team reported in 2013 in Biological Conservation.
In a separate study, Mumma and colleagues
analyzed aerial surveys of beaver populations
within seven broad regions in northeastern
British Columbia in 2011 and 2012. Proximity to
human activity, such as roadbuilding or oil and gas
exploration, didn’t seem to affect beavers’ decisions
to build at a particular locale. Nor did the presence
of wolves in the area, the researchers reported in
February in the Canadian Journal of Zoology.
Although having wolves nearby seemed to affect
the number of beavers present (quite possibly via
consumption), the predators didn’t seem to scare
the rodents away entirely, Mumma notes.
More beavers, fewer sick moose
Whether the presence of beavers on the Alaskan
tundra ends up boosting the numbers of moose
and other ungulates, the dam builders could
have a big, though indirect, impact on the hoofed
Roth and parasitologist Olwyn Friesen, now at
the University of Otago in Dunedin, New Zealand,
recently studied how a wolf’s diet affects the parasites it carries — which can then be passed on to
other creatures in the environment. The researchers analyzed 32 wolf carcasses collected by
provincial conservation officers in southeastern
Manitoba in 2011 and 2012. Those remains came
from hunters, trappers and roadkill.
In particular, the team tallied the parasites in
the wolves’ lungs, liver, heart and intestines. The
group also measured the ratio of carbon- 12 and
carbon- 13 isotopes in the wolf tissues, which provided insight into what sorts of prey each individual
wolf had eaten near the time those tissues formed.
Typical prey for wolves in this area are, from
most consumed to least: white-tailed deer, snowshoe hare, moose, beaver and caribou, Roth says.
Each of these creatures has a distinct ratio of the
two carbon isotopes in its tissues. That ratio gets
passed along to the predators that eat them.
The wolves with diets heavier in beaver had, on
average, fewer intestinal parasites called cestodes.
( Tapeworms are the best-known members of that
The implications are clear, Roth and Friesen
reported in 2016 in the Journal of Animal
Ecology. Beaver-eating wolves are much less likely
to excrete parasites into the environment where
they could be picked up by ungulates, such as moose
and caribou. Wolves don’t seem to be detrimentally affected by such parasites. But ungulates that
become infected — especially older animals — may
have reduced lung capacity, making escape from
predators more difficult.
A new resource
Although beavers may speed changes in the Arctic,
those effects may still take a long time to manifest.
Despite the proliferation of beavers in the
Lower Noatak River watershed in the last couple
of decades, “things around here grow so slowly,
they’re not really having a long-term impact yet,”
says local resident Kirk. Shrubs haven’t yet notice-ably spread into any areas of permafrost that have
been thawed by waters impounded by recent dam-building.
Nor have the beavers made much of a mark on
the local economy, he says. “There’s a lot of people harvesting them now, since there’s so many of
them around,” he adds. However, the pelts from
those rodents are so far used by the trappers
themselves, not sold to others.
The beavers haven’t become a big draw on the
local food scene, either. Even connoisseurs say the
meat has a gamey, greasy taste. As Kirk puts it, “we
haven’t adjusted our taste buds to them yet.” s
s Ken D. Tape et al. “Tundra be dammed: Beaver
colonization of the Arctic.” Global Change
Biology. October 2018.
Sid Perkins is a freelance science writer based in
Satellite images from
2005 and 2013 (middle
and right) show broad,
dark beaver ponds that
are not seen in a 1952
aerial image (left) of the
same Alaskan tundra.
The new ponds suggest
that the rodents have
been damming this
stream only in recent
1952 2005 2013