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Group size versus territory size in badgers
A large-sample field test of the Resource Dispersion Hypothesis
Journal
Oikos, Volume
95,Number 2, November 2001, pp. 265-274(10) -
Blackwell Publishing
Authors
Johnson D.D.P.; Macdonald D.W.; Newman C.;
Morecroft M.D.
Abstract
Badgers have been the
focus for the development of a pervasive model of social grouping behaviour,
relevant to a number of carnivore species and other taxonomic groups – the
Resource Dispersion Hypothesis (RDH). The RDH hypothesises that the dispersion
and richness of resources in the environment provide a passive mechanism for the
formation of groups, even without any direct benefits of group living. However,
few studies have tested the RDH in the field. The principal prediction is that,
as opposed to enlargement of territory sizes to accommodate more members,
territory size (TS) is independent of group size (GS). Instead, TS is determined
by the spatial dispersion of resources, while GS is independently determined by
the richness of those resources. However, these predictions provide only weak
correlative tests, especially in non-experimental field studies. The first
predicts an absence of correlation and is therefore prone to Type II error,
especially given the small sample sizes and errors in estimating TS and GS of
mammals in the field. We tested for independence of territory size and group
size in all years with available data since the beginning of the long-term
badger study in Wytham Woods in 1974. We used two methods of TS estimation, a
sequential Bonferroni technique to adjust for multiple inference tests, a
combined analysis and an analysis with pooled data. This prediction of the RDH
could not be rejected on the basis of any of these analyses. Given this evidence
that other processes are independently determining group size and territory
size, further predictions of the RDH will be worth investigating in considerable
detail.
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