Environmental and demographic drivers of male mating success vary across sequential reproductive episodes in a polygynous breeder

• Published in: Ecology and evolution Vol. 9; no. 9; pp. 5106 - 5117
• Main Authors: Manning, Jeffrey A., McLoughlin, Philip D.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-05-2019; John Wiley and Sons Inc
• Subjects: Abundance; Animal behavior; Animal populations; Availability; Breeding; Breeding seasons; Climatic conditions; Demographics; Demography; environmental gradient; Equus ferus caballus; Feral populations; Horses; Males; Mating; National parks; Original Research; reproductive episode; Resource availability; Sex; Sex ratio; Sexual selection; Social factors; Weather; Canada; Sable Island; resource availability; Equus ferus caballus; reproductive episode; environmental gradient; sex ratio; sexual selection
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.5066

Ecological and social factors underpinning the inequality of male mating success in animal societies can be related to sex ratio, sexual conflict between breeders, effects of nonbreeders, resource dispersion, climatic conditions, and the various sequential stages of mating competition that constitute the sexual selection process. Here, we conducted an individual‐based study to investigate how local resource availability and demography interact with annual climate conditions to determine the degree of male mating inequality, and thus opportunity for sexual selection across two sequential reproductive episodes (harem and subsequent mate acquisition) in a naturally regulated (feral) horse population in Sable Island National Park Preserve, Canada. Using a 5‐year, spatially explicit, mark‐resight dataset and hierarchical mixed‐effects linear modeling, we evaluated the influence of adult sex ratio (ASR) on mating success and then tested for effects of freshwater availability, density, unpaired male abundance, and precipitation during each breeding season. Unpaired male abundance, freshwater availability, and ASR differed in their effects on male mating success according to year and selection episode. Opportunity for sexual selection in males associated with harem acquisition increased with ASR, and unpaired male abundance further explained weather‐related interannual variation after accounting for ASR. In contrast, once a harem was secured, ASR had little effect on male mating inequality in regard to acquiring additional females, while interannual variation in mating inequality increased with decreasing freshwater availability. Our findings show that local demography, resource availability, and weather effect opportunity for sexual selection in males differently depending on selection episode, and can attenuate or accentuate effects of ASR.
Ecological and social factors underpinning the inequality of male mating success in animal societies can be related to sex ratio, sexual conflict between breeders, effects of nonbreeders, resource dispersion, climatic conditions, and the sequential reproductive steps (male selection episodes) that constitute the sexual selection process. We investigated how local resource availability and demography interact with annual climate conditions to determine the degree of male mating inequality, and thus opportunity for sexual selection across two sequential reproductive episodes (harem and subsequent mate acquisition) in a naturally regulated (feral) horse population on Sable Island, Canada. Our findings show that local demography, resource availability, and weather effect opportunity for sexual selection in males differently depending on selection episode, and can attenuate or accentuate effects of adult sex ratio.