The place are the beachmasters? Unexpectedly weak polygyny amongst southern elephant seals on a South Shetland Island – Journal of Zoology Weblog

Nichols, H. J., Fuchs, B., Paijmans, A. J., Lewis, G., Bonin, C. A., Goebel, M. E., & Hoffman, J. I. (2022). The place are the beachmasters? Unexpectedly weak polygyny amongst southern elephant seals on a South Shetland Island. Journal of Zoology, vol. 316, pp. 104– 117.

Elephant seals are a textbook instance of a polygynous species. In reality, huge male southern elephant seals (“the beachmasters”) combating over their harems on a seashore are the right image of a mating system the place male competitors achieves its climax amongst mammal societies. On this context, one might ask whether or not it’s even value learning these animals’ mating methods anymore. Don’t we already know all we have to find out about them? The reply is that we’re removed from having all of it discovered, even for a well-studied mammal. Over the previous few many years, behavioural and genetic research have revealed sudden variation within the energy of polygyny in pinniped populations from a number of species, together with elephant seals. We’re studying with every research that geographical and environmental components can decide the power of males to monopolize mates.

Southern elephant seals (Mirounga leonina). Picture by Carolina Bonin

On this research, we investigated the mating success of male elephant seals in a small inhabitants situated at a wide-open seashore on a distant island. With little competitors on this small inhabitants, males ought to have a straightforward time monopolizing mates. By the best way, the seashore is on Livingston Island, one of many South Shetland Islands, the place a variable variety of elephant seals (56–158) come ashore to breed each austral summer time. This variation is probably going pushed by seashore entry situations: in some years, entry to the seashore is blocked by heavy snow in the course of the time when the animals would usually arrive. We sampled each pup born along with many of the men and women current on the seashore each austral spring (October—December) from 2008 to 2016 and performed a genetic parentage evaluation. We had been shocked to search out that the beachmasters at our research seashore solely fathered round 10.7% of the pups born there. Essentially the most profitable male fathered solely seven pups over all the course of the research. These findings counsel that, even for a species thought of as a textbook instance of polygyny, essentially the most dominant males needn’t all the time monopolise many of the copy.

Elephant seal pup with its mom and a harem holding male. Picture by Carolina Bonin

We recognise that our sampling might have missed some males. Ideally, an observer ought to all the time preserve watch on the seashore and account for each seal coming ashore on daily of each season. However have you ever tried to sit down on an Antarctic seashore holding a pair of binoculars for greater than 2-3h? First, your fingers would doubtless freeze (even with gloves), and relying on the day, the wind would possibly blow you over! Additionally, our research website isn’t just a fast stroll from a area station. It’s extra like a area camp, solely occupied by 5 to 6 individuals who must work practically across the clock to cook dinner, clear, and monitor 5 pinniped species and two penguin species. Nonetheless, we thought of the opportunity of lacking a small variety of extremely profitable males by conducting an evaluation of “hypothetical fathers” based mostly on maternal and offspring genotypes. This strategy allowed us to deduce what number of extremely profitable “unsampled” males we’d have missed, and the reply was none.

In the long run, we consider that there’s extra to that seashore than meets the attention. Many females don’t breed yearly, and their breeding behaviour seems to rely upon the prevailing environmental situations. There may also be different mating ways, like mating within the water with sneaky males that hardly ever if ever come ashore. Regardless, future research will proceed to disclose thrilling patterns of mating and copy in elephant seals and different pinnipeds world wide.

Carolina Bonin

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