Walrus ethology. I. The social role of tusks and applications of multidimensional scaling

Abstract

Social behavior of male Pacific walruses. Odobenus rosmarus (L.), summering (i.e. outside the breeding season) on an Alaskan hauling ground is described. Social interaction on land is mostly agonistic. Visual presentation of tusks and striking with tusks feature prominently in most agonistic interactions: vocal communication occurs in a minority of them. Agonistic interactions are analyzed in R- and Q-approaches with MIN1SSA, a fully non-metric multidimensional scaling procedure programmed in the Guttman-Lingoes series. Large body size and long tusks characterize dominant walruses. Dominants are most frequently aggressive and threatening, and least frequently exhibit submissive, defensive, protective, and avoidance behavior. Subordinate walruses show the opposite trend. Walruses are bullies; individuals strongly disadvantaged in body size or tusk length, or both, receive numerous strikes and visual threats. Walruses tend to initiate agonistic interactions with smaller individuals. Walrus tusks are important in fighting, a fact which constrains evolutionary ritualization of their visual display.