Hunting, collisions with automobiles and trucks, and diseases from domestic animals are killing grizzlies, tigers and other large predators at alarming rates when they leave the confines of national parks, according to a study by the Bronx Zoo-based Wildlife Conservation Society (WCS) and Cambridge University. Published June 25 in the journal Science, the study warns that regional populations of these animals may collapse if such mortality continues.
The researchers have called for expanding "no-kill" areas outside of parks, hunter education to prevent accidental deaths and predator persecution, and an increase in park size to protect those animals that roam widely such as bears and big cats.
"You can have the best-run park in the world, but unless you prevent people from killing carnivores that wander outside of park boundaries, they will be essentially useless for protecting wildlife in the long term," said Dr. Joshua Ginsberg, director for Asia programs for WCS, and co-author of the study.
The researchers documented staggering death rates among predators along the borders of protected areas throughout the world. In Algonquin National Park in Canada, for example, humans caused more than half of all gray wolf deaths. In Yellowstone, 89 percent of grizzly bear deaths were human-related. Other areas of the world offered similar statistics: humans contributed to an average of 61 percent of African wild dog deaths in a variety of game reserves and parks throughout central and southern Africa; and nearly two-thirds of all Indian tiger deaths in Nepal's Royal Chitwan's National Park were caused by people.
According to the researchers, animals that range the farthest distances are the most likely to become extinct regardless of population density. For example, wild dogs which have extremely large home ranges, have already vanished from several protected areas in Africa.
Conservation biologists have long practiced under the theory that populations may be drive to extinction by random fluctuations in demography and loss of genetic diversity. But the authors warn that conservation measures that focus only on maintaining or bolstering populations within protected areas are unlikely to prevent extinctions.
Materials provided by Wildlife Conservation Society. Note: Content may be edited for style and length.
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