LANDER, Wyo. – The population of gray wolves in Wyoming, Montana and Idaho apparently has shrunk for the first time in over a decade.

Biologists aren't sure why their midyear estimate of the regional wolf population came in with about 350 fewer wolves than they had expected. The estimate was 1,455 animals, down slightly from an estimate of 1,513 wolves at the start of 2008.

Wolves were reintroduced in Yellowstone in the 1990s and they've been reproducing rapidly ever since. The regional population had been growing at about 24 percent a year.

A disease outbreak is one possible explanation for the decline. Another is that wolves have spread into most of the suitable habitat in the region.

Information from: Casper Star-Tribune – Casper, www.casperstartribune.net