The walrus, a massive Arctic marine mammal, possesses one of the most distinctive physical adaptations in the animal kingdom: its pair of elongated teeth known as tusks. These appendages are far more than mere decoration. Tusks are deeply integrated into the species’ survival and social structure, reflecting the unique challenges of the walrus’s icy environment. Understanding their functions reveals why these large, ivory canines became such a defining feature of the animal.
The Anatomy and Composition of Tusks
Walrus tusks are modified upper canine teeth that erupt from the mouth and grow continuously throughout the animal’s life. They are composed primarily of dentine, commonly known as ivory, and are covered by a layer of cementum. Both male and female walruses possess tusks, though those of adult males tend to be longer, straighter, and stouter, reaching up to 100 centimeters (39 inches). The tusks are not solid structures; they surround a central pulp cavity containing nerves and blood vessels. This neurological connection allows the walrus to receive sensory feedback, enabling it to feel vibrations and assess the ice’s thickness and stability.
Tools for Movement and Navigation
The prominent tusks are fundamental tools for navigating the walrus’s habitat of sea ice and frozen shores. The genus name, Odobenus, translates to “tooth-walker,” referencing the tusks’ primary practical use: hauling out. Walruses use their tusks as ice picks or anchors to pull their massive, ton-plus bodies onto ice floes or rocky beaches. This technique involves driving the tusks into the ice to secure a grip, then leveraging their powerful necks to pull themselves out of the water.
The tusks provide the necessary traction to overcome the slipperiness of the ice. Walruses also employ them to maintain open areas in the sea ice, chipping away to enlarge breathing holes from beneath the surface. While the walrus primarily uses its sensitive whiskers (vibrissae) to locate food, the tusks play a secondary role in foraging by plowing through soft seabed sediment. This action disturbs buried prey, such as clams and mollusks, which the walrus then detects and consumes.
Social Signaling and Defense
Beyond movement, tusks are powerful instruments for establishing social order within large walrus herds. The size and condition of the tusks correlate with social standing; longer, more symmetrical tusks signal age, health, and fighting capability. These tusks serve as visual threat displays during social interactions, often helping to settle disputes over hierarchy without physical combat.
During the mating season, male walruses use their tusks to challenge rivals and compete for access to females. These intraspecies conflicts involve tusk-to-tusk sparring, which establishes dominance and breeding rights. The tusks are also a formidable defense mechanism against natural predators, such as polar bears and killer whales. When threatened, walruses form a defensive perimeter with their tusks pointed outward toward the attacker.