Yellowstone wolf found near Denver
By Alice Wondrak Biel and Douglas W. Smith

“Finding vacant territory in Yellowstone in which to start a new pack is getting more difficult for a dispersing wolf.”

NPS/Jim Peaco

The experience of wolf F293 (not shown here) demonstrates that human challenges will be the major barrier to wolves becoming reestablished across the Rocky Mountains.

IN JUNE 2004, YELLOWSTONE WOLF F293, a two-year-old female, was found dead along Interstate 70 near Denver, Colorado. Wolf F293 originated from the Swan Lake Pack, whose territory includes the Mammoth Hot Springs area, in Yellowstone’s northwest corner; she was last located in Yellowstone in January 2004. Investigators estimated that F293 traveled 300–400 miles (483–644 km) of straightline distance. Because wolves usually travel in random patterns rather than in straight lines, however, she may have covered twice or as much as four times that distance before she was killed.

At the time she was found, rumors circulated that F293 actually had been killed elsewhere and was then dumped along the highway, which has been known to happen in the past. However, investigations by the U.S. Fish and Wildlife Service have shown that such is probably not the case here. Rather, wolf F293 traveled to Colorado on her own and was killed when she was hit by a car.

Wolf F293’s journey may have begun because finding vacant territory in Yellowstone in which to start a new pack is getting more difficult for a dispersing wolf. With 175 wolves in 15 packs, the Yellowstone wolf restoration program is meeting all expectations, and Yellowstone National Park probably is approaching its carrying capacity for wolves. Wolf F293 could likely have remained in Yellowstone if she had been willing to settle in a poor habitat area, but instead she moved on.

Also noteworthy is that large-scale moves such as this are characteristic of young wolves of either sex; the record straight-line wolf dispersal is 600 miles (965 km). Not much genetic segregation occurs in wolves for this reason; because they are such good travelers, they intermix. What makes F293’s dispersal remarkable is that she achieved it in the lower 48 states, where significant barriers to such movement—such as large interstate highways and humans prone to shooting them—exist.

The discovery of wolf F293 in the Denver area indicates that the existence of other wolves between Yellowstone and central Colorado is not very likely. Because wolves are extremely good at finding other wolves, if F293 had found a male mate, she would have stopped instead of continuing to travel. Although F293’s dispersal resulted in death, other wolves from the northern Rocky Mountains restoration are starting to establish territories in surrounding states. Whether they will persist outside protected lands depends on the management plans being developed by states in conjunction with the U.S. Fish and Wildlife Service.