Bioacoustics of Odobenus rosmarus

Breeding. Walruses are polygynous, with males competing with each other through visual and acoustic displays and occasionally physical battles in the water to defend access to estrous females resting nearby. Nevertheless, there are scant details on most aspects of breeding behavior of Walruses because their breeding season is in December—-March generally in areas with considerable cover of sea ice that are difficult to access and not often visited by researchers. It has been suggested that their breeding system might resemble a “lek system” whereby males use vocal and visual displays while in the water to attract females in areas where they are more densely distributed relative to suitable sea-ice conditions and food availability. Mating is thought to occur in the water. After impregnation, the egg develops briefly and then is dormant for ¢.5-6 months before the embryo attaches to the uterine wall and resumes development (i.e. delayed implantation). Single neonates are born from mid-April to mid-June, with a peak in May. Offspring nurse for 2-2-5 years. In some populations, birth interval may be as along as three years. Most young are weaned by c.3 years old when juvenile males tend to join male groups. Females can be sexually mature at c.8 years old, and many give birth for the first time when they are ten years old. Males mature a few years later, and although they are capable of mating at ten years of age, few evidently do until they are c.15 years old.