Science Friday: Healthy Horse Moms Play More With Sons

Healthy moms play more with their kids. It has now been proven. Cracked out moms passed out on the couch clutching a liquor bottle and a box of kleenex and KOOLS aren’t as good at their jobs as those who take La Leche League classes and go to aerobics three times a week and eat an apple a day. An article in by Jennifer Viegas tells us that it’s the same for horses. More reason to keep that dam healthy after foaling. I have made some mistakes out of ignorance in this area, so it feels right to post this article entitled, Promoting Strong Sons . What’s different about horses is that dams show a clear preference for their sons over their daughters!

Healthy wild horses show marked preference for investing time and energy in their sons.

A colt and young mare rub noses, in Montana. Scientists have discovered that healthier mares invest more in sons over daughters, with the investment consisting of more milk, protection and direct contact. These sons then played more, even at the expense of the moms, who temporarily lost weight and strength taking care of their boys. | image courtesy

Evidence from this study on horseplay suggests that the equine findings could carry over to other polygynous animals, including humans. The term, polygynous describes species with males that can mate with more than one female over a relatively short period of time, with the pairings all possibly resulting in pregnancies.

Mothers are advantaged differently by investing in sons or daughters in relation to their own condition and the future reproduction of their offspring. Sons have the highest potential payoff, as sons can leave you many more grand-offspring than daughters can.

This from Elissa Cameron, director of the Mammal Research Institute at the University of Pretoria in South Africa. She and her colleagues studied wild horses in New Zealand known as Kaimanawa. These horses live in year-round bands consisting of multiple mares, at least one stallion and their foals. Cameron and her team focused on the interactions between mothers and their young, and particularly on the foals’ play behavior. Horses play by manipulating objects, simulating courtship and mounting, running alone or with a partner, and by play fighting.

The scientists discovered that healthier mothers invested more in sons over daughters, with the investment consisting of more milk, more vigilant protection and increased direct contact. These sons then played more, even at the expense of the moms, who temporarily lost weight and strength taking care of their boys.

Mothers in overall poor condition, however, invested more time and resources in their daughters.

Cameron explained that while males in general breed more, not all male horses will turn out to be busy breeders, whereas almost all female horses that reach adulthood will breed at least once.

Therefore, if you have a lot of extra resources and can turn your son into a highly competitive male, he will leave you more grand-offspring. Alternatively, if you have few resources to invest, a son would be unlikely to ever breed, whereas your daughter would probably breed, thereby leaving you more grand-offspring.

Cameron added that sires might affect the process to some degree, as they occasionally groom and play with their foals, but the bulk of the parental care falls on mothers. The process results in a domino effect that influences the rest of the horse’s life. A horse that receives more care from its mother tends to play more. Since playtime appears to enhance both physical and mental health, playful individuals tend to grow into healthier adults, which then start the process all over again. The health of the mother may even predict the gender of the foal she will give birth to in the first place.

A separate study on 740 first-time pregnant human moms led by the University of Exeter’s Fiona Mathews found that mothers who ate a high-energy diet at the time of conception produced sons more often than moms who took in less nutrition before conceiving.

Here we have evidence of a ‘natural’ mechanism that means that women appear to be already controlling the sex of their offspring by their diet. This research may help to explain why in developed countries, where many young women choose to have low-calorie diets, the proportion of boys born is falling.

Jennifer Viegas writes, “While genetics also help to determine an individual’s sex, health, playfulness and more, the two studies reveal how mothers can play a major role in controlling the destinies of their children.”

© 2010, hurric@nekim. All rights reserved.

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