A blind, hairless, subterranean rodent is promising to improve understanding of how stress influences human fertility, scientists will report today.

Research into the breeding habits of the African naked mole-rat, which lives in semi-arid regions, is shedding light on how hormones released by stress can suppress ovulation and sperm production.

Although mole-rat colonies number between 100 and 300 animals, only the dominant “queen” breeds. She keeps the other females and many males reproductively inactive by bullying them, so that the resulting stress interferes with their ability to make sex hormones.

“The queen exerts her dominance over the colony by, literally, pushing the other members of the colony around,” said Chris Faulkes, of Queen Mary, University of London, who will present his work today at the European Society of Human Reproduction and Embryology conference in Lyons.

“She shoves them to show who’s boss. We believe that the stress induced in the lower-ranking animals by this behaviour affects their fertility. There appears to be a total block to puberty in almost all the non-breeding mole-rats so that their hormones are kept down and their reproductive tracts are underdeveloped.”

In non-breeding females, key fertility hormones appear to be suppressed by their subordinate position. In males, testosterone and sperm production are lowered except when the queen is about to mate with them, making it less likely that they will try to impregnate other females.

Stress is known to be linked to infertility in people, and Dr Faulkes hopes that his research into naked mole-rats will help to explain how this happens and how it might be treated.

“Social suppression of reproduction in marmoset monkeys is very similar to that in naked mole-rats, and as these are primates the applications to understanding human stress-related infertility aren’t so far-fetched,” he said, adding that the neurobiological process underlying the way in which mammals responded to social and environmental cues were still largely unknown.

However, he also pointed out: “Humans vary widely in the way in which they form social bonds with their partners, offspring and kin. By making careful comparisons with model species like mole-rats, we may be able to tease apart the relative contribution of genes, environment, upbringing and culture to complex social behaviour in our own species.”

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