Surf and turf

Maybe you can't tell a book by its cover, but it turns out you can sometimes tell what was once in an animal's stomach by analyzing its hair. Take the arctic fox, whose diet is a mix of the marine (seal carrion and seal pups) and the terrestrial (lemmings, bird eggs, caribou carrion). The ratio of the two stable isotopes of carbon--carbon-12 and carbon-13--in the fox's newly grown coat can show how much of its recent diet was marine, because marine fare is the richer in carbon-13.

The bad news is that because of global warming, the marine part of that diet may soon start drying up. James D. Roth, an ecologist at the University of Central Florida in Orlando, recently studied the hair of arctic foxes near Cape Churchill, Manitoba, on the west coast of Hudson Bay. In four years of observation Roth found that the animals' winter diet was higher in marine nutrients than their summer diet, particularly in years when Lemmings (the foxes' year-round favorite menu item) were scarce. It seems that in winter the foxes follow polar bears out onto the sea ice to grab the spoils of the bears' seat hunts. But if sea ice in the Arctic continues to decline, as it has in recent years, arctic foxes (as well as polar bears) will Lose access to an important part of their diet. ("Temporal variability in arctic fox diet as reflected in stable-carbon isotopes; the importance of sea ice," Oecologia 133: 70-77, August 10, 2002)

COPYRIGHT 2002 Natural History Magazine, Inc.
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