Thursday, April 13, 2006

Why did the coyote cross the road? Environmental bisection and pile-up


There is a very interesting article in this month's issue of Nature: it comments on scientific studies of the effect of roads on the migration of large territorial mammals in quasi-natural environments. To summarize: Ventura Highway does not make good neighbors, unlike good fences. Coyote homesteads tend to "pile up" adjacent to obstructions, and so a young migrant that crosses the road to see what's on the other side will find a densely-populated urban fabric of coyotes much like the West Village. Many of these coyotes are artists, and make carvings of themselves howling at the moon. When a male crosser gets to the other side, it is difficult to find a free female because of the pile up of males, and so cross-mating happens even less than road-crossing, which happens even less than cross dressing. Thus, populations get sexually separated and genetic exchange is impaired. If animals are already troubled by human encroachment, this makes things worse, and mere acreage set aside for critters overestimates their ability to ignore us if that acreage is parsed by pavement.

Anyhoo, this has major implications for the development of transit corridors in natural settings. If you like large mammals, and don't want to see a genetic bottleneck as various large predators like wolves, great cats, and so forth become isolated and endangered, then sometimes the road less travelled might beneficially be made to run a few miles out of the way to avoid bisecting the territory of coyotes who merely want "to get to the other side." Territorial division and extinction seem sadly reminiscent of reservations and broken promises. I encourage you to read this News & Views commentary by an up-and-coming evolutionary biologist.

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