PARENT SESSION
Oral Session # 16: Ecological Modeling I.
Presiding: C Ray
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.
General rules for the scaling of home range size and density in mammals.
Jetz, Walter1, Carbone, Chris2, Brown, James1, 1 Biology Department, Albuquerque, New Mexico, USA2 Institute of Zoology, London, London, UK
ABSTRACT- The energetic equivalence rule states that densities N should scale to the inverse of an animals metabolic needs Bi resulting a population energy flux BT that is independent of body size M: BT = Bi x N = b0 M3/4 x a0M-3/4 (Damuth 1981). There has been considerable evidence that this relationship holds true for a wide variety of mammals from different regions, and recently, Carbone & Gittleman (2002) showed that the fit of this scaling relationship in carnivores can be enhanced by including information on prey productivity. Secondary consumers appear to show a somewhat steeper scaling than primary consumers. A separate line of research has examined the scaling of home range size in mammals, and found a scaling of M-1 (Kelt & Van Vuren 2001). Carnivores appear to scale more steeply than herbivores, and recently fractal geometry of resource distribution has been invoked to explain this difference (Haskell et al. 2002). Here we present a model and empirical data that attempts to unify these disparate scaling relationships. Analyzing several hundred studies of mammalian home ranges and densities we find that density-derived per individual area estimates consistently show a scaling with an exponent that is by 1/4 smaller than for home range size. We show that this difference is explained by a positive 1/4 scaling of home range overlap. Higher degrees of overlap in larger mammals come from both increased sociality and increasingly soft home range boundaries, and can potentially be explained by the principles underlying the scaling of day range. Inclusion of information on prey productivity significantly enhances the scaling fit for both home range and density. Parsimony suggests that fractal resource distribution is not necessary to explain the steeper and trophically differing scaling of home range size.
Key words: home range size, mammals, scaling, density