Social Relationships:
Mating system: harem/ female-defense polygyny
Photo courtesy of Sounds of Science http://beca.sfsu.edu/sos/females.html
Southern elephant seal males reach the beach about a month before females. They fight for control of harems once the females arrive ( Jones, 1981). Northern elephant seal males establish dominance before cows arrive on the beach (Jones, 1981). Females birth about a week after arrival on the beach (McCann, 1980).
Males are considered either bachelors, those with no access to breeding, or bulls, with the most dominant bulls called harem masters (McCann, 1980). If there are less than 50 cows in a harem, there will only be one bull, but in larger harems, several bulls may be present ( Jones, 1981). The average harem size is 12 females per male. The most dominant male has the largest harem and copulates with the greatest number of females (Jones, 1981). In order to be a beachmaster, males must act as assistants for approximately four breeding seasons ( Jones, 1981). The size of harems varies within the breeding season, and when the harems are at their peak sizes, more males are permitted to breed. However, most males never secure a harem (Jones, 1981).
The size of the harem positively correlates with the age of the harem master, with 11 years old being the average age of the harem master. "Composite harems" often occur on large beaches and include multiple harems, which may include up to 1000 females total.
Male seals remain on the beach until the last female in his harem has been mated (McCann, 1980).
This mating system has evolved because females are in groups on the beaches for birthing pups and therefore groups of females can be defended by males.
Male/Male Relationships:
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Photo courtesy of California State Parks http://parks.ca.gov/central/bayarea/an228/an228m.htm |
During the mating season, males compete for harems through active fighting and through aggressive vocalizations. Males exhibit scars and wounds from fighting for dominance. When at sea, males forage alone. |
Female/Female Relationships:
Females have no social bond with each other. However, cows sometimes aggregate into harems even when no bulls are present (Guinet et al., 1992).
Parent/ Offspring Relationships:
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Photo Courtesy of SeaWorld http://www.seaworld.org/Pinnipeds/elephant.html |
Cows have a single pup, which they suckle for one month before returning to sea. Mothers fast during the nursing period and lose significant energy reserves. Pups form groups on the shore, where they remain for seven weeks alone before entering the sea (Bell, 1997). Male elephant seals sometimes unintentionally commit infanticide while attempting to mount pups. Up to 50% of weanlings are mounted by adult and subadult male seals, which sometimes results in pup death (Rose, 1991). There is no significant care of the young. |
