Human activities and habitat alterations associated with industrial development could interfere with movement, feeding, and breeding patterns and could result in exposure to contaminants (Amstrup et al. 1989; Amstrup 1995). In the Beaufort Sea of Alaska, polar bears have been exposed to activities related to hydrocarbon exploration and development for >30 years. Throughout those same 30 years, the population appears to have grown (Amstrup et al. 2001). The population growth during industrialization of the Beaufort Sea coast suggests that management of potential negative interactions between polar bears and humans has been successful. Proposed activities indicate increased vigilance may be necessary to continue those management successes. Oil development activities currently span >160 km of the Beaufort Sea coastal area, but proposed developments would more than double that. The potential for direct and indirect interactions between polar bears and humans only can increase with greater numbers of people and more activities, and more area under development.
If management is to respond properly to the added perturbations that could result from more expansive developments, the processes bringing about natural changes in polar bear populations must be understood. For example, responses to perturbations vary with population size if density plays an important role in population regulation. This means that when numbers are near carrying capacity, populations regulated largely by density-dependent factors may compensate for increased levels of mortality by increasing recruitment (McCullough 1979; Clutton-Brock et al. 1982). Such compensation would result in greater resilience of the population to perturbations than could be predicted from recruitment and survival rates measured prior to the perturbation. Accurate prediction of effects of human activities could only be made, therefore, if population-regulating factors and mechanisms are understood.
The potential for disturbances of denning polar bears may be especially great because undeveloped young must remain in a maternal den that protects them from the rigors of the arctic winter until they are approximately 3 months old (Lentfer and Hensel 1980; Stirling 1990; Stirling and Andriashek 1992; Amstrup 1993; Amstrup and Gardner 1994). Although polar bears may be less sensitive to activities near their dens than previously assumed (Amstrup 1993), the potential for disruptions can only increase as human activities in the Arctic escalate. The general distribution of dens is now known worldwide, but it is still largely unexplained. Except for some critical habitat requirements that can be defined, why bears chose to den at particular sites is unknown. The influences of slope, aspect, and elevation are beginning to be understood (Durner et al. 2001, 2003), although we do know that some bears make mistakes in their choices (Clarkson and Irish 1991). We have made much progress in describing the kinds of habitats polar bears prefer for denning. If we are to adequately manage human activities that could interfere with denning, however, we must either know how to predict which specific sites polar bears will use or learn how to detect newly established dens under the snow.
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