Animal Space Use Research Articles

Why do population density and inverse home range scale differently with body size?: Implications for ecosystem stability

Population density and home range are the two major ecological characteristics pertaining to the ecosystem-level energy use by the species. Home range usually grows more rapidly with body size than does individual metabolic rate. Neither this phenomenon nor the observed absence of isometry between inverse home range and population density (the latter often scaling as the reciprocal of metabolic rate in the inter-ecosystem comparisons) have received a general explanation. Here, we account in theory for the observed scaling exponents in the relationships of population density and inverse home range on body mass and verify our predictions by the available data on birds and mammals. In stable ecosystems, inverse population density and home range represent one and the same measure of animal space use and scale isometrically. Being tightly linked to many genetically encoded morphological and behavioral properties of the species, animal home range, unlike population density, does not change readily with the degree of ecosystem disturbance, thus representing a biological footprint of the undisturbed state of the ecosystem and the animal status within it. The difference between scaling exponents in the mass dependence of home range and inverse population density can reflect the degree of ecosystem disturbance.

The scaling of animal space use.

Space used by animals increases with increasing body size. Energy requirements alone can explain how population density decreases, but not the steep rate at which home range area increases. We present a general mechanistic model that predicts the frequency of interaction, spatial overlap, and loss of resources to neighbors. Extensive empirical evidence supports the model, demonstrating that spatial constraints on defense cause exclusivity of home range use to decrease with increasing body size. In large mammals, over 90% of available resources may be lost to neighbors. Our model offers a general framework to understand animal space use and sociality.

A Critical Evaluation of Research Techniques in Animal Ecology

A Critical Evaluation of Research Techniques in Animal Ecology

Space Use of Killdeer at a Great Basin Breeding Area

Wetland conservation efforts require knowledge of space use by a diversity of waterbirds. However, determining space use of animals requires intensive monitoring of individual organisms. Often, activity patterns during much of the annual cycle are neglected in analyses of home range and habitat use. From 1995-97, we monitored space use in a population of individually marked killdeer (Charadrius vociferus) that breed, and reside for a number of additional months each year, in the western Great Basin. We used linear distance measures and home range-area estimates, derived by fixed-kernel methods, to examine patterns of space use of adults prior to, during, and following nesting. Overall, killdeer used a local area of approximately 6 ha. Birds remained closer to nests while tending eggs than either before or after nesting, although extensive movements away from the nest were observed during all time periods. Females tended to move farther from nests than did males. Birds nesting farther from water bodies were generally observed at greater distances from nests than those nesting closer to shorelines during all time periods. Twenty-seven percent of individuals were observed greater than 1 km from nest locations, particularly during postnesting periods. During nesting periods, males were less likely to be observed at longer distances from nests than were females. There were no differences in home range size based upon sex, time period, or distance from water. We suggest that home range size may not always accurately measure differences in space use and that multiple measures, including distance from nests, should be considered. Understanding the sedentary nature of killdeer during much of the annual cycle and their intense use of local areas is important for making management decisions. Coupled with data on other shorebird species, this information also has broader implications for management of wetland systems by indicating large scale spatial and habitat requirements and the connectivity of geographically distinct habitat patches.

How animals use their environment: a new look at kinesis

The aim of this paper is to show how animals can orient themselves in relation to a stimulation gradient or exploid patchy environments using simple kinetic mechanisms. From a new look at klinokinesis and orthokinesis, the properties of these two mechanisms were determined and their respective contributions to the phenomenon of animal aggregation in the most suitable areas of the environment were specified. When movement regulation is a function of variations in the stimulus intensity, klinokinesis can be seen as an elementary spatial orientation mechanism, whereas orthokinesis seems to have no biological application. In contrast, when movement regulation is a function of the value of stimulus intensity, klinokinesis and orthokinesis can both be seen as elementary space-use mechanisms. Some examples of applications of the models are given. In particular, it is suggested how klinokinetic and orthokinetic models can formalize the ‘area-restricted’ searching behaviour exhibited by many foraging animals. Finally, the place of klinokinetic and orthokinetic mechanisms in the framework of a general theory of spatial orientation and space use in animals is discussed.