Mating Group Size and Stability in Reindeer <i>Rangifer tarandus</i>: The Effects of Male Characteristics, Sex Ratio and Male Age Structure

L'Italien, Léon; Weladji, Robert B.; Holand, Øystein; Røed, Knut; Nieminen, Mauri; Côté, Steeve D.

doi:10.1111/j.1439-0310.2012.02073.x

Cited by 27 publications

(31 citation statements)

References 53 publications

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“…Young males are known to have less developed social rutting behaviours than adult males, and to cause extra stress on females (Clutton-Brock and Parker 1992;Komers et al 1999;Tennenhouse et al 2012). Their behaviours when dominant, such as herding females, may also be less efficient (L'Italien et al 2012;Body et al 2014) and regularly turn into a chase. Females may also be responsible for this disturbance.…”

Section: Discussionmentioning

confidence: 97%

“…Within an enclosure, herd members split into unstable groups that undergo intense fission-fusion group dynamics (Holand et al 2006;L'Italien et al 2012;Body et al 2015). The number of groups in an enclosure, as well as the average group size varied throughout the breeding season in each year (Body et al 2015).…”

Section: Group Recordsmentioning

confidence: 99%

“…Foraging competition is therefore in conflict with the dilution effect of harassment. Obtaining protection from adult dominant males is also in conflict with foraging competition, as adult males are known to lead larger groups than young males (L'Italien et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Foraging competition in larger groups overrides harassment avoidance benefits in female reindeer (Rangifer tarandus)

Uccheddu¹,

Body²,

Weladji³

et al. 2015

Oecologia

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Male harassment toward females during the breeding season may have a negative effect on their reproductive success by disturbing their foraging activity, thereby inducing somatic costs. Accordingly, it is predicted that females will choose mates based on their ability to provide protection or will aggregate into large groups to dilute per capita harassment level. Conversely, increasing group size may also lead to a decrease in foraging activity by increasing foraging competition, but this effect has rarely been considered in mating tactic studies. This study examined the importance of two non-exclusive hypotheses in explaining the variations of the female activity budget during the breeding season: the male harassment hypothesis, and the female foraging competition hypothesis. We used focal observations of female activity from known mating groups collected during the breeding season from a long-term (15 years) study on reindeer Rangifer tarandus. We found that females were more disturbed (i.e., spent less time feeding) in the presence of young dominant males, and marginally disturbed in the presence of satellite males, which supports the male harassment hypothesis. We also found that female disturbance level increased with group size, being independent of the adult sex ratio. Consequently, these results rejected the dilution effect, but strongly supported the foraging competition hypothesis. This study therefore highlights a potential conflict in female behaviour. Indeed, any gains from harassment protection were negated by an increase of 6-7 females, since adult males lead larger groups than young males.

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Section: Discussionmentioning

confidence: 97%

Section: Group Recordsmentioning

confidence: 99%

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Foraging competition in larger groups overrides harassment avoidance benefits in female reindeer (Rangifer tarandus)

Uccheddu¹,

Body²,

Weladji³

et al. 2015

Oecologia

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“…The resulting decrease in fission rate, induced an increase in average group size [17]. Larger harems retain more estrous females [23]. Consequently, more efficient is the herding, the greater the number of estrous females a male can have in his harem, depleting mating opportunities from his competitors, and consequently increasing the opportunity for sexual selection [10].…”

Section: Discussionmentioning

confidence: 99%

Highly Competitive Reindeer Males Control Female Behavior during the Rut

et al. 2014

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During the rut, female ungulates move among harems or territories, either to sample mates or to avoid harassment. Females may be herded by a male, may stay with a preferred male, or aggregate near a dominant male to avoid harassment from other males. In fission-fusion group dynamics, female movement is best described by the group’s fission probability, instead of inter-harem movement. In this study, we tested whether male herding ability, female mate choice or harassment avoidance influence fission probability. We recorded group dynamics in a herd of reindeer Rangifer tarandus equipped with GPS collars with activity sensors. We found no evidence that the harassment level in the group affected fission probability, or that females sought high rank (i.e. highly competitive and hence successful) males. However, the behavior of high ranked males decreased fission probability. Male herding activity was synchronous with the decrease of fission probability observed during the rut. We concluded that male herding behavior stabilized groups, thereby increasing average group size and consequently the opportunity for sexual selection.

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“…; L'Italien et al . ). In contrast, paternity of males typically decreases in multimale groups (Belle & Estrada ; Fedigan & Jack ; Lardy et al .…”

Section: Introductionmentioning

confidence: 97%

The modulating role of group stability on fitness effects of group size is different in females and males of a communally rearing rodent

Ebensperger

Correa

León

et al. 2016

Journal of Animal Ecology

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Group size may influence fitness benefits and costs that emerge from cooperative and competitive interactions in social species. However, evidence from plural breeding mammals indicates that group size is insufficient to explain variation in direct fitness, implying other attributes of social groups were overlooked. We studied the natural population of a social rodent during 5 years to test the hypothesis that social stability - in terms of group composition - modulates the effects of increasing number of breeding females (a proxy of communal rearing) and males on the number of offspring weaned (sired) and on the number of offspring weaned (sired) surviving to breeding age (two proxies of direct fitness). We quantified the effects of social stability (measured as changes in female or male group members between mating and the onset of lactation) on these fitness measures. We used live trapping, telemetry and DNA markers to determine social and fitness measures. Social stability in degus was variable in terms of the number of changes in group composition across groups. Low stability was mostly due to mortality and emigration of group members. Results supported a modulating role of social stability on the relationship between group size and the number of offspring weaned (sired). Stability in female and male group composition were both modulators of fitness to females and males. The modulatory role of stability was sex specific, where high social stability was often fitness beneficial to the females. Instead, low social stability was fitness enhancing to the males.

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Mating Group Size and Stability in Reindeer Rangifer tarandus: The Effects of Male Characteristics, Sex Ratio and Male Age Structure

Cited by 27 publications

References 53 publications

Foraging competition in larger groups overrides harassment avoidance benefits in female reindeer (Rangifer tarandus)

Foraging competition in larger groups overrides harassment avoidance benefits in female reindeer (Rangifer tarandus)

Highly Competitive Reindeer Males Control Female Behavior during the Rut

The modulating role of group stability on fitness effects of group size is different in females and males of a communally rearing rodent

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