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Forecasting the effects of fertility control on overabundant ungulates

Date

2014

Authors

Raiho, Ann Marie, author
Hobbs, N. Thompson, advisor
Hooten, Mevin B., committee member
Noon, Barry R., committee member

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Abstract

Overabundant populations of native vertebrates can cause environmental degradation and loss of biological diversity. Culling or regulated harvest is often used to control over- abundant species. These methods become infeasible in residential areas and national parks. White-tailed deer populations on the eastern coast of the United States have grown ex- potentially during the urbanization of the 20th century causing severe environmental and economic damage. Managers of National Parks in the Washington, D. C. area seek to reduce densities of white-tailed deer from the current average (50 deer per km2). It has been shown theoretically that fertility control is not an effective way to reduce an overabundant populations, but these conclusions have not be verified with empirical models. Here, we present a Bayesian hierarchical model using 13 years of distance sampling data from 10 National Parks in the National Capital Region Network to forecast the effects of fertility control on overabundant ungulates. We estimated a survival probability for adult female deer that was the same as what we found in previous literature (adult female = 0.74). However, our estimation of adult male and juvenile probabilities were different than what has been found in past studies (adult male = 0.39, juvenile = 0.67). This may be because of the high densities of white-tailed deer in our study area. Our posterior predictive checks show that our model does adequately represent the data (β = 0.419). Our model experiments found that fertility control is not capable of rapidly reducing deer abundance unless a high relative effort over no action is feasible. However, it can be combined with culling to maintain a population below carrying capacity with a high probability of success. This gives managers confronted with problematic overabundance a framework for implementing management actions with a realistic assessment of uncertainty.

Description

2014 Summer.
Includes bibliographical references.
Zip file contains data files.

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