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Graphs

Wolf population in the Yellowstone area by location from 1995 through 2010. The Yellowstone National Park population includes the northern range plus the rest of the park. Initially wolf population growth rate was very high, averaging 40 to 50 percent per year for the first five years. It then declined to about 10 percent per year for the next several years, finally stabilizing in 2004.

1995 Yellowstone Wolf Pack Territories

Early on, wolves settled mostly on the northern range. This map shows the wolves’ territories in 1995.

2010 Yellowstone Wolf Pack Territories

Though today the wolf population remains especially dense on the northern range, where elk are more plentiful, in recent yaers interior packs–which must rely more heavily on bison–have also been faring well.

A key factor in the success of the wolf reintroduction to Yellowstone was the production of pups. Most years (1999 being a notable exception), pup survival averaged 75 to 80 percent.

While in winter wolves rely mostly on elk, they have in fact killed all eight ungulate species living in the park. Deer predation increases in the warm months due to migration of that animal into the park during early summer.

Since wolves were reintroduced into the national park, the elk population has declined by roughly 50 percent. While many attribute this drop entirely to wolves, in fact the elk population was declining before wolves were reintroduced. Elk decline is related to a number of factors, including hunting, drought, and multiple carnivores in addition to wolves.

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