Geoscience Reference
In-Depth Information
Figure 7-38.
Hundreds of juvenile northern elephant seals (
Mirounga angustirostris
) relax on the beach at Point
Piedras, California, United States (see also Fig. 3-20). Seen here in November, they await the return of adults who
have been foraging at sea as far away as the Aleutian Islands (Warburton 2010). Kite aerial photo by S.W. Aber and
J.S. Aber.
l ooding of nearby properties, such as agricul-
tural i elds, roads, recreational sites, and so on
(Figs. 7-43 and 7-44). Once beavers have decided
to move in, little can be done short of trapping
and relocating them far away.
Among the mammals that benei t from
beaver activity are muskrat and mink. Muskrats
(
Ondatra zibethicus
) are found just about
everywhere that cattails grow
-
in marshes,
swamps, ponds, ditches, etc. Native to North
America, they have also been introduced into
northern Eurasia, Japan and South America for
their valuable fur (Newell 2010). Cattail is the
primary food of muskrats, which eat the roots
and rhizomes, but they may also eat other veg-
etation and small animals. They dig tunnels
through the roots and use the stalks to build
lodges, much like beavers do (Fig. 7-45). Musk-
rats are important for controlling overgrowth
of cattails.
Mink are semi-aquatic animals with partly
webbed toes; they can swim like otters and live
on land like weasels (Collins, Collins and Gress
1994). They are generalist carnivores preying
on small animals of all types depending on
seasonal availability. Mink usually make their
Figure 7-39.
Polar bear (
Ursus maritimus
) on ice l oe
in Wager Bay, northern Canada. These bears are among
the largest and most powerful predators on land; they
hunt primarily ringed seals (
Pusa hispida
) and bearded
seals (
Erignathus barbatus
). Modii ed from original
photograph by A. Walk; obtained from Wikimedia
Commons
<
http://commons.wikimedia.org/
>
.
consequences from a human perspective. Among
other things, beavers cut down trees. That is
what they do for a living, but not all property
owners are happy to see their trees disappear
overnight. In addition, beaver dams may lead to
