Elephant seal female breeding histories at Año Nuevo

The elephant seal (Mirounga angustirostris) breeding colony at Año Nuevo,
California, was founded in 1961, and since monitored closely until the
present. Since 1968 a research group at the University of California,
Santa Cruz, has studied it in detail. Individually identified females were
monitored during the breeding season, and pupping records of many
throughout their lifetimes were assembled. We address here the maximum
reproductive success of females using the lifetime breeding histories.
Females lived to a maximum of 23 years and were observed breeding in as
many as 17 seasons. One female was observed with a pup nearby in 16
consecutive seasons, from age 4 through age 19. We compared females that
gave birth to 10 or more pups (Supermoms) with females that bred at least
once but produced fewer than 10 pups (Generic moms). Less than 17% of
female weanlings bred at least once. Only 0.87% of females in the sample
became Supermoms. We conclude that exceptional reproductive success in
elephant seals is associated with giving birth annually, living long and
weaning pups successfully. Once female elephant seals begin reproducing
they are pregnant or nursing throughout life until they die.