Date of Award:

8-2022

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Wildland Resources

Committee Chair(s)

Eric M. Gese

Committee

Eric M. Gese

Committee

Susannah S. French

Committee

Juan J. Villalba

Committee

Kari E. Veblen

Committee

Shane Roberts

Abstract

This study was conducted to increase our understanding of the influence of adult female pronghorn (Antilocapra americana) physiology on fawn summer survival. Pronghorn are a valued big game animal in Idaho, but are particularly sensitive to capture; therefore, we designed a noninvasive fecal sampling study to measure pregnancy (progesterone and estrogen), diet, nutrition (fecal nitrogen and DAPA), and stress (cortisol), during metabolically-demanding female life history stages (late gestation, early lactation, and breeding season). We also compared survey results between ground and aerial methods within mountain valley landscapes.

Pregnancy determination, via progesterone, is possible for pronghorn, but sample collection should occur during late April for hormone measures to be different from nonpregnant females. Fresh fecal samples are required for accurate hormone concentrations, given high hormone degradation rates.

Pronghorn diets were comprised of a majority of forb species during each sampling period, but protein intake from forbs peaked during early lactation. Protein intake from agricultural crops such as alfalfa were lower than expected.

Nutrition and stress measures had varying relationships across sampling periods and these measures differed by year, subpopulation, and sampling period. Pronghorn appeared to shift between diets high in nitrogen or digestible energy depending upon the metabolic demands of different life history stages.

The factors influencing fawn summer survival varied by sampling period, but diet and nutritional measures were the top influence each time. Of that, adult female fecal nitrogen values collected during early lactation had the greatest influence on fawn summer survival. This diet quality influence likely relates to the milk energy output of the female and subsequent fawn growth rates. We recommend wildlife managers increase habitat quality (fecal nitrogen), by increasing protein available to pronghorn (forbs), to increase fawn summer survival.

For survey results, we found differences in abundances and age and sex composition ratios of pronghorn from ground and aerial survey methods. Each survey method presented biases of composition results such as sight ability differences, pronghorn behavioral responses, as well as the influence on relative greenness of landscape and potential influence on pronghorn distribution.

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