Lack of good, summer nutrition may be one reason elk are spending more time on private Wallowa Valley and Zumwalt Prairie land and not in the national forest. KATY NESBITT / The Observer

Researchers John and Rachel Cook conduct ground-breaking work

Decreases in elk herd numbers have prompted agencies and biologists alike to look to their habitat for clues.

A series of studies, started in 1995, reveal a new piece to the puzzle: the importance of nutritionto elk health, reproduction and survival.

While working with a large herd of tame elk in the early 90s,La Grande researchers John and Rachel Cook of the National Council for Air and Stream Improvement started questioning the importance of nutrition.

Nutrition is an important mechanism of the animals performance that was understudied at the time we started our research, said John Cook.

Cook said recruitment of calves until adult age classes has declined by about half since the 1950s across the Blue Mountains. With this in mind, the Cooks set out to discover if nutrition is indeed a factor, if so, whats causing the problems, and to come up with solutions.

Elk are one the most studied wildlife species in the western United States, but the Cooks nutrition research was ground-breaking. The fact that elk herds were declining across the Northwest, said Cook, tended to shift the focus away from habitat quality, thermal cover, and roads, to understanding what it is about habitat thatdrives population dynamics and performance.

The Cooks have used both wild and tame elk for nearly two decades to learn about their nutritional needs. What they discovered is that a small difference in nutrition has a big effect on performance.

The tame elk study started with 60 elk, all around the age of 4 or 5 years old. They were divided into three groups to determine the effects of nutrition on reproduction.

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Elk and nutrition