Border Fence Blocks Bears in Migration, Study Finds

New York Times
December 21, 2011
by Marc Lacey

GILA BEND, Ariz. — The much-ballyhooed border fence has not just made it more difficult for illegal immigrants to slip across from Mexico into the United States. It has also become an obstacle, researchers say, for migrating bears.

A study published in this month’s edition of Biological Conservation warns that the black bear population just north of the border in Arizona may be threatened by the increasingly impermeable barriers at the border. Also fragmenting the bear habitat are the growing urban sprawl in southern Arizona and the expanding highway systems that slice through rugged terrain, the study found.

Researchers used hair snags — pieces of barbed wire set up near bait to catch genetic samples of foraging bears — to track various bear populations in Arizona. They found significant genetic disparities between black bears in the east-central part of the state and the subpopulation just north of the border. The border bears, the study said, were more closely related to bears found in northern Mexico.

The population density of the border bears was substantially lower than the bears living farther north, which had a wider habitat that was less vulnerable to development, the study found. The border is a unique region, from a biological point of view, researchers say, with many North American species reaching the southern limit of their distribution there and many South American species extending not much farther north.

“We want people to be cognizant of the impact of human activities and how they are impacting wildlife populations,” said Dr. Jon P. Beckmann, a bear researcher with the New York-based Wildlife Conservation Society and co-author of the bear study.

The authors, who include Todd C. Atwood and Julie K. Young of the United States Department of Agriculture’s National Wildlife Research Center, intend to share their findings with the Department of Homeland Security and other state and federal agencies along the border. Dr. Beckmann said that the paper could be used to help generate innovative solutions that take bears and other large carnivores into consideration when border security was discussed.

As for the efficacy of border fencing in stymieing illegal immigrants, an issue that has come up in the Republican presidential primary contest, Mr. Beckmann said, “We’re not weighing into that debate.”

http://www.nytimes.com/2011/12/22/science/earth/border-fence-affecting-black-bears-too-study-says.html