Abstract
With efforts to restore large mammal populations following extirpations, it is vital to quantify how they are impacted by human activities and gain insights into population dynamics in relation to conservation goals. Our objective was to characterize cause-specific mortality of black bears (Ursus americanus) throughout their range. We first quantified cause-specific mortality for 247 black bears in one harvested and two non-harvested populations. We then simulated a small recolonizing population with and without anthropogenic mortality. Lastly, we conducted a meta-analysis of all published black bear mortality studies throughout North America (31 studies of 2630 bears). We found anthropogenic mortality was greater than natural mortality, non-harvest anthropogenic mortality (e.g. poaching, defense of property, etc.) was greater in non-harvested populations, and harvesting was one of the major causes of mortality for bears throughout their range. Our simulation indicated that removing anthropogenic mortality increased population size by an average of 23% in 15 years. We demonstrated that bears are exposed to high levels of anthropogenic mortality, and the potential for human activities to slow population growth in expanding populations. Management and conservation of wide-ranging mammals will depend on holistic strategies that integrate ecological factors with socio-economic issues to achieve successful conservation and coexistence.
Highlights
With efforts to restore large mammal populations following extirpations, it is vital to quantify how they are impacted by human activities and gain insights into population dynamics in relation to conservation goals
Mortality is a fundamental principle of ecology[1], information on the cause and magnitude of different mortality sources is essential for quantifying the dynamics of wildlife populations
We found that the relative risk of anthropogenic mortality among male bears was 3.42 times higher than for females (Table 2)
Summary
With efforts to restore large mammal populations following extirpations, it is vital to quantify how they are impacted by human activities and gain insights into population dynamics in relation to conservation goals. The timing and magnitude of these mortality sources can indicate patterns regarding the ecology, evolution, and conservation issues of different populations[2] Human activities, such as habitat loss, hunting, and vehicle collisions, are responsible for more than one quarter of global terrestrial vertebrate mortality[3]. Harvesting www.nature.com/scientificreports is the main cause of mortality in hunted bear populations, though it varies across sex and age classes[24], and adult female bear mortality is usually lower than for males, it remains a key factor influencing population growth[25,26]. Black bears are currently the only large carnivore generally established across the eastern US with stable or increasing populations[28] and expanding geographic ranges[29], due to conservation and management plans, as well as repatriation and recolonization efforts (e.g.30,31). Since the early 2000s, six states in the US with increasing bear populations have established black bear hunting seasons: Florida, New Jersey and Maryland, after 21-, 33-, and 51-year closures, respectively, and Kentucky, Oklahoma, and Nevada for the first time in their management history[28]
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