 9) and maximum number of relocatio ns (n = 100) for tegus used in my analyses. In RS I captured one male and two female tegus, each of which I fitted with transmitter harnesses. Two of these animals (TL9, TL10) apparently wandered away


30 from the study site after 187 days and 227 days and we re not able to be relocated. Two large radio towers directly adjacent to RS caused signal interference with receivers across all frequencies (164mHz to 168mHz) and I was not able to hear pulses from transmitters (and therefore locate tegus) in the immediat e direction of these towers. This created regions where I was unable to accurately determine animal locations, although tegus often moved out of these areas within 24 72 hours. This occurred at the BBS site as well, but the effects of the towers were not a s extreme since the radio towers were further away. Additional sources of interference came from seasonally frequent thunderstorms in the summer and radio communication and heavy machinery from nearby construction sites. I tracked the movements of 9 tegus in total from April 2015 through October 2016. Two tegus were followed for all four seasons during the study period, and several tegus appeared in the data set for at least two seasons (Table 2 2). Tracking revealed seasonal variation in activity level, a nd therefore home range size. As I predicted, tegus had heightened activity in the spring after they emerged from brumation. This was followed by declining activity through summer and fall until a period of no, or nearly no activity, as they entered brumat ion again for the winter. Average temperatures during the brumation period from October 2015 through February 2016 remained above freezing and were occasionally relatively warm (Table 2 3) with maximum average bi weekly temperature climbing as high as 27C but dropping as low as 9C. Despite many days of warmer weather, tegus did not move away from their burrows. Home Range Home range size for tegus was highly variable by season (Table 2 4). As expected, tegus did not move much during the winter months whe n they were in


31 burrows. Since this period of inactivity did not represent a range, per se winter locations were not included in further analyses. The smallest home range was that of a female tegu in the summer (0.335 hectares) and the largest was a male i n the spring (144.937 hectares). Average home range in hectares varied among seasonal averages (total: 17.736 33.959, spring: 36.531 54.777, summer: 13.959 24.393, fall: 5.134 3.206) and by sex (male: 22.343 44.249, female: 12.13 20.167). Uneve n sampling may have contributed to some of the variation in home range sizes I observed (Table 2 (TL10) but no other overlaps occurred at that site. In BBS three tegus show ed periodic home range overlap (TL3, smaller male, TL4, larger male, TL7, female). In spring 2015 d 92% of longer in the study, however the large male tegu (TL4) overlapped 45% of the female Habitat Selection Results of Chi square analyses for design II (second order) data show tegus in the RS and BBS groups did not use available habitat in the same proportion across the df = 98, p < .001) and h abitat selection within study sites was non proportion to available habitat at second order and tegus showed individual variation in ha p < .001). Odds ratios (OR) for selection and Bonferroni confidence intervals varied at


32 second order by habitat and study site (Figure 2 2, Figure 2 3). The utility righ t of way, which did not occur on RS, was significantly selected by tegus at BBS [Odds Ratio (OR) = 6.429, SE = 1.722] and scrub habitat was selected on both sites (RS: OR = 1.506, SE = 0.169, BBS: OR = 1.85, SE = 0.166). Tegus exhibited a slight trend in s election for urban habitat on both sites (RS: OR = 1.17, SE = 0.087; BBS: OR = 1.359, SE = 0.226). On RS, tegus showed a trend in selection for upland forest (OR = 1.23, SE = 0.269) but avoidance of this habitat on BBS was statistically significant (OR = 0 .386, SE = 0.096). Other avoided habitats at second order included pasture/rangeland (RS: OR = 0.279, SE = 0.079; BBS: OR = 0.341, SE = 0.091) and wetlands, which were more strongly avoided by BBS tegus (RS: OR = .955, SE = 0.121; BBS: OR = 0.102, SE = 0.0 19). Rural habitat was avoided by RS tegus (OR = 0.453, SE = 0.077), whereas BBS tegus demonstrated a trend in selection for this habitat (OR = 1.132, SE = 0.2). Factor loading of habitats in eigenanalysis for second order habitat selection at RS and BBS did not cluster according to season (Figure 2 4, Figure 2 5). In RS, individual tegus selected either for urban and scrub habitat or neither but this was likely due to geographic proximity of the two habitat types. In fall of 2015 and the following spring of 2016 one tegu strongly selected upland forest habitat within its home ranges (TL10). Another tegu selected for urban habitat in the summer of 2016 but scrub habitat in the spring of the same year (TL11). The third tegu was only analyzed for a single sea son but strongly selected for rural habitat (TL9, fall 2015). In BBS tegus tended to select for only scrub or utilities or both scrub and utilities. Two tegus were captured and documented only in the northern portion of scrub habitat within the study site, but the


33 utilities corridor was at the extreme southern boundary of the scrub. Tegus in the southern region of the study site used both the utilities corridor and adjacent scrub. Several tegus in the design III study (third order) in both RS and BBS demo nstrated significant habitat selection within their seasonal home range (TL10 0, rati o analysis at third order showed slight variations from second order, with a trend in selection for upland forest and scrub habitat at RS, although Bonferroni confidence intervals showed individual selection for scrub was highly variable (Figure 2 6; Figur e 2 7; upland forest: OR = 3.129, SE = 1.429; scrub, Lower 95% CI = 0.642, Upper 95% CI = 6.9: OR = 7.885, SE = 7.186, Lower 95% CI = 11.072, Upper 95% CI = 26.842). Rural habitat was avoided in RS (OR = 0.147, SE = 0.098) but was strongly selected by so me animals in BBS (OR = 26.148, SE = 9.226). Utilities were also strongly selected in BBS (OR = 46.303, SE = 22.444) and scrub habitat showed a trend in selection among individuals (OR = 3.258, SE = 1.171). In BBS wetlands and pasture/rangeland were avoide d (wetlands: OR = 0.294, SE = 0.154; pasture/rangeland: OR = 0.016, SE = 0.012). Eigenanalysis demonstrated individuals did not cluster according to habitat, season or sex at third order and confirmed the selection ratio analysis. Winter Refugia In 2015 I tracked four tegus to winter refugia (burrows), two from the RS group (TL9, TL10) and two from th e BBS group (TL4 and TL7). I observed tegus entering


34 brumation in late October or early November. Burrow shape and size indicated initial burrows were constru cted by armadillos but did not show signs of recent activity. The female tegus (TL7, TL9, TL10) were not detected outside their burrows nor did they move to different burrows after they entered brumation until emergence in mid March. The battery of the tra nsmitter of TL9 failed during brumation, but due to her location on private property under a tree in extremely dense foliage it was not possible to excavate the burrow to retrieve the tegu and she was not subsequently caught the following spring. All four tegus chose burrows that were completely covered by brush, with two burrows (TL7, TL10) located in dense vegetation on habitat edges between natural areas and private property. Two tegus (TL4, TL9) chose burrows located in scrub situated under palmetto roo ts. Twice, TL4 chose hibernacula under palates of equipment used by contractors working on the utilities easement and had to relocate to a new refugia. Discussion My analysis revealed that individual selection is what drives variation in habitat use of in vasive tegu lizards at my study sites. Tests for second order habitat selection showed significant differences in habitat selection among individuals. Additionally, third order statistics indicated that tegus selected specific habitats within their seasona l home ranges, and this varied considerably among individuals. As a result, at the species level tegus tend to be habitat generalists, both when selecting home range (second order) and when selecting habitat within the home range (third order). Odds ratio s and lower confidence intervals for scrub habitat at second order were greater than one, indicating significant s election for scrub when available in a home range, which aligned with my original prediction H owever tegu association with


35 scrub was n ot as strong at third order. Here, as in second order selection, odds ratios were greater than one and upper confidence intervals were significantly above one. However, lower limits of the confidence intervals were below one, indicating a weaker trend in s election. In contrast, second and third order odds ratios and upper and lower confidence intervals were below one for wetland habitat, showing that tegus at my sites avoided wetlands. One exception to this was shown by tegu TL10 in the spring. This lizard used wetland habitat in RS during spring, but at no other time; possibly during a dispersal event after brumation. This finding coincides with results of tegu land use in South Florida (Klug et al. 2015) in which natural wetlands were used proportionately less than disturbed upland as a movement corridor. Tegus in my study used disturbed, human altered landscapes disproportionately and dissimilarly between sites. My prediction that tegus heavily use disturbed landscapes was not entirely accurate. Landscape s dominated by shrubs and grasses (e.g. pasture/rangeland and rural), similar to native habitat of tegus and those described by Klug et al. (2015), were either used in proportion to avail ability or avoided by tegus in c entral Florida except in one instance Heavy selection for rural habitat at third order at BBS could have been facilitated by its adjacency to scrub, utilities and urban habitats, whereas in RS this habitat type was positioned opposite these habitats and avoided. The most heavily selected hab itat in BBS at both second and third order was the utilities right of way, a disturbed habitat which did not exist at RS. The utilities right of way featured well mowed grass with artificial cover in the form of large wooden pallets and metal utilities pol es that resembled large fallen tree trunks in size and positioning. In addition, the right of way was bordered by barbwire fence along which grew clusters of


36 palmettos. I often located tegus along this edge and they appeared to be using the palmetto roots and leaf litter as nighttime refugia. With odds ratios greater to or very close to one at both sites, tegus did not avoid urban habitat overall. In RS urban areas were largely residential neighborhoods with manicured lawns, however in BBS the urban region consisted of 10 acre plots of land with homes, barns, grassy, well mowed lawns and small patches of palmettos and vines. Urban areas offer potential food resources (rodents, cockroaches, cultivated fruits) and tegus may be choosing to associate with this h abitat in order to access those resources despite the lack of vegetative cover and associated risks (such as dogs and lawnmowers). Upland forest habitat in BBS was avoided, despite being the largest available habitat type at that site. Across both sites, l ocations of tegus within the landscape tended to strongly coincide with habitat that was selected at the landscape level and locations did not tend to occur in habitats that were avoided. This indicates that tegus demonstrate a hierarchy where use of habit at at third order can be predicted by habitat selected in home ranges at second order. There were two exceptions in BBS where both wetlands and upland forest were slightly more selected at third order than at second order, but still avoided overall. Conver sely, there was a dramatic increase in selection for utilities and rural habitat for tegus in BBS at third order compared to second order, but this was likely driven by two individuals and not indicative of the average tegu within the population. When sel ecting winter refugia, two tegus selected burrows on the edge of urban areas (TL9, TL7), one tegu selected a burrow in scrub (TL10) and one (TL4) selected a burrow in the utilities right of way. This tegu originally selected refugia three times along the u tilities corridor but was disrupted twice by construction and forced to relocate. As


37 documented in previous studies, tegus used preexisting burrows for brumation (Fitzgerald et al. 1991, McEachern et al. 2015). It is unknown weather tegus left burrows to b ask during the winter months; however observations during telemetry sessions made at burrows indicated there was no disturbance at the burrow entrances which were partially or entirely obstructed by leaf litter. Although tegus avoided some habitats, no ha bitat appeared to be a significant barrier to tegu movement in my study. Individual level selection, rather than a general species trend, explained variation in selected habitat. This highlights the adaptability of ABWTs and indicates their ability to succ essfully establish in other regions should they be introduced to another hospitable climate in sufficient numbers. This adaptability is likely correlated with the wide range in which Argentine black and white tegus occur in their native habitat; from tropi cal eastern Brazil to subtropical central Argentina. Sample size was limited (n = 9) in my study and additional animals may have revealed stronger trends. However, the broad individual variation in habitat selection observed here sets a precedent for manag ement strategies to include multiple habitats in trapping and survey efforts and underscores the emphasis on trapping in multiple habitat types. The fact that tegus chose scrub at my sites is especially alarming. Given time and continued propagule pressure tegus are certainly capable of col onizing other natural areas in c entral Florida, such as the Ocala National Forest (ONF). There are several isolated tegu records from this region and adjacent areas to the south (see tegus point map at ), and should tegus eventually become


38 established here land managers may be faced with a scenario similar to the invasion of the Everglades by Burmese pythons. My study also creates a foundation for future research to understand tegu spatial ecology in an urbanized introduced range. Argentine black and white tegus are omnivores and known dietary generalists capable of eating species protected by state law, such as alligator eggs (Mazzotti et al. 2014) and hatchling gopher tortoises (see Chapter 3). Paired with their ability to subsist within a wide range of habitats, this demonstrates they should continue to be viewed as a serious threat to wildlife conservation in Florida. Continued action to remove tegus wherever found as part of an early detection/rapid response program, and efforts to educat e the public should be a priority for state and federal agencies. In addition, considerations should be made to restrict tegu ownership, breeding and importation into Florida and other states that have subtropical climates and mild winters. Prevention is t he most ecologically and economically cost effective approach to combating the introduction of invasive species (Harvey and Mazzotti 2014).


39 Figure 2 1. Location of study sites in Hillsborough County, Florida includi ng Rhodine Scrub in the north (A ) and Ba lm Boyette Scrub in the south (B ) Map data: 2017 Google Maps. A ) B )


40 Table 2 1. Tegu identification number; study site in Hillsborough County, Florida from which they were collected: Balm Boyette Sc rub (BBS) or Rho dine Scrub (RS), sex of tegu and size at capture. Tegu ID Study Site Sex Weight at capture (g) Total Length at capture (cm) TL1 BBS F 1200 83.8 TL2 BBS M 1500 88.9 TL3 BBS M 1500 91. 4 TL4 BBS M 2300 106. 4 TL5 BBS M 1950 102.2 TL6 BBS F 790 70.6 TL7 BBS F 1550 90.8 TL8 BBS F 1500 95.9 TL9 RS F 1900 81.1 TL10 RS F 1950 100.8 TL11 RS M 2100 102. 4 TL12 BBS F 1100 84.2


41 Table 2 2. Number of locations rec orded for each tegu each season. Spring 2015 Summer 2015 Fall 2015 Winter 2015 Spring 2016 Summer 2016 Fall 2016 TL3 3 19 TL4 6 17 22 14 29 5 7 TL5 10 TL7 17 29 14 18 13 2 TL8 9 TL9 16 12 TL10 13 21 1 TL11 12 21 18 TL12 16 6 Table 2 3. Bi weekly mean temperatures in Riverview, Flor ida near tegu study sites from October 4 th 2015 through the week of February 21 st 2 016 Temperature data obtained from web/. Temperature (C) Start Date Max Avg Min October 4 27 25 23 October 18 26 24 23 November 1 27 26 24 November 15 24 22 18 November 29 24 21 19 December 13 25 22 15 December 27 23 20 15 January 10 19 14 10 January 24 21 16 9 February 7 18 15 12 February 21 20 18 13


42 Table 2 4. Total tegu home range size in hectares (100% minimum convex polygon) number of relocations in each habitat type 100% MCP Home Ranges (hectares) and Recorded Points Tegu ID (Study Site) Year Season Total Wetlands Urban TL3 (BBS) 2015 Fall 7 .189 NA 0.412 2 TL4 (BBS) 2015 Spring 11 .866 0.112 1 1.951 1 Summer 5 .093 NA 0.134 1 Fall 5.916 NA 1.330 5 2016 Spring 41 .416 0.598 1 3.139 4 Summer 0 .577 NA NA Fall 5 .594 NA 0.100 1 TL5 (BBS) 2015 Summer 3 .819 NA NA TL7 (BBS) 2015 Summer 67 .850 1.432 9.222 1 Fall 10 .722 0.400 1 1.577 17 2016 Spring 6 .465 NA 0.703 4 Summer 16 .683 0.464 1 0.761 1 TL8 (BBS) 2015 Summer 3 .358 NA NA TL9 (RS) 2015 Fall 3 .671 NA 0.633 12 TL10 (RS) 2015 Fall 1 .270 NA NA 2016 Spring 7 .313 3.835 11 0.017 TL11 (RS) 2016 Spring 144 .937 22.501 3 76.183 5 Summer 7 .022 0.383 6.317 11 TL12 (BBS) 2016 Summer 0 .335 NA NA Fall 3 .630 NA NA


43 Table 2 4. Continued 100% MCP Home Ranges (hectares) and Recorded Points Rural Scrub Pasture/ Rangeland Upland Forest Utilities 2.832 6 2.010 2 NA 0.178 1 1.757 8 NA 8.560 2 NA 0.210 1.033 2 1.642 4 NA 0.347 1 0.283 2.686 7 0.898 1 0.176 NA 0.269 4 3.244 15 4.116 9 25.177 6 1.034 3.426 1 3.926 8 NA 0.032 1 NA 0.120 1 0.426 4 NA 4.998 6 NA 0.112 0.384 0.067 1 1.096 1 NA 0.896 1.761 7 6.906 4 35.605 3 1.836 1 8.143 3 4.706 5 0.470 2 4.142 3 NA 1.195 1 2.939 5 1.628 7 0.347 0.191 0.380 3.216 5 0.500 3 6.581 NA 6.697 2 1.681 4 NA 3.358 9 NA NA NA 2.068 4 0.346 0.455 0.169 NA NA 0.190 9 NA 1.080 3 NA NA 0.129 6 NA 3.332 2 NA 11.246 19.191 5 1.475 14.342 8 NA NA 0.025 NA 0.296 7 NA NA 0.335 16 NA NA NA NA 3.630 6 NA NA NA


44 Figure 2 2 Odds ratios (OR) with Bonferroni confidence intervals calculated for tegu second order habitat selection at Rhodine Scrub, Hillsborough County, FL. Intervals greater than 1 (dotted line) indicate selection for a particular habitat type and intervals below one indicate avoidance. 0 0.5 1 1.5 2 2.5 RS Second Order Bonferonni Confidence Intervals Odds Ratio (OR)


45 Figure 2 3 Odds ratios (OR) with Bonferroni confidence intervals calculated for tegu second order habitat selection at Balm Boyette Scrub, Hillsborough County, FL. Intervals greater than 1 (dotted line) indicate selection for a particular habitat type and intervals below one indicate avoidance. 0 2 4 6 8 10 12 BBS Second Order Bonferonni Confidence Intervals Odds Ratio (OR)


46 Figure 2 4 Results of Eigenanalysis for tegus within the Rhodine Scrub study site. Factor loading for habitat variables along the first two axes can be seen at the top (distance = 500 units) and marginality vectors for tegus on the factorial plane can be seen at the bottom (distance = 0.5 units). Tegus did not cluster according to habitat, sex, or season. d = 500 d = 0.5 TL11_sum16


47 Figure 2 5. Results of Eigenanalysis for tegus within the Balm Boyette Scrub study site. Factor loading for habitat variables along the first two axes can be seen at the top (distance = 200 units) and marginality vectors for tegus on the factorial plane can be seen at the bottom (distance = 0.5 u nits). Tegus did not cluster according to habitat, sex, or season. d = 0.5 d = 200


48 Figure 2 6. Odds ratios (OR) with Bonferroni confidence intervals calculated for tegu third order habitat selection at Rhodine Scrub, Hillsborough County, FL. Intervals greater than 1 (dotted line) indicate selection for a particular habitat type and intervals below one indicate avoidance. -15 -10 -5 0 5 10 15 20 25 30 RS Third Order Bonveronni Confidence Intervals Odds Ratio (OR) Lower 95% Upper 95%


49 Figure 2 7. Odds ratios (OR) with Bonferroni confidence intervals calculated for tegu third order habitat selection at Balm Boyette Scrub, Hillsborough County, FL. Intervals greater than 1 (dotted line) indicate selection for a particular habitat type and intervals below one indicate avoidance. -40 -20 0 20 40 60 80 100 120 BBS Third Order Bonferroni Confidence Intervals Odds Ratio (OR) Lower 95% Upper 95%


50 CHAPTER 3 DIET OF ARGENTINE BLACK AND WHITE TEGUS IN CENT RAL FLORIDA Introduction Invasive species are considered the greatest threat to global biodiversity after habitat loss ( Vitousek et al. 1997 ) and humans have facilitated introductions of non native species around the globe (Hulme 2009). Introduced predator s can be devastating to native wildlife, particularly on islands. In Guam, predation by introduced brown tree snakes ( Boiga irregularis ) resulted in the extirpation of twelve native bird species and a 90% population decline in eight other bird species from parts of the island (Wiles et al. 2003). Introduced cats on Ascension Island resulted in the loss of all but one species of colonial nesting seabirds (Ratcliffe et al. 2009). Even in mainland situations, invasive vertebrates can be extremely problematic t o native animals. For example, a study in Everglades National Park, Florida showed that presence of invasive Burmese pythons ( Python bivittatus ) alone explained the decline of marsh rabbits ( Sylvilagus palustris ), a key food resources for a variety of nati ve predators (Sovie et al. 2016) and another study implicated pythons as the reason for decline of raccoon, opossum and bobcat observations during road surveys (Dorcas et al. 2012). Impacts from invaders may not be apparent for decades after introduction events, allowing time for population establishment and expansion (Simberloff 2013). While there are multiple examples of species decline caused by invasive wildlife and feral animals on islands (Fritts and Rodda 1998, Wiles et al. 2003, Platenberg 2007, Ra tcliffe et al. 2009, Bastille Rousseau et al. 2017) comparatively few exist for mainland ecosystems (Gurevitch et al. 2004). It may not always be possible to disentangle anthropogenic declines from those caused by invasive species, but if human induced


51 dec lines are occurring, the presence of an invader could act as an accelerant (Gurevitch et al. 2004). Strategic allocation of limited funds and manpower by agencies tasked with managing the impacts of invaders requires quick and accurate identification of th reats to native wildlife from introduced species. To this end, determining the diet of an invasive predator is a first step towards understanding where impacts on native communities might occur. In Florida, 180 taxa of nonnative herpetofauna (reptiles and amphibians) have been found throughout the state (Krysko et al. 2016). Florida Fish and Wildlife risks posed by invasive wildlife and FWC has prioritized two snakes and two lizard s for removal and continued assessment because of the elevated risk they pose as predators of native wildlife ( ). These high priority species include the Burmese python ( Python molurus bivittatus ), African rock python ( Python sebae ), Nile monitor ( Varanus niloticus ) and Argentine black and white tegu ( Salvator merianae ). All four species are capable of preying upon a diversity of native wildlife including imperiled species (Sovie et al. 2016, Dove et al. 2011, Campbell 2005, Mazzotti et al. 2014). The Argentine black and white tegu is a large terrestrial Teiid lizard from South America, growing to 145 cm total length and weighing up to 8 kg (Lop ez and Abe 1999). This species has a wide native range and occurs in Brazil, Uruguay, Paraguay and Argentina in a variety of habitats (Fitzgerald et al. 1999, Presch 1973). Juvenile tegus are primarily insectivorous, but begin including a variety of verteb rates and fruits in their diet as they age (Mercolli and Yanosky 1994, Colli 1998, Kiefer and Sazima 2002). Two populations of Argentine black and white tegu (ABWT) have been introduced to Florida,


5 2 one in southern Miami Dade County and one in west central Hillsborough County. Tegus in south Florida are well established in and around wetland habitat, whereas in central Florida tegus are primarily concentrated around dry uplands, frequently in scrubby habitats ( ). This contrast implies tegus in south and central Florida may differ substantially in their ecology and impacts on native species. highest concentrations of threatened and endangered species (Scott 2004). Federal and state listed wildlife that inhabit Florida scrub and surrounding xeric habitats include unique mammals, birds, invertebrates and many terrestrial herpetofauna (Campbell 1992, Hum phery 1992, Deyrup 1994). Protected species that could be prey for tegus include the gopher tortoise ( Gopherus polyphemus ), indigo snake ( Drymarchon couperi ), short tailed snake ( Lampropeltis extenuate ), Florida pine snake ( Pituophis melanoleucus ), sand sk ink ( Neoseps reynoldsi ), gopher frog ( Rana capito ), scrub jay ( Aphelocoma coerulescens ) and the endemic Florida mouse ( Podomys floridanus ) (Campbell 1992, Humphery 1992). Scrub has been highly fragmented and converted to real estate development throughout Florida because of its well drained soils and relatively high elevation, and over 60 percent of scrub has been lost since the arrival of vulnerability of many scrub species to habitat loss, it is critical to quickly ide ntify and address threats to this habitat, especially when those threats could directly influence the decline in abundance of imperiled wildlife, such as the gopher tortoise ( Gopherus polyphemus ). As ecosystem engineers, gopher tortoises are a keystone species whose


53 burrows provide shelter for a wide variety of vertebrates and invertebrates (Pike and Mitchell 2013, Kinlaw and Grasmueck 2012). Currently, knowledge of tegu diets in their introduced Florida range is limited to the population in Miami Dade County to the south, with scant observations in Hillsborough County and central Florida (Barraco 2014, Mazzotti 2014, Enge 2006). The goal of my study was to assess the diet of tegus in central Florida and potenti ally identify vulnerable scrub species eaten by tegus, thus contributing to the body of knowledge of the risks associated with this invasive lizard in Florida. Materials and Methods Study Site The ABWT population in central Florida is located south of the town of Riverview in eastern Hillsborough County and extends east to the border of neighboring Polk County. It covers a region of 167 km (16,700 hectares) roughly bounded by Bloomingdale Ave to the north, CR 672 in the south, SR 301 to the west and CR 37 to the east, although tegus in Central Florida have been reported beyond this region (Figure 3 1). My study area was determined by historical reports of tegu sightings throughout the region ( ). Natural habitats within the core study area included a matrix of scrub, xeric hammock, upland hardwood forest, hardwood coniferous forest, mesic flatlands, marshes and freshwater forested and non forested wetlands. Human dominated l andscapes including urban and rural communities, cropland, rangeland and pasture were scattered among these natural habitats. Tegus collected between May 2012 and September 2016 within this region were included in my diet analysis.


54 Tegu Acquisition From May 2012 to September 2016, 105 Argentine black and white tegus were collected from central Florida in Hillsborough County. Tegus came from unpublished studies by the University of Tampa (36 tegus; collected 2012 2013), FWC (43 tegus; collected 2013 2014) and FWC/University of Florida (26 tegus; collected 2015 2016). I acquired 71 tegus from live trapping on a number of properties including 30 tegus from a single 40 acre property situated between two county preserves. Residents in the local community donate d 30 tegus removed from private property by live trapping or lethal force. An additional four tegus were collected as roadkill. Researchers trapped tegus and Use Committe e (protocol 201508846 for UF/FWC collection in 2015 2016). Traps were baited with whole, raw chicken eggs, set in the morning and checked within 24 hours. All bycatch (e.g. raccoons, opossums) was immedialty released on site. I placed traps near gopher tor toise burrows, wildlife trails or other locations where tegus were known to visit. I placed traps in bushes, or provided shade by covering traps with dried palmetto fronds and Spanish moss and provided water in the traps. Euthanasia was performed with CO 2 (University of Tampa collection) or captive bolt (FWC and UF collections). Diet Analysis Morphological data I collected for tegus included snout vent length, tail length, mass and reproductive status. Stomachs were removed from dissected tegus and emptie d into glass bowls (UT) or fine mesh sieves (FWC/UF) and washed. I separated stomach contents and identified and counted species eaten. I used unique features of stomach contents (e.g., number of limbs, mouth parts, wings or seeds) where possible


55 to count multiple individuals of one species, but when this was not possible I assumed a single individual. I assumed bird feathers and mammal fur to be from one individual unless multiple species could be confirmed though detailed identification. Feathers were ide ntified to Order using methods described by Dove and Koch (2010) in which feathers are fixed to slides, examined under a light microscope for diagnostic characteristics of the downy barb and compared to characteristics of known species. Guard hairs were us ed to identify mammals to Order or species using methods described in Debelica and Thies (2009) in which hairs are fixed to a slide, examined under a light microscope for diagnostic characteristics of the medulla and cuticular scale and compared to example s from known species. Although literature suggests tegus sometimes eat ants (Colli et al. 1998), I did not include ingested ants in my diet analysis. Tegus likely ingested ants inadvertently w hen eating bait or scavenged fruits and so I excluded them. Like wise, small beetles (<5mm), which were found in association with partially digested amphibians and identified in the stomachs and intestinal tract of whole ingested amphibians, were not considered as tegu prey. I recorded incidental ingestion of plant fibe rs (dried leaves, grasses and sticks) and inorganic items but did not count or include them in final analyses. I calculated frequency of occurrence (FO) and niche overlap (O jk ) on the number (not mass) of species consumed. As mentioned I excluded ants and plant fibers to avoid inaccurate analysis of prey consumption. For similar reasons I did not include the contents of intestinal tract in my diet analysis since some organic parts (e.g., exoskeletons, seeds) can be passed as solid pieces, whereas other par ts (e.g., bones, fruit) are partially or fully digested and unrecognizable in the intestine


56 Ontogenetic dietary shifts have been documented in tegus in their native range (van Leeuwen et al. 2011), so to calculate the overlap in diet of Central Florida t egus where P ij is the proportion of item i in group j and P ik is the proportion of item i in group k. The value of O jk ran ges between 0 (no overlap) and 1 (complete overlap). I grouped tegus as adults or juveniles, and males and females. Results Diet Composition I collected the stomach contents of 49 male, 48 female and 8 undetermined tegus, with most tegus acquired during th e spring and summer months (Figure 3 2). These included 57 reproductive adults and 39 juveniles, determined at time of necropsy, with 9 specimens of undetermined age class. Tegus measured between 10cm and 81.6cm snout vent length (mean=31.62cm 8.86, medi an=38.5cm) and weighed 20g to 3990g (mean=1342.59g 847.85, median=2150g). Out of 105 tegus analyzed, only 12 had empty stomachs. Stomach contents were often digested to one degree or another, but could reliably be identified to at least Order level (Tabl e 3 1). A total of 103 unique prey items were identified with 34 identified to species. Appendix 1 contains a list of all identified diet components, including inorganic items. Tegus ate a wide variety of taxa including invertebrates and their eggs, verte brates, bird and reptile eggs, and fruiting bodies of a variety of plants. Individual food items counted in tegu stomachs (n = 93) were comprised of 48% fruits and fruiting bodies, 37%


57 invertebrates and 15% vertebrates. However frequency of occurrence (FO) of these broad diet groups differed substantially; 51.61% of tegus consumed fruits, 84.95% consumed invertebrates and 80.65% consumed vertebrate prey. When grouped by season, FO of fruit, invertebrates and vertebrates varied (Figure 3 3). Fruit and invert ebrate consumption was greatest in summer (fruit: FO = 59.1%; invertebrate: FO = 93.2%) and vertebrate consumption was greatest in the spring (FO = 96.2%). Fruits were eaten by fewer tegus than vertebrates or invertebrates, although a wide variety of fruits were consumed. Small berries were eaten more frequently than larger fruiting bodies, accounting for the high percentage of individual food items contribut ed by fruits. Fruits from the genus Vaccinium (blueberries) in the Order Ericales accounted for nearly 45% of all individual fruits consumed by tegus and had the highest frequency of occurrence (FO = 15.05%), even though ten taxa of recognizable fruiting b odies were identified. The two most common Orders of fruits consumed after Ericales were Rosales (blackberries, cherries and strawberries; FO = 12.90%) and Arecales (palm drupes; 11.83%). Other fruits were less common (FO < 5%) including Vitales (grapes), Lamiales (lantana and beauty berries), Sapindales (hog plum and citrus), and Solanales (tomatoes). One tegu ate a mass of pelleted grain (animal feed), and acorns were occasionally found along with dried oak leaves but were considered incidental due to the high frequency which they occurred in the environment but few records from tegu stomachs. Vertebrates were a conspicuous part of tegu diets at my study site. The remains of hatchling gopher tortoises ( Gopherus pol yphemus ), an imperiled species, were found in the stomach contents of five tegus (FO = 5.38%). Other reptiles consumed included


58 snakes and their eggs, such as adult black racers ( Coluber constrictor ) (FO = 13.98%). Lizards (FO = 9.68%) such as brown anoles ( Anolis sagrei ) and eastern fence lizards ( Sceloporus undualtus ) were also eaten. Identifiable amphibians included frogs from families Ranidae (FO = 1.08%), Hylidae (FO = 7.53%) and Bufonidae (FO = 15.05%). Mammals consumed by tegus were primarily from Or der Rodentia (rats and mice; FO = 26.88%) but not all fur was able to be identified (FO = 19.35%). Other Orders identified at low frequency (<5%) included Lagomorpha (rabbits), Carnivora (raccoons and skunks), Soricomorpha (moles), Cingulata (armadillos) a nd Didelphimorphia (opossums). Birds and bird eggs were found in 12 tegus (FO = 12.90%) and three feathers were identified from three orders including Galliformes (chickens and quail), Passeriformes (songbirds) and Falconiformes (falcons and kestrels). A s ingle tegu ate fish (FO = 1.08%) in the form of seven young swamp eels ( Monopterus albus ). Swamp eels are invasive and can be found in lakes and rivers throughout Florida. The finding of new, previously undocumented population of swamp eels. A variety of arthropods were also consumed by the tegus. Stomach contents frequently included arthropods in the Orders Coleoptera (beetles; FO = 59.14) and Orthoptera (grasshoppers and crickets; FO = 5 2.69%), but also Blattoidia (cockroaches; FO = 17.2%), Hyminoptera and their nests (wasps; FO = 13.98%), Lepidoptera adults and larvae (butterflies and moths; FO = 11.83%), and Araneae (spiders; FO = 6.45%). Two burying beetles of the genus Nicophorus were identtified (though not the Federally endangered N. americanus ). Terrestrial gastropods, both slugs and snails, in the Order Panpulmonata were consumed by nearly a quarter of all tegus (FO = 23.66%). Other


59 invertebrate Orders that were consumed less frequ ently (<5%) included Dermaptera (earwigs), Diplopoda (millipedes), Chilopoda (centipedes), Diptera (flies and fly larvae), Hemiptera (stink bugs), Homoptera (cicadas), Isopoda (pillbugs), and Decapoda (crayfish). Niche Overlap The proportions of food item s in the diets of adult and juvenile tegus was not overlap showed adult (n = 57) and juvenile (n = 39) tegus had near complete overlap (O jk = 0.98). Diet overlap of male s (n = 43) and females (n = 43) was less, but still very near complete (O jk = 0.95). Discussion Understanding the diet of invasive wildlife is crucial to predicting impacts they may have in a new environment, especially when they occur in habitat managed for imperiled species. Although individual food items in tegu diets largely consisted of fruits, many fruits were small berries. Ten individuals accounted for 70% of all fruits consumed among 48 fruit eating tegus, suggesting that tegus gorge on fruits whe n available. Fruits are also seasonally abundant which may impact dietary choices. Tegus consumed fruits more frequently in the spring and summer, and less often in the fall (Figure 3 3). Of the study group, 45 tegus (~48%, n = 93) consumed no fruit or pla nt food items of any kind. A lower frequency of occurrence of vertebrates and invertebrates was also documented in the fall (Figure 3 3), likely because prey species are more active and abundant in the spring and summer months during mating season and seas onal dispersal of young. For these reasons it is important not to overlook the consumption rate of invertebrate and vertebrate animals by tegus.


60 My result show that tegus in and around scrub habitat are capable of consuming species of concern, namely goph er tortoise hatchlings, but also young and adult snakes. Although no other threatened or endangered species were identified, tegus were found to readily take small mammals, frogs and occasionally birds. Additionally, I was able to document predation by teg us on five invasive species: Cuban tree frog ( Osteopilus septentrionalis ), brown anole ( Anolis sagrei ), swamp eel ( Monopterus albus ), Japanease beetle ( Popillia japonicum ) and the plant lantana ( Lantana camera ). This indicates that tegus may benefit from t he presence of other invaders within the environment. Tegus were also shown to take food items that are considered toxic to other wildlife including a variety of caterpillars, lubber grasshoppers ( Romalea microptera ) and lantana. A small number of reptile eggs were documented in tegu stomach contents, however tegus are known to bite holes in eggs and only eat the contents (Milstead 1961, Barraco 2014). Once in the stomach yolk and albumen digest rapidly and become impossible to accura tely identify For this reason it is possible that tegus excavated and consumed eggs of terrestrial wildlife at a frequency greater than I was able to detect in this study. As documented in other studies, tegus in Hillsborough County eat a wide variety of foods including animal and plant matter (Colli et al. 1998, Mercolli and Yanosky 1998, Barraco 2014). This differs from two other large, invasive, predatory lizards in Florida the black spiny tailed iguana ( Ctenosaura similis) and the Nile monitor ( Varanus niloticus ). Spiny tail ed iguanas in Florida were found to include grasses and flowers as a large component of their diet along with arthropods, with comparatively few vertebrate prey (Krysko et al. 2009). Nile monitors in Florida consume a wide taxonomic range of


61 invertebrate a nd vertebrate prey, similar to ABWT (Campbell 2005). However, unlike tegus, monitors included aquatic insects in their diet, but few plants or fruits. In South Florida more ABWT consumed gastropods but fewer consume vertebrates compared to tegus at my site (Figure 3 4, Barraco 2014). This may simply be a result of differences in prey availability or innate differences in tegu ecology between the two sites. When compared to tegus in their home range in Brazil and Argentina, Central Florida ABWTs appear to be eating substantially more invertebrates and vertebrates (Figure 3 4). In all comparisons, Central Florida tegus appear to be including vertebrates as part of their diet more frequently than tegus found elsewhere. The diet identification methods used in m y study were very similar to those used by Barraco (2014), though prey identification remains a subjective process to some extent. Additionally time between capture and euthanasia can impact the contents of the stomach, as trapped tegus continue to digest but do not continue to forage. For this reason most tegus in my study were euthanized less than four hours after capture and immediately frozen to preserve stomach contents. Despite these caveats, the trend in consumption of vertebrate prey among central F lorida tegus is concerning. There are several explanations that could account for these observations. It is possible I was more thorough in my methods and was able to detect smaller fragments of prey (e.g., a single hair). It could also be that tegus prefe rentially sele ct for vertebrate prey, and in c entral Florida small vertebrates are abundant enough that tegus can ignore other available but less desirable food resources. Tegus are a unique predator to the region (e.g. diurnal, terrestrial, large and capa ble of entering burrows in search of prey), and species may not be adapted to effectively avoid tegu hunting strategies.


62 Patches of scrub that remain in Hillsborough and surrounding counties in central Florida contain source populations of wildlife that co uld one day disperse to restored scrub. Tegu presence in Hillsborough County is a direct threat to these species. In healthy scrub and upland environments they may directly and indirectly compete with native wildlife for food, and in habitat presently bein g restored they may prey upon scrub species as they arrive from dispersal sites. Like islands surrounded by a sea of heterogeneous landscape, it is difficult for endemics to emigrate or immigrate between scrub patches (Liebold 2004, Ricketts 2001). Because tegus are not confined to scrub and can be found throughout the region, they pose an additional risk to species as they In addition to threats to wildlife, tegus also have the potential to disperse seeds of domest ic and invasive plants. Fruits or drupes of cultivated plants such as strawberries, blueberries, tomatoes, oranges, palms and lantana were found in tegu stomach contents (Appendix 1). Strawberry season beings and ends during the months central Florida tegu s are in brumation so it is unlikely tegus would threaten this industry, although blueberries and tomatoes are commercially cultivated in and around the footprint of the central Florida tegu population. Even though tegus were found to consume these crops, domestic cultivars were not found with enough regularity in stomach contents for tegus to be considered agricultural pests. The diet of Argentine black and white tegus in central Florida is broad and includes a range of taxa from multiple trophic levels. Tegus are capable of consuming threatened and protected scrub species, most notably the gopher tortoise, a keystone species. It is unknown to what extent tegus currently impact scrub fauna in central


63 Florida, but they have the potential to compromise ongoi ng restoration efforts. Tegus should be considered a serious threat to native Florida wildlife and efforts should continue to educate public and remove of this large, omnivorous lizard wherever it is found.


64 Figure 3 1 Location of Central Florida invasive Argentine black and white tegus ( Salvator merianae ) within Hillsborough County. Numbers appearing in the inset represent credible tegu sightings in the study area. Map data: 2017 Google INEGI.


65 Table 3 1. Identified F ood items consumed by 93 argentine black and white tegus and frequency of occurrence (FO) Food Item Category Order Number of Tegus That Consumed Item FO Arthropods Insecta Blattoidia 16 17.20 Coleoptera 55 59.14 Orthoptera 49 52.69 Hyminoptera 13 13.98 Lepidoptera 11 11.83 Dermaptera 1 1.08 Diplopoda 1 1.08 Chilopda 2 2.15 Diptera 4 4.3 Hemiptera 1 1.08 Homoptera 3 3.23 Malacostraca Decapoda 1 1.08 Isopoda 1 1.08 Arachnid Araneae 6 6.45 Mollusks Panpulmonata 22 23.66 Fish Synbranchiformes 1 1.08 Amphibian Anura (Family Hylidae) 7 7.53 Anura (Family Ranidae) 1 1.08 Anura (Family Bufonidae) 14 15.05 unidentified Anuran 9 9.68 Reptile Squamata (Suborder Lacertilia) 9 9.68 Squamata (Suborder Serpentes) 13 13.98 Testudine 5 5.38 Retile egg 5 5.38 unidentified reptile 3 3.23


66 Table 3 1. Continued Bird Galliformes 1 1.08 Passeriformes 1 1.08 Falconiformes 1 1.08 unidentified 4 4.30 Bird egg 5 5.38 Mammal Rodentia 25 26.88 Carnivora 3 3.23 Lagomorpha 1 1.08 Soricomorpha 3 3.23 Artirodactyla 2 2.15 Didelphimorphia 2 2.15 unidentified mammal 18 19.35 Plant Ericales 14 15.05 Rosales 12 12.90 Solanales 3 3.23 Vitales 2 2.15 Lamiales 1 1.08 Sapindales 3 3.23 Arecales 11 11.83 other 14 15.05


67 Figure 3 2. Number of tegus collected by month (n = 96) 0 5 10 15 20 25 Tegus Collected by Month


68 Figure 3 3. Seasonal Frequency of Occurrence (FO) of fruits, invertebrates and vertebrates in invasive Salvator merianae in c entral Florida, expressed as percent (%) of tegus found to have consumed food from each group. 42.3% 59.1% 42.9% 84.6% 93.2% 64.3% 96.2% 81.8% 64.3% 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 100.0% Spring (Mar-May) Summer (June-Aug) Fall (Sept-Nov) Seasonal FO in Tegu Diets FO Fruits FO Invertebrates FO Vertebrates


69 Figure 3 4. Comparison of Frequency of Occurrence (FO) of plants, invertebrates and ve rtebrates in diets of invasive c entral Florida Salvator merianae to native (A) and introduced (B ) populations of S. merianae 0 10 20 30 40 50 60 70 80 90 Plants Invertebrates Vertebrates Comparison of FO to native S. merianae diets C. Florida Brazil Argentina 0 10 20 30 40 50 60 70 80 90 Plants Invertebrates Vertebrates Gastropods Comparison of FO in Florida S. merianae diets C. Florida S. Florida A) B)


70 CHAPTER 4 CONSERVATION IMPLICATIONS AND CONCLUSIONS In my study I f ound tegus to be habitat generalists that consume food from multiple trophic levels. The population of tegus in Central Florida did not strictly associate with one specific habitat type. Instead, habitat selection was variable among individual tegus. Many of these tegus selected for scrub, utilities right of ways and urban environments with varying degrees, but generally avoided wetlands and pasture/rangelands. Neither sex nor season influenced habitat selection of tegus. Tegu diets were broad. Tegus ate in vertebrates and vertebrates more frequently than fruits. Five tegus were found with the remains of gopher tortoise hatchlings in their stomachs, highlighting the threat tegus pose to imperiled native wildlife. The diets of wildlife are a reflection of habi tat selected for foraging, given that habitats are defined by the natural resources found within. In my study, many plant and animal species found in tegu stomach contents are characteristic of scrub and surrounding xeric habitat including fruits from blue berries ( Vaccinium sp ), palmettos ( Serenoa sp ) and grapes ( Vittis sp ) and animals such as the gopher tortoise ( Gopherus polyphemus ), oak toad ( Anaxyrus quercicus ), black racer ( Coluber constrictor ) and golden mouse ( Ochrotomys nuttalli ) (Appendix A, USFWS 1999). This coincides with my findings that tegus select for scrub at second and third order and demonstrates that scrub is a habitat in which tegus acquire food. Tegus consumed a wide variety of taxa such as ground dwelling beetles, r odents, snakes, amphibians and berries. Species from these groups are not restricted to scrub habitat and have a wide distribution in many habitats across Florida which suggests that diet will not restrict tegus to xeric habitats. However, tegus did show


71 s election for scrub habitat and did not select for wetland habitat, indicating they may choose to be in upland habitats for reasons that are not related to diet. Conclusions drawn from my habitat selection and diet studies may aid land managers in detection and removal of tegus. Vertebrates and invertebrates found in tegu stomachs include many species that are known to associate with gopher tortoise burrows (Christman 1988, Campbell 1992, Humphrey 1992, Deyrup and Franz 1994, Kinlaw and Grasmueck 2012), and tegus encountered traps placed near gopher tortoise burrows during the course of my study. During the radio tracking portion of my habitat selection study, all but two tegus (TL12, TL8) eventually included residential regions in their home range, or had re locations along a boundary between residential and natural areas. Tegus in Central Florida are found in a diverse matrix of habitats that offer no distinct corridor for movement. This means that trap lines are insufficient to ensure trap encounter. For the se reasons, when considering management strategies for the removal or control of tegus in upland habitats I recommend focused trapping near gopher tortoise burrows and along urban edges. Where tegu presence has not been confirmed, cameras placed at gopher tortoise burrows can be used to monitor for tegu presence and traps can be deployed if tegus are detected to ensure sensitive wildlife is not put at additional risk. Although my findings about tegu spatial ecology and diet have contributed to a more robust understanding of tegu presence in Florida, there is much yet to be learned. Because tegus pose an immediate threat to imperiled species, future studies should focus primarily on removal. Although tegus use a variety of habitats, they do not use all habita t in equal proportion. Identification of tegu dispersal and movement corridors


72 would allow agencies to focus trapping efforts and prevent tegus from spreading into new habitat and can be done by outfitting hatchling tegus with telemeter harnesses. Likewise continued effort can be made to advance trapping success of tegus in Central Florida. Here, movement corridors are ill defined and encounter rate is low in comparison to tegus in South Florida. Pheromones should be explored as a bait alternative and coul d potentially attract tegus from a greater distance while simultaneously reducing or eliminating bycatch. Efforts should continue for development and implementation of local and state wide EDRR programs for tegus. In my experience, the public is very recep tive to tegu removal efforts. A dedicated trap loan program in c entral Florida should be created or expanded to increase successful removal of tegus by citizens, an extension of citizen science. Central Florida tegu populations should continue to be monito red. Based on the findings presented in this thesis I recommend that public education as well as monitoring for and removal of tegus continue throughout the state. Finally, the results of my study, data from tegus in southern Florida, and the growing numbe r of records of this species across Florida (e.g., ), prove this lizard is a current and growing threat to native ecosystem, similar to the situation with Burmese pythons and Nile monitors. Therefore, by the Florida Fish and Wildlife Conservation Commission. These actions are key to preventing future impacts.


73 APPENDIX LIST OF ITEMS CONSUMED BY TEGUS Table A 1. Items consumed by tegus organized by taxa Phylum or Class Order Family Common Name (Species Name) Insecta Blattoidea Ectobiidae Cockroach Cockroach Egg Case Coleoptera Carabidae Tiger beetle Ground beetle, large dark Unidentified Ground Beetle (Carabidae) Cerambycidae Longhorn beetle ( Cerambycidae sp) Curculionidae Snout beetle Elateridae Click beetle Passalidae Bessy beetle Scarabaeidae Scarab beetle, possibly dung beetle May Beetle ( Phyllophaga sp) Scarab beetle, small yellow Unidentified scarab beetle (Scarabidae) Japanease beetle ( Popillia japonicum ) Silphidae Burying beetle ( Nicrophorus sp) Unidentified Unidentified beetle Larval beetle (grub) Dermaptera Unidentified Earwig Diplopoda Unidentified Millipede Diptera Sarcophagidae Fly larvae Tabanidae Large fly (horsefly or soldierfly) Unidentified Unidentified fly (adult) Hemiptera Cicadidae Unidentified cicada Cicada larva Lygaeidae Milkweed bug ( Oncopeltus fasciatus ) Pentatomidae Stink bug Unidentified unidentified planthopper Hymenoptera Crabronidae Cicada killer ( Sphecius speciousus )


74 Table A 1. Continued Phylum or Class Order Family Common Name (Species Name) Formicidae Ants Vespidae Unidentified wasp Paper Wasp ( Polisties sp)) Paper Wasp Nest w/Wasps ( Vespidae ) Lepidoptera Geometridae Inchworm Saturniidae Regal moth ( Citheronia regalis ) Moth ( Anisota sp.) Moth ( Agraulis sp) Unidentified Unidentified moth Unidentified caterpillar Mantodea Unidentified Praying mantis (egg capsule) Orthoptera Acrididae American birdwing grasshopper ( Schistocerca americana ) Short winged grasshopper ( Dichromorpha viridis ) Spur throated grasshopper Band winged grasshopper Shorthorned grasshopper (unidentified) Orthoptera Gryllotalpidae Mole cricket Orthoptera Romaleidae Lubber grasshopper ( Romalia microptera ) Orthoptera Tettigoniidae Katydid (green) Orthoptera Bush cricket Orthoptera Unidentified Unidentified Grasshopper Unidentified Unidentified insect Myriapoda Chilopoda Unidentified Centipede (green) Diplopoda Unidentified Millipede Arachnida Aranae Lycosidae Wolf spider Salticidae Jumping spider Unidentified Unidentified spider Crustacea Isopoda Armadilidiiae Pillbug Decapoda Unidentified Unidentified crayfish


75 Table A 1. Continued Phylum or Class Order Family Common Name (Species Name) Mollusca Gastropoda Ampullarioidea Apple snail ( Pomacea ) Planorbidae Unidentified snail Ramshorn snail ( Marisa cornuaurietus ) Veronicellidae Florida leatherleaf slug ( Leidyula floridana ) Unidentified Unidentified slugs Chordata Vertebrata Unidentified Unidentified vertebrate bones Amphibia Anura Bufonidae Southern toad ( Anaxyrus terrestris ) Oak toad ( Anaxyrus quercicus ) Unidentified toad Hylidae Cuban treefrog ( Osteopilus septentrionalis ) Green treefrog ( Hyla cinerea ) Pinewoods treefrog ( Hyla femoralis ) Unidentified treefrog Ranidae Bullfrog ( Rana catesbiana ) Unidentified true frog Scaphiopodidae Spadefoot toad ( Scaphiopus holbrooki i ) Reptilia Squamata Anguidae Eastern glass lizard ( Ophisaurus ventralis ) Colubridae Black racer ( Coluber constrictor ) Dipsadidae Ringneck snake ( Diadophis puncatatus ) Iguanidae Fence lizard ( Sceloporus undulatus ) Polychrotidae Cuban brown anole ( Anolis sagrei ) Cuban brown anole egg Unidentified Unidentified lizard Unidentified snake (vertebrae, skin) Unidentified snake eggs


76 Table A 1. Continued Phylum or Class Order Family Common Name (Species Name) Testudine s Testudinidae Gopher tortoise ( Gopherus polyphemus ) Unidentified Unidentified turtle eggs Aves Columbiformes Dove sp Falconiformes Hawk sp Galliformes Quail sp Passeriformes Songbird sp Unidentified Unidentified bird (whole or parts) Unidentified bird eggs Mammalia Carnivora Procyonidae Raccoon ( Procyon lotor ) Mephitidae Striped skunk ( Mephitis mephitis ) Cingulata Dasypodidae Nine banded armadillo ( Dasypus novemcinctus ) Didelphimorphia Didelphidae Virginia opossum ( Didelphis virginiana ) Lagomorpha Leporidae Eastern cottontail ( Sylvilagus floridanus ) Rodentia Unidentified rodent Cricetidae Cotton mouse ( Peromyscus gossypinus ) Deer mouse ( Peromyscus sp) Golden mouse ( Ochrotomys nuttalli ) Marsh rice rat ( Oryzomys palustris ) Hispid cotton rat ( Sigmodon hispidus ) Muridae Black rat ( Rattus rattus ) Saricomorpha Talpidae Eastern mole ( Scalopus aquaticus ) Unidentified Unidentified mammal (hair only) Actinopterygii Synbranchiformes Synbranchidae Asian swamp eel ( Monopterus albus )


77 Table A 1. Continued Phylum or Class Order Family Common Name (Species Name) Plantae Arecacae Arecacae Saw palmetto ( Serenoa repens ) Unidentified palm Ericales Ericaceae Blueberry ( Vaccinium sp) Lamiales Vervenaceae Lantana ( Lantana camara ) Rosales Rosaceae Wild cherry ( Prunus serotina ) Strawberry ( Fragaria ananassa ) Blackberry ( Rubus sp) Solanales Solanaceae Tomato ( Solanum lycopersicum ) Sopondias Anacardiaceae Citrus fruits ( Citrus sp) Hog plum ( Spondias mombin ) Vitales Vitaceae Wild grape ( Vitis sp) Unidentified Unidentified metallic blue fruit Unidentified berries Incidental Hairs Horse and human hair Plant parts Unidentified sticks Unidentified plant parts Poaceae Spartina bakeri Unidentified Grass Unidentified Grass Seeds Quercus Oak Nuts Live Oak Leaves Laurel Oak Leaves Water Oak Leaves Unidentified Oak Flower Rosaceae Haw Leaves ( Crataegus ) Inanimate Inanimate (sand, rocks, fibers, paper, etc.) Unidentified Unidentified mass, blob, etc. Bait Chicken Eggs (whole or shell pieces) Hotdog Pieces Parasite Nematoda nematodes


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85 BIOGRAPHICAL SKETCH Marie Therese Offner, known as Tessie by her colleagues and f riends, has had a passion for wildlife since early childhood. This passion was cultivated by her loving family who supplied many outlets for her curiosity of the natural world. She has fond memories of the Missouri countryside where she enjoyed endless opp ortunities for outdoor play. University of Tampa. She has over a decade of experience working in a career with wildlife, including roles as an environmental educator with The Florida Aquarium and as a nonnative species biologist with the Florida Fish and Wildlife Conservation Commission (FWC). She began working with Argentine black and white tegus in the summer of 2012 with Dr. Todd Campbell at the University of Tampa, and later transi of Florida with her advisor Dr. Steve Johnson. She graduated from the University of