The walrus can, at best give birth to a calf every second year. Among older animals, it is normal to have a calf only every 4 or more years. The calf normally stays with the mother for 2 years, until they are able to feed on benthic invertebrates. After this the young females normally stay with the group while the young males tend to leave the group to join groups of males. The higher mortality among the males may be caused by their aggressive behavior towards each other. The natural mortality rate appears to be about 2 percent per year and the major causes of death are malnutrition, predation and diseases(Fay et al. 1979). .
The walruses are mainly benthic feeders and their diet is mostly made up of bivalve mollusks. Most feeding takes place at a depth between 10 - 50 meters. They can dive much deeper but there is no point since the benthic organism they feed on cannot be found at extreme depths (Fay and Burns 1988). A walrus eats about 3000 - 6000 clams per day. However, the walrus does not only feed on benthic invertebrates. In times of need they also eat fish, seabirds and some walruses even kill and eat seals. .
According to the U.S. Marine Mammal Act of 1972, only Alaskan Natives are allowed to hunt walruses and then only for survival purposes for making Native handcraft. There is no fixed limit to the numbers that can be harvested. The numbers of animals killed is only restricted by what can reasonably be used. The walrus has been protected since 1952 in Norway and only residents with a license are allowed to hunt walruses in Greenland. .
The Pacific walrus has been hunted for approximately 150 years. The population has been severely reduced several times, but it has returned to its original population rate. The latest decline started in the 1930's and was the most severe. There were only 50 000 - 100 000 individuals in the 1950's. All of the major declines have been due to commercial overharvest (Fay et al 1989).