While elephants and elephant seals are taxonomically oceans apart, they both have size in common.
What are southern elephant seals and how big are they?
African elephants are known to be our biggest terrestrial mammal and southern elephant seals are the portliest of pinnipeds. In fact, the latter are so stupendously large that a bull seal can reach a weight comparable to that of a fully grown bull African elephant, with both topping the scales at around four tonnes. It is worth noting, though, that the seal’s moniker doesn’t derive from its gargantuan size, but from its trunk-like snout, which plays an important part in the mating game.
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All southern elephant seals must undergo a complete (or catastrophic) moult each year. They need to keep warm during this process, and with heat loss in cold water estimated to be 25 times faster than in air, their only option is to return to land during the summer.
Where do southern elephant seals live?
These mighty beasts spend between 9 and 10 months of the year feeding in brutally cold sub-Antarctic and Antarctic waters, and are often beneath the surface for up to 90 per cent of each 24-hour period, at depths of anywhere from 500m to 1,500m.
How do they reproduce?
However, mating and giving birth must take place on dry land so, come September, the seals head for remote sub-Antarctic islands.
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The bulls are first to come ashore, followed by the females up to a month later, most of them heavily pregnant. As more females arrive, they begin coalescing around the massive bulls dotted along the beach, with harems of 40 or 50 females not uncommon. The difference in size between the sexes becomes apparent, with a mature male often twice the length of a female and up to 10 times heavier.
The pups are born soon after the females’ return and immediately start suckling. A mother’s milk is so rich that she loses around 8kg a day and a total of 35 per cent of her bodyweight over the period, before finally fattening up again back at sea.
It’s thought only two or three per cent of males will be successful in winning breeding rights each season. This means that despite the bulls reaching sexual maturity at between five and six years old, they will rarely attempt to breed until at least nine years old.
Meanwhile, the males also eat into their considerable fat reserves, spending every waking hour defending their harem, until the females are ready to mate during the short window a few days before their pups are weaned. Being big and bullish is key to the males’ breeding success. They employ their large snouts to create a roaring sound, which is backed up by their intimidating size and aggressive posturing. Smaller, more inexperienced males are pushed to the fringes, where they are reduced to either a watching brief, or the somewhat riskier strategy of attempting a sneaky copulation when the incumbent’s back is turned.
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However, it becomes a totally different proposition when two equally sized, pumped-up males come together – particularly if ownership of a harem is at stake. The bulls face-off, using their front flippers to raise their enormous bodies to towering heights. If neither backs down at this point, they will lunge at each other with their large canine teeth to inflict damage around the neck area. These fights can quickly become bloody, with the males frequently leaning against one another as they attempt to wear down their opponent.
Despite appearing incredibly brutal, fights rarely last longer than a few minutes and invariably end with the loser beating a hasty retreat before any serious injury occurs. In reality, the seals most at risk during these titanic clashes tend to be hapless youngsters caught in the middle, with pup mortality often high in heavily populated breeding territories.
A study of southern elephant seals breeding on Marion Island over a 25-year period discovered that many females failed to show up during certain breeding seasons, yet returned the following year to give birth, leading to the conclusion that they may have been mating at sea with males lower down the pecking order.
Once they have mated and with their young weaned, the females and the near-spent males will then head back to sea with one mission – eating! But it may still be another four to six weeks before hunger drives the weaned pups out to sea. A steep learning curve then ensues as they attempt to avoid the dishonourable intentions of orcas, leopard seals and sharks waiting in the wings to prey on the careless or just the plain unlucky.
Where can you see elephant seals?
Península Valdés, Argentina
The only mainland colony of southern elephant seals, with around 15,000 pups born each year.
South Georgia
It’s estimated that this remote island hosts about 54% of the global population of southern elephant seals.
Kerguelen Islands
Around 80,000 females are believed to give birth annually on this archipelago, which forms part of the French Southern and Antarctic Lands.
Macquarie Island
The seal population at this Australian outpost recovered after hunting ceased, but recently numbers seem to have been declining, with around 19,000 females giving birth.
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