Comparing results of soft and hard releases in the restoration of wolves to the northern Rockies

J. Henry Fair Steve Fritts (right), U.S. Fish and Wildlife Service, USA with Bob Ream and Diane Boyd.

Steven H. Fritts, Edward E. Bangs, Michael D. Jimenez, Joseph A. Fontaine, U.S. Fish and Wildlife Service, 100 North Park Street Suite 320, Helena, MT 59601, USA; Curtis M. Mack, Timmothy Kaminski, Nez Perce Tribe, PO Box 365, Lapwai, ID 83540, USA; Douglas W. Smith, Kerry M. Murphy, Wayne G. Brewster, Yellowstone Center for Resources, PO Box 621, Yellowstone National Park, WY 82190, USA; Michael K. Phillips, Turner Endangered Species Fund, PO Box 1989, Gallatin Gateway, MT 59730, USA; Carter C. Niemeyer, USDA/APHIS, Wildlife Services, PO Box 982, Helena, MT 55635, USA

We reintroduced wild-captured gray wolves (Canis lupus) from western Canada into Yellowstone National Park and central Idaho in early 1995 and 1996, using soft and hard release protocols. The two wolf reintroduction/recovery areas were large (>50,000 km2), primarily in federal ownership, sparsely populated by humans, and supported ample wild prey. However, they differed in physiography, accessibility, and practicality of reintroduction techniques. Our general approach was to hard release individual wolves of at least minimum dispersal age into Idaho and soft release small packs (2-6 wolves) into Yellowstone. Hard releases consisted of delivery and immediate release of 35 mostly unrelated individuals in small groups to remote wilderness sites in January of both years. In Yellowstone, 31 wolves in 7 packs were held in 0.4 ha acclimation pens at remote locations for an average of 75 days before release in late March and early April of both years. Idaho wolves separated after release and moved extensively during the first three months, but most became more localized after 4-6 months. Hard-released wolves had a propensity to move northward, to wander extensively, and to settle north of release sites. Although considerable variation occurred, most members of Yellowstone groups remained together, showed less tendency to move toward 'home', explored less extensively, and then settled near their acclimation pens. Soft-released packs established territories that were 3.8-22.9 km (x = 14.5) from release pens, whereas the original hard-released wolves established territories 27-256 km (x = 92) from release sites. Soft release resulted in earlier reproduction (1995), the result of 4 of 7 packs breeding in captivity. Reproduction of hard released wolves was delayed (until 1996) until widely traveling solitary individuals found mates, pair bonded, and settled into territories. Survival was high in both areas and apparently not affected by release protocol. Some 63% of the original hard-released wolves and 71% of soft released wolves reproduced.

The project showed that soft and hard releases of wild-caught wolves can lead to population establishment. However, extensive movements of hard-released wolves (and to some degree soft-released wolves as well) should be expected, and a suitably large recovery area is essential. Confining wolves to specific areas is important in wolf restoration efforts for biological, social and political reasons. Soft releases, although more expensive and labor intensive, are more likely to establish wolves in a specific desired area, and therefore probably will be the protocol of choice in any future reintroduction programs.