The bowel movements of the largest creature on Earth have been captured on film and researchers say it can help piece together missing information of their once-mysterious behaviour.

Key points: The blue whale is the largest animal on the planet

The blue whale is the largest animal on the planet Its poo is described as smelling like a dog's, with the consistency of bread crumbs

Its poo is described as smelling like a dog's, with the consistency of bread crumbs A blue whale can excrete up to 200 litres of poo in one bowel movement

Blue whales are migrating south along the West Australian coastline with increased sightings off the viewing hotspot of Point Picquet, about three hours south of Perth.

Filming under permit, which enables pilots to fly drones within the 200-metre exclusion zone typically afforded to whales, Ian Wiese and Rodney Peterson captured separate incidents of blue whales defecating in the pristine waters.

"It was the first time I had seen a blue whale, which was incredible enough, but then I realised it was doing something pretty interesting," Mr Peterson said.

"Fair to say, it left quite a streak in the ocean."

The blue whale can excrete up to 200 litres at a time, which apparently smells like dog poo. ( Source: Ian Weisse )

Curt Jenner of the West Australian Centre for Whale Research said the footage provided evidence that blue whales were feeding within 100 nautical miles, or 24 hours' swimming distance from the waterway where they were filmed.

"It's an exciting development given [blue whales] are still one of the more endangered animals on the planet, yet we know so little about their behaviour," Mr Jenner said.

"Knowing they are able to source a regular food supply is an indication of the health of the ocean and that should be of interest to everyone."

Indispensable waste

Mr Jenner said a blue whale was capable of producing up to 200 litres of excrement with each bowel movement, which in itself plays a vital role in ensuring a constant food supply.

"Their poo is a key nutrient for the ocean environment which essentially creates 'pastures' for small fish and krill to feed on," he said.

"It also helps create the all-important algae that is the source for all marine life."

Blue whales are not actually blue but a steel grey colour that appears blue when submerged under the water. ( Supplied: Ningaloo Aviation )

Mr Jenner said the movements of whales immediately after they relieved themselves also played a vital role.

"As they swim along and beat their tails, they distribute their faeces and similarly, as they dive to the depths and surface again, they're mixing that throughout the different layers of the water columns," he explained.

"It's an incredible process of taking the bottom part of the food chain up to the surface then back down again."

When asked to describe the consistency of a blue whale's poo, Mr Jenner said it had the appearance of ping pong balls and the consistency of bread crumbs.

"Oddly, it smells a lot more like dog poo than anything fishy," he said.

"It's otherwise perfectly disgusting."