September 23, 2011
Yellowstone Wolf Population Update
If there’s one thing about Yellowstone’s wolf population we can always count on, it’s change. From dramatic wolf pack rivalries, to disease outbreaks and the impacts of extreme weather, there is constantly something new to learn or investigate. These wild wolves offer us a unique opportunity to see the forces of nature in action.
Each year, the Yellowstone Wolf Project staff complete an exhaustive report on the status of the wolf population and the work of project staff. The detailed information -- plus photos, charts, and feature stories -- help make the Yellowstone Wolf Project Annual Report a much-anticipated publication among wolf watchers. The following is information from the recently published 2010 report.
At the end of 2010, at least 97 wolves -- consisting of 11 packs and 6 loners -- occupied Yellowstone National Park. This is nearly the identical population size as in 2009 and represents a stable population after a tumultuous prior year.
The current population consists of significantly fewer wolves than the park-wide population peak in 2003 at 174 wolves, a decline that was brought about by disease and food stress, and suggests a long-term lower population equilibrium for wolves in Yellowstone.
The most dramatic changes have occurred on Yellowstone’s “Northern Range” (view map), where wolves have declined 60% since 2007 compared to a 23% decline for interior wolves during the same period. Northern Range wolves are very dependent on elk as a food source, and the elk population declined 70% since 1994. Park interior wolves prey on elk and bison, both of which are still widely available in the park interior.
Disease impacts have likely played a larger role in the wolf decline on the Northern Range because of its higher density of canids (wolves, coyotes, and foxes) than in the interior. The severity of mange -- a growing concern last year -- declined in 2010, and there was no evidence of distemper being a mortality factor after being linked to numerous pup deaths in 2008.
Good news arrived last year in the form of new pups! Breeding pairs increased from six in 2009 to eight in 2010, with eight of the 11 packs in Yellowstone reproducing last year and the average litter size increasing from 3.8 to 4.8 pups. Most importantly, a total of 38 pups in YNP survived to year end. This was significantly more surviving pups, up 39%, than in 2009.
Population counts are performed annually in the wintertime, so these figures reflect numbers as of the end of 2010, and updated counts should be available -- weather permitting -- in early 2012.
From the decline of the legendary Druid pack, to the rise of the Silver Pack which took over their territory, to the unusual visibility of the Canyon pack, there was no lack of drama and intrigue to report in 2010. The new report also includes complete updates on each of Yellowstone’s wolf packs.