Geoscience Reference
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portant resources. Coyotes (
Canis latrans,
Person and Hirth 1991), European
red squirrels (
Sciurus vulgaris,
Wauters et al. 1994), and perhaps red-cockaded
woodpeckers (Barr 1997) exhibit just such a pattern of partial territoriality and
defend only home range cores in some habitats. Alternatively, an individual
might allow territory overlap with a member of the opposite sex (Powell
1993a, 1994).
Food appears to be the limiting resource that stimulates territorial behavior
by many animals and territorial defense decreases in those individuals as pro-
ductivity or availability of food increases. Much research has been done on nec-
tarivorous birds (Carpenter and MacMillen 1976; Hixon 1980; Hixon et al.
1983; Powers and McKee 1994), voles (Ims 1987; Ostfeld 1986; Saitoh 1991,
reviewed by Ostfeld 1990), and mammalian carnivores (Palomares 1994; Pow-
ell et al. 1997; Rogers 1977, 1987). Black bears and nectarivorous birds (Car-
penter and MacMillen 1976; Hixon 1980; Powell et al. 1997) switch quickly
between territorial and nonterritorial behavior when productivity of food
moves across the lower or upper limits for territoriality, respectively. For large
mammals, I suspect that variation in territorial behavior around the upper limit
of food production varies only over long time scales of many years (Powell et al.
1997).
Territorial behavior by members of several species (e.g., black bears, Powell
et al. 1997; nectarivorous birds, Carpenter and MacMillen 1976; Hixon 1980;
Hixon et al. 1983) can be predicted from variation in the productivity of food,
which is good evidence that food is the limiting resource that stimulates terri-
torial behavior for those animals. For European badgers (
Meles meles
), territory
configuration can be predicted from positions of dens without reference to
food (Doncaster and Woodroffe 1993), indicating that the limiting resource is
den sites. However, no studies have rejected all other possible limiting re-
sources. Wolff (1993, personal communication) argued strongly that only
off-
spring
are important enough, and can be defended well enough, to be the re-
source stimulating territorial behavior. For the black bears I have studied, adult
females with and without young and adult and juvenile bears all responded in
the same manner to changes in food productivity and also responded in the
same manner to home range overlap with other female bears. Were Wolff cor-
rect, adult female bears with young would exhibit significantly different
responses to food and to other females than do nonreproductive females. In
addition, adult female black bears would be territorial in North Carolina, as
they are in Minnesota. For the nectarivorous birds studied by Hixon (1980;
Hixon et al. 1983), birds defended territories in the fall after reproduction but
before and during migration. Were Wolff correct, hummingbirds would not
