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Baby snowshoe hare

A 12-hour-old snowshoe hare

From an evolutionary perspective, prey animals like this 12-hour-old snowshoe hare, born into an environment fraught with danger, benefit if they are born wary and fearful, so they are automatically hiding, even though they have never seen a predator before.

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If a human mother is stressed while pregnant, research shows her child is much more likely to have emotional, cognitive or even physiological problems, such as attention deficit, hyperactivity, anxiety, language delay, obesity, diabetes and hypertension. On the other hand, the results of maternal stress on the offspring of other animals -- particularly wildlife under threat from predators -- is believed to be positive, and contributes to their survival.

According to Michael Sheriff, an assistant professor of mammalogy and ecology at PennState University's College of Agricultural Sciences, a great deal more needs to be known about the effects of maternal stress on animals. Sheriff says prenatal exposure to maternal stress in animals can influence offspring characteristics and behaviors and there are an increasing number of ecological studies linking biomedical findings to natural systems.

"If you have a mother that is stressed, her offspring will be born differently than if you have a mother that is not stressed -- and that is true as far as we know for all species," he said. "With wild animals, it is more often a better thing than a worse thing because it has been maintained through evolutionary time across taxa."

If it were a bad thing, Sheriff points out, biologists would expect to find some species, some animals, where this didn't happen. But they haven't, yet. Maternal stress, over long periods, contributes to species' survival, especially prey animals.

"If you are a prey animal and there are lots of predators around, from an evolutionary perspective, you're going to want your babies to be born scared and fearful, so they are automatically hiding already, even though they have never seen a predator before," he said.

Sheriff recommends that future maternal-stress research focus on identifying the mechanisms that allow offspring to modulate exposure to maternal stress, and examining the indirect, alternate maternal mechanisms of influence that can shape the evolution of maternal-stress effects.

This research was supported in part by the National Science Foundation (NSF).

Read more in the NSF News From the Field story More research needed on effects of maternal stress in wild animals. (Date image taken: 2005-2010; date originally posted to NSF Multimedia Gallery: May 29, 2018)

Credit: Photo by Jeff Werner

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