Walruses are social animals, and can be found in groups of from several to several hundred animals, depending on the time of year and the particular population being observed. When hauled out on land, walruses prefer to maintain body contact with one another, and tend to form a group which is roughly circular (Salter 1979). New additions to the group will walk around the periphery trying to find their spot or attempt to displace other animals (Salter 1979). Tusk displays and jabbing are particularly often seen in walruses hauled out on land, although walruses with comparatively short tusks struck much less frequently than did walruses with longer tusks (Salter 1979).
Photo: Mario Acquarone
Walruses are also very vocal animals, and can produce a wide variety of sounds. Males especially produce long and repetitive vocalizations of various types, with bouts of “singing” that can last up to 65 hours (Sjare et al. 2003). One type of sound produced are short, sharp pulses, termed taps and knocks. The rate at which they are given can vary from 1 to 15 per second (Stirling et al. 1983). Taps and knocks are given in at least four different patterns, termed double knock, tapping or knocking sequence, coda, and diving vocalization (Stirling et al. 1983).
The double knock is a distinctive call given by some males before surfacing to breath during a stereotyped vocalization cycle. In the long tapping or knocking sequences, pulses are usually given at a rate of about 1 to 3 per. The sequences start slowly in some cases but quickly in others. The last few taps or knocks are often given in a rapid burst, termed the “coda”, sometimes followed by a bell call. During stereotyped vocalizing cycles, the male always gives a distinct call, which was termed the diving vocalization, immediately after taking his last breath and descending from the surface (Stirling et al. 1983).
|Listen to walrus here and here!|
The vocalizations are an important part of the breeding behaviour of walruses. Breeding takes place in the winter, from January to mid April, in polynyas (open water areas within the ice) or areas of unconsolidated pack ice. The mating system of walruses is best described as “female defense polygyny” (Sjare and Stirling 1996). A large mature male walrus, probably at least 15 years old, will “attend” or monopolize access to herds containing potentially reproductive females for extended periods of time, chasing away other males that approach. Any females that come into estrus during that time will mate with the attending male.
Vocalizations appear to mediate at least some interactions between males during the breeding season. When attending a herd of females, a single male may continuously repeating a complex, stereotyped song (Sjare and Stirling 1996). It is thought that these vocalizations convey his social status. Other sexually mature males in the area behave as silent herd members, vocal satellite males, or sometimes both. In some cases, males become silent and move out of the area when a singing attending male approaches them (Sjare and Stirling 1996). Sometimes these interactions escalate into fighting: if a young adult male approaches a female closely or vocalizes, the attending male will attack and chase him away (Sjare and Stirling 1996).
Walruses like to maintain contact when hauled out. Photo: T. Jacobsen, polarimages.dk