Year of Award

2006

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Chair

Daniel H. Pletscher

Commitee Members

Erick Greene, Jack W. Thomas, L. Scott Mills, Matthew J. Kauffman

Keywords

birth date, birth weight, calf, Cervus elaphus, elk, monitoring, recruitment, survival, age ratio, ungulate

Abstract

Harris, Nyeema C., M.S., Spring 2007 Wildlife Biology MONITORING SURVIVAL OF YOUNG IN UNGULATES: A CASE STUDY WITH ROCKY MOUNTAIN ELK Chairperson: Daniel H. Pletscher Survival of young is an important determinant of population growth and persistence in ungulate populations. Therefore, monitoring the survival of young is an essential component in many research and management programs. The primary techniques used to monitor survival of young in ungulate populations are age ratios, obtained from herd composition surveys, and telemetry studies of marked individuals. Concerns about survival of young and the impact of predators on recruitment have recently arisen because of reported declines in age ratios (e.g. calf:cow, fawn:doe) in many ungulate populations. Despite their common and wide usage, it remains unclear what inferences are appropriate when changes in age ratios are observed. Alternatively, obtaining survival estimates from marked individuals is labor-intensive, expensive, invasive, and may not represent the source nor the amount of mortality that occurs in a population. In my thesis, I used a modeling approach to determine the relative importance of vital rates on age ratios. I also evaluated the ability of age ratios to reflect changes in vital rates and population growth (ë). Calf survival had the greatest impact on calf:cow ratios and explained most of the variation in calf:cow ratios (r2= 0.965). However, calf:cow ratios did not always quickly detect annual declines in calf survival. Calf: cow ratios do not reflect variation in any other vital rates including prime-age survival and pregnancy rates. In addition, calf:cow ratios positively correlated to population growth the previous year and were marginally successful in distinguishing between increasing,decreasing, and stationary populations. In the field component of my research, I captured neonatal elk to estimate summer calf survival, explored factors influencing calf survival, and quantified the impacts of predators on calf survival. I also compared survival estimates obtained from the marked samples to those obtained from changes in calf:cow ratios. Calf survival varied between 0.25-0.88 during the study period (2002-2006). Predation (68%), mainly bear predation, was the primary source of mortality, and early-born, small calves had the highest probability of mortality. Overall, summer survival estimates obtained from calf:cow ratios and the marked samples were comparable. However, survival estimates obtained from marked individuals provides insight into many of the mechanisms (e.g. birth weight) responsible for the annual variation in survival of young.

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© Copyright 2006 Nyeema Charmaine Harris