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Passive Range Exclusion: Evidence from the Badger
Journal
Journal of Theoretical Biology
-
Vol 184, Issue 3
,
7 Feb 1997,
pp 279-289
Authors
Paul D. Stewart, Carl Anderson and David W. Macdonald
from the Wildlife Conservation Research Unit, Oxford
Abstract
The Passive Range Exclusion (PRE) Hypothesis provides a mechanism whereby
species that rest or breed in communal residences, but forage independently on
dispersed food items, may avoid entering the core home ranges of neighbouring
groups. A stochastic simulation shows that as the occupants of a communal
residence travel outwards to feed, their activities create a gradient in food
availability. Food closest to the point of origin tends to be discovered first
and at the highest rate. As the foraging period continues, the probability of
encountering unexploited food increases with distance from the residence. Areas
of relatively high food availability persist as ridges between neighbouring
communal residences. The simulation predicts that once such a gradient is
established, a strategy of preferential feeding in these areas optimize food
intake. Feeding excursions deep into neighbouring ranges are disadvantageous
because areas of lower food availability are encountered and travel times back
to the home residence become longer. The observed reluctance of individuals to
forage close to neighbouring residences can therefore be explained partly or
wholly as a result of exploitation competition and feeding optimization, without
necessarily invoking territorial arguments about interference competition and
conflict avoidance.
At lower forager and food patch densities the simulation indicates that the
gradient is insufficient to award significant benefit to border feeding. Hence
border feeding strategies and the range exclusion that results should diminish
as food or forager densities decrease. We use the European badger (Meles meles.)
as a test case for the hypothesis and show that exploitation competition between
groups may be an important factor in shaping this species' home ranges.
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