5 things about Pacific walruses, which are gathering en masse due to climate change

You may have seen the stunning pictures by now - at least 35,000 Pacific walruses gathering on a remote Alaskan coastline.

The gathering en masse of the tusked pinnipeds is a "consequence of climate-induced warming", the US Geological Survey (USGS) said in a statement.

Here's a look at some peculiar features of the walruses and why climate change may be impacting their existence:

1. Most of them live in the same place

Alaskan waters house 95 per cent of the world's 200,000 to 300,000 strong walrus population, the USGS said in a short film that captured an expedition to track 400 of the animals.

The Chukchi Sea, which stretches from northern Alaska to Russia, is a particularly happy hunting ground, as it is shallower than normal. A continental shelf below the Chukchi Sea means it is only about 45m deep, giving the walruses, which forage on the sea floor for food, a rich buffet line to pick from.

This dense concentration also means that any major impact on the Chukchi Sea will have a detrimental effect on a large number of walruses.

2. Walruses use their "fingers" to forage on the sea floor

They may be hulking creatures but walruses primarily eat clams, marine worms, large snails and other things they find on the sea floor. They dive down to the sea bed and root around with the sensitive whiskers on the muzzles, which sweep the sea floor like fingers searching for a snack in a crowded fridge.

As you would expect, diving underwater for food is tough work. Walruses forage for seven minutes, then come up to breathe and take a two-minute break, before repeating the process for hours. They also take extended breaks before moving to a different clam bed.

3. Retreating sea ice means they need to commute to their food

Where do walruses prefer to rest? The very same sea ice that is retreating farther each year. The Chukchi Sea has seen a dramatic loss of sea ice due to climate change since 2007.

With the ice retreating north, and summer ice disappearing more quickly, the walruses have nowhere to rest. They then have to travel farther to find land to rest on, like the Alaskan coastline seen in pictures, effectively giving them a commute before they get to their food.

4. Young walruses are being trampled to death by the herds

Walruses are social creatures which love to be next to each other. USGS scientists describe them as "caring" and "gregarious". But the sheer size of the herds in which they gather pose a threat to those who need protection.

Walrus pups are about 68kg when they are born, but that pales in comparison to fully grown male pacific walruses, which can clock in at 1,700kg. When disturbed, the herd flees towards water, causing the younger walruses to be trampled and killed. The US Fish and Wildlife Service has told pilots to avoid flying too close to the animals, as they could stampede if alarmed by engine noise.

5. Are they at risk? We don't know yet

The waters in the Arctic are now open for a longer period, which has led to an increase in commercial activity such as shipping and tourism having an impact on the environment.

Are the walruses therefore at risk? The US Fish and Wildlife Service concluded in 2011 that listing the walrus as a threatened species was warranted, but information is still being gathered for a final decision in 2017.

The ICUN Red List of Threatened Species, an authority on conservation, listed the walrus as "data deficient" in 2008, saying that while there is evidence that the population is declining, climate change is expected to have severe consequences for walruses.  It added that there is little recent data on population sizes and trends.

Source: US Geological Survey, ICUN Red List