Yellowstone's Northern Range - Greater Yellowstone Science ...

ELK AND OTHER SPECIES
91
(number of years) are small.
Diet overlaps are large between
elk and bighorns on the
northern range (Houston 1982,
Keating 1982, Singer and
Norland 1994, 1996). The data
on elk-bighorn relations are as
inconclusive now (Singer and
Norland 1994, 1996) as they
were from earlier periods
reported by Houston (1982),
whose regressions of bighorn
sheep numbers for 1955-1978
showed no significant association
with winter severity or elk
numbers. Competitive interactions
between the two species
remain a real possibility, but
have not yet been demonstrated at the population
level.
While the importance of diet overlap between
elk and bighorn sheep is well known in the
literature, their actual on-the-ground habitat
separation is less clear and should be further
studied. Varley (1994, 1996) noted substantial
niche separation between elk, non-native mountain
goats, and bighorn sheep on summer ranges in the
Absaroka-Berutooth Mountains north of the
northern winter range but little work has been done
on the competitive interactions between these
species on winter ranges.
Findings by Smith (1991) that most bighorn
Figure 7.11. Bighorn
sheep numbers in and
near Yellowstone
National Park may
be lower than they
were before the
park's creation,
because of III/man
hunting, introduced
livestock diseases,
and the slowness with
which bighol71s
recolonize areas from
which they have been
extirpated. NPS
photo.
Northern Winter Range
Bighorn Sheep Range
6.2km
I
(10 mil
Figure 7.12.
Bighorn sheep winter
range, like their
slimmer range, is
confined to areas on
or near" escape
terrain": steep cliffs
where sheep are able
to outmaneuver and
elude predators.
Map by Yellowstolle
Spatial Analysis
Center alld
Yellowstone Center
for Resources.
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