Abstract. Many analyses of animal movements assume that an animal's position at time t + 1 is independent of its position at time t, but no statistical procedure exists to test this assumption with bivariate data. Using empirically derived critical values for the ratio of mean squared distance between successive observations to mean squared distance from the center of activity, we demonstrate a bivariate test of the independence assumption first proposed by Schoener. For cases in which the null hypothesis of independence is rejected, we present a procedure for determining the time interval at which autocorrelation becomes negligible. To illustrate implementation of the test, locational data obtained from a radio-tagged adult female cotton rat (Sigmodon hispidus) were used. The test can be used to design an efficient sampling schedule for movement studies, and it is also useful in revealing behavioral phenomena such as home range shifting and any tendency of animals to follow prescribed routes in their daily activities. Further, the test may provide a means of examining how an animal's use of space is affected by its internal clock.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Allen Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management.

Abstract.Although it is known that visual predation by planktivorous fish tends to be size selective, the mechanism by which fish select their prey has not previously been described.Experiments in which bluegill sunfish (Lepomis macrochirus) were given a binary choice be tween prey of different sizes presented at different distances showed the fish selected the prey that appeared largest, either because of its actual size or its proximity to the fish. This paper incorporates this mechanism of prey selection by apparent size into a model of bluegill predation. According to the model, bluegill, in choosing the apparently largest prey under all conditions, alter their diet composition depending upon the abundance of prey. When prey are abundant, bluegill predominantly select prey of the largest size class available because these have the greatest probability of appearing largest; as large prey become scarce and smaller prey have a greater chance of appearing large, the fish tend to eat more prey from smaller size classes. When the model is tested against data from published fish-feeding ex periments, the predicted size ratios of prey eaten correlate accurately with the observed ratios and numbers of prey eaten.

Abstract. The area occupied or traversed by an animal is a function of the time period considered, but few empirical estimates of the temporal component of home range use are available. We used a statistic called the "time to independence" to make an ecologically meaningful estimate of the amount of time required for an individual to traverse its home range. Data from 23 species of terrestrial mammals indicated the existence of a sizedependent time scale governing the rate of home range use. Foraging mode influenced the rate of home range use; central place foragers traversed their home ranges approximately five times as rapidly as comparably sized noncentral place foragers.Numerous physiological measures of time are related to body mass raised to the V* power. Our results suggest that the time scale governing the rate of space use by mammals is related similarly to body mass. This relationship permits a more critical examination of factors thought to influence home range size, including habitat productivity and social organization.

No abstract