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Regurgitative Food Transfer Among Wild Wolves

Methods


This study was conducted on Ellesmere Island, North West Territories, Canada (80° N, 86° W). There, wolves prey on arctic hares (Lepus arcticus), muskoxen (Ovibos moschatus), and Peary caribou (Rangifer tarandus pearyi) (Mech 1988). During 1986, the senior author habituated a pack of wolves to his presence and reinforced the habituation each summer (Mech 1988, 1995a,1995b; Packard et al. 1992). In addition to hunting, the pack we observed also scavenged from the refuse pile of a weather station. The wolf pack frequented the same area each summer and used the same den (Mech and Packard 1990) or nearby dens (Mech 1995b) during 5 of the 7 summers when they produced pups during this study. The habituation allowed us to watch the wolves regularly from distances of 10-100 m.

Data for the present study were collected from 1988 through 1996. We began observing between 14 and 28 June (when the pups were 10-25 days old) and ended in early August. We did not attempt to randomly sample behaviors; rather, we observed as many food deliveries as we could. Although our efforts varied with logistics and weather each year, general procedures were the same except in 1988 when we observed continuously for one 5-day period.

We identified adult-sized wolves on the basis of gender (from the urination posture), behavior toward the observer, fur coloration, and such individual features as a missing tooth, ear notch, and scars (Mech 1995b). Pups were not individually recognizable, but as yearlings they demonstrated the habituation they had received as pups. Nonhabituated wolves from other packs fled when approached (Mech 1995b).

Over 9 years, six adult-sized wolves were observed with six litters (Table 1). "Mom" produced pups from 1986 through 1989, and she remained as an auxiliary when post-reproductive, behavior we have not seen documented elsewhere. Her daughter, "Whitey", replaced Mom as breeder from 1990 through 1996 (Mech 1995b; L.D. Mech, unpublished data). No other offspring remained for more than 3 summers after its birth year. Presumably they dispersed or died (Mech et al. 1998).

Table 1.  Composition of the study pack of wolves.
Year No. of pups Breeders Auxiliaries
Female Male Female Male
1988 4 Mom Left Shoulder Whitey Grey Back
1990 1 Whitey Left Shoulder Mom
1991 2 Whitey Left Shoulder Mom
1992 3 Whitey Left Shoulder
1994 1 Whitey Left Shoulder Explorer Grey Back II
1996 2 Whitey Left Shoulder
Note: No data were collected in 1989; no pups were produced in 1993 or 1995.

Our observations were made at several home sites unobscured by vegetation. All behavior was recorded from the time a foraging wolf returned until it disappeared or observations were terminated. Each time a wolf regurgitated was one event, and all the regurgitation events after a return constituted a regurgitation bout. Only five observations of regurgitation bouts were incomplete (e.g., the wolves went behind a rock or ridge). In three cases when wolves regurgitated into a cache, the senior author later dug up the cache and weighed the contents.


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