Walruses are gregarious, traveling in small groups at sea or on ice pans and in large groups when resting or molting on land or ice. Despite the gregariousness the primary social bond seems to be that between a mother and her calf. Based on their behavior males appear to be polygynous although mating by identified animals or genetic paternity results to confirm polygyny are not available. In some situations males appear to follow females, competing directly with one another for the chance to mate. In other situations, males cluster around ice pans containing females that are likely receptive and compete through visual and vocal displays. The displays include in-air whistles and roars and underwater vocalizations that sound like taps, knocks, pulses and bells. It is thought that these sounds are made to attract females, which choose

Walrus (Odobenus rosmarus) tusks can reach 3 ft (90 cm) and weigh Despite its large cumbersome appearance, the walrus (Odobenus rosover 10 lb (4.5 kg). (Photo by Jeff Foott. Bruce Coleman, Inc. Repro- marus) is very agile in the water. (Photo by Len Rue Jr./Photo Reduced by permission.) searchers, Inc. Reproduced by permission.)

among the displaying males, but it is possible that some of the vocalizations also are threats aimed at other males.

Mother walruses, unlike any other pinniped species, nurse their young at sea as well as on land. In some instances the female floats on her back and the calf suckles on top of the female. In others, the female floats vertically in the water and the calf dives underwater, upside down to suckle. Young calves sometimes ride the backs of females while traveling at sea.

Both walrus males and females use their tusks for multiple purposes. They may be displayed as threats to gain a prime position in a resting or molting group or they may strike another with them in a fight. Tusks are useful defensive weapons against predators such as polar bears and killer whales. They may also be used to produce holes in the ice and to assist in hauling out of the water onto the ice. There is no evidence that the tusks are used to dig for food in the bottom substrate.

Digging or rooting for food at the bottom is done with the snout and mustacial vibrissae. Walruses use their tongue and lips to create a suction and suck the soft parts of prey from their hard shells.

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