U. S. Department of the Interior BLM-Alaska Open File Report 97 

Bureau of Land Management BLM/AKIST-04/016+6511 +020 

August 2004 

Alaska State Office 

222 West 7th Avenue, #13 

Anchorage, Alaska 99513 

Deterring Bears from Work Areas and Facilities 

Tim Craig 
The BlM Mission 

The Bureau of Land Management sustains the health, diversity and productivity of the public lands for the use 

and enjoyment of present and future generations. 

Cover Photo 

Close-up of alternating wires on bear safety fence installed at Seven Mile Administrative Site, Dalton Highway, 

Alaska. 

Authors 

Tim Craig is a wildlife biologist with the BLM Northern Field Office in Fairbanks, Alaska. 

Disclaimer 

The mention of trade names or commercial products in this report does not constitute endorsement or recommendation for use by the federal government. 

Open File Reports 

Open File Reports issued by the Bureau of Land Management-Alaska present the results of inventories or other 

investigations on a variety of scientific and technical subjects that are made available to the pUblic outside the 

formal BLM-Alaska technical publication series. These reports can include preliminary or incomplete data and 

are not published and distributed in quantity. 

The reports are available while supplies last from BLM External Affairs, 222 West 7th Avenue #13, Anchorage, 

Alaska 99513 and from the Juneau - John Rishel Minerals Information Center, 100 Savikko Road, Mayflower 

Island, Douglas, AK 99824, (907) 364-1553. Copies are also available for inspection at the Alaska Resource 

Library and Information Service (Anchorage), the USDI Resources Library in Washington, D. C., various libraries 

of the University of Alaska, the BLM National Business Center Library (Denver) and other selected locations. 

A complete bibliography of all BLM-Alaska scientific reports can be found on the Internet at: 

http://www.ak.blm.gov/affairs/sci~rpts.html. Related publications are also listed at 

http://juneau.ak.blm.gov. 
Deterring Bears from Work Areas and Facilities 

Tim Craig 

BlM-Alaska Open File Report 97
 

August 2004
 

u. S. Department of the Interior 

Bureau of Land Management 
ABSTRACT 

Bears are an important component of Alaska's ecosystems and 

are greatly valued by the public. Nonetheless, every year people and 

bears come into conflicts that sometimes result in injury or death. It is 

incumbent upon public employees to attempt to avoid these incidents. 

The Bureau of Land Management's Northern Field Office oversees 

more than 60 million acres of land in 5 administrative units in interior 

Alaska. Bears inhabit almost this entire area. Because land management activities require BLM personnel to spend time in remote areas of 

interior Alaska, it is necessary for them to exercise practices that deter 

bears from permanent and temporary work areas and campsites. This 

document describes practical techniques to secure such areas to help 

avoid confrontations between BLM employees and bears. 

Author's note: Nonmetric units of measurement have been used 

throughout this report except where cited references utilized metric 

(SI) units. In these cases, approximate conversions to nonmetric units 

appear in brackets. 

ACKNOWLEDGMENTS 

Most of the information contained in this document was synthesized from material produced by other agencies. In particular we wish 

to acknowledge the following individuals, who shared information 

with us during preparation of this publication: Dick Shideler, Wildlife 

Conservation Division, Alaska Department of Fish and Game; Tom 

Smith, Biological Resources Division, USGS, Anchorage, Alaska; Eric 

Follmann, University of Alaska, Fairbanks, Alaska; Tom Hawkins, 

Region 6, US Forest Service; C. R. Wenger, Region 4, US Forest 

Service; and Mike Madel, Montana Department of Fish, Wildlife and 

Parks, Missoula, Montana. Dick Shideler reviewed an earlier version 

of this manuscript. 
CONTENTS
 

Abstract i 

Acknowledgments i 

Introduction 1 

Permanent Fences 1 

Chain Link Fences 1 

Electric Fences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Temporary Fences 3 

General Considerations 5 

Conductors 5 

Posts 5 

Grounding 5 

Gates 6 

Fence Controllers 7 

Safety 8 

Maintenance 8 

Problems 8 

Alternatives to Fences 8 

Propane Guns 8 

Alarms " 8 

Taste Aversion Conditioning 9 

Recommendations 9 

Permanent Facility 9 

Long-term Seasonal Camp 9 

Short-term Camp '.' 9 

Literature Cited 10 

FIGURES 

Figure 1. Oblique view of animal deterrent fence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Figure 2. Design of a typical electric fence used to protect crops and apiaries from Asiatic 

black bear depredation in Nagano Prefecture, central Japan, in 1997 and 1998 2 

Figure 3. Schematic of electric fence designed to deter bears 4 

Figure 4. Electric fence gate at the BLM's Seven Mile Administration Site . . . . . . . . . . . . . . . . . . . . . . . 6 

Figure 5. Schematic of suggested electric fence gate .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

TABLES 

Table 1. Manufacturer and Model of electric fence controls which meet the requirements of 

Northern Continental Divide Grizzly Bear Ecosystem Food Storage Special Order 8 

ii 
INTRODUCTION 

Every year bears and humans clash in Alaska. 

These clashes, whether they involve competition for 

hunter-killed big game animals or damage to cabins, 

often result in financial costs and the injury or deaths 

of humans and bears. Between 1985 and 1996 over 

1000 bears were destroyed in Defense of Life and 

Property instances in Alaska (Tom Smith, USGS, 

written comm.). As human presence in bear habitat 

increases in Alaska, clashes between bears and humans can be expected to increase as well. Bears are 

still found throughout Alaska, but recent declines 

in brown bear populations on the Kenai Peninsula 

(Schwartz et al. 1999) show that even in Alaska, 

increased human use of bears or their habitat can 

jeopardize the continued health of the species. 

The public is highly interested in conservation 

of bear populations. Brown bears in particular are 

valued for wildlife observation (Tituset al. 1999) and 

for the perception that the species typifies wilderness 

(Gard 1971). Sighting a bear of any kind is a high 

point for visitors to Alaska (Albert et al. 2001). 

Because of the public's interest in bears as a natural 

part of the Alaska biome, it is important that BLM 

employees endeavor to avoid confrontations that 

may result in the destruction of bears. 

Several bear-human interactions were reported in 

2001 on Bureau ofLand Management (BLM)lands 

administered by the Northern Field Office. During 

the fire season black bears boldly threatened Alaska 

Fire Service personnel on 3 separate occasions, 

causing the relocation of a small fire camp at one 

site. Later in the summer, construction inspectors 

shot and killed a black bear as it ransacked their 

camp trailer. In the fall, a brown bear clawed its way 

through the wall of a BLM cabin at the Seven Mile 

Administrative Site on the Dalton Highway. Once 

inside, the bear did over $4000 of damage. 

The following series of options can help BLM 

personnel to reduce the number of adverse bearhuman incidents around facilities and remote 

work areas. It must be stated at the outset of this 

discussion that bears are individualistic and possess varying degrees of persistence and ingenuity. 

Factors that can affect bear-human interactions 

include: 1) individual experience and success in 

obtaining human food elsewhere; 2) seasonal availability of natural foods; and 3) local shortage of 

natural foods, e.g., a berry crop failure. As a result, 

these recommendations, even if implemented properly, may not eliminate all bear-human interactions. 

Furthermore, it must be stressed that education and 

safe storage of food and garbage should always be 

a primary consideration in preventing bear-human 

incidents. 

PERMANENT FENCES 

One way to reduce adverse bear-human interactions around facilities is to construct permanent 

bear-resistant fences around living, cooking and 

working quarters. The initial cost of these fences is 

high and they are not aesthetically pleasing. Nonetheless, the amortized expense is considerably less 

than other options because the life of the fence is 

long and maintenance costs are low. 

Chain link. One of the best materials to use for 

a bear-resistant fence is chain link. Follmann and 

Hechtel (1990) recommend the use of such fences, 

based on experiences spanning several years during 

construction and subsequent use oftheTrans-Alaska 

Pipeline. 

These authors specify a 2.4 m [- 8 ft] high fence 

with an overhanging "barb arm" that is set at an 

oblique angle to the fence and holds 3 separated 

High 

~~~~~\

Electrically 

charged 

wires. 

Figure 1. Oblique view ofanimal deterrent 

fence. (Follman and Hechtel1990) 

1 
strands of barbed wire (Fig. 1). In addition to 

the above-ground fence, their design incorporates 

an apron of buried chain link on the outside of 

the structure to prevent bears from digging under the fence. This apron should be about 1.2 m 

[- 4 ft] wide and be constructed of an "L"-shaped 

piece of chain link that is 1.8 m ["'"" 6 ft] wide. One 

side of the "L" is attached to the bottom of the 

above-ground portion of the fence at ground level, 

while the rest descends vertically into the ground 

0.6 m [- 2 ft], then bends 90 degrees outward, 

forming a buried apron of chain link 1.2 m [- 4 ft] 

wide under the ground. 

Where a more secure fence is desired, or where 

a non-electric chain-link barrier fence has not been 

effective in deterring bears, two strands of electrified high-tensile- strength wire can be added to the 

outside of the fence by means of outriggers at 

0.3m[-1 ft] and 1.5 m[- 5ft 9 inches] above ground. 

Alternatively, a second, freestanding electric fence 

may be erected beyond the existing chain-link fence. 

In this case, the electric fence should be placed near 

enough the chain-link fence to ensure that the bear 

touches both the electric and the grounding chainlink fences simultaneously. 

It is important to consider soil type when erecting any permanent fence. In some areas the heaving 

action of frozen soils may expel posts by a process 

known as "frost-jacking." Where this problem is 

anticipated, special precautions should be exercised 

in installing fence posts. 

Electric fences. Electric fences have been used 

for decades to deter bears, including black, brown, 

and other species, from entering facilities (Davies 

and Rockwell 1986) and from raiding agricultural 

crops (Storer et al. 1938; cited in Huygens and 

Hayashi 1999, original not seen). Electric fences 

that are placed around facilities have the added 

benefit of carrying the message, "You are in bear 

country" - a reminder to people to use caution 

when working in the area, disposing of garbage, or 

storing food. Properly constructed electric fences 

have proven very effective in deterring bears from 

permanent facilities; failures have usually resulted 

from improper maintenance. However, bears' thick 

fur and broad, leathery footpads make them poor 

conductors of electricity, so it is important to design 

the fence specifically to deter bears (Dick Shideler, 

Wildlife Conservation Division, Alaska Department 

of Fish and Game, written comm.). 

Various permanent electric fence configurations 

have been used with success for both black and 

brown bears. Huygens and Hayashi (1999) used 

Insultimber corner post 

for the main fence. 

Main fence: 4 lines 

of turbo wire. 

30 

23 

23 

Main fence posts 

(treadins or fiber glass).-------­......JI 

23 

23 

Trip fence: one line 

Trip fence post of turbo tape. (fiber glass). 

Figure 2. Design ofa typical electric fence used to protect crops and apiaries from Asiatic black 

bear depredation in Nagano Prefecture, central Japan, in 1997 and 1998. All lines were positively 

charged ( +). All units in em. (Huygens and Hayashi 1999) 

2 
electric fences to keep Asiatic black bears (Ursus 

thibetanus) away from sweet corn fields in Japan 

(Fig. 2). These researchers constructed fences using 

4 electro-plastic or "polywires" (woven plastic and 

stainless steel wire) set about 9 inches apart. The 

total fence height was about 3 feet from the ground. 

A fifth line, called a "trip fence," was placed outside 

of the enclosure about 12 inches in front of the main 

fence. Wide plastic webbing [-112 to I 1/2 inches 

wide] with stainless steel wires woven into the fabric 

was used for this conductor. All of the conductors 

(wires) were white to increase visibility. The fence 

was held up by Gallaghertm Insuitimber corner posts 

(GallagherPower Fence Systems, NewZealand) and 

fiberglass line posts. 

Because the above study took place in an agricultural area where soils were moist, all of the fence 

wires were positive conductors. However, the dry, 

gravely, or frozen soils common to Alaska are a 

poor conducting media and require a different fence 

configuration. Smith (1995) suggests that in these 

areas a permanent electricfence should be comprised 

of 8 wires with alternating ground and hot wires. 

The bottom wire should be a ground wire, and wire 

spacing up the fence should be at 2, 8, 14, 20,28, 36, 

44, and 54 inches as measured from the'ground. The 

arrangement of alternating ground and hot wires 

ensures that when a bear pushes through the fence, 

the animal will simultaneously touch both a positive 

and a ground wire. Like-charged conductors should 

be connected together at each corner of the fence. 

Light, fiberglass poles can be used for line posts, but 

larger diameter fiberglass or treated wooden posts 

should be used for corners. Corner posts must be set 

at least 3 feet in the ground and adequately braced 

to withstand the strain of the tension placed on the 

conductingwires (Fig. 3). Others have suggested the 

use of high-tensile-strength, smooth stainless steel 

wires (12.5 gage) that are tensioned to between 200 

and 250 lbs (Dick Shideler, Wildlife Conservation 

Division, Alaska Department of Fish and Game, 

written comm.). The stainless steel wires are longerlasting than polywires, and tight wires more effectively push into the bear's fur as the animal strains 

against the fence. 

"Jumpers" and "climbers" should be anticipated. 

Fences must be constructed so bears do not have 

"takeoff" points (elevated spots from which to 

jump). If trees are used as posts, conductors should 

be placed on the outside of the tree trunk to preclude bears climbing the tree and jumping into the 

compound (Dick Shideler, Wildlife Conservation 

Division, Alaska Department of Fish and Game, 

written comm.). Barbed wire is not recommended 

on these fences because jumping and climbing 

bears can get caught up in the wire and pull down 

the entire fence with their weight. Bears investigate 

low spots in a fence, so particular attention must be 

paid to construction and maintenance of fences at 

these locations. 

A perforated, metal can of oozing sardines can 

be attached to a positive conductor on the fence to 

ensure that a stubborn bear's first experience with an 

electric fence is unpleasant (Smith 1995). However, 

because it is unwise to attract bears to a facility 

with food, this tactic should only be attempted 

after bears have become a nuisance in the area and 

after checking with state and/or federal regulations, 

which may preclude this aversive training. 

TEMPORARY FENCES 

The most effective method to deter bears around 

temporary facilities is the electric fence. Such fences 

have effectively protected people and property from 

both black and brown bears at remote camps and 

work sites. 

Temporary electricfences have beenusedwith great 

success along the Rogue River, a National Wild and 

Scenic River in Oregon, to prevent black bears from 

consuming food brought on recreational float trips 

(Tom Hawkins, US Forest Service, pers. comm.). 

There, the US Forest Service seasonally erects and 

maintains several 12 ft by 12 ft, electric-fenced enclosures along the river. These enclosures are about 

40 inches high and are comprised of 6 strands of 

white, electro-plastic wire spaced 6 inches apart. 

Positive and ground wires alternate up the fence. 

The substrate along the river is rocky. Nevertheless, because the water table is high, only a single, 

2-foot-long grounding stake is required. In locations 

where ground rods can't be driven into the ground, 

they are buried horizontally in hand-dug trenches. 

Freestanding posts made of plastic pipe mounted 

on round metal bases are used where enclosures are 

located on solid rock. 

Similarly, biologists for the Salmon National 

Forest in Idaho have successfully used electric 

fences to deter black bears around campsites. They 

used a minimum of 4 smooth wires stretched tight 

and placed no more than 10 inches apart (C. R. 

Wenger, US Forest Service, pers. comm.). Again, 

3 
Wire around outside of tree. 

Connect all
 

like-charged
 

wires at
 

the corners.
 

Supplemental 

grounding _ ...... I 

rod at lowspot. 

Conductor height above ground. 

54" 

44" 

36" 

28" 

20" 

14" 

8" / 2" 

/ 

JI 

( 

I 

I 

I '\ Fiberglass or steel-line
 

I posts to maintain spacing.
 

Figure 3. Schematic of electric fence designed to deter bears. 

4 
this configuration necessitated good corner bracing 

and an adequate number of line posts to maintain 

the wire spacing between spans. 

While the above agencies and others (Gard 1971) 

have found that fewer wires can effectively deter 

bears, authorities in Alaska recommend using 7 

conductors (Dick Shideler, Wildlife Conservation 

Division, Alaska Department of Fish and Game, 

written comm.). These fences should have alternating positive-negative conductorsof smooth steel 

or polywire. Alternatively, aircraft cable has also 

been successfully used as a conductor. The cable is 

stiffer and heavier than polywire but more durable. 

Any of these fences can be assembled in town and 

rolled up for easier transportation and setup at field 

locations. 

Regardless of the material used, the top conductor should be placed at least 48 inches above the 

ground. It can by made of electro-plastic ribbon to 

increase visibility. The conductors for this fence are 

recommended to be at 2, 8, 14,22, 30, 38, and 48 

inches above the ground. The lowest wire should be 

a ground wire, whichcan contact the soil if necessary. 

Again, the wires should be tensioned adequately 

to avoid shorts and to make a good connection in 

the fur of any animal pushing its head between the 

conductors. 

The special "Food Storage Order"issued for federal 

lands in the Northern Continental Divide Grizzly 

Bear Ecosystem (Special Order No. FI0-016L98; 

USDA, Forest Service, MissoulaMontana) describes 

electric fence systemsthat meet agency requirements 

for the storage of bear attractantslike horse feed and 

human food. The specifications for these temporary 

fences are similar to those recommended by the 

Alaska Department of Fish and Game as discussed 

above (48-inch-highfence, 7conductors, alternating 

polarity). However, there is one notable difference: 

the order requires that the top two wires both be 

positively charged. The order further specifies that 

the wires (either smooth steel wires or polywires 

containing at least 6 strands of stainless steel wire) 

should be 6 to 10 inches apart and that the bottom 

ground wire should be no more than 2 inches off 

the ground. 

GENERAL CONSIDERATIONS 

Conductors. Electro-plastic (polywire) conductors, 

which are adequate for temporary fences, come in a 

variety of configurations, including ribbons or tapes 

of different widths and round "wires" of varying 

thicknesses and strengths. These conductors also 

come in different colors, such as high-visibility white 

and orange. The advantages of polywire conductors 

over high-tensile-strength steel wire include high visibility, elasticity, and light weight, a consideration 

where remote, fly-in camps are to be protected. 

However, most authorities recommend the use of 

high-tensile-strength 12.5-gage wire because it can 

be tensioned adequately and is resistant to environmental degradation. 

While alternating polarity is the best configuration for most applications, Smith (1995) suggests 

that where a temporary fence is located in a good 

grounding area (e.g., a moist soil area) all of the 

conductors may be positive. 

Posts. Temporary fences can be suspended from 

a variety of post types, including plastic, fiberglass, 

or steel. However, if steel posts are used, special 

attention must be paid to maintenance to avoid 

grounding the system; even songbird droppings can 

circumvent the insulator and ground the conductors to the steel posts. Regardless of post type, the 

corners must be braced to withstand the stress of 

tensioning the wires, and line posts should be placed 

so as to maintain fence height and spacing (sometimes as close as 8feet apart). Smith (1995) indicates 

that on portable systems, "wand"-type fiberglass 

poles that are just under 1/2 inch in diameter and 

about 5 ft long may be spaced between 15 to 25 

ft apart. He suggests the use of screw-on plastic 

insulators on these small poles. On bigger diameter 

fiberglass poles (2" diameter) or wood posts used for 

corners, he specifies the use of pin lock insulators. 

In any event, where trees are used as posts, the wires 

should run around the outside of the trunk so that 

bears cannot climb the trees and jump down into 

the compound. 

Yukon Flats National Wildlife Refuge uses 4 or 5 

strands ofpolywire to construct bear-prooffences at 

campsites. Refuge workers suspend the conductors 

from posts made of light conduit and from trees 

to which they nail insulators. In some places they 

have even used duct tape to attach the conductors 

to willows (Perry Grissom, pers. corom.). 

Grounding. Nearly every authority has identified 

grounding as the single most important part of a 

properly constructed electric fence. Where soilmoisture is adequate, groundingfor a temporary fence can 

be accomplished with as little as 2 ft of galvanized 

steel rod buried in the ground. However, where the 

5 
ground is dry, rocky, or frozen, grounding the fence 

can be a challenging problem. Precautions must be 

taken to adequately ground each fence in anticipation of the range of environmental conditions that 

might be encountered throughout the season. Dick 

Shideler (Wildlife Conservation Division, Alaska 

Department of Fish and Game, written comm.) and 

Smith (1995) both suggest locating ground rods at low 

spots in the fence, where they are most likely to be 

nearest the water table in all seasonal conditions. 

A minimum of three 1.6 em [5/8 inch] galvanized 

steel or copper grounding rods are suggested for 

most permanent fences. All three rods should be 

driven into the ground to a depth of 2.4 m [8 ft], 

placed about 3m [10ft] apart, and connected to each 

other with 12.5-gage wire and ground clamps. If it 

is not possible to drive the rods in vertically, they 

can be laid horizontally in trenches dug 2 ft deep. It 

is important to use special grounding clamps when 

connecting wires to the grounding rods, so that the 

metals bite into each other, resulting in a good connection. Itis also important to ground the fence and 

controller separately. 

Where it is necessary to build a fence around a 

large camp or facility, multiple ground rods should 

be placed along the fence at intervals. Different authorities have suggested different distances at which 

these rods should be placed, varying from every 150 

m [492ft] (Smith 1995) to every 307 m [1000ft] (Dick 

Shideler, Wildlife Conservation Division, Alaska 

Department of Fish and Game, written comm.). 

However, it should be remembered that generally 

"more is better" when it comes to grounding electric 

fences. In any event, each rod should be connected 

to every negative conductor. Where soil moisture 

allows the use of all positively-chargedconductors, a separate wire can be run from the negative 

terminal on the controller along the ground to the 

ground rod(s). 

Gates. Smith (1995) points out that gates are often 

the weak point in fence designs becausetheymust be 

secure enough to block bears but still allow people 

easy entry. He suggests swinging gates with attached 

outriggers of electric wire for wide openings (e.g., 

vehicle gates) and spring-handled gates (plastic or 

no-carbon rubber handles) for temporary or small 

gates. On the Rogue River, the US Forest Service 

uses simple wire gates with individual, springloaded plastic handles hooked on each conductor 

(Tom Hawkins, Region 6, US Forest Service, pers. 

comm.). They also install a switch outside of the 

fence so the electricity to the gate can be shut off 

while it is opened. 

In 2001 the BLM Alaska Fire Service constructed 

an electric fence around the Seven Mile Administrative Site facility on the Dalton Highway (Fig. 4). The 

gate was constructed by stretching the conductors 

across the gate opening to a single, fiberglass rod. 

This rod was in turn connected to the gatepost on the 

opposite side of the gate with two wire "bails," one 

at the top and one at the bottom of the fence (Fig. 

5). To open this gate, the fiberglass rod is tensioned, 

the top bail lifted off, and the entire gate pulled up 

out of the bottom bail and opened. 

Where continuous access to an area is necessary, 

for instance at landfills, an electrified cattle guard 

can be used (Smith 1995). The cattle guard is constructed of Schedule 40 steel pipes, placed side by 

side 9 inches apart (center to center) and laid on 

wood cribbing. The wood cribbing in turn rests 

on dry gravel, which acts as an insulator. The total 

width of the guard should be 2 m [6.6 ft]. This gate 

requires a more powerful charger than other bearFigure 4. Electric fence gate at BLMs Seven 

Mile Administration Site. 

6 
----- -----

F= 

(
 to--­

l--/" 

- -


-


I IIii -

Figure 5. Schematic ofsuggested electric fence 

gate. 

deterring fences, and "wings"of electric fence should 

be constructed on each side of the guard to prevent 

bears from crossing where the side fence and cattle 

guard meet. 

Fence controllers. Solar panels, rechargeable 

batteries and AC/DC chargers (ones that convert 

household AC current to DC current) can be used 

to power controllers to deter bears. Most fence 

manufacturers recommend using line current where 

possible. With line current the shape of the charge 

and consistent voltage provide more effective results 

when a bear contacts the fence, and there are no 

concerns about discharging batteries. All authorities 

stressed the importance of placing chargers, solar 

panels, and/or batteries inside the fenced area so 

bears cannot disrupt the power source. 

Several different makes of fence controllers (or 

chargers) can be used to deter bears. Comparison 

of the relative effectiveness of fence controllers is 

difficult because manufacturers measure the power 

their controllers produce in two different ways. 

Some manufacturers advertise the power of their 

products by listing the number of volts the units 

produce. Other manufactures rate the power of their 

controller's stored energy in joules. A few manufacturers list both values. 

Itis widely believed thatblackbears are more easily 

deterred by a weaker electrical charge. A controller 

delivering at least 6000 volts was thought to be adequate for black bears in some places in the western 

US (e.g., Salmon National Forest and elsewhere) 

or where the fence was temporary. On the Rogue 

River the US Forest Service uses a 7000-volt charger 

powered by a 12-volt RV battery (Tom Hawkins, 

Region 6, US Forest Service, pers. comm.). The 

battery lasts at least 3 months between recharges in 

thewarmsummer temperatures common to that part 

of Oregon. The agency does not use solar-powered 

chargers because of concerns that these expensive 

panelswould be stolen. Huygens and Hayashi (1999) 

energized the fences they used to deter Asiatic black 

bears with various chargers but preferred one that 

could deliver 1.6joules/6500-8000volts and could be 

powered by a 12-volt car battery or house current. 

A more powerful charger (circa 8000 volts) was 

usually indicated by authorities where brown bears 

were to be deterred orthe fence was permanent. Dick 

Shideler (Wildlife Conservation Division, Alaska 

Department of Fish and Game, written comm.) 

suggests the use of a charger that delivers at least 

8000 DC volts for permanent fences. In addition, 

he indicates that the charger should deliver low 

amperage and impedance and have an "on" time of 

approximately 0.0003 seconds with a rate of 40-50 

pulses perminute. For a temporary fence he suggests 

a charger delivering at least 6000 volts. 

Smith (1995) also suggests a charger delivering 

around 8000 DC volts in a short-duration pulse 

(i.e., 0.0004 seconds) with 0.75 seconds between 

pulses where brown bears might be encountered. 

He further indicates that solar panels work well if 

there is adequate day length. If not, he suggests the 

use of a 12-volt deep-cycle battery (80-90 amps) or 

even a truck battery. 

Montanawildlife officials in theNorthern Rockies 

have had good success deterring brown bears with 

fences charged by controllers producing as low as 0.5 

joulesof power(Mike Madel, MontanaDepartment 

of Fish, Wildlife and Parks, pers. comm.). There 

biologists constructed temporary fences around 

2 different horse carcasses in "core" brown bear 

habitats and powered these fences with a charger 

that produced 0.7 joules. The researchers then 

placed motion-sensitive cameras around these baits 

to record the number and species of bears visiting 

the sites and their reaction to the fences. The biologists recorded a total of seven visitations by brown 

bears, including several instances where it appeared 

that bears were shocked after touching the fences. 

None of the bears penetrated the enclosures. After 7 

days the researchers removed the fences, leaving the 

7 
horses carcasses unproteCted. Within 7 to 10 days, 

both carcasses had been entirely consumed by bears 

and other scavengers. 

The Special Food Order for the Northern Continental Divide Grizzly Bear Ecosystem specifies the 

use of controllers that produce a minimum stored 

energy of 0.7 joules with a minimum peak output 

voltage of 5000 volts and a rate of 40 shocks per 

minute. The Montana Technology and Development Center (MTDC) has published a list of manufacturers who produce controllers that meet these 

specifications (Table 1). 

Manufacturer Model 

Gallagher B75 

Gallagher B150 

Fi-Shock SS-7000 

Parrnak MAG-12SP 

Red Snap'r LIB-I5 

Speed-Rite SB 1000 

Speed-Rite SB 1500 

Speed-Rite SB 5000 

Table 1. Manufacturers and models of electric 

fence controllers that meet the requirements 

of Northern Continental Divide Grizzly Bear 

Ecosystem Food Storage Special Order (publication #9923-2321 MTDC) 

Safety. Modern fence chargers deliver shortduration shocks and generally are not a threat to 

people. However, two human safety issues should be 

noted in relation to the use of electric fences. First, 

there should always b e international warning signs 

installed along the fence line (Smith 1995). Second, 

it is imperative that the fence wires should never be 

attached directly to household AC current. 

Maintenance. Follman et al. (1980) point out that 

bears will test fences repeatedly. Therefore, electric 

fences must be checked often to repair broken wires 

and remove grounding vegetation. In addition, many 

people attach a small light to the fence to allow a 

quick visual inspection of the fence's operation. A 

good quality tester should be used to test line voltage and pulse frequency periodically. These tests 

should be conducted as far from the controller as 

possible. 

Problems. In dry soils where grounding is a problem, calciumchloride can be sprinkled on the ground 

to retainmoisture. Altematively, groundedwiremesh 

can be placed on or under the ground outside the 

fence to improve grounding and prevent bears from 

digging under the fence. 

ALTERNATIVES TO FENCES 

Propane guns. Propane guns have been used successfully to frighten brown bears away from bee 

yards and grain piles in the Northern Rockies (Mike 

Madel, Montana Department of Fish, Wildlife and 

Parks, pel's. corom.). Unfortunately, animals often 

become habituated to these devices and so their effectiveness declines over time. 

Alarms. Alarm systems have two values in bear 

country: first, they can frighten the animal away, and 

second, they alert people to an intruder in camp. 

One alarm system on the market attaches to a single 

strand of thin wire strung around the perimeter of 

a camp or work area. If a bear breaks the wire, the 

alarm sounds. Bear researchers in Alaska sometimes 

place this "tripwire alarm" system inside a temporary 

electric fence at camp sites so they know if the fence 

is breached (Tom Smith, USGS, pers. comm.). Another type of alarm system connects directly to the 

electric fence. When an animal touches a positive 

conductor, the device is activated, turning on a light 

and/or a security camera plus an audio alarm. 

Lastly, the Critter GitterTM, yet another type of 

alarm, has been used successfully in the Northern 

Continental Divide Grizzly Bear Ecosystem. This 

device detects movement and/or body heat and 

emits a piercing sound and flashing lights to frighten 

animals away in response to these stimuli. When 

the animal is gone, the device resets itself, but to 

a different sound pattern to prevent habituation. 

The effective area of detection around the device is 

about 40 feet, depending on the size of the animal 

detected. The Critter Gitter can be amplified with 

an additional siren/strobe light unit. 

In Montana, personnel with the Department of 

Fish, Wildlife and Parks have found that the Critter 

Gitter can be effective, especially when they added 

the siren/strobe unit (Mike Madel, Montana Department of Fish, Wildlife and Parks, pers. comm.). 

Specifically, they use this device where bears have 

entered an area at a specific spot and are likely to 

return-e.g., where a bear has dug into a cabin or 

broken into a bee yard. In these cases, they place the 

Critter Gitter near the entrance and aim the motiondetector at the "hole." Others have used multiple 

Critter Gitters, mounted so they face in different 

8 
directions, to obtain broader coverage around sleeping areas while backpacking in bear country. 

Taste Aversion Conditioning. Tement and Garshelis 

(1999) report that a small number of black bears 

habitually raided food caches and begged food 

from soldiers at Camp Ripley, Minnesota, causing 

damage to property and threatening soldiers. The 

authors used taste aversion therapy to change the 

behavior of the bears after rubber bullets and highpressure water had proven ineffective. Specifically, 

the researchers spiked the human foods most sought 

by the bears(Meals-Ready-to-Eat, aka MREs) with 

an emetic. Bears ate these MREs, became ill, and 

were conditioned to avoid this food source in the 

future. Unfortunately, the bears continued to enter 

the camp to look for other foods; their aversion was 

to MREs, not to the facility itself. 

RECOMMENDATIONS 

Permanent facility. Chain-link fence enclosures 

as detailed by Follmann and Hechtel (1990) should 

be used around permanent facilities. If this is not 

possible, a high-tensile-strength wire electric fence, 

as outlined in this document, should be considered. 

The fence should be 54 inches tall and comprised of 

8 conductors, each alternating in polarity. The conductors should be supported by one-inch fiberglass 

line posts with wooden posts used as corners. The 

controller should deliver at least 0.7 joules (or 8000 

volts if the manufacture does not provide information on joules) and can be powered by line current 

(AC/DC controller) or a 12-volt battery charged by 

a solar panel. An alarm system can be attached to 

the fence for added security if desired. 

Long-term seasonal camp. An electric fence 

should be used to surround long-term seasonal 

camps. The fence should be constructed of seven 

strands of polywire or stainless steel conductors 

suspended from fiberglass posts. Polarity should 

be alternated if grounding is questionable, and the 

top two wires should be hot. The fence should be at 

least 48 inches high. Wires should be about 8 inches 

apart, except the bottom ground wire, which should 

be close «2 inches) to the ground. Again, the controller should put out at least 0.7 joules of stored 

energy (or 8000 volts if the manufacture does not 

provide information on joules). The controller can 

be powered by a 12-volt deep-cycle battery that can 

be coupled with a solar charger. A trip wire alarm 

system should be installed inside the fence. In addition, an alarm system can be attached to the fence 

itself if added security is desired. 

Short-term camp. When weight is a consideration, 

7 strands of polywire (same configuration as under 

Long-term seasonal camp above) supported by 

"wand"-type fiberglass rods orby insulators on existing trees may be used. The controller should deliver 

at least 0.5 joules (or 6000 volts if the manufacturer 

does not provide information on joules). The unit 

should be powered by a 12-volt gel-cell battery. A 

flexible solar panel charger can be added if needed. 

The total weight for the charging unit and battery 

will be around 10 lbs. Their use, along with polywire, fiberglass wand posts and a single ground rod 

(where grounding is good), makes a very portable 

bear deterrent system for remote work sites. 

When transporting the components of an electric 

fence is not possible, multiple Critter Gitterscan be 

used around the perimeter of camp sites. The units 

should be mounted so that people entering and 

exiting tents or structures do not inadvertently trip 

the devices. In addition, keeping a clean camp is 

imperative-food odors must be avoided. 

9 
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10