Why can the Weddell seal survive in Antarctica? Why does it have to keep a hole into the ice? How does a female feed her Pup?

Weddell seals can live further south than any other
animals in Antarctica.  Females give birth from September through November. For the
first seven weeks, the young nurse from mother's mammary glands on milk, like all
mammals do. Then, they are weaned off the mother's milk. Females give birth to twin
pups. After that, they feed on fish, squid, krill, prawns, penguins. A sedentary adult
needs about 22 pounds of food per day, while an active one requires about 110 pounds of
food per day. They live near holes in the ice so that they can go into the water to hunt
for food. Also, during the coldest times of the year, they keep their bodies submerged
in the water to stay warm, with only their head poking out for
air.