SPATIAL SCALING OF ALLOMETRY FOR TERRESTRIAL, MAMMALIAN CARNIVORES

A regression slope of -0.75 between log(10) density and log(10) body m ass is thought to express equivalence of energy conversion among speci es' populations of similar taxonomic and trophic status. Using larger sample sizes than the usual 1-3 density estimates per species, we esti mated a regression slope of -0.71 for terrestrial mammalian carnivores . We investigated The sampling variation in this estimate, and those d erived from smaller intra-specific subsets, using 1000-iteration boots trap analyses to obtain 90% confidence intervals. As expected, these w idened, as random subsets were reduced in size, but always contained t he postulated -0.75. However, log(10) density also declined as 3/4 of the log(10) spatial extent of study area, and study area accounted for virtually all of the variation in density that was previously thought due to body mass. We removed the effect of study area by using the sp ecies-specific regression models between density and study area to pre dict density at a common scale of 400 km(2). These common-scale densit ies regressed against body mass with a slope of -0.16, but separated i nto body mass classes less than and greater than 11 kg, they produced slopes that were not significantly different from zero. We show that t he allometry of density could be a case of circular logic, whereby bod y mass has influenced the investigator's choice of study area, and the resulting scale-dependent densities are related back to body mass. To test the allometry hypothesis, the effect of study area on density es timates needs to be removed. This requires conducting larger-scale stu dies of the smaller-bodied species so that all species compared are re presented by an average study area that is near the common scale. Furt hermore, study sites need to be selected and designed to represent, mo re than the local detail in species' density.