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. https://doi.org/10.1111/jzo.12936
Elephant seals are a textbook instance of a polygynous species. In truth, 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 could ask whether or not it’s even value learning these animals’ mating methods anymore. Don’t we already know all we have to learn 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 surprising variation within the power of polygyny in pinniped populations from a number of species, together with elephant seals. We’re studying with every research that geographical and environmental elements can decide the flexibility of males to monopolize mates.
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 simple time monopolizing mates. By the way in which, 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 season. 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 sometimes 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 carried out a genetic parentage evaluation. We had been stunned to search out that the beachmasters at our research seashore solely fathered round 10.7% of the pups born there. Probably the most profitable male fathered solely seven pups over the complete course of the research. These findings recommend that, even for a species thought of as a textbook instance of polygyny, essentially the most dominant males needn’t at all times monopolise many of the copy.
We recognise that our sampling could have missed some males. Ideally, an observer ought to at all times hold watch on the seashore and account for each seal coming ashore on day-after-day of each season. However have you ever tried to take a seat on an Antarctic seashore holding a pair of binoculars for greater than 2-3h? First, your fingers would seemingly 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 discipline station. It’s extra like a discipline camp, solely occupied by 5 to 6 individuals who have to work almost across the clock to cook dinner, clear, and monitor 5 pinniped species and two penguin species. Nonetheless, we thought of the potential for lacking a small variety of extremely profitable males by conducting an evaluation of “hypothetical fathers” based mostly on maternal and offspring genotypes. This method allowed us to deduce what number of extremely profitable “unsampled” males we would have missed, and the reply was none.
Ultimately, 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 on the prevailing environmental situations. There may also be various mating techniques, like mating within the water with sneaky males that not often 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