Time of Day Tempers Tadpoles' Response to Predators

Aug 10, 2006

To a tiny tadpole, life boils down to two basic missions: eat, and avoid being eaten. But there's a trade-off. The more a tadpole eats, the faster it grows big enough to transform into a frog; yet finding food requires being active, which ups the odds of becoming someone else's dinner.

Scientists have known that prey adjust their activity levels in response to predation risk, but new research by a University of Michigan graduate student shows that internal factors, such as biorhythms, temper their responses.

Michael Fraker, a doctoral student in the laboratory of ecology and evolutionary biology professor Earl Werner, will present his results Aug. 10 at a meeting of the Ecological Society of America in Memphis, Tenn.

Fraker studied tadpoles of the green frog (Rana clamitans), which normally feed more at night, to see whether their responses to predatory dragonfly larvae differed with time of day.

"Green frog tadpoles, like many other aquatic animals, assess predation risk indirectly by sensing chemicals released by their predators into the water," Fraker said. Typically, the tadpoles respond to such cues by swimming down to the bottom, seeking shelter and remaining still. In his experiments, Fraker exposed tadpoles in a tank to the chemical signatures of dragonfly larvae for one hour during the day and one hour at night. Then he recorded their swimming and feeding activity during and after exposure. Both during the day and at night, the tadpoles initially responded similarly to the chemical cues, showing the typical plunge in activity. But at night they returned to feeding more quickly than during the day.

"My interpretation of these results is that green frog tadpoles behave more conservatively in response to a predator chemical cue during the day because predation risk may still be fairly high and the tadpoles are going to feed very little anyway. That means the growth rate-to-predation risk ratio is low. At night, the ratio is higher because that's when the tadpoles do most of their feeding. This favors a quicker return to their pre-cue activity levels."

Considering biorhythmic activity patterns in predator-prey studies is something of a new slant, Fraker said. "The main implication of my results is that prey behavior can be influenced by both external factors---the chemical cues released by the predators---and internal factors such as circadian rhythms. This is important for understanding the mechanisms of prey behavior, which need to be identified in order to make long-term predictions about the effects of prey behavior in ecological communities."

Source: University of Michigan

Explore further: Free the seed: OSSI nurtures growing plants without patent barriers

add to favorites email to friend print save as pdf

Related Stories

Light triggers a new code for brain cells

Nov 12, 2008

Brain cells can adopt a new chemical code in response to cues from the outside world, scientists working with tadpoles at the University of California, San Diego report in the journal Nature this week.

Recommended for you

Plants with dormant seeds give rise to more species

Apr 18, 2014

Seeds that sprout as soon as they're planted may be good news for a garden. But wild plants need to be more careful. In the wild, a plant whose seeds sprouted at the first warm spell or rainy day would risk disaster. More ...

Researchers successfully clone adult human stem cells

Apr 18, 2014

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

User comments : 0

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.