Fabiani, A., Galimberti,F., Sanvito, S and Hoelzel, A.R. (2004) Extreme polygyny 
among southern elephant seals at the Falkland Islands: behavioral estimates and 
genetic paternity Behavioral Ecology: In press

Elephant seals are known from long-term behavioral studies to be highly 
polygynous and to show high variance in reproductive success among males. 
However, genetic studies have determined that the level of polygyny varies 
between the closely related northern and southern elephant seals. In the present 
study, we investigate paternal success at the Sea Lion Island southern elephant 
seal colony in the Falkland Islands by using both behavioral measures and 
genetic markers. We find that the average success of harem holding males at Sea 
Lion Island is significantly higher than both the northern species and the 
nearby southern elephant seal population at Punta Delgada. We compare genetic 
paternity with various behavioral indices of male mating success, and we find 
that the behavioral measures provide a good estimate of the variance in male 
reproductive success. Only 28.2% of males achieved paternities, and among these, 
harem holders accounted for 89.6%. We discuss the implications of our results in 
the context of the demographic and physical environment. Specifically, a 
comparatively high variance in resource holding potential among males, 
differences in male social behavior, and a small tidal cycle limiting peripheral 
male access during female departure from the harem at this colony may be 
important factors leading to the comparatively high variance in male 
reproductive success at Sea Lion Island.