Values, Problems, and Methodologies in Managing Overabundant Wildlife Populations: An Overview

Abstract

The function of wildlife management is to satisfy social values, positive and negative, assigned to wild animal resources. The term “overabundant” applies to wildlife populations whose actions are considered by someone in society to have negative value. Societal values assigned to wildlife change over time. As a result, the public changes its judgement of what is “overabundance” and tolerates negative effects because society changes its valuation to a predominance of the positive. Wild animals worldwide consume cultivated and stored crops, range forage useful for livestock, and fish in aquaculture facilities; they also prey on domestic animals. They damage urban and suburban property, and are involved in bird-aircraft collisions. They prey on positively valued wildlife, including threatened and endangered species, and when unchecked or as exotics, significantly alter the compositions of “natural” ecosystems. Some wildlife attack humans, and serve as reservoir hosts and/or vectors of diseases communicable to humans and domestic animals. Negatively judged wildlife-human interactions can be generalized into a limited set of ecological or behavioral circumstances. In some cases there may be population increase of the problem species. In others, problems arise simply when humans and wildlife come into contact, or when animals change their behavior to take advantage of opportunities provided by humans. Predisposing circumstances include altered predation levels by both humans and wild animals, provision or improvement of habitat, and provision of food. Animals may alter movement and aggregation behavior, habituate to human presence in the case of urban problems, or revert to wild behavior in the case of feral domestic species. Modes of managing animal damage include a variety of ecological approaches that apply the same population-ecology principles as those to enhance positively valued wildlife. These include direct population reduction by lethal means, and trapping and removal; and by reproductive inhibition through the use of chemosterilants. Animal numbers also may be reduced by modifying habitat to the animals’ disfavor, and by changing agricultural practices to reduce the availability of cultivated crops as a food source. Negative effects by wildlife may also be reduced with chemical repellents, physical barriers against access to agricultural crops and domestic animals, and mechanical frightening devices. The presence of humans and guard animals also deter losses. Integrated pest management, a well-developed control strategy in economic entomology, has received less consideration in vertebrate damage control, but may have potential for future use.