In 1926, the last of the wild gray wolves were eliminated from Yellowstone National Park. The absence of wolves in the park meant that one of region's top predators was missing (other top predators in Yellowstone include coyote, mountain lion, grizzly bear, and black bear). This had significant impact on the Yellowstone area ecosystem. Elk, the wolves main prey species, experienced a population increase after 1926 as did other ungulate species within the park. The growing herds, in turn, had significant impact on the landscape of some areas of the park. More elk, moose, and other ungulates meant more pressure on grazing lands, and that pressure resulted in degraded land and altered vegetation structure (Smith 2003).

During the 1930s, after drought further weakened the park's landscape, a controversial program to cull elk, pronghorn, and bison was initiated. In 1969, a long overdue change in management approach was established. The new philosophy promoted a reliance on natural processes to regulate ungulate populations and discouraged the culling practices of the past. It was this philosophy that ultimately lead to the reintroduction of wolves back into the Yellowstone ecosystem (Smith 2003).

In January of 1995, the first step towards wolf reintroduction to Yellowstone took place. That month, fourteen wolves captured from Alberta, Canada were placed in acclimation enclosures in Yellowstone National Park. In March 1995, the pens were opened and the wolves were released into the wild. Another 11 wolves were released the following year and by 2004, the wolf population in Yellowstone had grown to an estimated 300 individuals.

Find out more:

• The Reintroduction of Gray Wolves to Yellowstone National Park and Central Idaho (US DOI and US FWS)
• Wolf Reintroduction (Wikipedia)
• Smith DW, Peterson RO, Houston, DB. 2003. Yellowstone After Wolves. Bioscience 53(4):330-340.
• State of the Wolf Report (Defenders of Wildlife)

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