PARENT SESSION
Oral Session 16: Statistics and Biometrics.
Presiding: E Garton and T Simons
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room D 139.
Improved approaches for estimating spatial distribution, home range, habitat selection, and density.
Horne, Jon*,1, Garton, Edward1, 1 University of Idaho, Moscow, Idaho, USA
ABSTRACT- Bartholomew (1958:82) suggested one of the most important questions to ask after identifying an organism is "Where do they live?" Many investigations of animals and plants have sought to answer this important question using spatially and temporally explicit occurrence data. For animals we use these data to evaluate home range and habitat use. For plants we evaluate distribution patterns and density. We developed several new approaches to simultaneously estimate home range, habitat selection and space use of animals which are also applicable to plant distributions and density. Among these approaches are: 3 new home range estimators for a uniform distribution of space use; a method for incorporating factors such as habitat into home range and density analyses; and an information theoretic approach for choosing among various models of probability of occurrence. Because the shapes of our uniform home range estimators have an ecological basis and are unbiased by sample size, they represent a significant improvement over current methods such as minimum convex polygon. We used maximum likelihood theory to combine location data with other variables affecting probability of occurrence (e.g., habitat, locations of other organisms). We found home range and density estimates were significantly improved by including additional information into the model. We then used information theoretic approaches to choose among competing models. By incorporating other factors into probability density models and framing the analysis as competing models, researchers can test ideas about the relative influence of various factors on animal space use and plant occurrence. Thus, we can go beyond the question "Where do they live?" to also ask "Why do they live there?" and obtain parsimonious answers to both questions.
Key words: habitat use, probability of occurrence, home range, distribution