Crandall, Wyo. (AP) – Researchers studying elk in the
Yellowstone National Park area want to expand knowledge about the
influences of habitat, climate and predators on elk migration,
reproduction and survival.
Even before its completion next spring, the Absaroka Elk Ecology
Project is presenting a tale of two herds within the Clarks Fork
area of Wyoming’s northern Park County.
A resident elk herd living around Heart Mountain and the
Absaroka Front is thriving, producing calves at twice the rate of a
nearby herd that spends winters in the Crandall and Sunlight areas,
and migrates into Yellowstone’s Lamar Valley during summer.
“Calf recruitment is what is driving our population dynamics in
the Clarks Fork and Sunlight and Crandall areas,” said Doug
McWhirter, a Wyoming Department of Game and Fish wildlife biologist
Researchers from the department, the University of Wyoming, the
U.S. Fish and Wildlife Service and the National Park Service are
working on the $500,000 study. They have placed tracking collars on
dozens of elk and several wolves from five packs.
The study also involves measuring the body fat of elk, charting
weather patterns, measuring the protein in forage and performing
ultrasound scans on pregnant elk.
McWhirter said the study already has yielded a wealth of data
about the forces that shape elk migration, reproduction and
The data hint that the mere threat of being chased by wolves may
drive what elk decide about where to graze. Minor changes in a cow
elk’s percentage of body fat can greatly influence the timing of
her breeding or even her ability to become pregnant.
“The hypothesis to be tested is: Does wolf predation risk
influence elk habitat selection, and does that habitat selection
influence their body condition, and hence, their pregnancy rates?”
The research has raised new questions such as why migratory elk
that spend their summers in Yellowstone aren’t as well-fed as the
herd that resides year-round along the Absaroka Front. It may be
that staying a step ahead of wolves means less time spent grazing
and more time running off fat reserves. Or it could be that the
cultivated forage in the irrigated fields of the front country has
more protein than wild grasses.
Data from the study also challenge the common idea that elk
under pressure from predators simply move to a new area. Instead,
the data indicate they circulate within a preferred area to avoid
predation, McWhirter said.