How healthy is Yellowstone's moose population? Yellowstone Association photo.

Editor's note: The following story came from the Yellowstone Association's April newsletter.

How healthy is Yellowstone National Park's moose population? That's a question a husband-and-wife team from Vermont hopes to answer over the course of a three-year study into the animals.

Ky and Lisa Koitzsch, who are wildlife biology consultants, have worked with the Yellowstone Wolf Project for more than six years and conducted moose research in New England and at Isle Royale National Park in Michigan. They began their Yellowstone study with a December flyover that spotted 11 moose, and then spent 29 days backcountry skiing more than 425 miles to collect moose pellets for DNA analysis. They estimate they sampled from approximately 60 moose. 

In winter, northern Yellowstone moose favor dense willow stands in stream drainages and old growth conifer forests. That makes them hard to spot from the air.

"They don't herd up like other ungulates. They often live alone except when males search for females in October," said park biologist Doug Smith.

In places like Yellowstone, there was no good tool for counting moose until development of the pellet collection method, said Ky Koitzsch. It's both accurate and cost-effective.

For 25 years, Montana and Wyoming have lowered moose hunting quotas, indicating a regional population decline, Koitzsch said. That parallels the known decline in portions of their southern range (below 45 degrees latitude) nationwide because of parasites, disease, and heat stress exacerbated by climate warming; habitat degradation; and predation.

Research by U.S. Forest Service biologist Dan Tyers suggests that the 1988 fires, which killed so much old growth forest, are the key to Yellowstone's steep decline in moose numbers. Predation data from the Yellowstone Wolf Project shows wolf reintroduction has had little effect, with just 52 definite, possible, or probable wolf kills from 1995 to 2012.

The Koitzsch study will provide a base number of animals on the Northern Range, so future studies can determine if the population is stable, rates of survival and population change, how those numbers compare to nationwide averages, and how far moose roam for food in winter.

"We think 80 to 100 animals on (Yellowstone's) Northern Range will end up being accurate, though we may surprise ourselves and find more," Koitzsch said. There is no reliable current moose estimate park-wide. Most sightings are reported in northeastern and southeastern Yellowstone.