Denning behavior of wolves on Yellowstone's northern range: Male and female strategies

Linda M. Thurston, Jane M. Packard, Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258, USA; Douglas W. Smith, Kerry M. Murphy, Yellowstone Center for Resources, PO Box 621, Yellowstone National Park, WY 82190, USA; Mike K. Phillips, Turner Endangered Species Fund, PO Box 190, Bozeman, MT 59730, USA

Canids are unusual among mammals in that their predominant mating system is monogamy. Since female gray wolves (Canis lupus) have a relatively large pre- and post-partum investment due to large litter mass, male effort in raising a litter of pups can be substantial. Few studies have examined biparental and allo-parental care in wild wolves, though in two studies den attendance by breeding females appeared to be related to conditions of food availability. In one study homesite attendance by two non-breeding wolves appeared to be related to phase of pup development.

We systematically compared den attendance of four wolf packs in Yellowstone National Park across three phases of pup development. Individual pack members were monitored during the first 15-weeks of the pup's lives over a two-year period. Den attendance patterns between male and female breeding pack members and within genders of non breeding pack members were compared in and between packs. In 1997 hand-held telemetry was used to record den attendance of radio collared wolves every half hour, 48-hours per week. In 1998 hand-held telemetry was used on two packs while two packs were monitored using automated remote telemetry systems that recorded the presence of each wolf at the den in six-minute intervals. In addition, each den was observed two days per week using spotting scopes to record behavior and support telemetry data. The frequency of time spent at the den site was studied for each wolf. Based on data for each wolf, smoothing splines were used to model individual behavior as a function of the age of the pups.

Preliminary analysis of two of the four packs showed that patterns of den attendance varied within and between packs. In one pack, the breeding female attended the den more than the breeding male for the first several weeks of the pup's lives, then both breeders decreased attendance as pups developed. Most subordinates in this pack had a constant den attendance pattern over time. In a second pack, den attendance patterns of the breeding male and female were dependent on one another and less predictable over time. For both of these packs, variation in den attendance of the non-breeders was greater than that of the breeding female.