Many variables may play a role in the male dominance hierarchy. The order of antler casting and animal age are two such variables. The number of interactions that a middle-ranked bull takes part in are contingent upon the stage in the antler cycle; interactions are highest during casting (Bartos, 1986). There exists a clear relationship between bull rank and agonistic activity. Bartos stated, “High ranking animals exhibit the greatest amount of agonistic behavior.”
Feeding does not affect dominance relationships, though it can be evidence of a hierarchy and it can affect the frequency of interactions. Group size has an effect on the alphas and on the omegas, but does not seem to change the behavior of the other animals. In fact, a larger group size increased agonistic activity in the most dominant individuals and suppressed it in the most subordinate (Bartos, 1986). Group size is also dependent on the season, as well as member age and individual ranks (Bartos, 1986). When food is scarce, groups become larger (1985). Rank and age are associated up to 5 years (Appleby, 1980).
William M. Ciesla, Forest Health Management International,www.forestryimages.org
Terry Spivey, USDA Forest Service, www.forestryimages.org
Some researchers have found a higher correlation between agonistic behavior and physical ability than with any other factor (Appleby, 1980; Weckerly, 2001). This possibility is more likely because the most dominant and most successful male elk will separate themselves. Such behavior would seem to dilute the social benefits that age and genetic relatedness may provide for that stag. Genetic relatedness in stags seems to play little role in affecting agonistic interactions.
In many mammals, agonistic interactions are most frequent among rank neighbors. It was found that in the elk social system this is not the case. Middle-ranked stags will form temporary coalitions with others of similar rank (Appleby, 1982). At the same time, as rank disparity increases, stags become less tolerant of other males. They spend more time with stags of similar rank and age for two reasons. Stags are most likely to be threatened and attacked by individuals that out-rank them considerably (Bartos, 1986). This occurs because fighting initiated by dominant animals is a primary means of maintaining social rank, and because the initiator wins the majority of the encounters (Veilberg, et al. 2004). The benefit/risk ratio involving agonistic encounters with similarly ranked bulls is too low to encourage fighting. Stags have a high chance of being wounded in an aggressive interaction with a similarly ranked opponent but little to win. Most encounters take place during the rut, and most harems are controlled by elder males rather than similarly ranked males.
