VALIDATION OF NUTRITIONAL CONDITION INDICES IN ELK
Rachel C. Cook
Wildlife Biologist, National Council for Air and Stream Improvement
1401 Gekeler Lane, La Grande, Oregon 97850, phone (541-963-9275), fax (541-962-6504),
email rcook@eou.edu,
John G. Cook
Project Leader, National Council for Air and Stream Improvement,
1401 Gekeler Lane, La Grande, OR 97850, phone (541-962-6536), fax (541-962-6504),
email cookjg@eou.edu,
Dennis L. Murray
Associate Professor, Departments of Biology and Environmental Resource Studies
Trent University, Peterborough, ON K9J 7B8, phone (705-748-1011), fax (705-748-1205),
email dennismurray@trentu.ca,
Pete Zager
Research Biologist, Idaho Department of Fish and Game
Lewiston, Idaho 83501, phone (208-799-5010), fax (208-799-5012),
email pzager@idfg.state.id.us,
Bruce K. Johnson
Project Leader, Oregon Department of Fish and Wildlife
1401 Gekeler Lane, La Grande, Oregon 97850, phone (541-962-6556), fax (541-962-6504),
email johnsobd@eou.edu and,
Michael W. Gratson
Former (deceased) Research Biologist, Idaho Department of Fish and Game
Lewiston, Idaho 83501
Productivity in many Northwest elk (Cervus elaphus) populations is now declining for unknown
reasons. Assessment of nutritional influences, a potential cause of these declines, is difficult because
many animal-based methods to determine nutritional status (e.g., serum and urine chemistry, various fat
indices) are not accurate, practical, and/or adequately tested. We evaluated existing and new indices of
nutritional condition of both live and dead elk. Forty-three captive-raised cows of varying ages and
conditions were euthanized and homogenized for chemical analysis of fat, protein, water, and ash content.
Estimates of fat, gross energy, and lean muscle were compared to each of the condition indicators, with
age and season as covariates. Unique to this study, we also intensely evaluated a subset of these models
for bias, sensitivity, accuracy, and precision across a wide range of body condition. Results indicated that
an arithmetic combination of a body condition score and ultrasonography of subcutaneous rump fat was
the best predictor of fat and gross energy for live animals; while a modified subset of the Kistner score was
the best predictor for dead animals. No serum or urine index proved sufficiently accurate or sensitive to
consistently predict body condition. Results also showed that many of the more commonly used indices
are the most limited. Several accurate and practical techniques evaluated, previously unavailable for live
animals, have potential to improve understanding of habitat’s effects, particularly nutrition’s effects, on
population dynamics of free-ranging elk.