Dam Wins Battle of the Sexes to Protect Foal

After witnessing a rare (and unsuccessful) infanticide attack by a stallion on a one-hour-old foal, behavior researcher Meeghan Gray, PhD, from the University of Nevada, Reno, reported findings from the macabre event.

"In this first report of an infanticide attempt in free-roaming feral horses, we learned that mares can successfully protect their foals against an attacking male and that horses (and other equids) have evolved practicing infanticide which supports the 'sexual selection hypothesis' in behavior research," explained Gray.

On April 12, 2005, Gray was observing the feral horse population in the Virginia Mountain Range outside Reno, Nev. The band stallion lunged toward the mare and foal within one hour of parturition, after the foal made an initial and unsuccessful attempt to stand. The stallion continued to attack the foal for approximately one minute, during which time the mare defended her foal by charging, biting, and kicking the stallion. The foal had minor wounds but did stand and nurse and was successfully weaned the next year.

"We later confirmed that the stallion was not the sire of the foal, which was suspected initially because the attacking stallion had only recently taken over the band" said Gray. "It is thought that this lack of paternity was the primary impetus for the attack; however, how stallions detect paternity is unclear at this time."

This observation suggests to Gray that infanticide is an inherent part of feral equids' social structure. While infanticide is 'beneficial' to the stallion in terms of reducing the interbirth interval and siring the subsequent foals, the loss of a foal is a huge energy expenditure, loss of investment, and clearly detrimental for the mare.

Gray's observations and hypotheses regarding infanticide can be read in detail in the study, "An infanticide attempt by a free-roaming feral stallion (Equus caballus)," which is scheduled to be published in the journal Biology Letters.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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