Diving with wildlife

A Weddell seal in the sea ice.
Weddell seals often use the dive holes as breathing holes, and sometimes exit/enter the water via the holes. (Photo: Chris Wilson)

Antarctica contains no permanent land-based mammals or birds. Seals, whales and penguins are only seasonal visitors to the coastal shores.

Early in summer, when the sea ice extends many kilometres out from the shore, the only large animals that occasionally visit the divers are Weddell seals (Leptonychotes weddelli). These large and curious mammals are adapted to life beneath the sea ice where predators are few. With specialised jaws that open very wide, these seals are able to locate cracks in the ice and enlarge them using their teeth via side-to-side rasping motions of their heads. This ability enables them to open breathing holes in the ice and to make holes large enough for them to exit the water to rest on the sea ice.

Not surprisingly, the large custom-made holes that are drilled through the ice by the divers are attractive to the Weddell seals. It is not uncommon for the divers to find several seals lying around the dive holes when they arrive to start diving in the mornings. Seemingly unconcerned by the divers, the seals either move further away from the holes and continue sleeping in the sun, or they enter the water via the dive holes. Divers are often circled by the curious seals while working underwater, and are entertained by their range of squeals, rumbles and whistles.

As summer progresses and the sea ice begins to melt and break up, the open water comes closer to the coast. At this time, diving is often conducted along the edges of the receding sea ice. Adélie penguins (Pygoscelis adeliae) are commonly encountered in these areas while they feed and frolic in the water. The penguins are extremely curious and will swim or waddle hundreds of metres to visit the divers. It is not uncommon for divers to have twenty or more penguins spiralling around them as they work, whizzing past with curious eyes before zooming up to the surface for a quick breath of air and plummeting down once more. These birds provide endless amusement both underwater and on the surface where they 'inspect' the surface equipment and then settle down nearby to doze in the sun.

Occasionally, the Adélie penguin's larger cousin, the emperor penguin (Aptenodytes forsteri) will visit the dive site. These majestic birds are usually lone visitors and will stand a small distance away while watching the surface activities of the divers. We have not had the pleasure of diving with this species yet.

The activity of penguins on the ice edge also brings the threat of large predators, such as leopard seals (Hydrurga leptonyx) and orca (or killer whales, Orcinus orca). So far we have not encountered these mammals during diving but we commonly see them while boating around the Casey region. They are a large unknown in terms of threats to divers, but protocols dictate that all divers must exit the water if either species are seen in the immediate vicinity.