Casual Quail Sex Leads to More Fearful, Fatter Offspring

Hookup buddies or long-term partners? It’s a key question in 21st-century rom-coms—and also in the world of bird romance.

The personality of Japanese quail chicks changes depending on the kind of relationship formed between parents, according to a new study to be published in the Journal of Experimental Biology. Quail chicks born from parents who were attached to each other are more social, lighter, and less fearful.

And this effect, found by a team of researchers at the University of Rennes, France, isn’t a question of quail parenting strategies. Instead, it’s entirely prenatal. It all depends on whether the parent quails had settled into a tight, exclusive pair bond.

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The personality of Japanese quail chicks changes depending on the kind of relationship formed between parents, a new study reports.

“If parents developed a pair bond, offspring are more social (although they have been reared without parents),” writes animal behaviorist Océane Le Bot, who led the study, via email. For their research, her team saved 30 male and 30 female broiler-line Japanese quail from an industrial farm.

Half of the paired-off quail got to engage in five-minute booty calls a few times a week. The other half were put into a sort of arranged marriage with randomly chosen mates in dual-occupancy cages.

After a few weeks, Le Bot’s matchmaking took. When separated into different cages, cohabitating quails of both sexes called out, actively searching around for their missing partners. And when reunited, these pair-bonded quails calmed down.

By contrast, the behavior of the quail-with-benefits suggested they were more relaxed when put in separate cages. Males became louder, moved around more, or engaged in courtship behaviors—something pair bonded males don’t do. They even seemed wary, stretching their necks tall in vigilance.

With bonds firmly in place and gendered clichés confirmed, Le Bot turned her attention to the products of these unions. To fully consider the prenatal impact of the parents’ relationship on the chicks’ nature, Le Bot raised the chicks in a big group under a heat lamp.

In terms of average behavior, chicks from pair bonded parents were different than chicks conceived during brief hookups. When confronted with a new environment or the sudden appearance of a weird object, known to elicit surprise—a black and yellow T-shaped block—they showed less fear, as judged through calls, posture, and attempts to escape. And when placed on the path to a cage with other quail chicks they had never met, the chicks from pair bonds were more eager to join these potential new friends.

Exactly how this happens prenatally is still unclear. Le Bot’s team checked hormonal differences between the eggs, but they haven’t yet found a smoking gun. It’s also possible that the mother’s prenatal state can subtly alter how the genetic code of the chick is expressed, a change known to affect behavior in birds and rodents.

“This study is suggesting that actually the interactions between mom and dad are really important,” says Allison Bell, a biologist who studies animal personality at the University of Illinois. The fact that chicks inherit traces from their parents’ world raises some interesting questions the field is trying to answer, according to Bell.

In some cases, like when mothers are extremely stressed, prenatal influences might disadvantage offspring, Bell says. “You can also think about cases where it might be adaptive…if parents can communicate something about the environment the offspring are likely to experience.”

That kind of communication may be what’s happening with the Japanese quail, where the parent’s relationship status somehow signals the chicks. In addition to their gregariousness, the chicks from pair bonds were on average lighter than their counterparts.

These chicks, Le Bot’s study suggests, might be prepared for two very different futures. If relationships are stable, prenatal messages tell offspring to be adventurous, open. That’s what happens in the wild, where quail almost always settle in to pair bonds. But if relationships are fleeting—as if due to predators—being a little heavier and a little more conservative might be a better survival strategy. Or, on a farm, it just might make a quail better for the broiler.

“The question is so interesting,” Bell says, underscoring the study’s surprising finding. “There’s something about parent care bonds that might actually influence offspring development, and that’s all happening prenatally.”