The southern elephant seal (Mirounga leonina) is a charismatic top-predator of the southern oceans with a very peculiar life style. Elephant seals have a circum-Antarctic distribution, with three main stocks: South Georgia, Macquarie Island, and Kerguelen Islands. The Falkland Islands population of elephant seals belong to the South Georgia stock.
In historical times, elephant seals were distributed all over the Falklands, but they were almost taken to extinction by the indiscriminate commercial sealing that happened during the 1800s and early 1900s. Currently there is a main breeding colony at Sea Lion Island (approximately 620 breeding females), plus small colonies on other islands and along the coastline of East Falkland. In recent years, elephant seals have increased in number at Sea Lion Island, and possibly in other breeding colonies.
Elephant seals have a mixed life style, and they spend two phases of their annual cycle on land, during the breeding and the moulting, and two phases at sea, for the post-breeding and post-moulting feeding migrations. When they are at sea, elephant seals are solitary, and spend most of their time diving to get food. Usually, they do not haul out during the aquatic phases, and they spend months at sea diving without rest. Elephant seals from Sea Lion Island forage mostly close to the breeding colony and the Falklands coastline, on the continental shelf, and over rather shallow waters. Apparently these seals are able to get good food resources close to their haul out sites, avoiding the very long feeding migrations that are typical of other elephant seal populations.
When they are on land elephant seals are very gregarious. During the breeding season females aggregate in harems, and each harem usually has a large male in charge, the harem holder. Males begin to haul out for the breeding in late August, with the oldest ones coming first. Males define dominance relationships by vocal threats, visual displays, and all-out fights. The most dominant males get control of harems, do most copulations, and sire most pups. A successful breeding male can sire more than one hundred pups per season!
Females begin to haul out during the first week of September, get to peak number on land around mid-October, and by mid-November most of them are already back to sea. Each female usually stays on land 3-6 days before giving birth to a single pup, suckles it for about 23 days, copulates, and returns to sea for feeding. When she goes back to sea, the pup is abruptly weaned. Pups are about 40-45 kg at birth, and they grow very fast, getting to an average weight of about 135-140 kg at weaning, with some of them weighing more than 200 Kg !!! Weaned pups stay on land for about 6 weeks before going to sea for their first feeding trip, that is a pretty risky business, because a large percentage dies and never returns to land again.
While just the breeders haul out during the breeding season, all individuals, of all age classes, need to haul out for the moult, to shed the old fur and skin. Young individuals moult first, in November and December, followed by juvenile males and breeding females, most of which moult in January, while the older sub-adult males and the adult ones moult in February and March.
The elephant seals have a rich social behaviour, in which communication has a very important role. Males vocalize to communicate their size, age, and stamina, and settle dominance contests without fights. Mothers and pups vocalize to recognize each other and establish the mother-pup bond that is essential for the development of the pups.
The Elephant Seal Research Group studied elephant seals at Sea Lion Island during the past twenty years, making it the longest running scientific study of mammals on the Falklands. Our research is focused on the individual survival and breeding strategies. Therefore, we mark each seal at birth and weaning with cattle tags. Those tags, that have a rather low loss rate, permit us to follow up each seal along its whole lifespan. We have lifetime information on thousands of females and hundreds of males. Long-term studies such as ours are invaluable because they permit the assessment of the complex interplay between the individual phenotype, the demography and socionomy of the population, environmental stressors like climate change, and disturbance due to human activities. Apart from collecting basic information about the seals by counts, individual identification, and observation of behaviour, we use a lot of techniques to obtain data about the phenotype, the social system, and the local environment. For example, we are using photogrammetry to estimate size of males, that are very large, we are mapping the seals using GPS and laser telemetry, we are deploying data loggers on the breeding and moulting beaches to assess the effect of micro-climate on seal behaviour, and we are studying the effect of killer whale predation on the seals demography. For further information about the ESRG research project please have a look at the research team website, www.eleseal.org.
Photographs: Elephant Seal Research Group
Layout: Bee Design
Printer: Cartor Security Printing
Perforation: 13 ¼ x 13 per 2cms
Stamp size: 38 x 30.6mm
Sheet Layout: 10 (5 se-tenant pairs)
Release date: 30 November, 2015
Production Co-ordination: Creative Direction (Worldwide) Ltd