B. Birth seasons. C. Frequency of birth. Most pregnancies are spaced at least two years apart for younger females. Older females probably bear calves less often. A female generally gives birth to a single calf at a time.
Twins are rare, although they have been reported.
Calves are usually born on the ice. E. Calf at birth. Calves are ashen gray to brown with dense, short soft fur. About two to three months before birth, the calf sheds a fine white layer of soft fetal hair called the lanugo. Within days or weeks, the calf becomes more robust.