Geoscience Reference
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not use. An arctic fox (
Alopex lagopus
) may be familiar with areas larger than
100 km2, yet use only a small portion (ca. 25 km2) where food is concentrated
(Frafjord and Prestrud 1992). Areas with no food are not visited often, if ever,
despite
and because of
the animal's familiarity with them. Should such areas be
included in the fox's home range? Other areas with food might not have been
visited in a given year simply by chance. Should those areas be included in the
fox's home range? Pulliainen (1984) asserted that any area larger than 4 ha (an
arbitrary size) not traversed by the Eurasian martens (
Martes martes
) he and his
coworkers followed should not be included in the martens' home ranges.
Through a winter, a marten crosses and recrosses old travel routes, leaving pro-
gressively smaller and smaller areas of irregular shape surrounded by tracks.
Pulliainen presumed that a marten's radius of familiarity, or radius of percep-
tion, would cover an area of 4 ha or less. But how wide might an animal's
radius of perception be? Some mammals can smell over a kilometer, see a few
hundred meters, but feel only what touches them. Which radius should be
used, or should a multiscale radius be used? In addition, areas not traversed
may have been avoided by choice. Hence, should no radius of familiarity be
considered? If we do not allow some radius of familiarity, or perception,
around an animal, we are reduced,
reductio absurdum,
to counting as an ani-
mal's home range only the places where it actually placed its feet. Clearly, this
is not satisfactory.
Related to this final problem is how to define the edges of an animal's home
range. For many animals, the edges are areas an animal uses little but knows;
the animal may actually care little about the precision of the boundaries of its
home range because it spends the vast majority of its time elsewhere. Except
for some territorial animals, the interior of an animal's home range is often
more important both to the animal and to understanding how the animal lives
and why the animal lives in that place. Gautestad and Mysterud (1993, 1995)
and others have noted that the boundaries of home ranges are diffuse and gen-
eral, making the area of a home range difficult to measure. That the boundary
and area of a home range are difficult to measure does not reduce in any way
the importance of the home range to the animal and to our understanding of
the animal, however. Even crudely estimated areas for home ranges have led to
insights into animal behavior and ecology (see the review by Powell 1994 of
home ranges of
Martes
species), suggesting that home range areas should be
quantified. However, we must keep in mind that home range boundaries and
areas are imprecise, at least in part, because the boundaries are probably impre-
cise to the animals themselves.
