February 21, 2010
To test how crickets learn to avoid spiders, researchers covered a wolf spiders' fangs with wax to render it harmless and then placed it into an enclosure with pregnant crickets. The spider could hunt the crickets to its heart's desire, but couldn't kill them. A second enclosure was left spider-free.
When the baby crickets hatched, researchers discovered major behavioral differences between the crickets whose mothers had faced stalking spiders and those from the spider-free enclosure. Crickets from spider-exposed mothers proved far more wary of wolf spiders: staying hidden 113 percent longer than crickets whose mothers hadn't met a spider. The crickets with a spider-exposed mother were also found to be more likely to 'freeze' when they ran into spider silk or feces, a behavior that could save them from being eaten. Not surprisingly, crickets whose mothers' had braved spiders had a higher survival rate when up against the predaotor.
The same results were found in the wild. Collecting pregnant crickets from their natural habitat, the researchers found that the offspring behaved differently toward spiders—i.e. more cautious or less so—in correlation with whether or not spiders were common or scarce in their mothers' habitat.
The researchers don't know how this transfer of information from mother to unhatched crickets occurs, but they speculate that anxious encounters with spiders may release a hormone in the mother that influences the development of her embryos.
Citation: Jonathan J. Storm and Steven L. Lima, "Mothers Forewarn Offspring about Predators: A Transgenerational Maternal Effect on Behavior." American Naturalist 175:3 (March 2010).
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