YELLOWSTONE NATIONAL PARK, Wyo. (AP) -- The number of wolves in Yellowstone National Park declined about 23 percent in 2009, a change that park biologists say is typical of natural fluctuations for wildlife species.

Yellowstone's wolf population dropped from 124 in 2008 to about 96 in 2009. Biologists say wolves killing each other, malnutrition and mange are the likely reasons for the decline.

The number of breeding pairs in the park remained the same at six.

Montana wildlife officials have said the number of gray wolves in Montana, Wyoming and Idaho remained stable from 2009 to 2008 at about 1,650.

Montana officials included the regional tally in court documents filed in January in a case in which environmentalists are trying to overturn the loss of federal protections for wolves in Montana and Idaho.

Copyright 2010 The AP.