Moose breed from early September to November and one
to three calves are born in May or June. Calves weigh
25 to 35 pounds at birth but grow rapidly; adult
females (cows) weigh up to 800 pounds and males
(bulls) up to 1300 pounds. Bulls are readily
identified by their large, palmate antlers, which are
shed annually, and their bells, an apparently useless
dewlap of skin and hair that dangles from the throat.
Moose live mostly solitary lives, and die from
disease, starvation, or predation by wolves and,
occasionally, by grizzly bears.
Surveys in the late 1980s suggested a total park
population of fewer than 1000 moose.
Research on radio-collared moose in northern
Yellowstone has shown that when snow depth forces
moose from low-elevation willow stands in November,
they move up to as high as 8500 feet, to winter in
mature stands of subalpine fir and Douglas-fir. They
browse fir almost exclusively during the deep-snow
winter months. Tyers (unpubl. data) found that moose
ate 39.6 percent subalpine fir, 25.5 percent willows,
10.6 percent lodgepole pine, 4.6 percent gooseberry,
and 4 percent buffaloberry. Snow is not as deep under
a canopy of conifer branches since some snow remains
on them, and a crust that may restrict moose movements
is less likely to form on shaded snow. However, Tyers
found that moose could winter in areas where snow
considerably deeper than that which elk could
withstand.
The moose calf crop has been declining since the fires
of 1988. During that summer there was also high
predation of moose by grizzly bears in small patches
of surviving timber. The winter following the fires
many old moose died, probably as a combined result of
the loss of good moose forage and a harsh winter. The
fires forced some moose into poorer habitats, with the
result that some almost doubled their home range,
using deeper snow areas than previously, and sometimes
browsing burned lodgepole pines. Unlike moose habitat
elsewhere, northern Yellowstone does not have woody
browse species that will come in quickly after a fire
and extend above the snowpack to provide winter food.
Therefore, the overall effects of the fires were
probably detrimental to moose populations. Park
managers, in cooperation with staff from the adjacent
Gallatin National Forest and the Montana Department of
Fish, Wildlife and Parks continue to seek good methods
to monitor the status of moose in northern
Yellowstone. Aerial surveys of willow habitats in
spring have shown some promise of providing an index
of moose population trends in Yellowstone, although
their current population and distribution remain
largely unknown.
Moose are commonly observed in the park's southwestern
corner along the Bechler and Falls rivers, in the
riparian zones around Yellowstone Lake, in the Soda
Butte Creek, Pelican Creek, Lewis River, and Gallatin
river drainages, and in the Willow Park area between
Mammoth and Norris. Summer moose migrations from south
and west of the park into Yellowstone have been
confirmed by radiotelemetry.
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