Analysis of a single hair can reveal bear's diet

A new chemical analysis technique developed at Washington State University has allowed scientists to determine the diet of a bear using a single hair sample.

Scientists say the newly developed method -- which measures for trace amounts of heavy metals -- will help biologists get a more accurate sense of a bear's nutritional health, as well as a monitor the animal's exposure to environmental contaminants like mercury.

"You can use the technology for both applications," Marie Noel, a researcher at Washington State and author of a new paper on the technique, explained in a press release. "You can see how much mercury they're getting but also estimate how much salmon they're eating."

The technique is a much sharper tool for researchers trying to understand the relationship between diet and animal health. Monitoring salmon runs and observing the feeding habits of bears allow scientists to make rough estimates about the health of local bear populations, but more specific information will improve biologists' understanding of species health and recovery.

"You can see bears chasing down salmon, but other than saying, 'bears eat salmon,' that really doesn't give you much information," said biologist Charles Robbins, director of Washington State's Bear Research, Education and Conservation Center. "So we'd like to know where the energy and protein is coming from to create either large bears or small bears or cubs and help them with their reproduction. We'd like something that integrates all that information over a 24-hour period, a week, a month, a year."

Researchers are able to isolate metal residues by shining a laser down the spine of the hair. The trace metals are vaporized and measured by a mass spectrometer.

Scientists measured the hair of captive grizzly bears as caretakers periodically rotated their diet -- switching from a combination of commercial bear chow, apples and white clover grazing to Yellowstone Lake cutthroat trout, which featured heightened mercury levels from nearby geothermal features. The controlled analysis offered researchers a baseline with which to compare the results from wild bear hair samples.

Though initially performed using grizzly bears, the analysis could also be applied to the study of other species like the especially vulnerable polar bear. The analysis method was recently detailed in the journal Science of the Total Environment.