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A mother's protective influence

NSF Award:

DISSERTATION RESEARCH: Can Hormone-mediated Maternal Effects Facilitate Adaptation to Changing Environments?  (Michigan State University)

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Parents play an important role in preparing their children for the environments they will encounter as they become independent. In the wild, the appropriate maternal preparation of young animals for the outside world can vary dramatically from one year to the next.

Over the past 22 years, a team of researchers has followed the survival and reproduction of wild red squirrels in the Yukon, Canada. Each year, the amount of food available to red squirrels fluctuates and the population density of squirrels varies as a result; under high-density conditions, only the fastest growing offspring survive. Although it is generally assumed that exposure to elevated maternal stress hormones early in life is detrimental to the young, research has shown that such exposure in red squirrels increased offspring growth rates. 

In a recent study, led by Ben Dantzer of Michigan State University, female red squirrels were tricked into thinking they were reproducing in a high-density environment using audio playbacks of territorial vocalizations. Under these conditions, pregnant females had elevated levels of stress hormones which produced the fastest growing offspring, despite not having access to additional food.

This research shows that female red squirrels can predict the type of environment their young will encounter and that adaptive changes in offspring characteristics improve the offspring's ability to survive in anticipated environmental conditions. The research highlights the importance of studying how hormones influence survival and reproduction in wild animals so that we can better understand the evolution of the same mechanisms in humans.

Images (1 of )

  • a red squirrel moves her pup from one nest to another
  • a red squirrel emits a territorial call known as a rattle
  • a red squirrel consumes seeds from a white spruce cone
  • juvenile red squirrels get ready for a weigh-in
  • a researcher holds several 25-day-old squirrels
  • a researcher readies a live-trap to capture a squirrel so it can be weighed
A red squirrel moves her pup from one nest to another.
Ryan W. Taylor
A red squirrel emits a territorial call. Pipe cleaners attached to ear tags ease identification.
Ryan W. Taylor
A red squirrel consumes seeds from a white spruce.
Ryan W. Taylor
Pups get ready for a weight check.
Ben Dantzer
A researcher holds 25-day-old pups.
Ben Dantzer
To check the squirrels' weight, researchers use live-traps.
Ben Dantzer

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