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Regurgitative Food Transfer Among Wild Wolves

Introduction


One aspect of parental care by wolves (Canis lupus) is regurgitation or disgorging food to family members. After feeding, wolves regurgitate to their pups or to the breeding female (Murie 1944; Young and Goldman 1944). Expectant recipients excitedly solicit regurgitation by licking and sniffing a wolf's muzzle (Murie 1944; Rutter and Pimlott 1968). The wolf either regurgitates directly or rushes up to 400 meters away and then regurgitates, sometimes repeatedly (Mech 1988). Food transfered via regurgitation supplements food carried in the mouth (Murie 1944; Haber 1977; Mech 1988; Packard et al. 1992).

Only incidental observations of regurgitation by free-ranging wolves have been reported, so detailed information comes only from captive packs. When offspring from previous litters remain with a breeding pair, they may both solicit and deliver regurgitations (Fentress and Ryon 1982; Packard et al. 1992; Mech 1995a). In two packs, only the breeding male did not solicit regurgitation (Fentress et al. 1978; Fentress and Ryon 1982; Paquet et al. 1982). In a pack with two breeding females, the breeding male regurgitated to all but an immature yearling female (Paquet et al. 1982). In another family, the breeding male regurgitated to yearlings but not to the pregnant female; after parturition he fed the lactating mother until the pups emerged from the den, then he fed the pups (Fentress et al. 1978). Eventually the yearlings fed the pups but not the mother, and the yearlings were often fed by the adults (Fentress and Ryon 1982). During a summer when the free-ranging wolves in the present study produced no pups, the breeding female regurgitated to a yearling (Mech 1995a). The results of two field studies suggested that some yearlings may be more likely to intercept than to deliver regurgitations (Harrington and Mech 1982; Ballard et al. 1991). This raised the question of whether offspring that remain with the family may compete more than contribute.

We present the first detailed description and analysis of regurgitation behavior in a free-ranging wolf pack and test the hypothesis that auxiliary pack members receive more regurgitations than they deliver. We also focused on (i) a comparison of the regurgitation behavior of the breeding female and breeding male, (ii) which individuals donated and received regurgitations, and (iii) correlations between litter size and relative effort by the breeding female.


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