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Introduction
Black bears (Ursus americanus) and humans share a long history of interaction in
national parks across the country. From the Smoky Mountains in Tennessee to the Tetons in
Wyoming, food has served as the common thread linking people and bears. For many years,
bears were encouraged to forage in open garbage dumps, and bear feeding shows were popular
entertainment for visitors to national parks. However, conflicts arose when bears began
looking for food in visitor areas and threatening visitor safety and private property. In
their persistence for human food and garbage, bears were breaking into camps, cars, tents,
backpacks - anything containing human food. As a result, human-bear conflicts escalated.
Unfortunately, human-bears conflicts often resulted in the destruction of
‘problem’ bears, and in Yosemite National Park (YNP), over 200 bears were killed
between 1960 and 1972. In 1975, managers at YNP initiated a Human-Bear Management
Plan aimed at reducing the number of human-bear conflicts by developing and enforcing food
storage regulations, educating visitors about appropriate behavior in bear country, and
eliminating ‘problem’ bears through aversive conditioning, relocation, or
euthanasia. Although these efforts have shown promising results, bears continue to modify
their behaviors and demonstrate a high degree of persistence in finding human foods.
Learned Behavior
Bears must focus a lot of energy on food acquisition since they do not eat while
hibernating and must accumulate sufficient energy reserves during the foraging season.
Nutrition is tied to all aspects of bear health including age of first reproduction,
breeding interval, litter size, body mass, and ability to find mates. Black bears manage
their intake needs by being generalist feeders that utilize a wide variety of resources,
spatially and seasonally. A certain degree of curiosity has been innately selected for in
bears because it has aided them in their survival, probably through the discovery of new
foods that contribute to their varied diets. The physiological ability to digest a wide
variety of foods is also an inherited characteristic coded in bears genes, which allows
them to be opportunistic feeders, capable of adapting to variable environmental conditions
and food availability.
Learning occurs through direct observation and participation with conspecifics or through
individual experience, and over the course of a relatively long lifetime, the process of
learning and remembering is extremely valuable to bears. Bear cubs depend heavily upon
their mothers for the first 2-3 years of life. During this period, cubs learn about their
environment, identification of food, and how to respond to potential predators and
dangerous places. The role of social learning from mother to cub is believed to be
incredibly important for bears and is probably the basis for most of their behavior. Early
learning from siblings may also be very important, and throughout their lifetimes bears
come to depend on individual learning to adapt to new environments. Learning to forage on
human foods includes two adaptive processes for bears. First, they must develop a
preference for human foods. Secondly, bears must be willing to tolerate humans and areas
characteristic of human presence. Food preferences are developed through the ‘gut
feedback system’, which responds to ingested items somewhere along the continuum of
high energetic reward and stimulation of the emetic system. Whether cubs learn from their
mothers or through their own experience, the palatability and digestibility of the food
items must be perceived to be beneficial to the animal, whether it be an energetic reward
or a relief from some kind of discomfort. Although some human foods, and especially some
of the trash inadvertently consumed while foraging on human foods, may occasionally make
bears ill, the ‘take home’ message needs to be that human foods are good for
health and survival in order for a food preference to develop. Bear probably even learn
which specific human foods are better to eat than others and forage selectively on those
items. For example, one observer in YNP watched a bear peel the wrappers off energy bars
before eating them.
Most of the literature considers habituation, attraction, and avoidance to be functions of
learning. However, some researchers suggest that there is a genetic basis for such
behaviors. Others propose that such behaviors may also be explained by culturally
transmitted behavioral learning, which occurs when behavior patterns are passed down
through generations of animals. This idea of genetically coded and culturally transmitted
behaviors is very interesting and could explain the unique persistent foraging behavior of
the Yosemite bear population.
Aversive Conditioning
Alteration of bear behavior through aversive conditioning has recently received
considerable attention in national parks. Two techniques may be employed, depending on the
nature of the problems and available resources: physical and chemical aversion. Physical
methods include the infliction of pain, fear, and surprise, sometimes carried out by
firing rounds of noise-makers and rubber bullets at animals. Chemical aversion includes
the use of compounds that induce nausea and stimulate an animal’s emetic system. Such
conditioning would require that every bear in Yosemite’s bear population be averted
to every type of human food or garbage item that could possibly be encountered. On the
level of a national park, such an intensive effort would be logistically impossible. For
this reason, the Bear Management Team in YNP focuses its efforts on physical conditioning
techniques, including sling-shots, cracker shells, bean bag and rubber bullet rounds, a
Karelian bear dog, and bear rangers on duty throughout the night during most of the
foraging season. As a relatively new effort, no quantitative results are available on the
effectiveness of YNP’s aversive conditioning efforts, but preliminary findings are
only marginally encouraging.
Aversive conditioning may be effective in deterring habituated bears (those accustomed to
human presence) from becoming food-conditioned, thus preventing aggression in bears and
reducing human-bear conflicts. However, bears that are already food-conditioned will prove
a more challenging management issue and may have to be tolerated or destroyed. If bears
are depredating in certain areas, aversive conditioning may be effective in specific
locales, given consistent and intensive hazing efforts. Aversive conditioning techniques
that prove most effective are those that are applied to newly habituated bears, and
incorporate a pain and fear stimuli coupled with an auditory cue. These efforts will be
most successful if applied consistently and repeated even after the desired conditioning
has been observed. Notably, use of dogs as bear deterrents has been met with encouraging
reviews.
Conclusion
The bottom line is that while aversive conditioning may show some promise, the real
training needs to be focused on park visitors. Given limited park resources and expertise
to devote to aversive conditioning, efforts would be best spent in enforcing food storage
regulations and training those beings that we can reason with most effectively: us
humans.
Important References
Douglas-Hamilton, I., and O. Douglas-Hamilton. 1975. Among the Elephants. Collins and
Harville, London, England.
Gilbert, B.K. 1999. Social learning in bears in Mammalian Social Learning, edited by H.O.
Box and K.R. Gibson. Cambridge University Press, London
Jope, K.L. 1992. Behavioral ecology of learning in bears. International Conference on Bear
Research and Management 8:
McCarthy, T.M. and R. J. Seavoy. 1994. Reducing nonsport losses attributable to food
conditioning: Human and bear behavior modification in an urban environment. International
Conference on Bear Research and Management 9:75-84.
Whittaker, D. and R.L. Knight. 1998. Understanding wildlife responses to humans. Wildlife
Society Bulletin 26:312-317. |
