Magazine article Science News

Besieged Tadpoles Send Chemical Alert

Magazine article Science News

Besieged Tadpoles Send Chemical Alert

Article excerpt

Tadpoles have a stinky way of warning each other to hunker down when a predator looms, according to a new study.

Like many aquatic species, tadpoles use their keen olfactory sense to identify danger, locate good food, and recognize family. Scientists also know that the amphibians, when captured, send out chemical distress signals. Now, researchers have learned that tadpoles that are merely harassed also release such distress signals. The new findings show that the signal's chemistry includes ammonium.

"This is something that, in my opinion, it's amazing people haven't discovered earlier," comments Lee B. Kats of Pepperdine University in Malibu, Calif.

In the recent study, Joseph M. Kiesecker of Yale University and his colleagues put two groups of tadpoles of red-legged frogs in an aquarium partitioned by a screen that blocked visual and acoustic communication between the groups. Water, however, flowed freely through the partition.

When a wooden heron stalked the tadpoles in one compartment, those on the other side slowed down, moved away from the divider, and ducked under a shelter, the researchers report in the June ANIMAL BEHAVIOUR. Undisturbed tadpoles did not elicit these defensive behaviors in their neighbors. The researchers conclude that the beleaguered tadpoles released a chemical signal that penetrated the screen.

"If [such signaling] is a common occurrence, which I think it is, it may be an effective way that prey animals can avoid predation," says Kiesecker.

Several other water-dwelling animals, including crayfish, hermit crabs, and a fish called the Iowa darter, also release a chemical distress signal. …

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