Wolf Predation on Caribou: The Nelchina Herd Case History, a Different Interpretation

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Abstract
The Nelchina caribou (Rangifer tarandus) herd in southcentral Alaska [USA] erupted from 1953 to 1961, declined from 1961 through 1972, and increased again after 1976. Calf recruitment was low prior to gray wold (Canis lupus) control in 1949-51. After wolves were reduced recruitment improved from 1952 to 1956. Recruitment of 2.5-year-old caribou from 1952 to 1967 was correlated with wolf numbers (r = -0.693, n = 16 [excluding 1967, r = -0.871]) but not with winter snow depths (r = -0.373, n = 16). However, in 1964, 1965, and 1966 heavy snow cover may have prevented females from reaching the calving grounds and cows calved at lower elevations nearer to predators. In these 3 years, recruitment was low and the loss of these 3 cohorts was a major factor in the decline from 1961 to 1972. There was no evidence of winter starvation in any year. After 1976, the wolf population was again reduced, caribou recruitment improved, and the herd increased. We conclude that predation of young animals was the most consistent natural limiting factor in the dynamics of this herd from 1950 to 1984.