Information about animals fascinate me, but I also like to delve into the history of how animals got their names, both common and scientific. As a life-long learner, I enjoy researching facts and that is what K’s Kreature Feature is really all about – a sharing of the knowledge that I have found particularly fascinating; also so that more people can learn about the amazing animals that inhabit our ocean.
Today I would like to introduce you to the southern elephant seal (Mirounga leonina). They form part of the ‘true seal’ (Phocidae) family. Being a true seal means that they do not have ear-like appendages (pinnae) on their heads. It also means that they have backward-facing hind flippers and look particularly ungainly, when moving around on land – imagine yourself trying to move elegantly whilst stuck lying in a sleeping bag. True seals, however, make up for this in the water, as they are very streamlined and efficient swimmers. There are two different types of elephant seal, the northern and the southern. I will focus on the southern elephant seal, as we have recently had some visit our shores, here in Cape Town, South Africa.
Buffel, the southern elephant seal that returned to Cape Town in February 2020 (Image credit: Jean Tresfon)
Before I get into the biological facts about the actual animal, I always like to explain how the animal got its name. The common name of this animal is rather self-explanatory – southern elephant seals are the largest living carnivores, apart from whales, of course. They are larger than any of the land-dwelling bear species, even the polar bear, and larger than walruses. Male southern elephant seals are usually 40% larger than females. Males can reach up to 5.8 metres in length and weigh up to 4 000 kg. So, truly a huge animal. Apart from their size, their funny looking nose also reminds you of an elephant trunk. This nose is quite special, as it serves two purposes: in males, they use it to generate loud noises as a form of dominance; and, both males and females, use their noses as a storage unit for moisture, to be used after a period of fasting. Interestingly, in the 1800’s the elephant seal was also sometimes called the ‘bottle-nosed seal’.
Local celebrity southern elephant seal Buffel underwater, captured by Steve Benjamin from Animal Ocean
The scientific name of the southern elephant seal is Mirounga leonina. The genus name, Mirounga, was described by a gentleman called John Edward Gray, a British zoologist. The word is not Latin and is said to be derived from ‘miouroung’, which possibly has origins from the Australian aboriginal language. The person who described the southern elephant seal species, however, was no other than the Swedish ‘father of modern taxonomy’, Carl Linnaeus. He created the current taxonomic system of binomial nomenclature and described 4 400 animal species, in total. The species name of the southern elephant seal, leonina, comes from Latin and means ‘lioness’. A leonina was also a coin issued under the rule of Pope Leo XII in the 19th century.
Now that we know why the elephant seal is called what it is, let us look at the biological facts about this animal. Southern elephant seals are only found in the southern hemisphere and live in sub-Antarctic and Antarctic waters. They breed on land, noteably on the Falkland Islands, Tristan da Cunha and the South Shetland Islands, but are otherwise found on pack ice around Antarctica. Sometimes they show off their amazing long-distance swimming skills and visit the shores of South America, New Zealand and South Africa. A southern elephant seal can swim up to 33 800 km each year.
The reason why southern elephant seals swim so far is to find food. Being carnivorous, they eat animals like squid, crustaceans, sharks, bony fish and molluscs. Male elephant seals tend to migrate and hunt in the same areas each year, along continental shelves and the ocean floor, whereas females look for food more randomly, and favour the open ocean. They are amazing divers, on average, reaching depths of up to 1 000 metres and staying submerged for up to 20 minutes. One southern elephant seal was recorded diving to 2 000 metres, however, and stayed underwater for two hours! Clearly, they are able to perform well beyond the average, when they are intent on finding food. What enables them to dive so deep and for so long is that they have very high levels of haemoglobin in their blood. They can also significantly reduce their heart rate, while diving; from a normal 50-120 beats per minute, to only 5-15 beats per minute.
Even other seal species fall prey to elephant seals (Image credit: Jean Tresfon)
Male southern elephant seals have a harem of females and spend most of their life fending off other potential suitors. Female seals reach sexual maturity at age three, and males only at age six. Generally, males are only ready to fight for and defend their own harem at age nine. These fights can get alarmingly physical and most large males will have several scars from their altercations with other males. Very rarely does a fight end in death, though. Male southern elephant seals have developed a layer of fibrous protein under the skin on their chest, which protects them from more severe blows from their opponents. Females can live up to 25 years, whereas males tend to have an average life span of 15 years.
Presently, there are not many threats to southern elephant seals. They have a few natural predators, although the pups are vulnerable to attacks from sharks and leopard seals. Orca whales are also known to attack pups and, occasionally, even adults. Some populations have declined, possibly due to food shortages linked to the climate crisis and overfishing. Historically, both the northern and southern elephant seals were almost hunted to extinction by humans. They have since recovered and their estimated population size is now around 650 000 individuals. They are listed as ‘least concern’ by IUCN.
Annie and Luis, two adult loggerhead turtles release off the coast of Cape Town, have together already travelled more than 4000 km in 20 days.
Claudine van Zyl completed her Work Imtegrated Learning (WIL) internship with us last year. Her research project was: ‘The characterisation of plastics in stranded post-hatchling loggerhead turtles along the South African coastline from 2015 to 2020’.
Bob, a green turtle in our care, has been with us since November 2014. While he is not ready for release yet, we are preparing him so that he has the best chance of survival back in the big blue. Alex Panagiotou, one of our turtle team specialists, is working with Bob through enrichment programmes and research.