Wednesday, May 18, 2011

New Study: Most Larger Mammals Killed by Humans

Medium and large-sized wild mammals in North America are more likely to be killed by humans than by predation, starvation or disease, according to research conducted at the New York State Museum.

The study was conducted by Christopher Collins, a graduate student from the State University at Albany and Dr. Roland Kays, the State Museum’s curator of mammals and has been published online in the journal Animal Conservation. The research shows the extent to which humans are affecting the evolution of mammals today and will be used to predict the conservation threats that mammals face.

Although studies of mortality causes have been conducted for many mammal species, this is the first to gather this data together and examine trends across species. Collins and Kays reviewed data for 2209 individual animal deaths in 69 North American mammal populations across 27 species. They only considered studies that used radio tracking
collars to monitor animals because they are the least biased in finding recently deceased animals.

Of the 1874 deaths that had known causes, 51.8 percent were caused by humans. Hunters killed 35.3 percent of the animals studied — 29.9 percent legally and 5.4 percent illegally through poaching. Vehicle collisions caused 9.2 percent of the deaths and 7.2 percent resulted from other human causes. Predation by other animals caused 35.2 percent of the deaths, disease accounted for 3.8 percent, starvation for 3.2 percent and other natural causes for 6.1 percent.

Data included animals that lived in a variety of habitats throughout North America including urban, rural and wilderness areas. Animals in urban areas were more
likely to die from vehicle collisions, while animals in rural and wilderness areas were more likely to die from hunting. Animals living in protected areas had a 44 percent lower level of human-caused mortality.

Kays noted that “this shows that legal protection has a direct impact on the survival and evolutionary pressures faced by animals.” Larger species, especially carnivores, are more likely to be killed by humans, with smaller species, particularly herbivores, dying more from predator attacks.

Although the deaths attributable to hunting by humans were very high, none of these hunted populations were endangered. “These results may be more important when considering the forces driving modern evolution of species, than their conservation status,” said Collins.

The study suggests that animals with traits that allow them to escape these prominent mortality causes for longer will have a selective advantage. However, the scientists conclude in the study that the pace of “human activity may exceed species’ ability to adapt, particularly in the face of habitat loss and climate change.”

The research also noted a scarcity of knowledge about smaller species, and Collins and Kays have since initiated new field research on the cause of mortality in small mammals in New York State.

Photo: A fisher is shown wearing a tracking collar. Collars like these allow field biologists to track the movement and ultimate fate of an animal, finding them regardless of their ultimate cause of death, and providing the most accurate data on what actually kills wild animals. (Photo courtesy of NYS Museum).

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