Caterpillars' 'Leftovers' Delicious To Mountain Mammal

Mary Sussman, ISNS Contributor

Date: 30 May 2013 Time: 05:15 PM ET

(ISNS) -- University of Alberta researchers recently discovered a special relationship between mammals that are roughly the size of hamsters, called collared pikas, and Arctic woolly-bear moth caterpillars. The two animals share a food source in an alpine valley in Canada's Yukon Territory, but do not compete over the food source. 

The study, published in Biology Letters, found that pikas prefer to chomp on patches of vegetation that the woolly-bear moth caterpillars grazed upon earlier in the growing season. 

"In general, we tend to view species using the same resources as competing with each other," said David Hik, a researcher at the University of Alberta involved in the study. But, in this case and others, he said, those interactions can be positive.

The findings suggest that the caterpillars' foraging may have stimulated the plants to replace the growth that the caterpillars had eaten, which could make them more nutritious and attractive to pikas. Scientists often study caterpillars and other invertebrates because they can be destructive. This study, however, suggests that positive interactions between invertebrates and vertebrates -- such as caterpillars and pikas -- may occur more frequently than previously thought.

The researchers did not determine why pikas actively prefer the pre-grazed patches, but suggested several hypotheses that might be factors. 

One possibility is that the caterpillars only consume a small portion of the foliage, and that pikas do not rule out eating the leftovers because of the pre-nibbling. 

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