Food Habits of Furbearers of the Upland Post Oak Region in Texas

Abstract

A food habits study is one of the most important single aspects of an ecological study of any animal or group of animals. A close interrelationship exists between an animal and other species of the biota as a result of their feeding habits. A knowledge of the foods aids in explaining these interrelationships. It also helps to explain much of the behavior and daily and seasonal movements of the species and gives suggestions for management. Much of the literature recording the foods eaten by carnivores is based on an analysis of the stomach content or of fecal remains but little is known of the reliability of each. Little is also known of the comparative value of the various sections of the gut in a food analysis. An analysis can be done on a quantitative and/or qualitative basis. The quantitative method, recorded by weight or volume, designates the items that make up the major part of the food; however, small items occurring frequently might be pushed into the background. If, however, recorded only as frequency of occurrence, these lesser foods may be overemphasized. The purpose of the present study is to give meaning to the food habit study. The mere fact that an animal eats an item has little meaning in itself. The importance of an item in the annual diet has, in fact, little meaning unless some ecological significance can be attributed to it such as its abundance, its importance in the diet of other species, or the selection of the item in the presence of other foods. This study also trys to evaluate the various methods employed in food habit studies; to compare the reliability of a measured value with the visual estimated value in common use; to determine the results of an analysis based on scats and one based on digestive tract contents when both were collected in the same area during the same period; and to evaluate the relative importance of the sections of the gut as a quantitative and qualitative indicator of foods eaten. The study is based on material collected over a two-year period (January 1950-January 1952) in the uplands of the Post Oak Woods of eastern Texas. The contents of both scats and digestive tracts were analyzed for raccoons (Procyon lotor), opossums (Didelphis marsupialis), gray foxes (Urocyon cinereoargenteus), striped skunks (Mephitis mephitis), and ringtails (Bassariscus astutus). The area studied can best be described as an ecotone between the eastern deciduous forest and the tall grass prairie. Bailey (1905) referred to it as the Austroriparian Division of the Lower Austral Life Zone, and Blair (1950) classified it as part of the Texan Biotic Province. It is represented by a rather open stunted forest dominated by post oak and black jack oak. The understory of the climax is a scattered complex of yaupon, deciduous holly, parsley haw, French mulberry, and huckleberry which becomes greatly intensified under heavy grazing. Open areas that are heavily grazed produce an abundance of persimmon, grape, hackberry, dewberry, deciduous holly, yaupon, and several other less 406 Vol. 85, No. S