<p>Male southern elephant seals are the largest pinnipeds,
larger even than northern elephant seals, <span
class="taxon"><em>Mirounga angustirostris</em></span>, their
closest relatives. <span class="taxon"><em>Mirounga
leonina</em></span> males have been documented reaching over six
meters long and weighing over 4000 kg. This is in sharp contrast
to females, which are rarely over 800 kg or four meters long. In
fact, both species of the genus <span
class="taxon"><em>Mirounga</em></span> are more sexually
dimorphic than any other mammal. This dimorphism stretches
beyond just size. Males also have a large, inflatable proboscis,
which enhances vocalizations used to challenge other males for
mating rights. The southern elephant seal proboscis is slightly
smaller than the proboscis of northern elephant seals,
overhanging the mouth by only about 10 centimeters compared to
30 centimeters in their northern relatives.</p> <p>Breeding
populations vary in size. In the South Georgian population,
males average 450 cm in l