Group Title: Circular
Title: A "Bear-proof" fence
Full Citation
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 Material Information
Title: A "Bear-proof" fence F.A. Robinson
Series Title: Circular
Physical Description: 4 p. : ill. ; 28 cm.
Language: English
Creator: Robinson, Frank A
University of Florida -- Agricultural Extension Service
Publisher: Florida Agricultural Extension Service, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1965
Subject: Fences -- Florida   ( lcsh )
Beehives -- Protection -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
General Note: Cover title.
General Note: "June 1965."
 Record Information
Bibliographic ID: UF00084361
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 80914839

Full Text
June 1965
Circular 289

A "Bear-Proof" Electric Fence
F. A. Robinson


Florida Agricultural Extension Service
University of Florida

A "Bear-Proof" Electric Fence
F. A. Robinson, Assistant Apiculturist
Florida Agricultural Experiment Station

Bears destroy thousands of dollars worth of bee colonies
and honey in Florida every year. In addition to these direct
losses, beekeepers are kept from using thousands of acres of
good bee pasturage because the presence of bears makes it too
hazardous to put bees in these areas.
Generally bears are most troublesome in the state's national
forests where some of the best bee pasturage is found. Since
many of these areas are game preserves and the destruction of
wildlife is prohibited or strictly regulated, beekeepers have long
sought an inexpensive, but reliable, method of protecting their

Electric Fence
An electric fence including a wire mat around the outside
perimeter of the enclosure is the best method of preventing bears
from destroying bee colonies. To determine the effectiveness of
electric fences, experiments with different types of fence con-
struction were conducted for a three year period.
To be suitable for use in commercial beekeeping operations,
an electric fence must meet several specifications. First, it must
be easy and relatively cheap to construct. Second, the fence must
be dependable enough to remain in operating condition for
several weeks at a time. Third, since bears are usually most
troublesome in wilderness areas where electric power is not
available, the fence must be designed to operate satisfactorily
when charged with a battery powered fence controller.
Location of the electric fence is important in protecting
colonies of bees. Select a site where there are no overhanging
trees. Limbs or moss falling across the wires may render the
fence inoperable. It is quite common for bears to climb trees
and then drop down inside the fence.
The most satisfactory fence is constructed from standard
woven wire, 48 inches high. The fence is fastened to the posts
so that the bottom edge is at ground level. Place a strand of
barbed wire eight inches above the ground, and a second strand
eight inches above the top of the woven wire. Securely fasten
the barbed wires to heavy-duty screw-on insulators, and connect
the wires to the output side of the fence controller. Ordinary
nail-on insulators are not satisfactory since they will not with-

stand the strain when the barbed wire is stretched tight enough
to prevent being short circuited to the other parts of the fence.
In areas of light sandy soils a bear has little or no difficulty
in digging under most fences. Solve this problem by installing
a wire mat on the ground around the outside of the fence. Make
the mat from any type of heavy fence wire. It must be fastened
securely to the fence posts and to short posts set along the outer
edges. Mats 18 inches wide prevent bears from digging under
the fence.

Electric Wiring
The common "single wire" type fence construction, which
depends on soil conductivity for a complete circuit, is not satis-
factory for a bear fence. With their thick hair covering, bears
are quite well insulated. Light sandy soils, especially when dry,
are poor conductors. To assure maximum shocking power, the
woven wire on the posts and the wire mat around the fence
should be connected to the ground terminal of the fence con-
troller. Solder all connections to avoid poor electrical contact
which might be caused by rust or corrosion.

Electric Controllers
Regardless of how strong and well built a fence may be,
it will not provide protection against a determined bear unless
it is electrified with a sufficiently powerful fence controller.
When electricity is available, any of the more powerful con-
trollers designed for 110-volt operation are satisfactory.
A transistorized controller designed to operate with a 6-volt
battery, yet equalling or exceeding the output of most controllers
designed to operate from a 110-volt power supply, was used for
two years during this research. It was found to have shocking
power adequate to stop all attempts by bears to get through the
None of the other types of battery powered controllers
manufactured by three different companies delivered a sufficient-
ly strong shock when operated from a 6-volt battery, and bears
went over, under or through the fences. When output of the con-
trollers was doubled by using 12-volt batteries, all were effective.
Even though all controllers operated satisfactorily at the
higher voltage, there is too much risk of mechanical failure of
the controller to recommend this practice. Examination of the
chargers after several months of operation at the higher volt-
ages disclosed that breaker points were badly burned, due to
excessive arcing. This could cause the points to stick, in which
case the controller would no longer operate.

Kill Weeds
To insure continued successful operation of the fence, it is
essential to prevent grass and weeds from contacting the
charged wires. This is especially important during rainy
weather, since the wet weeds can "short" the fence, and cause
battery failure. To prevent weed growth, apply a permanent
type weed killer to a three or four foot strip of soil under the
fence. Since most weed killers contain arsenic and are highly
toxic to honey bees, apply carefully, so the spray does not drift
and cause injury to the colonies.

Several fences, constructed according to the recommenda-
tions given in this circular, are being used with success by com-
mercial beekeepers in Florida. One of these is shown on the
cover of this circular. It was built at a cost of $209.10, and will
accommodate 55 colonies. The materials used and their costs are
given below.

42 Posts 7 Feet Long .---__--.__ -- .._.- .-- .-- .. ---- ----$12.60
1 Roll Hog Wire (For the Mat) ----------- -----_--------_ ..._._ 14.00
1 Roll 4 Prong Barbed Wire ---_--------------.--.... .....__.... 5.00
1 Roll 48" Woven Wire -------------- 10.00
Screw-On Insulators -_.__ -- -- ---------- 14.00
Lumber, Brace Wire, Nails, etc. -__- __----_ ---- 10.00
Battery (6-volt Automobile) ----.. -------1-- .00_-----...........__--- 15.00
Fence Controller -------- ------.......- -- 47.50
Labor (54 hours) -...---...---... ---- _------.....-- ---- 81.00

TOTAL _--.. $209.10

Some beekeepers place their colonies on elevated platforms
for protection. Platforms, when properly constructed, are bear-
proof; but they are not used extensively. The main objection
to platforms is the difficulty of routine management operations
on an elevated platform. They are also very expensive to build.

Other beekeepers have tried protecting their colonies by
strapping them together with steel tape or clamping them to-
gether with heavy timbers, but this method is often vulnerable
to a very determined bear.

(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida,
Florida State University and United States Department of Agriculture, Cooperating
M. O. Watkins, Director

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