Are low infidelity rates in feral horses due to infanticide?
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A growing number of studies conducted on diverse taxa have shown that extra-pair/group paternity is higher than what would be predicted from behavioral observations alone. While it may be beneficial for females to mate with multiple males, this often results in offspring not sired by the behavioral father, which could influence offspring survival, especially in social mammals. Feral horses (Equus caballus) maintain stable social relationships over several years, usually with one stallion defending a harem band of unrelated mares against other males. Sneak copulations by subordinate males have been observed and mares sometimes change bands, both of which can result in foals sired by males other than the dominant band stallion. We measured female fidelity in free-ranging feral horses in 23 bands, with 51 foals over four foaling seasons and tested offspring paternity against parental behaviors. We used 12 polymorphic microsatellite loci and the program CERVUS 2.0 to determine and exclude potential sires. The majority of mares remained in the band with the sire of their foal resulting in most foals being sired by the band stallion. Most foals that were not sired by the band stallion were born in the year after a round-up and we could not determine if they were the result of band changing or sneak copulations. Foals born into a band without their sire had lower survival rates and mothers were significantly more protective of foals not sired by the band stallion. These findings suggest that band stability increases the reproductive success of mares and support the importance of infanticide risk in equid social structure.
KeywordsEquus caballus Fecal DNA Microsatellites Parental behavior Paternity Wild horse
We thank Kris Krus from the Nevada Genomics Center for providing fragment analysis and technical support. This research was supported the Nevada Arid Rangeland Initiative NOA15353CG, 110615253BS, 140115253BS, 140215253BS, Hatch Grant 13215353BS, and a research grant from the American Society of Mammalogists. We thank several anonymous referees for valuable criticisms of earlier versions of this manuscript.
Conflict of interest
The authors declare that they have no conflict of interest.
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