A. Fabiani, F. Galimberti and A.R. Hoelzel

MALE REPRODUCTIVE SUCCESS IN SOUTHERN ELEPHANT SEALS (MIROUNGA LEONINA):
BEHAVIOURAL ESTIMATES AND GENETIC PATERNITY

The southern elephant seal (Mirounga leonina) is one of the most
polygynous species of all mammals and its mating system thought to be
among the purest forms of harem defence polygyny. Molecular methods
provide the opportunity to reassess mating systems from a genetic
perspective and to gain accurately estimates of reproductive success.
Reproductive success is a fundamental component of fitness and its
estimation a major problem in behavioural and evolutionary biology. In
this study we estimate paternity in a population of southern elephant
seals using microsatellite DNA analysis and we evaluate the
relationships between observational and genetic measures of male mating
success. The research was carried out on Sea Lion Island (52¡26'S;
59¡05'O), Falkland Islands, and samples for this study were collected
during three breeding seasons, from 1996 to 1998. In total, 104 males
and 192 mother/pup pairs belonging to seven harems (range dimension = 18
- 91 females) were typed for 9 microsatellite loci. All the sampled seal
were marked and behavioural estimates of male mating success were based
on records obtained with standard observation techniques. Behavioural
data indicate that a small proportion of males (about 30% of all)
achieved at least one copulation and, among males that copulated, the
copulation distribution is highly asymmetric, indicating a strongly
polygynous mating system. Genetic results also show a very high level of
polygyny. Within each harem the alpha male was the male with the highest
proportion of copulations (for seven harem: mean proportion = 0.80;
range = 0.4 - 0.92). In each case behavioural observations were strongly
supported by genetic results.

EUROPEAN CETACEAN SOCIETY, 15TH ANNUAL CONFERENCE, 6 - 10 May 2001, Rome
(Italy)