SOUTHEASTERN NATURALIST 2011 10(3):389Â–398 Long-distance Movement by American Alligators in Southwest LouisianaValentine A. Lance1,*, Ruth M. Elsey2, Phillip L. Trosclair III2, and Leisa A. Nunez2Abstract As part of an ongoing study on growth and sexual maturation of Alligator mississippiensis (American Alligator) on Rockefeller Wildlife Refuge, LA, 3601specimens, ranging in total length from 28 to 361 cm, were captured from June 2000 through August2004. Additionally, 70 alligators were collected opportunistically as part of a teaching exercise in August 2005, and 248 more were collected in 2006 (and one in January 2007) as part of a study evaluating the effects of Hurricane Rita on alligators. Representative samples from size classes greater than 60 cm were collected in most months of the year between 2000 and 2004. Each animal was tagged, measured, sexed, and released immediately at the site of capture. A large number of these marked alligators were recaptured outside the refuge boundaries during annual alligator hunts in September. Of the 286 recaptured alligators, 214 were males, 68 were females, and four were of undetermined sex. From each recaptured alligator, total body length and date of recapture were recorded, and minimum distance from initial capture site estimated. From these preliminary data, we calculated the time interval between captures, and plotted minimum distance moved. The number of days between first capture and recapture ranged from 29 to 3336 days (9.1 years).Distance moved from initial capture site to final capture site ranged from 0.3 to 90.2 km.Eleven alligators moved between 30.0 and 39.9 km, and eight moved 40 km. Six of these moved between 40.0 and 49.9 km, and the others moved 87.4 and 90.2 km.These results greatly extend previous estimates of long-distance movement by alligators and demonstrate that both sub-adult and sexually mature animals move considerable distances. These data also showed that smaller alligators moved greater distances than larger alligators ( P = 0.0002), and that the longer the time between captures, the greater the distance moved ( P < 0.0001). Introduction Home range and dispersal (total distance moved) have been studied in a number of Alligator mississippiensis Daudin (American Alligator) populations using capture-recapture of marked animals or radiotelemetry. One of the earliest studies (Chabreck 1965) involved a total of 2024 alligators marked over a sevenyear period on Rockefeller Wildlife Refuge (RWR) and Sabine National Wildlife Refuge in coastal southwest Louisiana. Of these marked alligators, 131 were recaptured; of these, eighteen were recaptured twice, and two were recaptured three times. The conclusions of the study were that immature alligators moved greater distances than adults, and that the longer the interval between rst and second capture the greater the distance moved. The longest movement recorded was approximately 16 km for an animal recaptured after four years. This study 1Graduate School of Public Health, San Diego State University, San Diego, CA 92128. 2Louisiana Department of Wildlife and Fisheries, Rockefeller Wildlife Refuge, Grand Chenier, LA 70643. *Corresponding author firstname.lastname@example.org.
Southeastern Naturalist Vol. 10, No. 3 390 was limited to recapture attempts made within the refuge boundaries, and it is likely that any alligators that had moved greater distances to surrounding private lands would not have been recaptured. In the Florida Everglades, Hines et al. (1968) marked approximately 1000 alligators and recaptured 33. The longest reported distance moved was 11 km for an alligator recaptured after 850 days. Joanen and McNease (1970) were the rst to use radio-telemetry to study the movement of alligators on Rockefeller Refuge. Five adult females were tted with radio-collars and monitored for a period of six months. The results showed that nesting females did not move far from the nesting/den site, with home ranges of 2.6 to 16.5 ha. Taylor (1984) tted radio-collars on nine adult female alligators in a lake habitat in north Louisiana and reported home ranges of 0.6 to 256 ha. A study by Rootes and Chabreck (1993a), in which fteen adult female alligators (in southwest Louisiana) were tted with radio-collars and followed for one year, indicated home ranges of 6.1 to 165 ha. In none of these studies on female alligators was the longest distance from initial site of capture reported. On the other hand, 14 adult male alligators on Rockefeller Refuge tted with radio-collars and followed for up to one year, moved considerable distances and had estimated home ranges of 183 to 5083 ha (Joanen and McNease 1972). The greatest distance an adult male alligator moved from the initial capture site to where it was observed 146 days later was approximately 53 km; another adult male moved 22 km (Joanen and McNease 1972). Elsey (2005) reported an adult alligator photographed in the Gulf of Mexico some 63 km from the nearest land. Studies on juvenile alligators tted with radio-collars (McNease and Joanen 1974, Taylor et al. 1976) reported no differences in home range between male and female alligators, but found that juveniles exhibited greater daily activity than adults and moved greater distances overall. Rootes (1989) suggested that radio-telemetry units attached as Â“collarsÂ” placed over the neck of alligators are likely stressors that could greatly limit mobility. Thus, distances moved by alligators monitored with telemetry units might be biased toward lower distances due to restricted movement. Similar observations on juvenile alligator activity (i.e., that they generally moved greater distances than adults) were made by Chabreck (1965) and Hines et al. (1968) using mark-recapture rather than telemetry. In this paper, we present data on long-distance movements of alligators based on a large sample of juveniles and adults of both sexes captured and recaptured over a period of nine years in southwestern Louisiana. Materials and Methods Rockefeller Wildlife Refuge (RWR) is a coastal marsh in southwestern Louisiana encompassing some 29,380 ha (Fig. 1) of wetlands of varying salinities (fresh: <2 ppt, intermediate: 2 to 6 ppt, brackish: 6 to15 ppt, and saline: >15 ppt; Keddy et al. 2007). As part of an ongoing study on growth and sexual maturation of American Alligators (immature: 50 to 180 cm; adult: >180 cm TL) on RWR, 3920 specimens (1960 males, 1926 females, 34 of unknown sex) ranging in total length (TL) from 28 to 361 cm were captured from June 2000 through January 2007; however, the majority of captures (3601) were made by August 2004. Representative samples from size classes 60 cm were taken in most months.
V.A. Lance, R.M. Elsey, P.L. Trosclair III, and L.A. Nunez 2011 391Small alligators were caught by hand from an airboat, and larger animals were captured using a cable noose snare attached to a long pole (see Lance et al. 2009 for details). Each animal was marked with a monel tag in the webbing of both rear feet (Elsey et al. 2000), TL was measured, a blood sample was collected from thespinalvein (Zippel et al. 2003), a dorsal scute was removed from the tail, and sex was determined before being immediately released near the site of capture. During the annual fall alligator harvest, Louisiana Department of Wildlife and Fisheries (LDWF) employees were stationed at checkpoints where harvested alligators were brought for processing. Recaptures were identi ed by presence of tail notches and web tags; these specimens were measured, and distance from site of original capture was calculated by plotting the minimum distance between the property where the alligator was captured to the capture site on RWR. Alligator trappers are issued harvest tags to be used on speci c wetlands they own or lease, thus enabling determination of the approximate capture area. Additional data were provided on mail-in forms for reporting the take of a marked alligator, which were supplied to all licensed trappers prior to the harvest season. Data were analyzed using SAS statistical software. First, multiple regressions were used to determine if there was a linear relationship between total distance moved and either initial body size or number of days between release and recapture. Multiple rather than simple regression was used because the data collected on a single alligator are not independent from one another. Data were Figure 1. Satellite map of coastal southwest Louisiana showing Rockefeller Wildlife Refuge (outlined) and locations of alligators that moved the greatest distance from site of rst capture (white lled circles). The Gulf of Mexico is due south of the Refuge.
Southeastern Naturalist Vol. 10, No. 3 392 separated by sex, as plots of the raw data suggested an obvious difference between males and females. These regressions were performed without an intercept, as the distance moved should be zero when either initial body size or number of days is zero. The model for each sex was: Distance = 1(Days) + 2 (Length) + where represents the random variation for each subject. Both models violated the assumption of normality of residuals ( P -values for both sexes were <0.0001), and also showed evidence of violating the assumption of homogeneity of variance. Consequently, the Spearman rank correlation coef cient was calculated to determine the nature of the relationship between total distance moved and either initial size or number of days between release and recapture. This statistic does not require the relationships to be linear, and the distribution need not be either normal or de ned. The values of this coef cient fall between -1 and 1, with negative values indicating a decreasing relationship, and positive values indicating an increasing relationship. The P -values correspond to the hypothesis that the coef cient is zero (no relationship). Alligators recaptured on Rockefeller Refuge were not included in the analysis. Results A total of 286 alligators were recaptured outside of RWR, including 214 males, 68 females, and four of unknown sex. Eleven alligators moved between 30.0 and 39.9 km, and eight moved more than 40 km. Six of these moved between 40.0 and 49.9 km, and the other two moved 87.4 km, and 90.2 km (Table 1). Although more than half of the alligators (155) moved <10 km from point of rst capture, there was a signi cant positive relationship between number of days since capture and distance moved (Fig. 2). There was also a signi cant negative relationship between size at initial capture and distance moved; i.e., smaller alligators moved greater distances than larger alligators (Fig. 3). Although the correlation coef cients for each of these relationships are low, the results were highly signi cant (Spearman Rank Correlation [ n = 281] for distance moved and number of days since rst capture, = 0.26652, P < 0.0001; distance moved and length at rst capture, = -0.22354, P = 0.0002) when a non-parametric analysis is conducted. Thus, smaller alligators tended to move greater distances, and distances moved were greater with increasing time since rst capture. Table 1. Distances moved by American Alligators marked on Rockefeller Wildlife Refuge, LA and later recaptured outside of the refuge boundaries. Of the 286 total, only data for those that moved 10 km are shown. Distance moved (km) Number of alligators 10.0Â–19.9 73 20.0Â–29.9 39 30.0Â–39.9 11 40.0Â–49.9 6 50.0Â–59.9 0 60.0Â–69.9 0 70.0Â–79.9 0 80.0Â–89.9 1 90.0Â–99.9 1
V.A. Lance, R.M. Elsey, P.L. Trosclair III, and L.A. Nunez 2011 393 The multipleregression analysis for females had an r2 value of 0.8273 ( F2,65= 161.5, P < 0.0001), and for males had an r2 = 0.5544 ( F2,212 = 134.15, P < 0.0001). Larger females tended to move greater distances than smaller females (regression parameter = 0.11808, P < 0.0001); this relationship was not evident in males; i.e., smaller males tended to move greater distances. Greater distances were moved over longer time periods (number of days) for both sexes, with regression Figure 2. Plot of days between rst and nal capture and distance moved of American Alligators ( n = 286) captured outside of the boundaries of Rockefeller Wildlife Refuge, LA. Figure 3. Plot of distance moved and total length at rst capture for American Alligators ( n = 286) captured outside of the boundaries of Rockefeller Wildlife Refuge, LA.
Southeastern Naturalist Vol. 10, No. 3 394 parameters of 0.00664 ( r2 = 0.8325, P = 0.0035) for females and 0.00302 ( r2 = 0.5586, P < 0.0001) for males. In addition to obtaining recapture data from the recovery of marked alligators outside RWR during annual hunts, 551 of previously marked alligators were captured alive during mark-recapture efforts on RWR. Of these, 423 were recaptured once, 54 were recaptured twice, and six individuals were recaptured three times. As these were all caught within the refuge boundaries, we did not expect many to have traveled a great distance (minimum distance between eastern and western boundaries of sampling sites = 22.9 km). However, seven alligators moved over 10 km (range = 12.5 to 21.3 km) within RWR, and 154 (27.9%) moved from the impoundment in which they were initially caught to adjacent areas, although distances were <10 km. Most live recaptures (390 of 551, 70.8%) within RWR remained within the same impoundment in which they were originally caught. This result was not unexpected as live recapture efforts were limited to the original area wherein the alligators were marked. Most of these impoundments are rectangular in shape, 2 to 3 km in length and width, and encompassing areas of 600 to 800 ha; thus alligators could move substantial distances, but still remain within a single impoundment. Additionally, 208 marked alligators were recaptured in the nuisance harvest on RWR. As expected, most did not move long distances, and recoveries were all within the boundaries of RWR. However, ve of the nuisance alligators moved >10 km from the initial capture site (range of minimum dispersal distance = 10.7 to 16.3 km), and two others moved a minimum of 9.1 and 9.3 km from the initial capture site to the harvest site. Discussion The results of this study document unusually long distance movements by juvenile and adult alligators over a nine-year period. In this study, we were able to collect data unavailable to previous researchers, and thus greatly increase both recovery of marked individuals and con rmation of distances moved. One of the unplanned bene ts of a well-regulated hunting program is the ability to collect biological data from captured alligators; thus, with a small number of trained biologists and technicians, we were able to monitor numerous sites for marked animals captured during the hunt. Hence, we were able to collect data that previous studies, carried out before legal hunting was established, were unable to do. For example, Chabreck (1965) marked 2024 alligators, but only recaptured 131 (6.4%). Likewise, Hines et al. (1968) marked approximately 1000 alligators and recaptured only 33 (3.3%). In contrast, we marked 3920 alligators on RWRand obtained data on 286 (7.3%) recaptured on lands outside of the refuge, a considerably greater number than recovered in previous studies, in part because of the long duration of our study. Long-term studies obviously have a higher likelihood of detecting longrange dispersal over time. For example, Campos et al. (2006) studied a population of Caiman crocodilus yacare Daudin (Caiman) in the Brazilian Pantanal over a 16year period and recovered 532 of 7618 marked individuals (6.9%). We previously reported a male bias (58%) among sub-adult alligators in Louisiana (Lance et al. 2000). In the present study, 216 of 283 (76%) alligators were males, a higher percentage than previously reported for this population (Lance et
V.A. Lance, R.M. Elsey, P.L. Trosclair III, and L.A. Nunez 2011 395al. 2000). As these alligators were collected during the annual September hunt, a male bias is not unexpected, because this harvest is timed such that most females with young will not be accessible to trappers (Elsey et al. 1994). Instead, predominantly surplus adult males are harvested, limiting the incidental take of breeding females that occupy a different habitat (Elsey et al. 1994). Despite a harvest that selects for males, when the percentage of total males is compared with the percentage of total females at the 10 to 20 km (27.6% and 19.1%) and 20 to 30 km distances (14.5% and 10.3%), these differences were not as pronounced (Table 2). In fact, the longest distance traveled (90.2 km) was by a female. This female was initially marked on 10 August 2000, and recaptured on RWR on 17 October 2000 at a site 24.9 km from the initial capture. The alligator was then harvested on private wetlands outside the refuge on 16 September 2003, some 65.2 km from where it was caught in October 2000. Clearly, a large portion of the total distance moved (90.2 km) occurred within the rst two months after capture. The total number of recoveries ( n = 1045) by all methods (286 harvested on private wetlands outside the refuge boundaries, 551 recaptured alive on the refuge and released, and 208 recaptured on the refuge during the controlled nuisance harvest) indicates 29.7% of marked individuals were recovered. These data support the long-held dogma that alligators have few predators, excepting other alligators (Rootes and Chabreck 1993b), after reaching a total length of about 60 cm (approximately two years of age). One factor that appears to facilitate the dispersal of alligators is ooding (Chabreck 1965). High winds and strong currents caused by Hurricane Audrey in 1957 swept alligators northward from RWR for distances Â“ranging from three to ten milesÂ” (4.8Â–16.1 km). For alligators marked in our study, a small number (between two and seven annually) were caught from 2001Â–2005 on privately owned wetlands, north of RWR. Some of these had moved 10 to 20 km in the interval between being marked and recaptured. Following Hurricane Rita in late 2005, the number of marked alligators recovered in this area increased markedly to 22 in 2006. Another 15 were recovered north of RWR in 2007 (one recovered 33.9 km from the initial capture site), and 16 in 2008, one of which moved 39.8 km from the initial capture location. Some of these may have simply attained a harvestable size, having earlier moved onto privately owned wetlands when they were too small to be harvested. However, a far more likely explanation is that these alligators were pushed northward by the extensive storm surge of Hurricane Rita. Table 2. Sex ratio of American Alligators marked on Rockefeller Wildlife Refuge, LA and later recaptured 10 km away, outside of the refuge boundaries. Distance moved (km) Males Females 10.0Â–19.9 59 13 20.0Â–29.9 31 7 30.0Â–39.9 8 3 40.0Â–49.9 4 2 50.0Â–59.9 0 0 60.0Â–69.9 0 0 70.0Â–79.9 0 0 80.0Â–99.9 1 1
Southeastern Naturalist Vol. 10, No. 3 396 A few previous reports of long-distance movements by individual adult alligators are available. A 1.5-m female alligator rst captured on Wasaw Island, GA was seen on Hilton Head Island 15 days later, a straight-line distance of >50 km (Tamarack 1989). Similarly, Joanen and McNease (1972) and Elsey (2005) documented individual alligator movements of 53 km and 63 km, respectively. In contrast to adult alligators, there is a notable paucity of published data concerning long-distance movements by juveniles. The distances moved by some juvenile alligators in our study exceed previous estimates by a wide margin. One juvenile was captured >90 km and another >80 km from site of rst capture; several others moved >40 km. These ndings are consistent with earlier studies by Chabreck (1965) and Hines et al. (1968) that found juvenile alligators move greater distances than adults. However, at the time of nal capture, some juveniles in our study had attained adult size; therefore, it is possible that some long-distance movements occurred after these alligators reached sexual maturity. Of note, in May 2007, we incidentally recovered an immature (total length = 103 cm) nuisance alligator, which had moved >80 km from the site of its initial capture on 20 May 2002. A long-term study of C. crocodilus in the Brazilian Pantanal reported movements of up to 18 km in males and 16 km in females over a 15-year period (Campos et al. 2006). Direct comparison with our study is not possible, because this tropical habitat differs markedly from coastal south Louisiana by having distinct wet and dry seasons and widespread ooding in the wet season. During the dry season, caiman are restricted to small pools and rivers, but during the wet season they are able to disperse throughout the ooded Pantanal. However, similar to our study, smaller caiman moved greater distances than larger caiman, and there was a signi cant positive relationship between the number of days from rst capture to distance moved (Campos et al. 2006). Long-distance movements by adult crocodiles are well documented. Allen (1974) estimated that a large adult male Crocodylus porosus Schneider (Estuarine Crocodile) observed on Ponape, Eastern Caroline Islands had traveled >1300 km across open ocean. Juvenile and sub-adult C. porosus disperse long distances up and down river systems in northern Australia (Kay 2004, Webb and Messel 1978). It is dif cult to compare marsh-dwelling alligators with crocodiles inhabiting rivers, but most species of crocodilians appear to exhibit a pattern of juvenile dispersal, usually beginning one to two years after hatching (Chabreck 1965, Cintra 1989, Dietz 1979). Dispersal in juvenile Crocodylus johnstoni Krefft (Australian Freshwater Crocodile) was studied by Tucker et al. (1997, 1998). Similar to alligators, immature C. johnstoni had larger home ranges than adults, and males approaching sexual maturity entered a Â“nomadicÂ” phase before establishing an adult home range (Tucker et al. 1998). Earlier studies indicated that juvenile alligators have larger home ranges than adults (McNease and Joanen 1974, Taylor et al. 1976). However, movements of 30 to 90 km are clearly too large to be considered part of the home range of a juvenile alligator. The fact that smaller alligators moved greater distances than larger alligators suggests that juveniles are less able to defend a territory from larger conspeci cs. Aggression towards juveniles and even cannibalism by adults is known to occur in crocodilians (Cott 1961, Hunt 1977, McNease and Joanen 1977, Rootes
V.A. Lance, R.M. Elsey, P.L. Trosclair III, and L.A. Nunez 2011 397and Chabreck 1993b). It is unlikely that juvenile crocodilians actually have large home ranges; instead, the reportedly larger home ranges may be dispersal events that occur when juveniles are driven out of an area by adults. In conclusion, our long-term study clearly documents the great distances alligators move over extended periods. Although many alligators remain within a relatively small area for long periods of time, others move unusually long distances. Additional research may provide information on why alligators select one location over another, despite similar habitat and prey availability. Acknowledgments We thank Lisa Morris of Louisiana State University for help with the statistics and numerous LDWF employees for assistance with capture and sampling of alligators at night and collection of harvest data in the eld, especially Dwayne LeJeune, Jeb Linscombe, George Melancon, and Karen McCall. Literature Cited Allen, G.R. 1974. The marine crocodile, Crocodylus porosus from Ponape, Eastern Caroline Islands, with notes on food habits of crocodiles from the Palau Archipelago. Copeia 1974:553. Campos, Z., M. Coutinho, G. Mouro, P. Bayliss, and W.E. Magnusson. 2006. Longdistance movement by Caiman crocodilus yacare : Implications for management of the species in the Brazilian Pantanal. Herpetological Journal 16:123Â–132. Chabreck, R.H. 1965. The movement of alligators in Louisiana. Proceedings of the Southeastern Association of Game and Fish Commissioners 19:102Â–110. Cintra, R. 1989. Maternal care and daily pattern of behavior in a family of caimans, Caiman yacare in the Brazilian Pantanal. Journal of Herpetology 23:320Â–322. Cott, H.B. 1961. Scienti c results of an inquiry into the ecology and economic status of the Nile Crocodile ( Crocodilus niloticus ) in Uganda and Northern Rhodesia. Transactions of the Zoological Society of London 29:211Â–356. Dietz, D.C. 1979. Behavioral ecology of young American Alligators. Ph.D. Dissertation, University of Florida, Gainesville, FL. 152 pp. Elsey, R.M. 2005. Unusual offshore occurrence of an American Alligator. Southeastern Naturalist 4:533Â–536. Elsey, R.M., T. Joanen, and L. McNease. 1994. Louisiana's alligator research and management program: An update. Pp. 199Â–229, In Proceedings of the 12th Working Meeting of the Crocodile Specialist Group. IUCN Publications, Gland, Switzerland. 304 pp. Elsey, R.M., L. McNease, and T. Joanen. 2000. LouisianaÂ’s alligator ranching programme: A review and analysis of releases of captive-raised juveniles. Pp. 426Â–441, In G.C. Grigg, F. Seebacher, and C.E. Franlin (Eds.). Crocodilian Biology and Evolution. Surrey Beatty and Sons, NSW, Australia. 446 pp. Hines, T.C., M.J. Fogarty, and L.C. Chappell. 1968. Alligator research in Florida: A progress report. Proceedings of the Southeastern Association of Game and Fish Commissioners 22:166Â–180. Hunt, R.H. 1977. Aggressive behavior by adult MoreletÂ’s Crocodiles, Crocodylusmoreletii toward young. Herpetologica 33:195Â–201. Joanen, T., and L. McNease. 1970. A telemetric study of nesting female alligators on Rockefeller Refuge, Louisiana. Proceedings of the Southeastern Association of Game and Fish Commissioners 24:175Â–193.
Southeastern Naturalist Vol. 10, No. 3 398 Joanen, T., and L. McNease. 1972. A telemetric study of adult male alligators on Rockefeller Refuge, Louisiana. Proceedings of the Southeastern Association of Game and Fish Commissioners 26:252Â–275. Kay, W.R. 2004. Movements and home ranges of radio-tracked Crocodylus porosus in the Cambridge Gulf region of Western Australia. Wildlife Research 31:495Â–508. Keddy P.A., D. Campbell, T. McFalls, G.P. Shaffer, R. Moreau, C. Draguet, and R. Heleniak. 2007. The wetlands of Lakes Ponchartrain and Maurepas: Past, present, and future. Environmental Review 15:43Â–77. Lance, V.A., R.M. Elsey, and J.W. Lang. 2000. Sex ratios of American Alligators (Crocodylidae): Male or female biased? Journal of Zoology 252:71Â–78. Lance, V.A., D.C. Rostal, R.M. Elsey, and P.L. Trosclair III. 2009. Ultrasonography of reproductive structures and hormonal correlates of follicular development in female American Alligators, Alligator mississippiensis in southwest Louisiana. General and Comparative Endocrinology 162:251Â–256. McNease, L., and T. Joanen. 1974. A study of immature alligators on Rockefeller Refuge, Louisiana. Proceedings of the Southeastern Association of Game and Fish Commissioners 28:482Â–500. McNease, L., and T. Joanen. 1977. Alligator diets in relation to marsh salinity. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 31:36Â–40. Rootes, W.L. 1989. Behavior of the American Alligator in a Louisiana freshwater marsh. Ph.D. Dissertation. Louisiana State University, Baton Rouge, LA. 84 pp. Rootes, W.L., and R.H. Chabreck. 1993a. Reproductive status and movement of adult female alligators. Journal of Herpetology 27:121Â–126. Rootes, W.L., and R.H. Chabreck. 1993b. Cannibalism in the American Alligator. Herpetologica 49:99Â–107. Tamarack, J.L. 1989. GeorgiaÂ’s coastal alligators, variation in habitat and prey availability. Pp. 105Â–118, In Proceedings of the 8th Working Meeting of the Crocodile Specialist Group. IUCN Publications, Gland, Switzerland. 405 pp. Taylor, D. 1984. Management implications of an adult female telemetry study. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 38:222Â–227. Taylor, D., T. Joanen, and L. McNease. 1976. A comparison of native and introduced immature alligators in northeast Louisiana. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 30:362Â–370. Tucker, A.D., C.J. Limpus, H.I. McCallum, and K.R. McDonald. 1997. Movements and home ranges of Crocodylus johnstoni in the Lynd River, Queensland. Wildlife Research 24:379Â–396. Tucker, A.D., H.I. McCallum, C.J. Limpus, and K.R. McDonald. 1998. Sex-biased dispersal in a long-lived polygynous reptile ( Crocodylus johnstoni ). Behavioral Ecology and Sociobiology 44:85Â–90. Webb, G.J.W., and H. Messel. 1978. Movement and dispersal patterns of Crocodylusporosus in some rivers of Arnem land, northern Australia. Wildlife Research 5:263Â–283. Zippel, K.C., H.B. Lillywhite, and C.R.J. Mladinich. 2003. Anatomy of the crocodilian spinal vein. Journal of Morphology 258:327Â–335.
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1 SPATIAL ECOLOGY OF THE AMERICAN CROCODILE, CROCODYLUS ACUTUS IN EVERGLADES NATIONAL PARK, FL By JEFFREY SCOTT BEAUCHAMP A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2014
2 2014 Jeffrey Scott Beauchamp
3 ACKNOWLEDGMENTS This project could not have been completed without the help of many people. First, I thank Frank Mazz otti, my major professor, who has guided my professional development for many years. I thank Kristen Hart who has been so generous in her advice and project direction. I thank Rob Fletcher who stuck with the project and was always willing to help wheneve r I needed it. Additionally, I want to thank Jerry Lorenz from the National Audubon Society who generously provided data and initial project guidance. To all the people that helped in the field Brian Jeffery, Mike Cherkiss, Rafael Crespo, Mat Denton, Ry an Lynch and Gareth Blakemore I thank all of you because this project would not have been finished if it was not for your help. I also thank everyone that listened to me talk about this project during our team building sessions. Additionally, I would li ke to thank USGS Priority Ecosystem Science fund and Save Your Logo, Lacoste, for generously supporting my project. Lastly, I would like to thank my parents that have always been there for me no matter what crazy idea I had, and supported me unconditionall y.
4 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ ............... 3 LIST OF TABLES ................................ ................................ ................................ ........................... 5 LIST OF FIGURES ................................ ................................ ................................ ......................... 6 ABSTRACT ................................ ................................ ................................ ................................ ..... 7 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .................... 9 2 METHODS ................................ ................................ ................................ ............................. 13 Study Area ................................ ................................ ................................ .............................. 13 Home Range and Movements ................................ ................................ ................................ 15 Generalized Linear Mixed Model ................................ ................................ ........................... 16 3 RESULTS ................................ ................................ ................................ ............................... 19 Home Range and Core Area Use ................................ ................................ ............................ 19 Shifting Core Areas ................................ ................................ ................................ ................ 20 Core Area Overlap ................................ ................................ ................................ .................. 21 Daily Movements ................................ ................................ ................................ .................... 21 4 DISCUSSION ................................ ................................ ................................ ......................... 25 Implications for Restoration ................................ ................................ ................................ ... 28 Hypotheses ................................ ................................ ................................ .............................. 29 Management implications ................................ ................................ ................................ ....... 31 Recommendations ................................ ................................ ................................ ................... 32 APPENDIX A SEASONAL CORE AREA AND HOME RANGES FOR ADULT FEMALE AMERICAN CROCODILES IN SOUTH FLORIDA ................................ ........................... 34 B LIST OF PUBLISHED CROCODILIAN HOME RANGE AND MOVEMENT STUDIES. ................................ ................................ ................................ ............................... 38 REFERENCE LIST ................................ ................................ ................................ ....................... 42 BIOGRAPHICAL SKETCH ................................ ................................ ................................ ......... 48
5 LIST OF TABLES Table page 3 1 Summary table showing the date and location of each crocodile, as well as the total length (TL) and mass. CS indicates the crocodile was captured in Cape Sable; NFB indicates the crocodile was cap tured in northeastern Florida Bay. ................................ .... 22 3 2 The breakdown of number of locations with percentage in parenthesis in each location class for the adult females American crocodiles tagged in this stu dy. LC3 represents locations with accuracy estimate ................................ ................................ ...... 22 3 3 The results from a generalized linear mixed effects model investigating what factors y movement rates in South Florida. ..... 24
6 LIST OF FIGURES Figure page 2 1 Study site locations in South Florida. ................................ ................................ ................ 17 2 2 Locations of environmental sampling stations. NFB1 5 are locations in northeastern Florida Bay. CS1 3 are locations in Cape Sable. ................................ ....... 18 3 1 Box plots of the c ore area and home range sizes of adult female American crocodiles in South Florida. CS represents Cape Sable crocodiles and NFB represents northeastern Florida Bay crocodiles. ................................ ................................ ................. 23 3 2 Nesting se ason core area overlap at Cape Sable and northeastern Florida Bay in South Florida. Light grey represents the core areas with no overlap and dark grey represents areas with at least 2 crocodiles overlapping ................................ ..................... 24 4 1 A 500m by 500m grid across South Florida with number of tracking days calculated in each cell. ................................ ................................ ................................ ........................ 33 A 1 Nesting season core areas (50% KDE) and home ranges (95% KDE) of adul t female American crocodiles at Cape Sable. ................................ ................................ .................. 34 A 2 Nonnesting season core areas (50% KDE) and home ranges (95% KDE) of adult female American crocodiles at Cape Sable. ................................ ................................ ...... 35 A 3 Nesting season core areas (50% KDE) and home ranges (95% KDE) of adult female American crocodiles in northeastern Florida Bay. ................................ ............................ 36 A 4 Nonnesting seas on core areas (50% KDE) and home ranges (95% KDE) of adult female American crocodiles in northeastern Florida Bay. ................................ ................. 37
7 Abstract of Thesis Presented to the Graduate School of the University of Florida in P artial Fulfillment of the Requirements for the Degree of Master of Science SPATIAL ECOLOGY OF THE AMERICAN CROCODILE, CROCODYLUS ACUTUS IN EVERGLADES NATIONAL PARK, FL By Jeffrey S Beauchamp May 2014 Chair: Frank Mazzotti Major: Wildlife Ecology and Co nservation The American crocodile ( Crocodylus acutus ) in Florida is a large, upper trophic level predator that was recently down listed by the United States Fish and Wildlife Service to threatened due to an increase in number of individuals and nests. In Florida, prime habitat of the American crocodile, the South Florida estuary, is expected to incur changes due to Everglades restoration and global climate change. These changes will potentially affect the distribution, growth, survival and spatial patter ns of American crocodiles. Understanding different movement tactics and habitat use patterns of highly mobile top predators allows for a greater understanding of the interactions between top predat ors and the habitats they use Here I used satellite telem etry to determine the current spatial use and movement patterns of American crocodiles I deployed fifteen transmitters on adult female s from D ecember 2010 to December 2012 and used k ernel density estimates (KDE) to calculate home range (95% KDE) and core a reas (50% KDE). Mean overall home ranges was 66.8 33.3 (SD) km 2 and mean core area size was 14.2 7.2 (SD) km 2 Average daily distance moved for croc odiles was 1.0km. Additionally, s alinity and temperature, the environmental parameters most likely to change due to Everglades restoration and global climate change, significantly American crocodile in Florida conti nues to recover and expand into its historic range and the
8 environment undergoes potentially dramatic changes, understanding how crocodiles will spatially respon d to these changes will inform us as to how crocodiles influence food web dynamics, create habi tat linkages, and adjust their spatial use strategies to this changing environment
9 CHAPTER 1 INTRODUCTION Studies of movement patterns of wildlife are important to understand how species inhabit, restrict, or change their movements and spatial use in dy namic environments. As biotelemetry technology continues to advance (Rutz and Hays 2009) a better ecological understanding is emerging of wildlife, particularly those that are cryptic, as well as those that have low population numbers and are vulnerable to extinction (Millspaugh and Marzluff 2001). The s ize, shape and temporal pattern of home ranges and movements have been shown to change due to prey availability (Ebersole 1980, Pejchar et al. 2005, Sulok et al. 2005) body mass (McNab 1964) age or sex (Webb and Messel 1978, Hutton 1989, Dahle et al. 2006, Gehrt and Fritzell 1997), predation risk (Tufto et al. 1996, Fortin et al. 2005, Mao et al. 2005) population density (Wolf 1985), and specific habitat requirements (i.e. nesting locations; Odum and Ku enzler 1955, Kay 2004). Understan ding the factors that influences the size of home ranges and movements for imperiled species as well as highly mobile top predators is becoming more important as populations recover or, in some cases, continue to decline (Abbitt and Scott 2001, Thorbjarnarson 2002). The American crocodile ( Crocodylus acutus ) is a large, upper trophic level predator that inhabits mostly estuarine habitats throughout its range, which within the United States encompasses the souther n tip of Florida from Vero Beach to Tampa Bay ( Kushlan and Mazzotti 1989a). American crocodiles prefer relatively deep, open water habitats with low saline environments (less that 50% sea water) that are protected from wind and wave activity (Kushlan and Mazzotti 1989b). During the nesting season (March 15 September 15) adult female American crocodiles can travel up to 35.5 km (Cherkiss et al. 2007) to nesting habitat that generally consists of sandy coastal beaches or man made berms created by dredgi ng activities.
10 Nests in northeastern Florida Bay (NFB) are primarily located on sandy beaches along the coast and on keys, which are sometimes a good distance (approxima tely 10s of kms) from foraging habitat (Kushlan and Mazzotti 1989b) Nests in the rel atively newly colonized location of Cape Sable (CS) are predominantly located on man made berms created by dredging East Cape Canal and Homestead Canal, although some nesting activity occurs on coastal beaches along the southwestern coast of mainland Flori da from Flamingo to Middle Cape. Adult female American crocodiles excavate their nests and assist in the hatching process (Ogden and Singletary 1973). They can travel long distances with the newly hatched crocodiles, but generally do not show signs of pro longed parental care (Kushlan and Mazzotti 1989b) that is seen in other crocodilians (Cott 1971, Kushlan an d Kushlan 1979). American crocodiles also nest communally with some nests as close as a meter from each other, and aggregations of adult females can be observed in proximity to each other during the nesting season. It has long been thought that crocodilians rarely tolerate adult conspecifics of the same sex unless they are congregated at breeding sites or in captivity (Lang 1989). However, it is unk nown how tolerant adult female American crocodiles are of each other for the duration of the nesting season and during the nonnesting season (September 16 March 14) Key habitat of the American crocodile in Florida the Everglades estuary has undergo ne dramatic changes due to diversion of freshwater flow to nearby urban areas in order to support increasing human consumption. This diversion has limited the amount of fresh water entering South Florida estuaries thereby inhibiting American crocodile gro wth and survival (Mazzotti 1999). Currently, restoration projects aimed at restoring near historic water flow to marshes and estuarine habitats in South Florida (U.S. Army Corps of Engineers, 1999) are planned, many of which will affect hydrological regim es and those animals that rely on healthy
11 estuaries (Green et al. 2013). Given their ability to exhibit biological responses to changing hydrological patterns, American crocodiles are important indicators to how restoration proceeds (Mazzotti et al. 2009) Additionally, the South Florida estuary faces threats from global climate change and sea level rise (Meehl et al. 2005) which could adversely affect the success of low lying nests and also increase salinities in coastal estuaries. Newly established ex otic species may also be a threat to American crocodiles through competition or predation from Burmese pythons ( Python molurus bivittatus ) or potential predation on crocodile eggs by Argentine black and white tegus ( Tupinambis merianae ) Furthermore, a re cent cold front in South Florida highlighted the vulnerability of American crocodiles in Florida to extreme climatic events, as over 150 American crocodiles died due to an extreme winter freeze ( personal observation ), and these extreme events could be incr easing in number and intensity (Easterling et al. 2000). It is unknown how American crocodiles will respond spatially to these changes or how their movement patterns will respond to Everglades restoration as well as the above mentioned threats. My objecti ves were three fold The first objective was to quantify home ranges, delineate core areas, and quantify daily movements of adult female American crocodiles in Florida; I also sought to compare values from this research to previous home range estimates of crocodilians to determine if any patterns exist within crocodilian spatial ecology The second objective was to determine if salinity and temperature, the environmental parameters expected to change due to restoration and global climate change (Rahmstorf 2007) influence adult female cr ocodile movement patterns. T he last objective was to test three hypotheses. 1) Nesting season home range size, core area size and daily movements are larger for adult female crocodiles in
12 NFB than CS due to increased travel distances betw een nest locations and foraging habitat in NFB. Essentially the crocodiles in CS will act similar to reported behavior of American alligators that reside in marsh habitats that create smaller home ranges around nesting sites (Joanen and Mc Nease 1970, Goodwin and Marion 1980, Rootes and Chabreck 1993), and the crocodiles in NFB would act similar to reported values of C. porosus that make long distance movements to nesting habitat in riverine habitats (Kay 2004, Hamish et al. 2013). 2) Nest ing season core areas will be similar for adult female crocodiles, but there will be a shift in core area from the nesting season to the nonnesting season and that shift will be greater in NFB due to the increased tr avel distance to nesting sites. T he dis tance between nest sites and preferred foraging areas will not increase the size of core areas (Hypothesis 1), but the distance between nesting season core areas and nonnesting season core areas will be greater in NFB due to nesting generally occurring far ther from preferred foraging areas than CS nesting. 3) There will be a NFB due to the known large nesting aggregations in CS.
13 CHAPTER 2 METHODS Study Area E verglades National Park (ENP) is a 1.5 million acre (approximately 607,000 ha) Wetland of International Importance, World Heritage Site, and International Bioreserve. I conducted this study at two sites within ENP, the historic crocodile nesting area of Northeastern Florida Bay (NFB), and the more recently discovered nesting area of Cape Sable (CS; Figure 2 1). The hydrology of NFB is primarily driven by the Taylor Slough drainage, which is currently undergoing restoration projects that will increase fre shwater flow to the estuary. Most of the crocodile nesting in NFB takes place on keys within the bay or on coastal beaches, sometimes a considerable distance (10s of km) from foraging and nursery habitat (Mazzotti 1999). The vegetation in NFB is dominate d by red mangrove ( Rhizophora mangle ) forest and scrub with interspersed black mangrove ( Avicennia germinans ) forests and hardwood hammocks. Egler (1952) described the herbaceous wetlands in NFB as dominated by spikerush ( Elocharis cellulose ) with some cl umps of sawgrass ( Cladium jamaicense ). These wetlands have all but vanished from coastal habitats of NFB due to the changes in the hydrology (Lorenz and Sarefy 2006). At CS, the hydrology is more tidally and rain influenced than NFB with salinities consist ently close to those found in sea water (approximately 30 ppt ). Nesting activity is mostly on berms created from the dredging of the East Cape Canal and Homestead Canal although there is some nesting along the coastal beaches of CS. Black mangroves domin ate the forest structure with red mangroves becoming more prevalent inland. Additionally, CS has a large expanse of mud banks that become more exposed on lower tide, as well as salt tolerant herbaceous species interspersed between the mud banks and mangro ve forests (Roberts et al. 1977).
14 I captured all crocodiles using self locking snares (Thompson Snares, Annabel, MO), working from both motorboats and land. I marked each crocodile with a distinct scute clip pattern using established protocols (Mazzotti 1983, Mazzotti and Cherkiss 2003) and measured, with a flexible tape measure, head length (HL), snout vent length (SVL), total length (TL), tail girth (TG) and mass to the nearest mm. After taking morphometric measurements, I outfitted crocodiles with a satellite transmitter (Wildlife Computers, Redmond, WA, SPOT5, 0.5 Watts, 70 mm long, 41 mm wide, 27 mm high, and 110 g weight ) and a VHF radio transmitter (Holohil, Ontario, Canada, model SI 2). The VHF transmitter was attached to locate animals if their satellite signal stopped transmitting. Attachment protocols followed Brien et al. (2010) with slight modifications to suit American crocodiles in South Florida. Before attaching transmitters, I cleaned the area around the nucal rosette with Betadine sol ution and administered 6 8 injections of lidocaine (approximately 3ml) around the cleaned area. I threaded stainless steel wire (90lb test) underneath the nucal rosette using an 8 inch (203 then threaded the wire through hole s fabricated in the transmitter and crimped together. I then epoxied a VHF transmitter adjacent to the satellite transmitter. After completing the attachment, which lasted approximated 45 minutes, I released all crocodiles at the capture location. During the hatching season (end of June to September 15), I deployed transmitters only on females known to have hatched their nest, which ensured females did not abandon their nests (Kushlan and Mazzotti 1989b). I programmed satellite transmitters to transmit ev ery hour for the length of their deployment and locations were determined by the Argos system which gives an accuracy location class (LC) to each position. Location class accuracies are designated as follows with error accuracy in parenthesis: LC3 (< 250m ), LC2 (250m < 500m), LC1 (500m < 1500m), LC0
15 (> 1500m), LCA (unknown), LCB (unknown), LCZ (failed). Since 2011, Argos locations are Kalman filtered as opposed to least squares filtered. This significantly improves the location accuracy (Lopez and Malarde 2011). For this study, I used LC3 LC1for home range and core area analysis and only LC3 for movement analysis. Home Range and Movements I performed all statistical analysis in Program R (R core team 2013) and determined statistical significance at 0.1 To determine home range size, I used fixed kernel density estimates (KDE) to put less emphasis on peripheral locations and eliminate areas that crocodiles may travel through only briefly (Worton 1989). This method allows for a more accurate represe ntation of home range and core area use because American crocodiles are known to travel long distances to nesting sites. I also selected KDEs to compare current home ranges to those reported in previous literature. I used least squares cross validation ( LSCV) technique as the smoothing parameter (Seaman and Powell 1996). To minimize spatial autocorrelation, I calculated a mean daily location for each crocodile in Program R and then used the programs Geospatial Modeling Environment (GME; Beyer 2012) and A rcGIS 10.1 (ESRI 2011) to create the KDEs; I used 50% and 95% KDE to depict core areas (50% KDE) and overall home ranges (95% KDE) of the telemetered crocodiles (following Worton 1989). A dditionally, I created a 500m x 500m grid across the study sites and calculated the number of crocodile tracking days in each grid cell using LC3 locations to show areas of concentrated use I used a linear regression to determine if there was an effect of female size on home range and core area use. I calculated the dai ly distance moved (rate of movement; ROM) in GME from the mean daily locations and only included locations where subsequent days were recorded so as not to over or under
16 To determine seas onal changes in core area use and ROM I calculated KDEs (both 50% and 95%) and ROM during the nesting (March 15 September 15) and non nesting (September 16 March 14) seasons (Kushlan and Mazzotti 1989b). Next, I calculated the centroid of each core area in GME and then measured the dist ance between the nesting season centroid and nonnesting season centroid to determine if there was a seasonal shift in core areas. As a proxy I assessed the level of core area overlap for adult female crocodiles using ArcGIS to determine that overlapped with other crocodile core areas. Generalized Linear Mixed Model I used a generalized linear mixed effects model (GLMMg) with the gamma distribution using R pa influence of salinity and temperature on ROM. Additionally, I compared a linear mixed effects model (LMM) and a generalized linear mixed effects model (GLMMp) with family Poi sson to the GLMMg by examining the output and comparing the Akaike information criterion (AIC). For all three models, the response variable was ROM with model parameters of temperature, salinity, location (CS or NFB), and season (nesting or nonnesting). I also included crocodile ID as a random effect. Hourly temperature and salinity measurements were automatically taken from 8 water stations across the southern estuary of ENP (Figure 2 2). Three stations are located in CS and five are in NFB; all are ma intained by the Audubon Society of Florida. I averaged the hourly measurements from the stations to get a daily mean temperature and salinity for each station. Next, I pooled the CS and NFB measurements and got a daily mean temperature and salinity for e ROM
17 Figure 2 1. Study site locations in South Florida.
18 Figure 2 2. Locations of environmental sampling stations. NFB1 5 are locations in northeastern Florida Bay. CS1 3 are locations in Cape Sable.
19 CHAPTER 3 RESULTS I satellite tagged 15 adult female crocodiles, 8 in CS and 7 in NFB with satellite transmission times between December 2010 to December 2012. Crocodiles ranged in size from 235.8 cm to 303.5 cm (Table 3 1). Satellite tracking periods ranged from 3 days to over 406 days (196 104 SD days), although 6 transmitters were still transmitting data after the December 2012 cutoff date for analysis. It is unclear why one transmitter lasted only 3 days, althou gh I observed a different transmitter that lasted 58 days to be missing the antenna portion of the unit. Transmitters deployed after this observation were reinforced at the base of the antenna at the factory, thereby minimizing additional losses due to an tenna failure. Except for the crocodile with only 3 days of transmitter life, all crocodiles had more than 20 daily fixes (most with multiple high quality locations per day). Two crocodiles in NFB only received fixes during the nesting season and 1 croco dile in CS did not have enough fixes to produce KDE estimates during the nonnesting season (see Table 3 2). Home Range and Core Area Use Overall home ranges (95% KDE) for adult female crocodiles in South Florida ranged from 23.4 113.5 km 2 (mean = 66.8 3 3.3 SD), and core areas (50% KDE) ranged from 3.5 22.0 km 2 (mean = 14.2 7.2 SD). During the nesting season, home range sizes for crocodiles at CS ranged from 11.3 84.8 km 2 (mean = 47.2 28.7 SD) and core area sizes were 2.6 21.7 km 2 (mean = 10.2 7.2 SD). Home range sizes at NFB during the nesting season ranged from 26.6 106.1 km 2 (mean = 62.3 30.1 SD) and core areas were 3.9 18.0 km 2 (mean 12.7 6.0 SD). During the nonnesting season, home range sizes for crocodiles at CS ranged from 31.3 167.0 km 2 (mean = 75.3 47.5 SD) and core area sizes were 6.6 35.6 km 2 (mean = 16.6 10.0 SD). Home range sizes at NFB during the nonnesting season ranged from 6.4 69.8 km 2 (mean
20 = 32.0 24.4) and core areas were 0.9 17.9 km 2 (mean = 7.3 6.7 SD) (Figure 3 1 Appendix 1). There was no statistical difference between CS and NFB crocodiles in the size of the overall home range (t = 0. 683, p = 0.508), overall core a rea (0.448, p = 0.663), nesting season home range (t = 0.957, p = 0.357), nesting season core area (t = 0.714, p = 0.489), and nonnesting season core area use (t = 1.829, p = 0.102). There was a significant difference between the CS and NFB crocodiles in the nonnesting season home range (t = 1.944, p = 0.0892 ) with crocodiles at CS ha ving larger home ranges. Linear regression analysis showed that adult female size did not influence home range size (F = 0.050, p = 0.827) or core area size (F = 0.002, p = 0.962). One female (#5631) tagged at CS moved to the Fox Lake complex before the start of the nesting season and remained in that area throughout the nesting season. This is approximately 7 km from known nesting areas and I postulate this female did not nest during the transmitter deployment. Another female at NFB (#481) hatched her nest in mid July and was subsequently captured and tagged. She then moved to an area more inland, approximately 9 km from her nest, and remained there until she moved back to the exact same nesting location (less than 1 m) the following March where she suc cessfully hatched another nest. Shifting Core Areas The mean distance between centroids of an individual cr during the nesting and non nesting season was 2.9 0.7 (SD) km and 2.7 2.5 (SD) km for NFB and CS respectively. There was a s ignificant difference in variance (F = 9.06, p = 0.015 Levene test) between CS and NFB wit h three pat terns emerging. C rocodiles at NFB shifted their core area at least 2 km and the largest shift was 3.7km. C rocodiles at CS either shifted a consi derable distance (3.3, 5.8 and 5.4 km) or barely shifted at all (0.4, 0.7 and 0.7 km). Two crocodiles at CS that shifted their core areas a large distance likely nested along the western coast of Florida, a
21 considerable distance from the capture location and preferred foraging area. The third crocodile moved farther inland to preferred foraging habitat and presumably did not nest. The three crocodiles that did not have a large shift in core area nested nea r to preferred foraging habitat (Figure 3 1 ) C ore Area Overlap There was extensive nesting season core area overlap (Figure 3 2 ) at CS with a mean proportional overlap of 63.1%. Each satellite marked crocodile at CS shared their core area with at least one other satellite marked crocodile and four of the seven shared their core area with five other crocodiles. In NFB, mean proportional overlap was significantly smaller (mean 14.7 %; W = 46, p = 0.0041 Wilcoxon) than CS. There were two crocodiles that had very small overlap of their core areas (0%, 0.002%) and none of the crocodiles in NFB shared more than 32% of their nesting season core areas. Nonnesting season followed the same trend with core area overlap of 80.8% and 21.3% for CS and NFB, respectively, which was significant different (W = 28, p = 0.021 Wilcoxon). Daily Movements During the nesting season, crocodiles at NFB (mean movements = 2.0 km/day 0.67 SD) moved significantly longer distances (t = 1.787, p = 0.0995 ) than crocodiles at CS (mean movements = 1.3 km/day 0.75 SD). There was no significant difference in the daily movements (t = 0.0997, p = 0.923) during the nonnesting season between crocodiles at NFB (mean = 1.4 km/day 0.80 SD) and CS (mean = 1.3 km/day 0.78). The AIC values of the GLMMp (1227779), LMM (16656) and GLMMg (15674) indicated GLMMg was the best fit model. GLMMg showed a significant effect of temperature, season, and salinity when combined with location and season on ROM (Table 3 3).
22 Table 3 1. Summary table showing the date and location of each crocodil e, as well as the total length (TL) and mass. CS indicates the crocodile was captured in Cape Sable; NFB indicates the crocodile was captured in northeastern Florida Bay. ID Date Captured Capture Location Recapture Status TL (cm) Mass (kg) 5058 12/22/2010 CS No 235.8 46.5 5631 1/14/2011 CS No 303.5 86.0 1548 3/14/2012 CS Yes 256.0 66.0 6628 3/13/2012 CS No 262.6 67.0 6620 2/21/2012 CS No 249.5 58.0 202 2/21/2012 CS Yes 275.8 87.0 5151 7/11/2012 CS No 293.3 N/A 792 5/9/2011 NFB Yes 287.1 80.0 1076 7 /6/2012 NFB Yes 255.7 53.0 481 7/12/2012 NFB Yes 266.4 N/A 6700 4/26/2012 NFB Yes 290.1 85.0 775 4/27/2012 NFB Yes 251.7 56.0 575 5/2/2012 NFB Yes 257.6 48.0 1760 5/2/2012 NFB Yes 250.0 53.0 Table 3 2. The breakdown of number of locations (%) wit h percentage in parenthesis in each location class for the adult females American crocodiles tagged in this study. LC3 represents locations with accuracy estimate <250 m resolution. LC2 represents locations with accuracy estimate between 250 m and 500 m. LC 1 represents locations between 500 m and 1500 m. ID LC 3 LC 2 LC 1 Total 1760 268 ( 42.7 ) 220 (35.1 ) 139 (22.2 ) 627 1548 445 (50.7 ) 287 (32.7 ) 145 (16.5 ) 877 6700 56 (38.9 ) 58 (40.3 ) 30 (20.8) 144 575 97 (40.6 ) 85 (35.6 ) 57 (23.9 ) 239 6628 295 (43.5 ) 257 (37.9 ) 127 (18.7 ) 679 5058 120 (33.8 ) 139 (39.2 ) 96 (27.0 ) 355 775 218 (35.1 ) 255 (41.0 ) 148 (23.8 ) 621 1076 82 (45.6 ) 60 (33.3 ) 38 (21.1 ) 180 481 231 (37.8 ) 216 (35.4 ) 164 (25.8 ) 611 792 28 (20.4 ) 63 (46.0 ) 46 (33.6 ) 137 51 51 126 (46.7 ) 79 (29.3) 65 (24.1 ) 270 6620 169 (44.7 ) 131 (34.7 ) 78 (20.6 ) 378 202 384 (34.7 ) 436 (39.4 ) 287 (25.9 ) 1102 5631 77 (29.0 ) 110 (41.5 ) 78 (29.4 ) 265 Mean 185.4 171.1 107.0 463.2
23 Core Area Use Home Range Fig ure 3 1 Box plots of the core area and home range sizes of adult female American crocodiles in South Florida. CS represents Cape Sable crocodiles and NFB represents northeastern Florida Bay crocodiles.
24 Figure 3 2 Nesting season core area overlap at C ape Sable and northeastern Florida Bay in South Florida. Light grey represents the core areas with no overlap and dark grey represents areas with at least 2 crocodiles overlapping Table 3 3. The results from a generalized linear mixed effects model inve stigating what factors Parameters F statistic df P value Temperature 9.17 891 0.003 Salinity 0.31 649 0.579 Season 5.75 919 0.017 Location 2.03 632 0.155 Temperature Season 0.32 935 0.572 Temperature Location 0.11 907 0.740 Salinity Season 3.65 921 0.056 Salinity Location 9.91 488 0.002
25 CHAPTER 4 DISCUSSION This study was the first to comprehensively report on home range size, core area use and daily move ment patterns of adult female American crocodiles with average tracking duration just under one year. Compared with previously reported home range estimates for American crocodiles, the results of this study showed much larger areas of spatial use. Kushla n and Mazzotti (1989a) reported an average home range si ze of 107 ha (approximately 1. 1 km 2 ) for 5 crocodiles with more than 18 locations for each crocodile. This estimate was determined by enclosing the locations of each crocodile with a polygon (100% m inimum convex polygon). The difference between home ranges estimated in the current study versus those in Kushlan and Mazzotti (1989b) could be attributed to the satellite transmitter ability to transfer remote signals Coastal habitats in ENP are dominated by mangroves in which penetrati on and navigation by boat is difficult. When crocodiles were using those habitats they might not have been detected with the VHF receivers in the previous Kushlan and Mazzotti (1989b) study. There was considerable overlap in overall home ranges (95% KDE) across the study site and this supports previous finding of Kushlan and Mazz otti (1989b). However, there was very little overlap in core areas in NFB (Figure 4) This pattern of habitat use was different at CS where there was extensive overlap in both overall hom e range and core use areas (Figure 4). Each of the seven crocodiles that were tagged in CS made trips to the Fox Lake complex with repeated and sometimes extended stay s for most of the crocodiles. Approximately, 2 3 % of all locations at Cape Sable occur red within or near the Fox Lake complex (Figure 5). This area is known to have large numbers of adult crocodiles (personal observation), particularly during the dry season. It is unclear why there are observed large congregations and core overlap in the Fox Lake complex, but there could be a fresh water source in the area that provides a respite to the
26 high coastal salinities. In addition, the observed core area overlap of adult crocodiles might enhance mating opportunities. Finally, although it is unkn own how dense the prey base is in the Fox Lake complex, plentiful food availability could allow for greater concentrations of adult crocodiles and allow the crocodiles to become more tolerant of one another. Understanding why this area can support the amo unt of core area overlap of adult female crocodiles is an important next step in managing this threatened species. My results confirmed those found by Kushlan and Mazzotti (1989b) that females return to their nest site on subsequent years. For example, cr ocodile #481 was captured one day after she hatched her nest on Deer Key in mid July and subsequently moved to northeastern Little Madeira Bay, approximately 9 km from her nest site. She stayed there for the duration of the nonnesting season, after which s he returned to the exact same nest location ( < 1 m distance ) on Deer Key in mid Mar ch the following yea r This study also confirmed that adult female crocodiles do not nest every year with crocodile #5631 staying in the Fox Lake complex for the entire nesti ng season ; t his result has implications for population modeling, as fecundity terms for females are not an annual rate for all individuals Other than C. porosus and A. mississippiensis scant data are available to make comparisons to other crocodilians ( but see Appendix B for a summary table of the published home range estimates and movement studies on crocodilians). Joahnen and McNease (1970) reported on 4 adult female A. mississippiensis tracked for approximately 6 months in a coastal marsh in Lou isiana ; their animals had home range estimates ranging from 6.4 41.0 acres (0.026 0.17 km 2 ) with the largest home ranges occurring during courtship and breeding periods. These results paralleled those found by Goodwin and Marion (1979) where they tracked 5 fem ale lorida for 2 years and found home range was largest during
27 spring with a mean home range size of 15.6 ha. Rootes and Chabreck (1993) tracked 15 adult female alligators in a marsh in northern Louisiana and found slightly large r home ranges (mean 35.8 ha), which were very similar to home range values Morea et al. (2000) found for adult female alligators in the Everglades (mean 36 ha). Lastly, Taylor (1984) reported the largest mean annual home range of 56.0 ha, as well as cons iderable variation (range 1 256 ha), for adult female alligators in a northern Louisiana lake. These home range estimates for alligators are markedly smaller than the home range estimates in the present study, but this was expected because female alliga tors tend to move more during the spring breeding season, and limit their movements during the summer nesting and hatching season, as well as the winter season when they typically find a den to avoid cold temperatures (Chabreck 1965, Joanan and McNease 197 0, Goodwin and Marion 1980). This movement patterns lends itself to small home ranges, which is not the pattern detected in the present study. Even though South Florida is the only place where alligators and American crocodiles are found together, Ameri can crocodiles are mostly found in the extreme southern tip of Florida. The results of this study showed that adult female American crocodiles are highly mobile crocodilians with mean ROM of 1.7 km/day for all crocodiles in the nesting and a mean of 1.3 k m/day in the nonnesting season. The largest ROM detected in this study was a female that moved 10.4 km during an excursion in April, between egg laying and hatching. Previously reported alligator ROMs are much smaller. Taylor (1984) and Rootes and Chabre ck (1993) reported ROMs < 0.1 km/day, Morea et al. (2000) reported ROMs of 0.2 km/day during the spring, and Joanen and McNease (1970) reported the highest ROM of 0.5 km/day. The results of this study show American crocodiles in Florida have both larger h ome ranges and movement patterns than reported values for alligators across their range.
28 Home range values for C. porosus are variable; Brien et al. (2008) reported small er home ranges than my study (range 1.18 7.67 ha) at a seasonally isolated water hole in northern Queensland, Australia, and Kay (2004) and Hamish et al. (2013) reported larger home range values for C. porosus in riverine systems in Australia. Hamish et al. (2013) was the first to use satellite/GPS technology and tracked eight male an d four female crocodiles to report on home range values for crocodilians and their results are similar to my results. Kay (2004) and Hamish et al. (2013) both tracked C. porosus in riverine systems and tracked females during long journeys (15 62 km) fro m dry season locations to nesting locations. Kay (2004) provided small estimates for dry season core areas, but did not provide estimates for wet season core areas, and Hamish et al. (2013) found that by removing area not contained within the river system the estimates for home range and core areas decreased by 90% and 71 %, respectively. American crocodiles in Florida are not restricted in their movements like C. porosus that occupy riverine systems or isolated water holes. Therefore, it is not surpris ing that I found home range values to be larger in this study. Implications for Restoration As the large and ambitious effort to restore hydrologic patterns in the Greater Everglades to historic flows proceeds, understanding how the hydrologic changes affe ct animals, particularly important upper trophic level species, is extremely important. Previous work by Mazzotti (1999) and Mazzotti et al. (2009) showed that American crocodiles directly respond to changing hydrology by either decreasing or increasing t heir growth and survival. My research showed the importance of examining American crocodiles spatial and movement dynamics. First, I showed that American crocodiles can be tolerant of conspecifics given enough habitat. This is important because when sal inities change and historic food webs respond (Lorenz and Serafy 2006) more foraging habitat will become available to crocodiles. Second, I showed that adult female
29 American crocodiles directly respond (ROM) to changing environmental conditions (temperatu re and salinity). This is most likely due to crocodiles searching for food and moving into less saline enviornments. Lorenz and Serafy (2006) showed that prey base fish populations decrease during times of increased salinity which could result in crocodi les increasing their movements in search of prey. Hypotheses The first hypothesis I tested was whether the crocodiles in CS during the nesting season would act similar to reported home range C. porosu s C. niloticus during the nesting season. In general, those studies showed that adult female crocodilians had relatively small home ranges around nesting sites ; this is the pattern I expected to see a t CS. In NFB, I expected to see the pattern Kay (2004) and Hamish et al. (2013) reported on C. porosus In riverine systems, C. porosus make long distance journeys to nesting sites and have larger reported home range estimates. There was no significant difference in the nesting season home range or core area s izes for the crocodiles at CS in comparison with NFB. There was a significant difference in the ROM however, with crocodiles in NFB have significantly longer daily moveme nts during the nesting season ; t hi s is what I expected due to the necessary increased travel distance to the nesting locations. However, the nonnesting season core areas were significantly larger for the CS crocodiles and this may be due to increased trips to the Fox Lake complex whereas the NFB crocodiles had a decrease in their daily movements during the nonnesting season because they did not have to make journeys to the nesting areas. There was no significant difference detected in the nonnesting ROMs. The second hypothesis I tested wa s that nesting season core areas would not be statistically different between CS and NFB, but there would be a shift in nesting season core area
30 use and that shift would be greater in NFB due to the increased travel distance to nesting locations. Althoug h there was no significant di fference between CS and NFB, an interesting pattern emerged. There was a significant difference in the variance between NFB and CS and this is mostly due to the crocodiles in CS either remaining near the nesting location resul ting in a small shift (the overall pattern I expected), or moving a good distance to nesting locations along the west coast or to the Fox Lakes. The third hypothesis was that there would be a larger proportion of core area overlap at CS. Recent work by Br ien et al. (2008), Kay (2004), and Hamish et al. (2013) showed that adult male C. porosus can have overlapping home ranges, but Brien et al. (2008) found very little overlap in adult female C. porosus In this study I showed two distinct spatial patterns used by adult female American crocodiles in Florida. The crocodiles in CS had extensive overlap and the crocodiles in NFB had very little overlap in core areas. There could be a few explanations for this spatial pattern. First, we captured all crocodile s at CS in East Cape, whereas I captured all NFB difficult to target adult female crocodiles in NFB during the nonnesting season when they are generally away from habit at that is accessible by motorboat. T he spatial overlap pattern I detected in this study was not likely due to where the crocodiles were captured because one group of three crocodiles in NFB nested within 3 km of each other and shared very little nest ing season core area overlap, and another group of two crocodiles in NFB nested within a few hundred meters of each other did not share any nesting season overlap. Additionally, two of the areas where overlap occurred at CS were approximately 8 km from th e capture locations.
31 The second explanation for observed spatial pattern was that the habitat at CS is more conducive for crocodiles to share their core areas. At CS, the crocodiles that stayed in the East Cape area to nest and the crocodiles that move d to the western coast to nest made trips to the Fox Lake complex. The complex of lakes could provide a respite to the high coastal salinities, provide additional prey opportunities, or provide mating opportunities. I expect that the historic redirecting of freshwater flow from Florida Bay and the subsequent decrease in prey may have limited the ability of the crocodiles to respond as we saw in the increase in nesting at CS after the initial damming of East Cape Canal (Mazzotti 2007). This pattern did sh ow that adult female crocodiles can share core areas. Management implications In this study, I identified key areas of high crocodile use previously suspected but never quantitatively shown. The Fox Lake complex is a high trafficked area by adult croco diles, but the reason this area is important is still yet unknown. As the population of American crocodiles continues to grow and expand into new areas it is important to know how much and what kind of habitat is needed to sustain a healthy population. Ad ditionally, American crocodiles are known to make long distance journeys to nest sites (Cherkiss et al. 2008) and nuisance crocodiles have also been known to make long distance trips from Miami to Naples, across the southern tip of Florida (L. Horde, perso nal communication). My results also show crocodiles move larger daily distances than was initially thought with ROMs in this study averaging over 1km/day. Previous work by Rosenblatt and Heithaus (2011) showed the importance of highly mobile top predato rs to dispersal of nutrients across the landscape and creation of habitat linkages. T he crocodiles tagged in this study may be creating the same linkages across the South Florida ecosystem by having large home ranges and large daily movements Additional ly, I identified the importance
32 of spatial and movement dynamics to changing environments, which will be increasing in South Florida due to restoration, and global climate change and sea level rise. Recommendations Understanding to what extent prey influen ces home range and movement dynamics is an important next step to the continued management of this threatened species by either conventional stomach pumping (Taylor et al. 1978) or more advance d stable isotope analysis (Rosenblatt and Heithaus 2011). Most of the differences identified in home range size and movement patterns for crocodilians have been attributed to sexes and size classes. Understanding how male and non adult American crocodiles are moving within the landscape would enhance the spatial pict ure forming from the current study. Notably, none of the females tagged in this study moved between the two study sites. I expect male American crocodiles to have larger home ranges and movements patterns as reported in other crocodilians, and may possibl y link these two geographic areas. The increase in observations of crocodiles in urban areas (L. Horde pers. c omm. ) also increases the potential for human/crocodile interactions. The methods described in this paper would shed light on the manag ement of these urban crocodiles as they continue to move into their historic range. Additionally, expanded sampling of adult females could shed light on the proportion of adult females that reproduce and nest each year, thereby enhancing our ability to mod el the population of American crocodiles. Lastly, my research identified that temperature and salinity influence the movement patterns of adult female crocodiles, but it is unclear to what extent they influence those patterns. More advanced movement mode lling would allow researchers and managers to better understand the environmental influences and hopefully lead to the inclusion of these types of analyses in determining effects of restoration and global climate change.
33 Figure 4 1. A 500m by 500m g rid across South Florida with number of tracking days calculated in each cell.
34 APPENDIX A SEASONAL CORE AREA AND HOME RANGES FOR ADULT FEMALE AMERICAN CROCODILES IN SOUTH FLORIDA Figure A 1. Nesting season core areas (50% KDE) and home ranges (95% KD E) of adult female American crocodiles at Cape Sable.
35 Figure A 2. Nonnesting season core areas (50% KDE) and home ranges (95% KDE) of adult female American crocodiles at Cape Sable.
36 Figure A 3. Nesting season core areas (50% KDE) and home ranges (9 5% KDE) of adult female American crocodiles in northeastern Florida Bay.
37 Figure A 4. Nonnesting season core areas (50% KDE) and home ranges (95% KDE) of adult female American crocodiles in northeastern Florida Bay.
38 APPENDIX B LIST OF PUBLISHED CROCO DILIAN HOME RANGE AND MOVEMENT STUDIES.
39 Source Tracking Method Species N Location Findings Chabreck (1965) Mark Recapture Alligator mississipiensis 131 Rockefeller Wildlife Refuge, LA, USA Immature alligators moved greater distances than adults. Transloc ated animals moved 3 to 4 times more than non translocated and showed strong homing instincts. Joanen and McNease (1970) Radio Alligator mississipiensis 5 Rockefeller Wildlife Refuge, LA, USA Nesting females showed greatest movement during courtship and b reeding period. Minimum home range was 6.4 41.0 acres. Joanen and McNease (1972) VHF Alligator mississipiensis 14 Rockefeller Wildlife Refuge, LA, USA Adult males exhibited high daily movements. Mean of 2411 ft/day and a maximum distance of 27,750 ft/d ay. Minimum home range was 452 12,560 acres. Taylor et al. (1977) VHF Alligator mississipiensis 23 Black Bayou Lake & Wham Brake Reservoir, LA, USA Minimum home range was 0.8 321 hectares for immature animals. Webb and Messel (1978) Mark Recapture Croco dylus porosus >1500 Arnhem Land, Northern Australia Large movements of juvenile animals, possibly attributed to the habitat structure of the study site. Translocated animals showed a homing instinct. Goodwin and Marion (1979) VHF & Visual Alligator missi ssipiensis 9 Newnan's Lake, Alachua County, FL, USA Adult alligators showed the largest movements in spring. Females wer e more sedentary throughout the year, with preference for swamp in su mmer for nesting. Males used open lake in spring & summer. Web b et al. (1983) Mark Recapture Crocodylus johnsoni Unknown McKinlay River Area, NT, Australia Most (83%) of the juvenile animals recaptured were within 1 km of the initial capture location. There was no difference in movement of males and femal e s, but youn ger animals moved more than older animals Taylor (1984) VHF Alligator mississipiensis 9 Clear Smithport Lake, DeSoto Parish, LA, USA Adult females daily movement rate ranged between 2.3 238 m. Minimum home range was 0.8 256 hectares. Rodda (1984) VHF Crocodylus acutus 10 Gatun Lake, Panama Movement of juvenile animals showed relatively small home ranges generally around the nesting location. Ouboter and Nanhoe (1988) VHF Caiman crocodilus 11 Northern Surname Problems with transmitter failure. Caiman followed the water levels in the creeks. Adult females remained near the same locale all year. Long distance movements coincided with end of the rainy season. Hutton (1989) Mark Recapture and VHF Crocodylus niloticus 100 (21 VHF) Lake Ngezi, Zimbabwe Mos t animals were nocturnal, but adults occasionally moved during day. Adult females had relative small home ranges near prime nest locations. Kushlan and Mazzotti (1989) VHF Crocodylus acutus 10 Everglades National Park, FL, USA Mean activity area was 106 h a. Female activity into Florida Bay was related to nesting occurrence. Females appeard to have 2 activity ranges.
40 Source Tracking Method Species N Location Findings Hocutt et al. (1992) VHF Crocodylus niloticus 5 Lake Ngezi, Zimbabwe Movement of translo cated animals showed exploratory behavior with no established home ranges. An adult female moved over 12 km after release, nested and then remained at site. A juvenile resident traversed 15 km of shoreline. Rootes & Chabreck (1993) VHF Alligator mississip iensis 15 Lacassine National Wildlife Refuge, Cameron Parish, LA, USA Adult females showed no difference between nesters (30%) and non nesters in home range or daily movements. Home range and movements were greatest in the spring breeding season. Mean ann ual home range 35.8 hectares. Tucker et al. (1997) Mark Recapture Crocodylus johnstoni 742 Lynd River & Fossilbrook Creek, Queensland, Australia Annual movement averaged less than 1 km except for pubescent males, which seem to be nomadic. Females normall y remained near breeding sites even when not breeding. Linear home ranges were 0.6 km for mature females and 1.6 km for adult males. Morea et al. (2000) VHF Alligator mississipiensis 31 Everglades, Florida Mean annual home range for males (122 hectares) w as greater than females (36 hectares) and male alligators moved (167 m/day) more than females Munoz and Thorbjarnarson (2000) VHF Crocodylus intermedius 8 Capanaparo River, Venezuela Captive released males moved a considerable amount 1st month after rele ase with the maximum distance moved of 11.6 km after 4 months. After initial movement, crocodiles became more sedentary. Kay (2004) VHF Crocodylus porosus 16 Ord River, Cambridge Gulf, Queensland, Australia Females had small core linear ranges 1.3 0.9 km during the dry season, but moved up to 62 km for nesting in the wet season, then returned to same core area the next dry. Males moved considerable distances the entire year. Weerd et al. (2006) VHF Crocodylus mindorensis 3 Northeast Luzon, Philippines Adult female animal movement rate was 0.04 km/day and had a home range of 79 hectare (95% KDE), which was small than the subadult female (110 hectares). Read et al. (2007) Satellite Crocodylus porosus 3 Cape York Peninsula, Queensland, Australia Transloca ted adult male animals returned back to capture site after spending time at release site. They travelled distances of 56, 99 and 411 km of coastline for return trips. Brien et al. (2008) VHF Crocodylus porosus 13 Seven Mile Waterhole, Lakefield National P ark, Queensland, Australia Animals occupied larger home ranges during late dry/mid wet sea s on 10.64 2.86 hectares, than the dry season 3.20 1.02 hectares. Males had larger home ranges than females, 23.89 2.36 ha compared to 5.94 1.34 ha in the late dry/mid wet, with no difference in the dry season. Strauss et al. (2008) VHF & GPS Crocodylus niloticus 15 (13 VHF, 2 GPS) Flag Boshielo Dam, Mpumalanga, South Africa Showed not to mount radio transmitters on animals' tails with 80% failure, and 60 % brok e off of tail.
41 Source Tracking Method Species N Location Findings Subalusky et al. (2009) VHF Alligator mississipiensis 21 Ichauway, Baker County, GA, USA Sub adult animals showed movement overland to wetlands and creek areas, some remained where capture d. One out of three adult females stayed in wetland of capture. The other two moved from the creek to wetlands for 1 3 months then back to the creek. All adult males stayed in the creek or river of capture with no movement overland. Lang and Whitaker (20 10) VHF Gavialis gangeticus 10 Chambal River, India Seasonal movements averaged 9.6 km, but had relatively short transits. Animals had individually distinct residency patterns. Rosenblatt and Heithaus (2011) Acoustic Alligator mississipiensis 16 Shark Ri ver Estuary, Everglades National Park, FL, USA Adult male alligators show individual movement patterns 13% remained in mid estuary habitat, 56% travelled from mid or upper estuary to downstream (more saline) habitat, 31% travelled from mid estuary to ups tream (less saline) habitat. Lance et al. (2011) Mark Recapture Alligator mississipiensis 286 Southwest Louisiana Distance moved ranged from 0.3 to 90.2 km. Smaller alligators moved greater distances than larger alligators and the longer the time between captures, the greater the distance moved. Wang et al. (2011) VHF Alligator sinensis 3 Anhui Province, China Animals had overlapping home ranges. Introduced male had slightly larger home range than introduced female. Campbell et al. (2013) GPS Crocodylu s porosus 12 Cape York Peninsula, Queensland, Australia Adult females animals showed long distance movement to nesting locations. Males exhibited two behavior patterns site fidelic and nomadic.
42 REFERENCE LIST Abbitt, R.J.F. and J.M. Scott. 2001. Exam ining differences between recovered and declining endangered species. Conservation Biology. 15:1274 1284. Bates, B., M. Maechler, B. Bolker, S. Walker. 2013. Linear mixed=effects models using Eigen and S4. R package version 1.0 5. Available: http://cran.r project.org/ package = lme4. Beyer, H.L. (2012). Geospatial Modelling Environment (Version 0.7.2.1). (software). URL: http://www.spatialecology.com/gme. Brandt, L.A., F.J. Mazzotti, J.R. Wilcox, P.D. Barker Jr., G.L. Hasty, and J. Wasilewski. 1995. Status of Crocodylus acutus at a power plant site in Florida. Herpetological Natural History 3:29 36. Brien, M.L., M.A. Read, H.I. McCallum, G.C. Grigg. 2008. Home range and movements of radio tracked estuarine crocodil es ( Crocodylus porosus ) within a non tidal waterhole. Wildlife Research. 35:140 149. Brien, M.L., G.J.W. Webb, C. Manolis, G. Lindner, and D. Ottoway. 2010. A Method for Attaching Tracking Devices to Crocodilians. Herpetological Review. 41:305 308. Burt, W .H. 1943. Territoriality and home range concepts as applied to mammals. Journal of Mammology. 24:346 352. Cherkiss, M.S., M.W. Parry, and F.J. Mazzotti. 2007. Crocodylus acutus (American Crocodile). Migration. Herpetological Review. 38:72 73. Cott, H.B. 19 71. Parental care in the Crocodilia, with special reference to Crocodilia niloticus IUCN Publication, New Series, 32:166 180. Dahle B, O. Stoen, and J.E. Swenson. 2006. Factors influencing home range size in subadult bears. Journal of Mammology. 87:859 86 5. Easterling, D.R., G.A. Meehl, C. Parmesan, S.A. Changnon, T.R. Karl, and L.O. Mearns. 2000. Climate extremes: observations, modeling, and impacts. Science 289:2068 2074. Ebersole, J.P. 1980. Food density and territory size: An alternative model and a t est on the reef fish Eupomacentrus leucostictus The American Naturalist. 115:492 509. Egler, F.E. (1952). Southeast saline Everglades vegetation, Florida and its management. Vegetatio 3 :213 265. ESRI. 2011. ArcGIS Desktop: Release 10. Redlands, CA: Envir onmental Systems Research Institute
43 Fortin, D., H.L. Beyer, M.S. Boyce, D.W. Smith, T. Duchesne, and J.S. Mao. 2005. Wolves influence elk movements: behavior shapes a trophic cascade in Yellowstone National Park. Ecology. 86:1320 1330. Gaby, R., M.P. McMah on, F.J. Mazzotti, W.N.Gillies, and J.R.Wilcox. 1985. Ecology of a Population of Crocodylus acutus at a Power Plant Site in Florida. Journal of Herpetology. 19:189 198. Gaidet, N., J. Cappelle, J.Y. Takekawa, D.J. Prosser, S.A. Iverson, D.C. Douglas, and S .H. Newman. 2010. Potential spread of highly pathogenic avian influenza H5N1 by wildfowl: dispersal ranges and rates determined from large scale satellite telemetry. Journal of Applied Ecology 47 :1147 1157. Gehrt, S.D. and E.K. Fritzell. 1997. Sexual diff erences in home ranges of raccoons. Journal of Mammology. 78:921 931. Goodwin, T.M., and W.R. Marion. 1979. Seasonal activity ranges and habitat preferences of adult alligators in a north central Florida lake. Journal of Herpetology 13:157 164. Green, T.W ., D.H. Slone, E.D. Swain, M.S. Cherkiss, M. Lohmann, F.J. Mazzotti, and K.G. Rice. 2013. Evaluation effects of Everglades Restoration on American Crocodile populations in South Florida using spatially explicit, stage based population model. Wetlands. 1 12 Cambell, H.A., R.G. Dwyer, T.R. Irwin, and C.E. Franklin. 2013. Home range utilization and long range movement of estuarine crocodiles during the breeding and nesting season. PLoS ONE 8(5): e62127. doi:10.1371/journal.pone.0062127. Hutton, J. 1989. Movem ents, home range, dispersal, and the separation of size classes in Nile crocodiles. American Zoologist. 29 :1033 1049. Joanen, T., and L. McNease. 1970. A telemetric study of nesting female alligators on Rockefeller Refuge, Louisiana. Proceedings of the Ann ual Conference of the Southeastern Association of Game and Fish Commissioners. 24 :175 193. Kay, W.R. 2004. Movements and home ranges of radio tracked Crocodylus porosus in the Cambridge Gulf region of Western Australia. Wildlife Research. 31 :495 508. Kush lan, J.A. and M.S. Kushlan. 1979. The function of nest attendance in the American alligator. Herpetologica. 23:1 7. Kushlan, J.A. and F.J. Mazzotti. 1989a. Historic and Present Distribution of the American Crocodile in Florida. Journal of Herpetology. 21:1 7. Kushlan, J.A. and F.J. Mazzotti. 1989b. Population Biology of the American Crocodile. Journal of Herpetology. 23:7 21.
44 Kuznetsova, A. 2012. Tests for random and fixed effects for linear mixed effects models (lmer objects of lme4 package). R package ver sion 2.0 3. Available: http://cran.r project.org/ package = lmerTest Lopez, R., and J.P. Malarde, 2011. Improving ARGOS Doppler location using Kalman filtering. Ramonville Saint Agne, France Lorenz, J.J., and J.E Serafy, J. E. 2006. Subtroprical wetland fish assemblages and changing salinity regimes: Implications for everglades restoration. Hydrobiologia 569 : 401 422. Lorenz, J.J., C.C. McIvor, G.V. Powell, and P.C. Frederick. 1997. A drop net and removable walk way used to quantitatively sample fishes over wetland surfaces in the dwarf mangroves of the southern Everglades. Wetlands 17: 346 359. Martell, M.S., C.J. Henny, P.E. Nye, and M.J. Solensky. 2001. Fall migration routes, timing, and wintering sites of Nort h American Ospreys as determined by satellite telemetry. The Condor 103 :715 724. Mao, J.S., M.S. Boyce, D.W. Smith, F.J. Singer, D.J. Vales, J.M. Vore, and E.H. Merrill. 2005. Habitat selection by elk before and after wolf reintroduction in Yellowstone N ational Park. Journal of Wildlife Management. 69:1691 1707. Mazzotti. F.J. 1983. Ecology of Crocodylus acutus in Florida. Ph.D. Thesis. Pennsylvania State University, University Park, Pennsylvania. Mazzotti. F.J. 1989. Factors affecting the nesting success of the American crocodile, Crocodylus acutus in Florida Bay. Bulletin of Marine Science. 44:220 228. Mazzotti. F.J. 1999. The American Crocodile in Florida Bay. Estuaries. 22:552 561. Mazzotti, F.J., G.R. Best, L.A. Brandt, M.S. Cherkiss, B.M. Jeffery, a nd K.G. Rice. 2009. Alligators and crocodiles as indicators for restoration of Everglades ecosystems. Ecological Indicators. 9:137 149. Mazzotti, F.J., L.A. Brandt, P.E. Moler, and M.S. Cherkiss. 2007a. American Crocodile ( Crocodylus acutus ) in Florida: Re commendations for Endangered Species Recovery and Ecosystem Restoration. Journal of Herpetology. 41:121 131. Mazzotti, F.J., M.S. Cherkiss, M.W. Parry, K.G.Rice. 2007b. Recent Nesting of the American Crocodile ( Crocodylus acutus ) in Everglades National Par k, Florida, USA. Herpetological Review. 38:285 289. Mazzotti, F.J. and M.S. Cherkiss. 2003. Status and Conservation of the American Crocodile in Florida: Recovering an Endangered Species While Restoring an Ecosystem. University of Florida, Ft. Lauderdale R esearch and Education Center. Tech. Rep. 2003. 41 pp. McNab, B.K. 1964. Bioenergetics and the determination of home range size. The American Naturalist. 97:133 140.
45 Meehl, G. A., J.M. Arblaster, and C.Tebaldi. 2005. Understanding future patterns of increas ed precipitation intensity in climate model simulations. Geophysical Research Letters 32 L18719. Miller Rushing, A.J., T.L. Lloyd Evands, R.B. Primack, and P. Satzinger. 2008. Bird migration times, climate change, and changing population sizes. Global Ch ange Biology 14 :1959 1972. Millspaugh, J., and J.M. Marzluff. (Eds.). (2001). Radio tracking and animal populations Academic Press. Moler, P. 1992. American Crocodile Population Dynamics. Final Report. Study Number:7532. Bureau of Wildlife Research Flori da Game and Fresh Water Fish Commission. Morea, C. R., K.G. Rice, H. Percival, and S. Howarter. 2000. Home range and daily movement of the American alligator in the Everglades. In IUCN The World Conservation Union. Crocodiles, Proceedings of the 15th Worki ng Meeting of the Crocodile Specialist Group. Gland, Switzerland, IUCN. 486. Munoz, M.D.C., and J. Thorbjarnarson. 2000. Movement of captive released Orinoco crocodiles ( Crocodylus intermedius ) in the Capanaparo River, Venezuela. Journal of Herpetology. 34 :397 403. Odum, E.P. and E.J. Kuenzler. 1955. Measurement of territory and home range size in birds. The Auk. 72:128 137. Ogden, J.C. 1978. Status and Nesting Biology of the American Crocodile, Crocodylus acutus (Reptilia, Crocodilidae) in Florida. Journal of Herpetology. 12:183 196. Ogden, J.C. and C. Singletary. 1973. Night of the crocodile. Audubon 75:32 37. Pejchar, L., K.D. Holl, J.L. Lockwood. 2005. Hawaiian honeycreeper home range size varies with habitat: implication for Native Acacia koa forestry Ecological Applications. 15:1053 1061. Platt, S.G., J.B. Thorbjarnarson T.R. Rainwater, and D.R. Martin. 2013. Diet of the American Crocodile ( Crocodylus acutus ) in Marine Environments of Coastal Belize. Journal of Herpetology. 47:1 10. R Core Team (20 13). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3 900051 07 0, URL http://www.R project.org/ Rahmstorf, S. 2007. A semi empirical approach to projecting future sea level rise. Science. 315:368 370. Read, M. A., J.D. Miller, I.P. Bell, and A. Felton, A. 2005. The distribution and abundance of the estuarine crocodile, Crocodylus porosus in Queensland. Wildlife Research 31: 527 534.
46 Read, M.A. G.C. Grigg, S.R. Irwin, D. Shanahan, and C.E. Franklin. 2007. Satellite tracking reveals long distance coastal travel and homing by translocated estuarine crocodiles. PLos One. 2: 949. Roberts, H.H., T. Whelan, and W.G. Smith. 1977. Holocene sedimentation at Cape Sable, South Florida. Tidal Sedimentation. 18:25 60. Rodda, G.H. 1984a. Homeward paths of displaced juvenile alligators as determined by radio telemetry. Behavioral Ecology and Sociobiology. 14 :241 246. Rodda, G.H. 1984b. Movements of juvenile Am erican crocodiles in Gatun Lake, Panama. Herpetologica. 40 :444 451. Rootes, W. L., and R.H. Chabreck. 1993. Reproductive status and move ment of adult female alligators. Journal of Herpetology. 27 :121 126. Rosenblatt, A.E., and M.R. Heithaus. 2011. Does v ariation in movement tactics and trophic interactions among American alligators create habitat linkages? Journal of Animal Ecology 80 :786 798. Ross J. P. 1998. Crocodiles: status survey and conservation action plan. 2 nd Edition. Published online at: http://www.iucncsg.org/ph1/modules/Publications/action_plan1998/plan1998a.htm Ruts, C., and G.C. Hays. 2009. New frontiers in biologging science. Biological Letters. 5:289 292. Seaman, D.E. and R.A. Powell. 1996. An evaluation of the accuracy of kernel density estimators for home range analysis. Ecology 77 :2075 2085. Sulok, M., N.A. Slade, and T.J. Doonan. 2004. Effects of supplemental food on movements of cotton rats ( Sigmodon hispidus ) in Northeastern Kansas. Journal of Mammology. 85:1102 1105. Taylor, D. 1984. Management implications of an adult female alligator telemetry study. In Proceedings of the Annual Conference of the Southeastern Association of Fish and Wild life Agencies 38:221 227. Thomas C.D., A. Cameron, R.E. Green, M.Bakkenes, L.J. Beaumont, Y.C.Collingham, B.F.N. Erasmus, M.F. de Siqueira, A. Grainger, L. Hannah, L. Hughes, B. Huntley, A.S. van Jaarsveld, G.F. Midgley, L. Miles, M.A. Ortega Huerta, A. T Peterson, O.L. Philips, and S.E. Williams. Extinctino risk from climate change. Nature. 427:145 148. Thorbjarnarson, J., X. Wang, S. Ming, L. He, Y. Ding, Y. Wu, and S.T. McMurry. 2002. Wild populations of the Chinese alligator approach extinction. Biolo gical Conservation 103 :93 102.
47 Tilman, D., R.M. May, C.L. Lehman, and M.A. Nowak. 1994. Habitat destruction and the extinction debt. Nature. 371:65 66. Tufto, J. R. Andersen, and J. Linnell. 1996. Habitat use and ecological correlates of home range size i n a small cervid: the roe deer. Journal of Animal Ecology. 65:715 724. Tucker, A.D., C.J. Limpus, H.I. McCallum, and K.R. McDonald, 1997. Movements and home ranges of Crocodylus johnstoni in the Lynd River, Queensland. Wildlife Research. 24 :379 396. U.S. A rmy Corps of Engineers, 1999. CERP Central and Southern Florida Comprehensive Review Study. Final Integrated Feasibility Report and Programmatic Environmental Impact Statement, Jacksonville District, U.S. Army Corps of Engineers, Jacksonville, FL. USFWS (U nited States Fish and Wildlife Service). 1975. Federal Register 40:44149. USFWS (United States Fish and Wildlife Service). 2007. Federal Register 72:13027 13041. Webb, G.J.W., and H. Messel. 1978. Movement and dispersal patterns of Crocodylus porosus in so me rivers of Arnhem Land, northern Australia. Australian Wildlife Research. 5 :263 283. Wolf, J.O. 1985. The effects of density, food, and interspecific interference on home range size in Peromyscus leucopus and Peromyscus maniculatus Canadian Journal of Z oology. 63:2657 2662. Worton, B.J. 189. Kernel methods for estimating the utilization distribution in home range studies. Ecology. 70:164 168.
48 BIOGRAPHICAL SKETCH Jeffrey S. Beauchamp was born in Fairfax, Virginia, and spent his childhood in the subu rbs of the District of Columbia and San Francisco digging holes in the backyard of his After graduating from high school, Jeff followed another childhood passion and bec ame a firefighter in the U.S. Army. After serving four years, he completed his undergraduate degree at the University of Virginia. After graduating and largely due to one amazing class, Jeff began his career in wildlife management. He traveled to Hawaii Arkansas, Georgia and California before being employed at the University of Florida. This is where Jeff caught the bug, so to speak. He wanted to be a crocodilian biologist. His time in Florida working with Frank Mazzotti and Kristen Hart with the USGS has taken him to Brazil, Jam aica and Cuba and eventually le d to his acceptance into the University of Florida m crocodilians.