Crossing Over
JB: This is Earth and Sky. It’s known that some wild animals can’t or won’t cross roads – or don’t reproduce if they cross.
DB: And if wild populations remain cut off long enough, inbreeding can threaten these creatures’ survival. In the mountains of southern California, outside of Los Angeles, wildlife ecologists studied the effects of roads on two resilient and common predators in the U.S. – bobcats and coyotes.
JB: Fifty bobcats and 80 coyotes were tracked using radio collars. Once scientists knew when the animals crossed a road from their original habitat, they performed genetic tests to see if the animals were contributing to the gene pool on the other side. Some bobcats and coyotes are getting across.
DB: But not enough of them seem to be breeding, so genetic differences are indeed occurring within a single species, on two sides of a road. Scientists think the best solution to this problem would be to have natural habitat right up to the side of a road on both sides, and to have a crossing point – either a tunnel or an overpass specifically for wildlife.
JB: This solution has been successful in Canada and parts of Europe, and there’s now increasing interest in the United States in making sure that the roads that carry people from place to place don’t continue to be barriers for wildlife. And that’s our show. Thanks today to the U.S. Forest Service and the National Fish and Wildlife Foundation. We’re Block and Byrd for Earth and Sky.
Links:
““Effects of urbanization and habitat fragmentation on bobcats and coyotes in southern California.”“:http://www.nps.gov/gis/mapbook/tech/63.html – Santa Monica Mountains NRA (Denise Kamradt)
Author’s notes: Seth Riley adds: It would be possible to move animals to increase genetic diversity, and in fact this has been done in the past. Florida panthers, an endangered sub-species of mountain lions that had been reduced to 50 animals or less, were exhibiting significant impacts from inbreeding, such as low sperm counts and cryptorchidism (when only one testicle descends). Some mountain lions were brought in from Texas and the inbreeding and its deleterious effects seem to have been significantly reduced at this point. There is certainly debate about whether it is a good idea to be bringing in genetic material from far away places like this, but it does seemed to have helped with inbreeding. So, if the resources and political will were there, it could be possible to move animals from a threatened population across a barrier to increase genetic diversity.
The following person was interviewed for today’s show. Our thanks to:
Seth P. D. Riley, Ph.D.
Wildlife Ecologist
Santa Monica Mountains National Recreation Area
National Park Service
Thousand Oaks, CA
Additional Teacher Resources
World Conservation Society, Saving Wildlife: Highway Impact on Wildlife on the Flathead Reservation
Roads are one of the biggest causes of habitat fragmentation in the United States. Understanding road impacts on wildlife and developing tools to predict and diminish these impacts are important for wildlife conservation. This report explains why.
Pennsylvania Department of Conservation and Natural Resources: Fragmentation?Impact of Roads
Roads and other forest-dividing cuts such as utility corridors can act as barriers for some wildlife. High road density or the presence of a large roadway can decrease the quality of wildlife habitat. Highways are particularly notable barriers for wildlife and often have structural barriers such as concrete walls and wire fences. Even if wildlife can cross into the pavement area, the concrete barrier traps them in the danger zone leaving little opportunity for survival.
Washington Department of Fish & Wildlife, Game Trails: Impact of Roads on Elk and Other Wildlife
The proliferation of roads across the landscape has been a major concern to wildlife biologists for a long time. Besides the obvious, that roads destroy valuable wildlife habitats, scientists have been researching the relationship of roads and their impacts on elk and other wildlife. This report explains what they have found.
