Behavioral Ecology Blog

Pinnipeds have traditionally been thought of as a model system for exploring models of mating system evolution. The typical system involves sexual dimorphism with males being much larger. These males control a territory, and the females that reside on this territory. This usually results in polygyny- the mating system defined as the sexual relationship involving 1 male and >2 females. The role of female choice in these systems is thought to be based on things like territory quality etc…

Now, from stage left comes the Antarctic fur seals (Arctocephalus gazella), whose mating system can be described as polygyny. But let me make it clear, this is not your granny’s polygyny- it is actually pretty different (hence the Nature paper describing it). Here males are sedentary on land, moving less that one body length during the whole breeding season (and Kate, you call ME lazy!!). The females however are vagile (OK, vagile for a seal on land) and move in an apparent bid to get in the sack with the sexiest seal possible. For fur seals though, sexy has to do more with genetic diversity than with the absence or presence of “skid-marks”.

This is extra-cool because while mate choice is readily observed in the animal world (note human mate choice), the actual basis of choice (when no direct benefits are provisioned) has been pretty difficult to demonstrate, as additive genetic variation is expected to decrease rapidly… (BTW, this problem has been loosely termed the “paradox of the lek” **) The authors use this study where (1) choice is based on a low heritability trait, and (2) choice is non unanimous to get at a possible solution to the paradox.

** While the formulation of the paradox of the lek in this paper strictly involved the “why females choose”, the traditional paradox asks why choice is unanimous among females, especially when there is little genetic difference between males (Little additive variance). They seen to be talking about something a little different, as in this system there is not unanimous choice, and thus extreme diminution of additive genetics variance is not expected.

See more coverage of this story here,