Mating Tactics and Mate Choice in Relation to Age and Social Rank in Male Mountain Goats

In polygynous mammals, mating success of males often depends on intense male–male competition and the use of alternative mating tactics. Because reproduction incurs substantial energetic costs and risks of fight injuries, mate selection by males should be expected, particularly when females vary in their ability to produce offspring but can only be defended 1 at a time. Here, we investigated during 3 ruts how age and social rank of male mountain goats (Oreamnos americanus) affected the formation of consort pairs with females (‘‘tending’’ tactic) in a marked population at Caw Ridge, Alberta, Canada. Among consort pairs, we quantified the behaviors of males and females, and the use of an alternative mating tactic by competing males, ‘‘coursing,’’ which consists of disrupting the pair to gain temporarily access to the female, often by pursuing her. Mate choice was assessed by testing if old and dominant males observed in consort pairs tended experienced females more often than younger females, because reproductive success of females increases with age. Males in consort pairs were 4 years old and most (86%, n 1⁄4 59) were in the top one-half of the dominance hierarchy. Age and social rank of males were positively related to age of females and the total number of young produced by the tended female. All observed matings (n 1⁄4 32) occurred between 14 November and 2 December and 91% were between males and females in consort pairs. Subordinate males gained mating access to females through coursing, but this tactic was rare. Our study provides evidences of mate choice by males for experienced females in an ungulate and the 1st quantitative information on the rut of mountain goats.