The sperm whale has 20 to 26 teeth on each side of its lower jaw. The teeth are cone-shaped and weigh up to 1 kilogram (2.2 lb). The purpose of the teeth is unknown. Teeth do not appear to be necessary for capturing or eating squid, and well-fed sperm whales have been found in the wild without teeth. One hypothesis is that the teeth are used in aggression between males.  Bull sperm whales often show scars which seem to be caused by the teeth of other bulls. Rudimentary teeth are also present in the upper jaw, but these rarely emerge into the mouth.
The origin of the word itself has variously been attributed to combinations of the Dutch words walvis ("whale") and ros ("horse") or wal ("shore") and reus ("giant"). However, the most likely origin of the word is the Old Norse hrossvalr, meaning "horse-whale", which was passed in a juxtaposed form to Dutch and the North-German dialects as walros and Walross. The now archaic English word for walrus—morse—is widely supposed to have come from the Slavic. Thus морж (morž) in Russian, mors in Polish, also mursu in Finnish, moršâ in Saami, later morse in French, morsa in Spanish, morsă in Romanian etc. The compound Odobenus comes from odous (Greek for "tooth") and baino (Greek for "walk"), based on observations of walruses using their tusks to pull themselves out of the water. The term divergens in Latin means "turning apart", referring to the tusks.
The walrus prefers shallow shelf regions and forages on the sea bottom. Its dives are not particularly deep compared to other pinnipeds; the deepest recorded dives are around 80 metres (260 ft). However, it can remain submerged for as long as a half hour. The walrus has a highly diverse and opportunistic diet, feeding on more than 60 genera of marine organisms including shrimps, crabs, tube worms, soft corals, tunicates, sea cucumbers, various mollusks, and even parts of other pinnipeds. However, it displays great preference for benthic bivalve mollusks, especially species of clams, for which it forages by grazing along the sea bottom, searching and identifying prey with its sensitive vibrissae and clearing the murky bottoms with jets of water and active flipper movements.The walrus sucks the meat out by sealing the organism in the powerful lips and drawing the tongue, piston-like, rapidly into the mouth, creating a vacuum. The walrus palate is uniquely vaulted, allowing for extremely effective suction to be generated by the tongue. Aside from the large numbers of organisms actually consumed by the walrus, it has a large peripheral impact on the benthic communities while foraging. It disturbs (bioturbates) the sea floor, releasing nutrients into the water column, encouraging mixing and movement of many organisms and increasing the patchiness of the benthos. Seal tissue has been observed in fairly significant proportion of walrus stomachs in the Pacific, but the importance of seals in the walrus diet is debated. There have been rare documented incidents of predation on seabirds, particularly the Brünnich's Guillemot Uria lomvia. Due to its great size, the walrus has only two natural predators: the orca and the polar bear. It does not, however, comprise a significant component of either predator's diet. The polar bear hunts the walrus by rushing at beached aggregations and consuming those individuals that are crushed or wounded in the sudden exodus, typically younger or infirm animals. However, even an injured walrus is a formidable opponent for a polar bear, and direct attacks are rare.
he walrus lives around 50 years. The males reach sexual maturity as early as 7 years, but do not typically mate until fully developed around 15 years of age. They go into a rut in January through April, decreasing their food intake dramatically. The females can begin ovulating as soon as 4–6 years old. The females are polyestrous, coming into heat in late summer and also around February, yet the males are only fertile around February; the potential fertility of this second period of estrous is unknown. Breeding occurs from January to March with peak conception in February. Males aggregate in the water around ice-bound groups of estrous females and engage in competitive vocal displays. The females join them and copulation occurs in the water. Total gestation lasts 15 to 16 months, though 3 to 4 of those months are spent with the blastula in suspended development before finally implanting itself in the placenta. This strategy of delayed implantation, common among other pinnipeds, presumably evolved to optimize both the season when females select their mates and the season when the birth itself occurs, determined by ecological conditions that promote survival of the young. The calves are born during the spring migration from April to June. They weigh 45–75 kg (99–170 lb) at birth and are able to swim. The mothers nurse for over a year before weaning, but the young can spend up to 3 to 5 years with the mothers. Because ovulation is suppressed until the calf is weaned, females give birth at most once every two years, resulting in the walrus having the lowest reproductive rate of any pinniped. In the non-reproductive season (late summer and fall) the walrus tends to migrate away from the ice and form massive aggregations of tens of thousands of individuals on rocky beaches or outcrops. The nature of the migration between the reproductive period and the summer period can be a rather long distance and dramatic. In late spring and summer, for example, several hundred thousand Pacific Walruses migrate from the Bering sea into the Chukchi sea through the relatively narrow Bering Strait.