AD 2018 Q1

thick hide was used for leather, and their tusks were
a source of ivory. Though hunting has mostly been
banned now, walrus numbers have recovered very
slowly because females are not sexually mature until
they are 6 to 9 years old, and
mature females bear just one calf
every three years.
Besides humans, the only
predators of walruses are orcas
and polar bears, which are
functionally obligate carnivores
and are physiologically dependent
on consuming the blubbery
bodies of marine mammals.
Other foods simply cannot meet
their energy needs over the long
run. Polar bears prefer to prey
on seals, but when seals are
unavailable they will seek other
nourishment. Walruses’ bodies
are full of nutritive blubber, but
they are difficult to hunt because
they are powerful, suspicious,
have thick skin and live in large colonies. When
assaulted by a polar bear, all members of the colony
mobilize and begin moving as one, which can disorient
the polar bear. The bear needs to minimize the risks
and maximize the result of each attack if it is to meet
its caloric needs in the context of its evolving habitat.
But sometimes the resulting chaos causes some old or
very young walruses to be injured, and in these rare
occasions they become easy prey
to fill the starved bear’s belly.
Walruses eat sea worms,
mussels and clams, which they
suck from the seafloor. They find
food with the help of up to 700
mystacial vibrissae that cover their
faces; extremely sensitive tactile
organs, the vibrissae are a broad
mat of stiff bristles around the
walruses’ tusks that help them
differentiate shapes. Walruses’
eyesight is not as sharp as that
of other pinnipeds because
acute vision is not necessary for
their survival since they feed
on sedentary bottom-dwelling
animals. After foraging, they
usually congregate on land to rest
and digest, yawning and stretching their whiskers with
hollow grunts. Like whales, they blow water when they
surface after dives, but they use both nostrils and their
mouths to exhale.
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