untitled

populations. An example of the effect of interference on carnivore population

dynamics is the American marten, a mustelid carnivore in the forests of the USA and

Canada (Fryxell et al. 1999).

Many wildlife species are territorial, meaning that they defend an area of (more

or less) exclusive access from usage by other members of the population. Males,

females, or both sexes may be territorial, depending on the ecological circumstances

that apply. Territories may be defended solely during the breeding season, as in many

birds, or throughout the year, as in many vertebrate carnivores; and they may be

defended by individuals, such as in tigers, or by a pack of individuals, such as in

gray wolves. The multitude of territorial forms mean that many different factors con-

tribute to the adaptive significance of territoriality. Conversely, the consequences of

territoriality at the population and community levels can also vary considerably.

Central to most arguments about the ecological basis of territoriality is the notion

of economic defendability(Brown 1964; Dill 1978; Kodric-Brown and Brown 1978;

Schoener 1983; Stephens and Dunbar 1993; Fryxell and Lundberg 1997). It would

make little sense to try to defend any territory offering trivial benefits or whose costs

are astronomical. Let us assume that the purpose of a territory is to gain access to

THE ECOLOGY OF BEHAVIOR 75

1

0.1

0.1 1 10 100

Predator density

Food intake

1.0

0.8

0.6

0.4

0.2

(^0123)
Log 10 oystercatcher density
Log
10
feeding rate
Site 1
Site 2
Fig. 5.11Changes in
food intake as a
function of predator
(forager) density due to
interference between
predators.
Fig. 5.12Food intake
by oystercatchers at two
sites in the Netherlands
declines as population
density increases. (After
Sutherland 1996.)
5.6.3Territoriality
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