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Images

Images

O. rosmarus 1 (A full-color drawing of the habitus)
O. rosmarus dv skull (Dorsal view of the skull)
O. rosmarus vv skull (Ventral view of the skull)
O. rosmarus lv skull (Lateral view of the skull)
O. rosmarus dvm skull (Dorsal view of the mandible)
O. rosmarus 2 (A walrus on an ice-floe)
O. rosmarus map (Distribution map)

Audio

Audio

O. rosmarus track 1 , RUTTING WHISTLES OF A MALE PACIFIC WALRUS (Odobenus rosmarus divergens), Walruses are extremely social animals which use a number of sensory modalities to exchange information with conspecifics. The most conspicuous signals are in air sounds, but underwater sounds are also produced. One of the in air sounds is a 'rutting whistle', produced by male walruses in spring. Fay et al. (1984) describe walruses in the Bering Sea producing loud whistles when swimming alongside a herd of female walruses, which were hauled out on the ice in March. The bulls were diving and surfacing at short intervals (1 - 3 minutes). The females, however, seemed to pay little attention to the diving bulls, although the diving sometimes continued for 5 hours. Miller (1985) also describes Pacific walrus whistles. A bull, swimming close to a hauling ground, lifted its head out of the water and produced whistles through its pursed lips. Sometimes the signal had a noisy character, but at other times it was an almost pure tone.The frequencyof the rutting whistle fundamental varies between roughly 1 and 2 kHz. The whistle starts at 1184 Hz, sweeps down to 1056 Hz, keeps this frequency for 0.8 s and rapidly increases to 1952 Hz. The total duration of the whistle is approximately 1.8 seconds. Sometimes a 'false' tone, consisting of two fundamentals, is heard. The average Source Level in air is 120 dB re 1 pW. Using certain assumptions concerning the walrus hearing system and the propagation conditions, the range of the walrus' whistle signal, to be heard by conspecifics in their natural environment, is calculated to be 1100 (+/- 100) m (Verboom and Kastelein, 1995).The rutting whistle differs considerably from other Walrus in-air vocalisations, which are described as knocks, roars, clicks, grunts and a bell-sounds (the last two signals are emitted under water as well). The knock is a short, broadband pulse with a frequency contents of 100 - 4000 Hz. The sound seems to originate from deep out of the throat, without the animal moving the jaws. Roars are long, loud calls with most of the energy around 300 Hz. Grunts are brief calls, also with a low-frequency spectrum. How the bell-sound (pure tone around 500 Hz with harmonics) is produced is not clear (Schevill et al., 1966; Fay et al., 1984).

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Walrus (Odobenus rosmarus)