By Richard Black
Environment correspondent, BBC News website, the Canary Islands
The long arm of the whale tagger: Attaching a D-tag
Just as the humble torch broke humankind's inability to see through night, new technology based on acoustics and video imaging is giving scientists unprecedented glimpses of a whale's life.
Even elusive, reclusive creatures such as beaked whales are giving up data in previously unthinkable detail.
El Hierro, the southernmost point of the Canary Islands, is one of the best places ever found for studying the animals. But even so, they come to the surface apparently randomly and for only brief periods of time.
It is a far cry from the acrobatics of the humpback whale or the ebullient eruptions of dolphins.
But these brief appearances have been enough to allow scientists to fix tags to beaked whales and register what they do beneath the waves.
See how land-based teams help Song of the Whale in its work
Researchers from the University of La Laguna in Tenerife first identified beaked whales here in 2003.
Already, a team from Woods Hole Oceanographic Institute near Boston, US, had developed devices called D-tags that could be stuck to the backs of other whales and taken down in the animals' deepest dives, registering sounds, depths and movements.
Collaboration clearly made sense; and it has worked.
"The importance of D-tags is that we have acoustic information, and information in three dimensions on the pitch, roll and heading of the animals," says Patricia Arranz, a member of the La Laguna team.
"It was the first time that vocalisations of Blainville's beaked whales had been described, and the first time you could receive echoes from prey."
The tags are a canny mix of space-age materials and low-tech improvisation.
Sticking one onto a whale entails sidling up in an inflatable dinghy, hoping the animal does not take flight, and then deploying the tag on the end of a five metre pole.
It sticks to the whale's back with suction cups, a system that chimes well with the overall intention of causing the animals as little stress as possible.
"We have to minimise the effect of these devices on the whales," says Mark Johnson, who developed the tags in the Marine Mammal Behavior Laboratory at Woods Hole.
"They are exquisitely streamlined animals, and so the tag has to be small. Luckily, they work pretty well on beaked whales."
1. Visual reflectors, to aid in retrieval 2. Instrumentation, including pressure sensors, hydrophones, accelerometers, compasses, battery and 13Gb flash memory 3. Syntactic foam; consists of air-filled glass beads set in epoxy resin, to provide buoyancy whilst resisting implosion at great depths 4. Antenna 5. Suction cups allow device to attach to whales, self-detaching when necessary; the casing is filled with oil to prevent implosion at great depths
Inside the tags are hydrophones to record sound, accelerometers and magnetometers to measure movement in three dimensions; a battery, and 13Gb of flash memory
"The whales dive down to about 2,000m; and when they do, the tags are under about 200 atmospheres of pressure, which will crush pretty much anything with air in it," says Dr Johnson.
"There are two ways to get round that - you either make a strong housing, which would be made of metal and really thick and heavy - or you find electronic components that can stand the pressure, and most of them, it turns out, can.
"Then you put the electronics in a plastic bag full of vegetable oil."
Some tags slide off the animals' backs within a few hours. Those that stay on are automatically released with an ingeniously low-tech system.
The suction cups all have a piece of plastic tubing, as used in medical wards worldwide, leading into them. The tube is bent over and secured with a twist of nickel-chromium wire.
The wire will last for years in seawater. But put three volts across it, and it dissolves away within minutes, allowing water into the suction cup and releasing the tag.
A buoyant foam brings it to the surface, where a VHF antenna signals "I am here".
So far, tagging projects conducted here suggest beaked whales typically dive in an approximate pattern of one long and deep, then three short and shallow - and other scientists have shown how this may leave them prone, for reasons not completely understood, to a decompression-like sickness that can be triggered by military sonar.
D-tags have registered dives by Cuvier's beaked whales that are longer and deeper than any other cetacean documented.
"Tags have given us new insights into the acoustic behaviour of beaked whales," says Ollie Boisseau, a research scientist with the International Fund for Animal Welfare (Ifaw) which is now also engaged in beaked whale research around El Hierro.
"They can certainly help answer certain questions, and they pose several more - it's a very promising area of research."
The tagging projects were made much easier by the establishment of a land station, a work area perched on El Hierro's hills.
Nienke van Geel scans the sea for signs of beaked whales
Observers there scan the seas with binoculars and report possible whale sightings to the waiting dinghies.
Now, the land station is also being used by researchers from the Sea Mammal Research Unit (SMRU) at St Andrews University in Scotland, to field test a range-finding system that uses video and computing.
The system starts with a high-tech pair of binoculars with video camera attached, connected umbilically to a laptop computer.
With Jeppe Dalgaard, a St Andrews researcher spending the summer months here, I peer against the sparkling morning sun at the laptop screen.
He shows me the coastline, the blob marking our location, and another indicating the Ifaw boat Song of the Whale, a few kilometres out to sea.
"When we have a [whale] sighting, we use the bearing and the range program to get the distance; and when we have the bearing and the distance, that automatically plots the position of the sighting for us," he explains.
Jeppe's equipment knows where Song of the Whale is because it picks up the yacht's periodic Automatic Identification System (AIS) broadcasts.
The bearing to a whale sighting is simple, because the binocular's tripod has an old-fashioned gauge showing which way they are pointing.
What is new is the way the system measures the range to the whales.
Images of each sighting are sent from the video camera into the laptop.
Using a variation on traditional trigonometry, the program measures the vertical distance on the image between the sighting and the horizon, and converts that into the horizontal distance from land station to whale. This quickly becomes a pair of co-ordinates for the sighting.
Suction cups are released when electrical corrosion lets water in
Radioed down to Song of the Whale, it raises the odds that the yacht can get close to the cetaceans by using GPS to hit the right co-ordinates.
"This is a simple but effective way of measuring range at sea," says SMRU's Jonathan Gordon, one of the system's principal developers.
"There is an alternative from shore stations which is to use a theodolite; but the problem with marine mammals is they're only there for a short period of time, whereas using video allows us to capture a frame and analyse it."
Dr Gordon says his system is accurate to within about 1%, and can be used on board ships as well.
"I've been really pushing it because I have very little faith in my own ability to estimate distance at sea, but it's been a strangely uphill battle to persuade people they should be using it rather than just estimating distance by eye or crude instruments."
Off the slab
From my own brief time on board Song of the Whale, and from peering through binoculars from the land station, I have seen at first hand how hard it can be to see and track beaked whales.
They spend perhaps 8% of their time at the surface; and although they can be fairly vocal, they only seem to make sounds at depth.
But D-tags have generated a lot of new data about them. Recording the locations of sightings accurately using the St Andrews system could in time help establish whether they pursue typical foraging paths, and perhaps identify key habitat.
Meanwhile close range photography, which the University of La Laguna team also pursues, is getting to the stage where individuals can be distinguished from each other. The team is able to suggest that El Hierro may be home to a resident population of Blainville's beaked whale (Mesoplodon densirostris) numbering about 100.
The Woods Hole, St Andrews and Ifaw groups are all using acoustics to identify and track the animals when they vocalise at depth.
Not so long ago, the only information we had on beaked whales came from examination of dead animals.
For some species, hydrophones and D-tags and video positioning and photo identification mean that era is most definitely over.
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