Effectiveness of deterrents on black bear (Ursus americanus) to anthropogenic attractants in urban-wildland interfaces

The effectiveness of bear-resistant containers, electric fences, ammonia sprayed on food, and pepper sauce sprayed on food were tested as deterrents to black bears (Ursus americanus) anthropogenic food sources on the Hoopa Valley Indian Reservation, California. Deterrents were tested at multiple sites at different locations with presumably different bears and the results of the deterrents were compared to controls. The number of days that bait was removed by bears at ammonia and pepper sauce stations was not significantly different than the controls (P = 0.31). Bear-resistant containers deterred bears from eating the bait 100% of the time at sites that tested deterrents experimentally, and bears removed bait at the electric fences significantly less often than at control sites (P 0.001). The mean number of return visits and time spent at bear-resistant containers and electric fence stations did not vary between bears that visited the deterrents first as a proactive deterrent (bait had not previously been obtained at a station by an individual bear) or first as a reactive deterrent (bait had been previously been obtained at a station by an individual bear). When proactive and reactive visits to bear-resistant containers were pooled, the mean number of return visits was less than at control sites (P 0.05). Likewise, when proactive and reactive visits to electric fences were pooled, the mean number of return visits was less than at control sites (P 0.05). Also, the amount of time spent per visit at bear-resistant containers and electric fences was greater during the time bait was available and deterrents were not functional than when the bait was available and deterrents were functional (P 0.001). Amount of time spent at bear-resistant containers and electric fence stations did not vary between individual bears (P = 0.99), but amount of time bears spent varied between the two deterrents (P 0.001). The amount of time spent at electric fences increased over time (r2 = 0.61), and amount of time spent at the bear-resistant containers decreased over time (r2= 0.69). Three of the 10 identified bears that had contact with the electric fence during the time the deterrent was functional returned once the fence was not energized. Bears that returned to the electric fence and bears that the electric fence failed to deter had significantly more visits to all stations than bears that did not return (P = 0.001, P = 0.008, respectively). Levels of vigilance behavior were compared between three groups of bears based on frequency of visitation (1 visit, 2-10 visits, and 11-110 visits) to determine if vigilance behavior varied with the number of total visits to stations. Decreased vigilance behaviors (e.g. grooming and resting) were greater for groups with 2-10 visits and 11-110 visits than bears with one visit (P = 0.01). Deterrents were placed at 14 residential sites based on complaints made by residents about black bears. One of nine bear-resistant containers at residential sites had bait removed from the container by a bear. However, bears did not remove attractants from any of the eight electric fences placed at residential sites. Bear-resistant containers and electric fences were effective at reducing access by bears to anthropogenic foods and reduced the amount of time bears spent at a location. Deterrents were not effective 100% of the time, but reductions in access by bears to anthropogenic food sources through the use of deterrents would potentially decrease the number human-bear conflicts over time. When addressing a community concerned with nuisance black bears, managers need to be aware that deterrents do not deter all bears, and bears that have received a food reward at a location are more likely to return.