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Abstract
The behavior of two populations of tule elk Cervus elaphus nannodes bulls was studied with the objective of looking at how herd characteristics and interactions between bulls changed during and outside the rut. I reviewed factors which may lead to formation of herds and cause agonistic interactions outside the rut.
Tule elk bull were observed to live in consistent herds comprised of large and medium sized bulls. Members of core bull herds lived in a definitive home range. Site fidelity and herd fidelity were important factors determining where herds were located. Bull movement was limited. Most interactions between bulls from different herds were aggressive.
Bulls and cows lived in separate home ranges for most of the year except during the rut. Spikes suffered high mortality in winter causing a female biased secondary sex ratio.
The type and intensity, as well as motor pattern used in agonistic interactions between bulls tracked the antler growth phase. A higher rate of agonistic interactions occurred after bulls cast antlers and when they were in velvet: when non antler threats were used. Majority of those interactions involved boxing and kicking. Bulls who had cast antlers won against bulls with antlers majority of the time. Parallel walks and antler clashes only occurred during the rut. Reversal in rank between bulls were frequent during the pre-rut period. Antlers may only be one of the characters used in assessment of a bull's fighting ability. Actually, bulls interacted very rarely. No post conflict reconciliation were observed.
When in rut, herding bulls were very aggressive towards spikes. When two estrous cow herds were close together, bulls herded more and bugled more frequently. Bugling was correlated with cow herd sizes while herding was correlated with the number of bulls at the periphery of the herds. Estrous cows transferred from small herds to large herds where per capita harassment by the herding bull was reduced. Cows were frequently lost to neighboring herding bulls. Tule elk behavior is compared with that of other mammals.
