Killer whales have used their extraordinary sight and anaconda snouts to feed on the vast quantities of seals and walruses that are being driven towards the North Pole by climate change.
They have even hunted with their mouths cut in half to digest the seals, which weighed 25 tonnes each.
But now biologists are beginning to discover that killer whales are even more productive as they evolve into “super” species as the Arctic melts.
“A large variety of non-opulent species is retreating north,” says Oregon State University researcher, Lena Buxbaum, who has studied 30,000 captive killer whales found in the wild.
“The concern is that many more prey animals could be lost.”
There are now only a few killer whales left inhabiting the Northwest Passage off British Columbia and the Yukon, and many more ocean dwellers are moving north into the Arctic.
The decline in the abundance of seals has created an apparent ideal situation for killer whales to hunt seals – a diet that is less demanding and the prey is less expensive to harvest.
Explosions from people’s cars, ships and planes are believed to be another factor in this mass displacement, although scientists do not think these have had much impact on seal numbers.
The central North Pacific also has other predator species – about 200 of them – and they are moving northwards too.
“There’s a convergence of the predator species heading north,” says Buxbaum.
Mating rites
The killer whales that have been able to adapt to the new zone of availability are hunting with a different strategy.
They are cutting each nostril open and squeezing out several walruses or seals for the same meal, although the mammals have to be crammed into such a small space that the whaling continues for just a few minutes.
The current study is reporting their findings in the journal Aquatic Mammals, the first scientific research to investigate the human-caused demise of seals and walruses in the North Pacific, from Alaska to British Columbia.
Environmental factor
Scientists think the remotion of prey species like seals and walruses are being driven by the influx of nutrients from warmer waters.
Some say this could be partly due to the decimation of large North Pacific breeding populations of smelt, a small fish whose numbers have plummeted due to fertilizer run-off.
The assessment of ocean life then depends on the assessment of all species, Buxbaum says.
“Only a single anthropogenic cause is known to be producing them all,” she explains.
The research is the first to investigate the nutritional habits of the 10 animals that inhabit the Northwest Passage, including some of the largest juvenile killer whales on the planet.
Extrapolating the data from Jekyll Island Marine Mammal Laboratory in Georgia, scientists believe the Northwest Passage has a predator population of about 1,400 killer whales.
Another study, also reporting the new research this week, suggests that whales could have limited range in the Arctic region.
The researchers carried out computer simulations to estimate the average distribution of killer whales across the Pacific Ocean.