Socio-ecological dynamics of wolves and prey in a subarctic ecosystem

Haber, Gordon

(Adapted from author's abstract.) This 1977 Ph.D. thesis includes the results of an eight-year field study conducted from 1966-1974 in the Denali region of Alaska. The study focused primarily on two adjacent wolf packs ("Savage" and "Toklat" packs) to obtain information on their social dynamics and interactions with moose, sheep, and caribou. Mean food "adequacy" per wolf per day was calculated for both packs each winter, based on observed rates of consumption and requirement estimates corrected for winter-to-winter travel variations. A computer simulation model of the Denali wolf-moose-sheep interaction was developed from field data on 1) environmental conditions (snowfall); 2) moose and sheep reproduction and non-wolf mortality; 3) wolf reproduction, mortality, and social behavior; and 4) wolf predation and scavenging in relation to prey density and other factors, replacement mortality, and potential adjustments in wolf territory size. The analysis suggests a form of coevolution between the wolves and prey. It was concluded that wolf predation had virtually nothing to do with causing a decline from high density, but that it was the primary factor which held a caribou herd down once dispersal had reduced it from a food-limited peak. The prolonged low enabled range (food) conditions to recover, whereupon the herd built up to a subsequent peak following dispersal from another herd which had just peaked. At present the Alaska-Yukon caribou herds have approached a condition of synchrony at low density - due to heavy harvests it is argued, and a range of harvest restriction-wolf control recovery options is discussed. It is recommended that once recovery is achieved, human exploitation should proceed by pulse-harvesting rather than according to the traditional approaches of sustained yield management.