ORAL SUCTION OF A PACIFIC WALRUS (ODOBENUS-ROSMARUS DIVERGENS) IN AIRAND UNDER WATER

Walruses mainly eat sessile bentic prey. Of bivalve molluscs, usually only the siphons and feet are found in walrus stomachs, and it is thou ght that walruses use oral suction to separate the molluses from their shells. Low pressure in the buccal cavity is caused by retraction and depression of the tongue which acts like a piston. The pressure in th e oral cavity of a female walrus was measured during several in-air an d underwater suction tests. The lowest pressure recorded in air was -8 7.9 kPa (-0.879 Bar, almost vacuum) when the walrus sucked on the pres sure transducer. The lowest pressure recorded under water was -118.8 k Pa (-1.188 Bar) when the walrus was sucking on a mackerel. The walrus has good control over its tongue muscles and over both the pressure an d the duration of suction.