Why do these 3,500kg giants of the sea wash up on the south west coast?

As the largest seal species on earth, Southern Elephant Seals are one of the big kahunas of the Southern Ocean. Massive, deep-diving predators that thrive in icy waters, they occasionally drop into Portland and other south west Victorian locations. 

But as ocean temperatures rise due to the warming of the planet, finding food and places to swim is becoming more challenging for the seals.

“The increase in sea surface temperature and habitat loss affects the seals’ foraging behaviour and food availability,” the Australian Marine Conservation Society’s Alexia Wellbelove told the Brolga.

Erosion of land where seals rest - “haul out” sites - is also a concern.

“Warming water temperatures can impact distribution and location of their food source, deep sea squid and fish, and climate change may also impact their haul out sites if these are washed away, or no longer suitable if too exposed,” Wellbelove said.

She pointed to bird flu and entanglement in fishing gear as other concerns for the species.

Portland’s favourite southern elephant seal, Sammy, a frequent visitor to the town, reappeared last week near the Botanic Gardens, but typically seeing these giants on the mainland is a rarity.

“Generally they come on land to breed, at the breeding colonies, not on mainland Australia, to rest and moult their fur,” Wellbelove explained.

“It is thought that they may show up because they have become disoriented, or it may just be that they have followed a food source and then need to haul out to rest afterwards.”

She said southern elephant seals spend around 90 percent of their lives at sea. 

“Once they come onshore they will just haul out on the nearest beach. They generally don't seek any shelter and will stay near to the sea, although there are always the exceptions to the rule.

“They won't be very active on land, but move on their bellies like a caterpillar. This is pretty slow and awkward, but they can do short, fast bursts, so it is always advised to give any animal space so that they don't feel threatened and need to protect themselves.”

Breeding season runs from September to November, before the animals return to the water for several months. From January to March they haul out again to moult, resting for around four weeks before heading back to the deep. 

“Elephant seals forage widely across much of the Southern Hemisphere, and breed in dense colonies on subantarctic islands,” said the Antarctic and Southern Coalition. 

The coalition said while they are found primarily in the Southern Ocean, small, remnant or vagrant populations can be found in Australia, South Africa and South America, and as far north as Mauritius and Oman.

“On land, they are big and cumbersome, but they are superb swimmers and divers,” Wellbelove said. 

Their torpedo-shaped bodies allow them to dive to a depth of more than 1,500 metres and stay submerged for up to two hours, making them the deepest diving seals in the world.

They can grow up to five metres long and weigh more than 3,500 kilograms. By comparison, the maximum kerb weight of a Toyota Hilux is about 2,300kg. The seals can live for about 20 years.

Once hunted almost to extinction for their oil, southern elephant seals are now protected under international agreements and Australia’s Environment Protection and Biodiversity Conservation Act. 

A common misconception about the species is that they have trunks, but the name is only attributed to the males’ trunk-like snouts.

Image credits: laikolosse via Flickr CC BY 2.0