Spotting Whales From The Shore, The Sea And Space

There are many ways to monitor whales, but not quite so many to count them. And carrying out a cetacean census - despite their phenomenal size - poses something of a problem for marine biologists, primarily because they are often difficult to access and most methods available are either expensive, or inefficient.

I for one have spent many an arduous hour huddled beneath a fishing umbrella, tucked inside the cosiest part of a Cornish cliff face on the watch for whales. Well, whales and whatever other wildlife I could catch a glimpse of while clutching a pasty in one hand and a telescope in the other. With British weather being what it is, many of these days were murky, miserable occasions, making it all the more frustrating when at the end of it you still haven't got your eye on the prize. Other cliff faces make much better watch points though. Peninsula Valdés, for example, overlooks a shallow sea favoured by breeding baleen whales and is a great spot to study them from. But not all sites are so well suited - I would have gladly given up my pasty to have a go at pinning down the population of southern right whales round the Peninsula. Even at such a great spot, the state of the sea can still stir up trouble - "was that a whale or a wave?," you find yourself asking. And the seldom sunny day (in the UK at least) is not quite the respite you were hoping for either. Blinded by the glare of the sun, you find yourself killing for some clouds, which would give you a much better chance of discerning whales in the distance.

A much better way to count them (provided you don't have the luxury of a breeding ground beside your cliff face) is to step aboard a ship and zig-zag over the ocean, scanning the sea for signs of a whale. Scientists can do a similar survey from a plane.

With one biologist at the mast and the others covering the front and sides, you're chances of getting a decent handle on the local population are on the increase. From here, you can even take photos of flukes (tails) as the whales dive down into the water. The patterns on a fluke are a whale's fingerprint, so you don't just know what's in the water, but who.

There's still room for improvement though. We can only catch a glimpse of whales when they're at the surface, so what about all the ones out of sight? Hydrophones (underwater microphones) make up for our lack of sight under the surface and provide scientists with the opportunity to tune in to which whales are beneath the waves.

Perhaps driven by the fact that this local data just doesn't cut the mustard when you're trying to get a handle on whale populations worldwide, scientists from the British Antarctic Survey have come up with an incredibly cheap and effective solution - spotting whales from space.

This might sound strange, as while whales are pretty large they don't exactly stand out from the edge of the Earth. But using very high resolution satellite data, Peter Fretwell and his team found you can get a very good handle on what's in the water. They were able to pin things down to pixels that were 50 cm across - since southern right whales (their target species) are about 14-18 metres long, whales were on the radar. They had another trick up their sleeves too - using light from the far blue end of the spectrum, which isn't absorbed as strongly as other wavelengths, the team could see 15 metres below the sea surface.

Another benefit of satellite imagery is that you can have a lot of it, but all this data would take a long time to go through, so the team developed an automated whale-selecting system. The findings, published in PLoS ONE, show the new method can automatically detect about 90% of the whales in the water - pretty neat!

Like other methods though, rough water can spoil the view and potentially make it impossible to pick out members of the population. Fretwell's study was conducted in a very calm protected bay, meaning the whales stood out relatively well against the water. To do this somewhere less protected would be much more difficult, particularly because wind creates a white foam on the water and photo imaging software would have a hard time picking out whales from all the mess. It's certainly an exciting new development, but like any method, you have to make sure you're working within its limitations - in this case, keep to the calm spots and steer clear of the waves.

Reference

Fretwell, P. T., Staniland, I. J. and Forcada, J. Whales from Space: Counting Southern Right Whales by Satellite. PLoS ONE 9 e88655 (2014)

Images

1) Southern right whale seen from the air. Credit: Georgia Wildlife Resources Division via Flickr

2) The tale of a humpback whale, also known as a fluke. Credit: Alan Vernon via Flickr

3) Southern right whales seen from space. Credit: Fretwell at al. (2014)