Built-up earwax taken from a blue whale carcass offers insights into the creature’s life


Using built-up earwax taken from a blue whale carcass, researchers have been able to reconstruct a picture of its life by the chemicals and hormones in its ears.

The whale in question was a male blue whale that died after it was struck by a ship near Santa Barbara, Calif., in 2007. Researchers removed a 10-inch ear plug from the carcass during a necropsy. They did a careful chemical analysis of it to measure what the whale had been exposed to in its lifetime. The study appeared in a recent edition of the journal Proceedings of the National Academies of Science.

The scientific community has been excited about the possibilities raised by the new method “once they get past the ‘eew!’ factor of it being earwax,” says Stephen Trumble, lead author on the paper and a biology professor at Baylor University in Waco, Texas.

Baleen whales are known to accumulate layers of earwax in their ear canal. These create a waxy plug that can be over a foot long. The earwax is laid down in layers, a dark one when the animal is feeding and a light one when the animal is migrating and eats very little. The layers are routinely used to determine whale ages.

Now by analyzing the chemicals, pollutants and other matter that accumulated in that wax, researchers were able to build a very complete picture of the animal’s life and exposure to chemicals.

The whale was likely born around 1995. It was exposed to large concentrations of persistent organic pollutants such as DDT and other pesticides in the first six months of its life, most likely while it was still nursing. Many mammals are known to pass chemicals through milk and researchers believe that’s what happened to this whale.

DDT is one of a group of persistent organic pollutants that can take decades to break down in the environment. Although it was banned in the United States in 1972 it is still found in the world’s oceans, and was present at higher levels when this whale was born.
There were also two spikes in its exposure to mercury, around ages 5 and 10. The researchers think these might have occurred as the animal migrated past the coast of California, possibly exposing it to higher levels of pollution than it encountered in the open ocean and when passing less polluted land masses.

When it was about 10 years of age researchers believe it became sexually mature because of increases in testosterone. Its stress hormones spike right around that time, too, which the researchers believe might have been linked to breeding competition or social bonds it formed during this period.

The method offers researchers a much easier and more precise way of measuring what whales are exposed to than previous methods, which included examining whale blubber, blood, feces and blowhole spray, says Sascha Usenko, a professor of environmental chemistry and one of the Baylor researchers.

Since their paper was published they’ve been getting offers of whale earwax specimens, called plugs,from around the world. “We’re going to receive one hopefully this week that’s about three and a half feet long from a bowhead whale from Barrow, Alaska,” Trumble said.


Blue whales perform underwater acrobatics to attack their prey from below


The massive mammals are known for lunge-feeding; gulping up to 100 tonnes of krill-filled water in less than 10 seconds.

Using suction cup tags, US researchers have recorded the surprising manoeuvrability of the giants.

They found that the whales roll 360 degrees in order to orientate themselves for a surprise attack.

The results are published in the Royal Society journal Biology Letters by Dr Jeremy Goldbogen and colleagues for the Cascadia Research Collective based in Washington, US.

“Despite being the largest animals to have ever lived, blue whales still show an impressive capacity to perform complex manoeuvres that are required to efficiently exploit patches of krill,” said Dr Goldbogen.

Blue whales feed exclusively on krill: small crustaceans that have excellent escape responses, requiring the mammals to have efficient foraging strategies to be able to meet their energy demands.

To understand how these giants manage to capture prey, despite their size reducing their mobility, Dr Goldbogen and his team tagged a group of animals off the coast of southern California, US.

Using suction cups to safely attach the acoustic recording tags without harming the animals, the team were able to track the whales’ movements with the help of underwater microphones.

Results revealed that the whales were executing impressive spins below the waves in order to access large patches of krill.

“As the blue whale approaches the krill patch, the whale uses its flippers and flukes to spin 180 degrees so that the body and jaws are just beneath the krill patch,” explained Dr Goldbogen.

“At about 180 degrees, the mouth just begins to open so that the blue whale can engulf the krill patch from below.

As the blue whale engulfs the prey-laden water, it continues to roll in the same direction and completes a full 360 roll and becomes horizontal again ready to target and attack the next krill patch.”

The researchers were able to record video footage of the impressive acrobatics using a video camera worn by another animal to capture natural behaviour.

“We did not expect to see these types of manoeuvres in blue whales and it was truly extraordinary to discover,” said Mr Goldbogen.

Previous research has identified similar behaviour in other rorqual whale species such as humpback whales, but these animals rarely exceed 150 degree turns.

In these smaller whale species the ability to twist and turn was attributed to long fins and tail flukes.

For blue whales however, scientists suggest the extra effort of turning rewards the massive mammals with enormous meals.

They also propose that the acrobatics optimise the animals’ field of view.

“As in all cetaceans, [blue whales’] eyes are positioned laterally, and thus rolling the body should enhance panoramic vision in multiple dimensions,” the study reported.

Dr Goldbogen commented that the results will fuel further research into the complex behaviour of whales, especially regarding predator-prey interactions.

“This extraordinary ability is only a glimpse into the diverse repertoire of manoeuvring behaviours performed by foraging animals,” he told BBC Nature.

“Future tagging work has the potential to reveal many more unique insights into the daily lives of animals in their natural environment.”