Patterns of reproductive effort in male ungulates

Abstract

In ungulates, males and females have contrasting life histories, as usually only the females raise the young. How reproductive effort in males varies with individual level and population level characteristics has received little attention in the literature. Using published information on direct (weight loss during the rut) and indirect (rutrelated changes in activity budgets, fighting frequency, etc.) measures of reproductive effort, we tested whether effort in males increased with (H 1 ) increasing age, (H 2 ) increasing body size, (H 3 ) decreasing population density, (H 4 ) increasingly female-biased sex ratio and with a younger male age structure. Consistent with H 1 , reproductive effort was consistently higher in prime-aged than in younger males in a large number of studies. Among younger males, sub-adult males had an equal or higher effort than yearling males. Prime-aged males had more typical rutting behaviour (e.g. roaring, tending, fighting and chasing frequencies) and they often lowered their intake of forage during the rut. However, reproductive effort usually declined for very old age classes. Reproductive effort increased with size (H 2 ) also after accounting for age. Data on effort vs (H 3 ) density and (H 4 ) sex ratio/male age structure were inconclusive. Clearly, far more studies relating effort to population characteristics are needed before the rutting ecology of male ungulates can be understood.

Variation in Growth Pattern of Male MooseAlces alcesAfter Two Contrasted Periods of Hunting

“…Higher somatic growth before prime age is expected to detract from reproductive resources (Yoccoz et al 2002, Mysterud et al 2004, Garel et al 2006. In our study, the growth rates of both body weight and antler size were higher after mixed age class harvest, but contrary to our predictions, on the coast also the maturation size (when reaching prime age) was higher (Fig.…”

Timing of Reproductive Effort Differs between Young and Old Dominant Male Reindeer

“…Activity was higher for old than young dominant males during the early-and peak-rut weeks. Past studies found activity during the mating season to be generally higher for old than for young males (Skogland 1989, Kojola 1991, Mysterud et al 2004. During the late-rut week we found that old males reduced their activity level.…”

“…For capital breeding mammals, the amount of weight lost over the mating season is considered a direct indicator of male reproductive effort (Yoccoz et al 2002, Mysterud et al 2005, Galimberti et al 2007. Behavioural indices, such as performance of agonistic behaviours or activity budgets during the mating season, are also often used in studies as indirect measures of male reproductive effort (see references in Mysterud et al 2004). Few studies have looked into the relationship between these two measures.…”

Reproductive effort of bison bulls (Bison bison) in semi-natural conditions

“…In several ungulate species, males experience serious weight loss during the rut, which is considered a direct measure of RE (Lott 1979;Mysterud et al 2004). Indirect measures of RE are rut-related changes in activity budgets, fighting frequency and tending of females (Mysterud et al 2004).…”

“…In several ungulate species, males experience serious weight loss during the rut, which is considered a direct measure of RE (Lott 1979;Mysterud et al 2004). Indirect measures of RE are rut-related changes in activity budgets, fighting frequency and tending of females (Mysterud et al 2004). Males face a trade-off between investment in current reproduction or in other fitness components such as survival (Mainguy and Côté 2008) and need to balance their activity budgets between investing in RE (access to females, competition to males, patrolling territory) and investing in maintenance activity such as feeding and resting (Willisch and Ingold 2007).…”