An Early Education: As Embryos, Frogs Sniff Out Predators

By Brett Israel | November 2, 2009 7:00 am

tadpole-webFrog tadpoles have a good nose for danger: Scientists know that they go from headlong swimming to total stillness when they smell a predator. Now, researchers have discovered that frogs get that odoriferous training very early on. When they’re still embryos, they can learn to assess the threat level by sniffing for a predator’s pheromones.

Embryos put into water containing the odour of a salamander and the odour of injured tadpoles learned that the predator’s smell was a threat [BBC News]. The idea was to see if the amphibian embryos could learn to associate the smell of injured tadpoles with the smell of a predator. This type of learning behavior has also been observed in previous experiments with fish, larval amphibians, and larval mosquitoes, however this was the first study to document the behavior in embryos.

In an experiment sure to make PETA squirm, crushed tadpoles were mixed with water in which a tiger salamander had been swimming. Embryos were raised in this water with different concentrations of crushed tadpoles. Once the embryos had hatched into tadpoles, researchers tested their response to only the salamander odor. The tadpoles that were exposed to a higher concentration of the injured tadpole odour stayed motionless for longer in response to the salamander cue [BBC News]. The scientists say this demonstrates that these tadpoles learned as embryos that salamanders were more dangerous predators. The researchers published their findings in the journal Behavioural Ecology and Sociobiology.

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Image: Maud Ferrari, UC Davis

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