Aggressive behavior of Roosevelt elk (Cervus canadensis rooseveltii) was studied at Prairie Creek Redwoods State Park in northwestern California for a one year period. The principle method used was field observation. Aggressive behavior was expressed within the bounds of a fairly well-developed dominance hierarchy, with more overt forms of aggression occurring where a less stable hierarchy existed. Little aggression was observed within different age groups of elk, other than within the calf group; a relatively high degree of aggression was observed between age groups, with the older individuals usually being dominant. Redirection of aggression resulting in chain reactions of aggressive activity was common. Aggressive patterns were observed developing among calves at one month of age, and a stable calf hierarchy was observed formed by the time the calves were six months of age. Size seemed to be the major determining factor in the outcome of encounters between calves. Antlers proved to be an important display mechanism used in aggressive interaction between bull elk. Signposting is one of the more complex aggressive patterns observed, functioning as a means of spacing groups and individuals; feeding may be a secondary function of this behavior during certain periods of the year. Special aggressive patterns are observed for the bull elk during the rutting season. Initiated aggressive responses often are observed to conflict with withdrawal and fear drives, resulting in redirection, displacement, immobility, appeasement, and response combinations. Through these patterns of aggressive behavior expressed within the limits of a dominance hierarchy basic life requirements can be more efficiently fulfilled at both the group and individual level.
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