Long-term resource variation and group size: A large-sample field test of the Resource Dispersion Hypothesis

Abstract

BackgroundThe Resource Dispersion Hypothesis (RDH) proposes a mechanism for the passive formation of social groups where resources are dispersed, even in the absence of any benefits of group living per se. Despite supportive modelling, it lacks empirical testing. The RDH predicts that, rather than Territory Size (TS) increasing monotonically with Group Size (GS) to account for increasing metabolic needs, TS is constrained by the dispersion of resource patches, whereas GS is independently limited by their richness. We conducted multiple-year tests of these predictions using data from the long-term study of badgers Meles meles in Wytham Woods, England. The study has long failed to identify direct benefits from group living and, consequently, alternative explanations for their large group sizes have been sought.ResultsTS was not consistently related to resource dispersion, nor was GS consistently related to resource richness. Results differed according to data groupings and whether territories were mapped using minimum convex polygons or traditional methods. Habitats differed significantly in resource availability, but there was also evidence that food resources may be spatially aggregated within habitat types as well as between them.ConclusionsThis is, we believe, the largest ever test of the RDH and builds on the long-term project that initiated part of the thinking behind the hypothesis. Support for predictions were mixed and depended on year and the method used to map territory borders. We suggest that within-habitat patchiness, as well as model assumptions, should be further investigated for improved tests of the RDH in the future.

Association with humans and seasonality interact to reverse predictions for animal space use

“…A priori , we delineated foraging patches using tree canopy and building coverage because: 1) wet season canopy cover regulated soil moisture between rainfalls, increasing vertical migration of macrofauna, and closed canopy habitat had more invertebrates than open canopy habitat [ 48 ]; 2) trees, hollow logs, and buildings provided den sites and predation and temperature refugia for mongooses. We estimated patch dispersion using mean nearest neighbor distances [ 51 , 52 ]. Thus we measured the mean distance from each tree or building (a patch) to its nearest neighboring patch for each mongoose group’s home range.…”

Early‐life seasonal, weather and social effects on telomere length in a wild mammal

“…Badgers do not hibernate (Johansson, 1957) but do undergo facultative winter torpor, reducing their body temperature by up to 8.9°C (Fowler & Racey, 1988), and thus reducing energy expenditure (Newman, Zhou, Buesching, Kaneko, & Macdonald, 2011). Badgers in Britain mainly feed on earthworms (Lumbricus terrestris; Johnson, Baker, Morecroft, & Macdonald, 2001;Kruuk & Parish, 1981). Earthworms are sensitive to microclimatic conditions (Edwards & Bohlen, 1996;Gerard, 1967;Newman, Buesching, & Macdonald, 2017), making their abundance and distribution highly dependent on weather conditions.…”