Continued Studies of the Status, Socialization, and Relationships of Isle Royale Wolves, 1967 to 1970

Abstract

Studies of the wolf (Canis lupus) and its prey in Isle Royale National Park commenced in 1958. Numbers, pack structures, and observed relationships are reported herein for winter periods of the 4 years, 1967 to 1970. An important feature of the period was the immigration of a pack of seven wolves in 1967. Four of the seven were black and thus identifiable. This addition raised wolf numbers on Isle Royale to at least 28. Through mortality not compensated for by recruitment, and possibly by the egress of a pack of six to Canada, the population was reduced to 15 in 1968. Estimates for the winters of 1969 and 1970 were 17 and 18, respectively. In 2 years considered to be environmentally favorable, there were unexpectedly small population gains toward an earlier mean of 24. In the period 1967 to 1970 the common size for major packs on the island was six or seven, and evidence is accumulating that the area may not accommodate more than a single breeding group. The smaller packs did not evidence any decrease in predation efficiency relative to that observed for a large pack of 16 prior to 1967. Territorial antagonism, however, between the largest pack and a group of four apparently resulted in a clash in 1969 during which one of the four was killed. In the winter of 1970 the dominant pack contained eight wolves at the highest count. The alpha male in this pack was a large gray animal that appeared bonded with the same female in 1969 and 1970. The pair was closely attended in 1970 by a large black male that evidently was the beta animal in the male hierarchy.