Biologists use deer pellet DNA to estimate population size

Submitted by Marmian Grimes
Phone: 907-474-7902
06/19/09

University of Alaska Fairbanks scientists have successfully refined a noninvasive technique that extracts DNA from deer droppings and enables wildlife managers to accurately estimate deer and other ungulate population numbers in areas where visual counting of animals isn’t feasible.

Scientist Todd Brinkman, a UAF Ph.D. candidate, will present his research during the American Society of Mammalogists 89th Annual Meeting June 24-28 at UAF.

"This study is groundbreaking in the sense that it finally gives managers a firm estimate of abundance for a very important game species," said Kris Hundertmark, a wildlife geneticist at the UAF Institute of Arctic Biology, who serves as one of Brinkman’s academic advisors.

The technique refined by Brinkman and Hundertmark extracts DNA from skin cells attached to the outer surface of the fecal pellets and identifies DNA fragments in each pellet. Every deer has a unique combination of fragments and this technique can tell one deer from another, which allows Brinkman to tell how many different deer are present in a sampled area.

In the 1990s, hunters on Alaska’s Prince of Wales Island began saying that they were having trouble harvesting enough deer to meet their needs, says Brinkman. The rainforest environment of Southeast Alaska makes direct visual and aerial counting impossible. For years, wildlife management agencies have counted deer pellets to estimate population size.

"They were simply counting pellets. More pellets meant more deer," Brinkman said. But there was no way to know whether pellets came from one deer or a dozen, and estimates lacked precision.

The lack of reliable data prompted the United States Forest Service to create a committee to address how to improve population estimates. Brinkman, an active hunter and outdoorsman, had come to UAF to do large-game-animal research at about this time. He saw the USFS call for research as a perfect opportunity to combine his interest in hunters and game species through IAB’s interdisciplinary graduate Resilience and Adaptation Program.

For three years between February and May, Brinkman and assistants hired from Prince of Wales Island communities walked a systematic grid of deer trails on the island carrying backpacks filled with small plastic vials, each large enough to hold 4-6 pellets. At the end of each field season, the vials were shipped to UAF, where Brinkman and Hundertmark conducted the DNA analysis.

With unique DNA, called genotypes, and multiple "recaptures" of the same individual deer on subsequent sampling occasions, Brinkman could estimate the number of deer in each grid. His results showed a steady decline in deer numbers during the three-year study, which he and colleagues attributed to consecutive severe winters.

Before beginning his field collections or laboratory analyses, Brinkman spent the spring and summer of 2004 and 2005 getting to know some of the Prince of Wales Island hunters whose concerns prompted the project. He interviewed 88 hunters from 11 island and two off-island communities about their perceptions of changes in deer populations, deer hunting patterns, deer habitat and hunting access.

"Sitka black-tailed deer are the most important big-game species, both culturally and nutritionally, to subsistence and sport hunters in this region," said Brinkman.

The technique Brinkman and Hundertmark developed will provide insight into factors that influence deer survival and population trends such as winter weather, predation and land use.

"There’s really no better place to do large-game management research than Alaska," Brinkman said. The IAB Resilience and Adaptation Program at UAF was a perfect match. "I could use an interdisciplinary, integrative approach to combine the social and biological science aspects of my two areas of interest."

CONTACT: Todd Brinkman, PhD candidate, todd.brinkman@uaf. Kris Hundertmark, IAB wildlife researcher, ASM conference co-chairman, at 907-474-7159, ffkh@uaf.edu. Marie Gilbert, IAB information officer, at 907-474-7412, megilbert@alaska.edu. Marie Gilbert will be available only by email June 19-July 5. Kerynn Fisher, UA Museum of the North communications coordinator, at 907-474-6941, klfisher@alaska.edu.