Post by warsaw on Dec 13, 2011 7:59:55 GMT -9
1.2.1 Characteristics of bears responsible for nuisance problems
Prior to the use of firearms, natural selection likely favoured bears that avoided humans. When indiscriminate killing reduced the numbers of bears in North America during the late 19th and early 20th century, aggressive bears may have been selected against and timid bears may have been favoured (Herrero 1989). Although specific exceptions do exist, such as if a person is caught between a female and cubs, or the bear has no perceived avenue of escape, the natural response of most wild, free-ranging American black bears to humans is avoidance (Herrero 1985). The root cause of nuisance activity by bears is positive interactions with humans and their property, in the form of access to food (Gilbert 1989, Warburton and Maddrey 1994, Ternent et al. 2001, Virginia Dept. of Game and Inland Fisheries 2002,). A thorough understanding of the factors affecting changes in nuisance activity over time requires an understanding of the behaviour of bears who gain access to human food sources.
Bears have the highest brain to body-mass ratio of all carnivores (Gittleman 1986). Their behaviour is heavily influenced by learning (Eagar and Pelton 1978, Gilbert 1989), and the transmission of learned behaviour to offspring (Herrero 1985, Gilbert 1989, Gralenski 2001.
Ternent et al. 2001). Learned responses of bears to humans depends on the history of interactions between humans and bears. Interactions between bears and humans may be categorised as negative, neutral, or positive (Gilbert 1989). Negative interactions involve pain or discomfort on the part of the bear; they can lead to avoidance of an area, of people, or increased aggression when confronted (Gilbert 1989). If a bear’s initial interactions with humans are negative ones, future conflicts may never occur. Neutral interactions do not severely affect behaviour, but can cause bears to lose their fear of humans (Gilbert 1989), a condition known as habituation. Habituation can occur even when no food rewards are involved if bears frequently encounter humans without consequence (Aumiller and Matt 1994). Positive interactions involve successful foraging on human foods. They inevitably lead to aggressive food seeking and use of developed areas (Gilbert 1989). Bears that aggressively seek out human foods are referred to as food conditioned.
Habituated and food-conditioned bears are responsible for most attacks on people (Herrero 1989, Herrero and Fleck 1990), and are often responsible for increased nuisance problems (Will 1980, Warburton and Maddrey 1994). Such bears tend to become bolder the longer they are allowed to exploit human food sources without negative consequences (Kelly 2001, Ternent et al. 2001). One or a few food conditioned bears can create the impression of many bears entering a developed area, by establishing foraging routes within and around the area (Ternent and Garshelis 1999, Gralenski 2001, Kelly 2001). Food conditioned bears anticipate similar rewards in similar situations (Gilbert 1989, Ternent et al. 2001). If intentionally fed by one person, they are likely to approach other people; if successful in attempts to forage near
homes, they will approach other homes (Ternent et al. 2001).
There is evidence to indicate that, once food conditioned, black bears rarely revert to “wild” behaviour (i.e., exhibiting fear of humans and avoidance of developed areas), and that only infrequent rewards may be necessary to perpetuate food conditioning (McCullough 1982). Bears that become accustomed to approaching houses and people often become chronic nuisances, and end up being relocated or destroyed (Falker and Brittingham 1998, Kelly 2001). Keay and Webb (1989) documented nuisance activity by food conditioned bears at campsites, even after installation and mandatory use of bear-proof dumpsters and food storage containers. The bears in question exhibited “more sophisticated behaviour that permitted access to human foods”, rather than switching to natural food items (Keay and Webb 1989). In Shenandoah National Park, nuisance problems continued for several years after management to prevent bear access to human foods. Removal of known problem bears was necessary to realise a reduction in
incidents (Garner and Vaughan 1989). Extensive and varied aversive conditioning of three bear cubs to the presence of humans that had become habituated in captivity failed to instil fear of humans in the bears (Ratajczak et al. 2001). The cubs learned to avoid the sources of discomfort (hose, dogs, charger prods, pepper spray), but would still approach people when none of these were present (Ratajczak et al. 2001).
In cases where nuisance bears were relocated, the majority returned to within a few kilometers of the location of capture (McArthur 1981, Massopust and Anderson 1984, Rogers 1984, Inglis 1990, Landriault 1998, Pastuck 2001), and some continued nuisance activity (Beeman and Pelton 1976, Alt et al. 1977, Massopust and Anderson 1984, Inglis 1990, Shull et al. 1994). Bears that have been relocated and successfully homed are likely to return home if relocated again (Beeman and Pelton 1976, Inglis 1990, Landriault 1998). Subadults are less likely to home than adult bears, but may be likely to become engaged in nuisance activity after
release (Shull et al. 1994). Yearling and subadult males are less likely to home after being relocated than any other age class of bears (Inglis 1990, Landriault 1998).
Capture and on-site release has also been used in attempts to deter problem bears from using developed areas (Brady and Maehr 1982, Wooding et al. 1988, Clark et al. 2002). Researchers noted that bears tended to avoid capture locations after immobilisation and handling for the collection of biological data (Amstrup and Beecham 1976, Chi et al. 1998). Others noted that bears trapped and released on-site after raiding apiaries rarely returned (Brady and Maehr 1982, Wooding et al. 1988). In Arkansas, 12 of 15 bears did not repeat nuisance activity at the capture site after handling and release (Shull 1994). In Great Smoky Mountains National Park in Tennessee, 40% of bears released on-site were later observed at the release location, 37% required further management action, and 27% eventually had to be relocated (Clark et al. 2002). It is not known whether the bears handled during the course of the above studies continued nuisance activity in other areas. Clark et al. (2002) found that the behaviour of the bear when captured (shy/passive vs. aggressive/conditioned) was a significant correlate with the success of capture and on-site release as a deterrent of nuisance activity by individual black bears. Bears captured and released near picnic areas and campgrounds did not avoid the area in future (Clark et al. 2002). It seems likely that bears caught near these potential sources of human food had already received positive reinforcement associated with the area, and may have been food-conditioned and/or habituated to humans. Bears exhibiting nuisance activity in the daytime were more likely to cause problems after capture and release than bears causing problems at night, and this was attributed to the bears’ increased level of habituation and conditioning (Clark et al. 2002).Forbes et al. (1994) compared the frequency of problem bears in two national parks in New Brunswick of about equal size and with similar garbage management programs. Despite there being more visitors in Fundy National Park (FNP) the number of encounters with black bears averaged 8.6/yr, less than one-third the rate of Kouchibouguac National Park (KNP) (32.3/yr). Forbes et al. (1994) attributed the much lower encounter rate in FNP to higher harvest levels in the adjacent area (24/yr) than in the area adjacent to KNP (15/yr). The authors suggested that the higher harvest level around FNP sensitised FNP bears to humans explaining why there are fewer problem bear incidents. The authors did not explain how unharvested bears would learn to be wary of humans.Males are consistently over-represented in samples of nuisance bears relative to their representation in the population (Piekielek and Burton 1975, Rogers et al. 1976, Garshelis 1989, Inglis 1990, McLean and Pelton 1990, Clark et al. 2002). The greater mobility of male bears, their encountering of unfamiliar areas as they disperse from natal areas, and possibly their fearlessness contribute to this overrepresentation (Rogers 1987, Garshelis 1989). Young males in particular are frequent offenders (Rogers et al. 1976, Garshelis 1989, Inglis 1990). Young males may become involved in nuisance activity as they disperse and explore unfamiliar areas (Garshelis 1989), or because they are excluded from habitat far from humans by larger males (Garshelis 1994). The fact that fewer old males cause problems may reflect the fact that there are fewer large males in the population, due to selection for them by hunters (Rogers 1976).
It may also be the case that large male bears secure habitat distant from humans (Garshelis 1994).
Nutritionally stressed bears become bolder when attempting to obtain sources of food, and so are more likely to approach humans and developed areas while foraging (Hygnstrom and Craven 1996). Increases in nuisance activity have been correlated with natural food shortages
www.bearsmart.com/docs/LitRev-FactorsAffectNuisance.pdf
Prior to the use of firearms, natural selection likely favoured bears that avoided humans. When indiscriminate killing reduced the numbers of bears in North America during the late 19th and early 20th century, aggressive bears may have been selected against and timid bears may have been favoured (Herrero 1989). Although specific exceptions do exist, such as if a person is caught between a female and cubs, or the bear has no perceived avenue of escape, the natural response of most wild, free-ranging American black bears to humans is avoidance (Herrero 1985). The root cause of nuisance activity by bears is positive interactions with humans and their property, in the form of access to food (Gilbert 1989, Warburton and Maddrey 1994, Ternent et al. 2001, Virginia Dept. of Game and Inland Fisheries 2002,). A thorough understanding of the factors affecting changes in nuisance activity over time requires an understanding of the behaviour of bears who gain access to human food sources.
Bears have the highest brain to body-mass ratio of all carnivores (Gittleman 1986). Their behaviour is heavily influenced by learning (Eagar and Pelton 1978, Gilbert 1989), and the transmission of learned behaviour to offspring (Herrero 1985, Gilbert 1989, Gralenski 2001.
Ternent et al. 2001). Learned responses of bears to humans depends on the history of interactions between humans and bears. Interactions between bears and humans may be categorised as negative, neutral, or positive (Gilbert 1989). Negative interactions involve pain or discomfort on the part of the bear; they can lead to avoidance of an area, of people, or increased aggression when confronted (Gilbert 1989). If a bear’s initial interactions with humans are negative ones, future conflicts may never occur. Neutral interactions do not severely affect behaviour, but can cause bears to lose their fear of humans (Gilbert 1989), a condition known as habituation. Habituation can occur even when no food rewards are involved if bears frequently encounter humans without consequence (Aumiller and Matt 1994). Positive interactions involve successful foraging on human foods. They inevitably lead to aggressive food seeking and use of developed areas (Gilbert 1989). Bears that aggressively seek out human foods are referred to as food conditioned.
Habituated and food-conditioned bears are responsible for most attacks on people (Herrero 1989, Herrero and Fleck 1990), and are often responsible for increased nuisance problems (Will 1980, Warburton and Maddrey 1994). Such bears tend to become bolder the longer they are allowed to exploit human food sources without negative consequences (Kelly 2001, Ternent et al. 2001). One or a few food conditioned bears can create the impression of many bears entering a developed area, by establishing foraging routes within and around the area (Ternent and Garshelis 1999, Gralenski 2001, Kelly 2001). Food conditioned bears anticipate similar rewards in similar situations (Gilbert 1989, Ternent et al. 2001). If intentionally fed by one person, they are likely to approach other people; if successful in attempts to forage near
homes, they will approach other homes (Ternent et al. 2001).
There is evidence to indicate that, once food conditioned, black bears rarely revert to “wild” behaviour (i.e., exhibiting fear of humans and avoidance of developed areas), and that only infrequent rewards may be necessary to perpetuate food conditioning (McCullough 1982). Bears that become accustomed to approaching houses and people often become chronic nuisances, and end up being relocated or destroyed (Falker and Brittingham 1998, Kelly 2001). Keay and Webb (1989) documented nuisance activity by food conditioned bears at campsites, even after installation and mandatory use of bear-proof dumpsters and food storage containers. The bears in question exhibited “more sophisticated behaviour that permitted access to human foods”, rather than switching to natural food items (Keay and Webb 1989). In Shenandoah National Park, nuisance problems continued for several years after management to prevent bear access to human foods. Removal of known problem bears was necessary to realise a reduction in
incidents (Garner and Vaughan 1989). Extensive and varied aversive conditioning of three bear cubs to the presence of humans that had become habituated in captivity failed to instil fear of humans in the bears (Ratajczak et al. 2001). The cubs learned to avoid the sources of discomfort (hose, dogs, charger prods, pepper spray), but would still approach people when none of these were present (Ratajczak et al. 2001).
In cases where nuisance bears were relocated, the majority returned to within a few kilometers of the location of capture (McArthur 1981, Massopust and Anderson 1984, Rogers 1984, Inglis 1990, Landriault 1998, Pastuck 2001), and some continued nuisance activity (Beeman and Pelton 1976, Alt et al. 1977, Massopust and Anderson 1984, Inglis 1990, Shull et al. 1994). Bears that have been relocated and successfully homed are likely to return home if relocated again (Beeman and Pelton 1976, Inglis 1990, Landriault 1998). Subadults are less likely to home than adult bears, but may be likely to become engaged in nuisance activity after
release (Shull et al. 1994). Yearling and subadult males are less likely to home after being relocated than any other age class of bears (Inglis 1990, Landriault 1998).
Capture and on-site release has also been used in attempts to deter problem bears from using developed areas (Brady and Maehr 1982, Wooding et al. 1988, Clark et al. 2002). Researchers noted that bears tended to avoid capture locations after immobilisation and handling for the collection of biological data (Amstrup and Beecham 1976, Chi et al. 1998). Others noted that bears trapped and released on-site after raiding apiaries rarely returned (Brady and Maehr 1982, Wooding et al. 1988). In Arkansas, 12 of 15 bears did not repeat nuisance activity at the capture site after handling and release (Shull 1994). In Great Smoky Mountains National Park in Tennessee, 40% of bears released on-site were later observed at the release location, 37% required further management action, and 27% eventually had to be relocated (Clark et al. 2002). It is not known whether the bears handled during the course of the above studies continued nuisance activity in other areas. Clark et al. (2002) found that the behaviour of the bear when captured (shy/passive vs. aggressive/conditioned) was a significant correlate with the success of capture and on-site release as a deterrent of nuisance activity by individual black bears. Bears captured and released near picnic areas and campgrounds did not avoid the area in future (Clark et al. 2002). It seems likely that bears caught near these potential sources of human food had already received positive reinforcement associated with the area, and may have been food-conditioned and/or habituated to humans. Bears exhibiting nuisance activity in the daytime were more likely to cause problems after capture and release than bears causing problems at night, and this was attributed to the bears’ increased level of habituation and conditioning (Clark et al. 2002).Forbes et al. (1994) compared the frequency of problem bears in two national parks in New Brunswick of about equal size and with similar garbage management programs. Despite there being more visitors in Fundy National Park (FNP) the number of encounters with black bears averaged 8.6/yr, less than one-third the rate of Kouchibouguac National Park (KNP) (32.3/yr). Forbes et al. (1994) attributed the much lower encounter rate in FNP to higher harvest levels in the adjacent area (24/yr) than in the area adjacent to KNP (15/yr). The authors suggested that the higher harvest level around FNP sensitised FNP bears to humans explaining why there are fewer problem bear incidents. The authors did not explain how unharvested bears would learn to be wary of humans.Males are consistently over-represented in samples of nuisance bears relative to their representation in the population (Piekielek and Burton 1975, Rogers et al. 1976, Garshelis 1989, Inglis 1990, McLean and Pelton 1990, Clark et al. 2002). The greater mobility of male bears, their encountering of unfamiliar areas as they disperse from natal areas, and possibly their fearlessness contribute to this overrepresentation (Rogers 1987, Garshelis 1989). Young males in particular are frequent offenders (Rogers et al. 1976, Garshelis 1989, Inglis 1990). Young males may become involved in nuisance activity as they disperse and explore unfamiliar areas (Garshelis 1989), or because they are excluded from habitat far from humans by larger males (Garshelis 1994). The fact that fewer old males cause problems may reflect the fact that there are fewer large males in the population, due to selection for them by hunters (Rogers 1976).
It may also be the case that large male bears secure habitat distant from humans (Garshelis 1994).
Nutritionally stressed bears become bolder when attempting to obtain sources of food, and so are more likely to approach humans and developed areas while foraging (Hygnstrom and Craven 1996). Increases in nuisance activity have been correlated with natural food shortages
www.bearsmart.com/docs/LitRev-FactorsAffectNuisance.pdf