Walruses are only found in the Northern Hemisphere. They inhabit both the Northern Atlantic and Pacific oceans, with the Pacific walrus being larger (3% longer and 10% heavier) than the Atlantic walrus. Pacific walruses also have longer tusks than Atlantic walruses, as can be seen in the photos above. The walrus on the left appears to be the Pacific subspecies since its tusks are significantly longer than the walrus on the right, most likely an Atlantic walrus. Walruses are also sexually dimorphic, with males growing much larger than the females. In this species the males are 20% longer and 50% heavier than females. Walruses are most noted for their large canine tusks. In fact, their scientific name means "tooth-walker" since walruses sometimes use their large tusks to help them move around. They have small heads that sit upon large bodies. Their skin is tough and males are covered by wart-like nodules or tubercles (fibrous, callous-like skin patches) that protect them from tusk attacks by other males. Compared to other pinnipeds that feed on fish and organisms in the water column, walruses have a unique feeding style - they feed on small organisms on the sea floor.

The sounds produced by walruses are most often heard in association with mating. Males make underwater vocalizations that sound like taps, knock, pulses, and bell-like sounds. Walrus calls range in frequency from 100 Hz - 10 kHz. These sounds are typically followed by visual displays at the surface.

References
• Nowicki, S.N., Stirling, I. and Sjare, B. 1997. Duration of sterotyped underwater vocal displays by male Atlantic walruses in relation to aerobic dive limit. Marine Mammal Science 13(4): 566-575.
• Reeves, R.R., Stewart, B.S. and Leatherwood, S. 1992. The Sierra Club Handbook of Seals and Sirenians. San Francisco, CA: Sierra Club Books.
• Richardson, W.J., Green, C.R. Jr., Malme, C.I. and Thomson, D.H. 1995. Marine Mammals and Noise. San Diego, CA: Academic Press. pg 200-201
• Sjare, B., Stirling, I. and Spencer, C. 2003. Seasonal and longer-term variability in the songs of the Atlantic walruses breeding in the Canadian High Arctic. Aquatic Mammals 29: 297-318.
• Stirling, I., Calvert, W. and Cleator, H. 1983. Underwater vocalizations as a tool for studying the distribution and relative abundance of wintering pinnipeds in the High Arctic. Arctic 36: 262-274.

Additional Resources
• Born, E.W. 2005. The Walrus in Greenland. Ilinniusiorfik Education, Ministry of Environment and Natural Resources, Nuuk, Greenland. 79 pp. English translation by Christina Lockyer and E.W. Born.
• Sjare, B. and Stirling, I. 1996. The breeding behavior of Atlantic walruses, Odobenus rosmarus rosmarus, in the Canadian High Arctic. Canadian Journal of Zoology 74: 897-911.
• Stirling, I., Calvert, W. and Spencer, C. 1987. Evidence of stereotyped underwater vocalizations of male Atlantic walrus. Canadian Journal of Zoology 65: 2311-2321.
• Stirling, I. and Thomas, J.A. 2003. Relationships between underwater vocalizations and mating systems in phocid seals. Aquatic Mammals 29(2): 227-246.
• Alaska Science Center: Pacific Walrus Research
• BBC News: Most Walruses Are Right-flippered
• PBS Nature: Toothwalkers: Giants of the Arctic Ice