Unexpected Food Cooperation Between Species In The Arctic

Arctic researchers have discovered unexpected cooperative behavior in a scare food environment between caterpillars and pika.

University of Alberta researchers analyzed how the two herbivores competed for scarce vegetation in alpine areas of the southwest Yukon.

The caterpillars come out of their winter cocoons and start consuming vegetation soon after the snow melts in June. Weeks later, the pika starts gathering and storing food in its winter den. For the experiment, Barrio altered the numbers of caterpillars grazing on small plots of land surrounding pika dens.

"What we found was that the pikas preferred the patches first grazed on by caterpillars," said Barrio. "We think the caterpillar's waste acted as a natural fertilizer, making the vegetation richer and more attractive to the pika."

Professor David Hik, who supervised the research, says the results are the opposite of what the team expected to find.

"Normally you'd expect that increased grazing by the caterpillars would have a negative effect on the pika," said Hik. "But the very territorial little pika actually preferred the vegetation first consumed by the caterpillars."

The researchers said it was surprising to see the veritable food co-op between the two creatures in an environment where resources are scarce and the winters long. The two creatures spend their whole lives looking for food.

According to a press statement, the arctic caterpillars stay in their crawling larval stage for up to 14 years, sheltering in a cocoon during the long winters before finally becoming Arctic woolly bear moths for the final 24 hours of their lives. The pika does not hibernate and gathers a food supply in its den. Its food-gathering territory surrounds the den and covers an area of around 700 square meters (about 7,500 square feet).

The study was published in the journal Biology Letters.