Alaska Science Forum
July 8, 2009
Newborn moose calves fight very slim odds
This column is provided as a public service by the Geophysical Institute,
University of Alaska Fairbanks, in cooperation with the UAF research
community. Ned Rozell is a science writer at the institute. This column
originally appeared in 1998.
Any moose calf alive in mid-summer is a lucky animal. If the calf was born a
twin, it has probably seen its sibling pulled down and eaten by a bear. If
the calf was born alone, it probably stood close to its mother as she reared
on her hind legs and pounded a predator with her hooves.
In late May all over Alaska, female moose find a secluded spot to birth a
calf, twin calves or sometimes triplets. In the weeks that follow, many of
these gangly newborns fall prey to bears and wolves. In most areas of
Alaska, more moose calves die than survive.
Mark Bertram is a U.S. Fish and Wildlife Service wildlife biologist at Yukon
Flats National Wildlife Refuge. In a study he did more than a decade ago,
while a helicopter pilot distracted cow moose from the air, Bertram and
others scrambled to birthing sites and attached radio collars to newborn
calves. By following radio signals after the calves stopped moving, the
biologists were able to find dead calves and determine what killed them.
In the study at Yukon Flats, an area larger than Maryland where Alaskaıs
longest river reaches north of the Arctic Circle, Bertram has found the
remains of a majority of the 29 moose he collared. Fifty-five percent died
in one month. Three-quarters of those baby moose were killed by either black
bears, which are abundant in Yukon Flats, or grizzly bears.
When Bertram approaches a kill site, thereıs usually not much left to
identify the carcass as a moose calf. He said bears generally crush a calfıs
skull to first eat the brain, tongue and other soft tissue, and then work
their way back to consume the entire carcass. A moose calf is a major score
for a bear or a wolf, as is seen in the woeful numbers of calves that reach
their first birthday.
³Itıs real common for just 30 percent of calves to survive their first
year,² Bertram said.
In studies done elsewhere in Alaska and the Yukon, the numbers agree. North
of Tok, 25 percent of calves collared survived their first year. Just 19
percent survived in a study performed in southwest Yukon. Around 30 percent
made it through a year in two studies done around Galena and Nelchina. Terry
Bowyer, a biologist formerly with the University of Alaska Fairbanksı
Institute of Arctic Biology, collared cow moose in Denali National Park and
kept track of her young for four years. Only five calves out of 44 made it
through their first summers. A vast majority of those were killed by grizzly
Moose calves are often easy prey for bears and wolves until they gain some
agility, Alaska Department of Fish and Game biologist Rod Boertje said.
³Caribou calves can outrun bears in 10 days,² he said. ³It takes moose
calves about five weeks until they can outrun a bear. Theyıre vulnerable for
a lot longer.²
Boertje said the moose calves that survive are probably the ones that stick
close to the cow no matter how frightened by an attacking bear or wolf.
Those that let their mothers fight their battles for them are probably the
moose that survive to be adults in a struggle that is lost more often than
1967.jpg: Within the first few months of life, moose calves often fall prey
to wolves and bears.
U.S. Fish and Wildlife Service photo by Leroy Anderson.