The Blainville beaked whale is seen around the Canaries

Beaked whales are probably the least understood large mammals on the planet, but sound can help us track their mysterious movements.

It was a late start for me today, having been up until the early hours on the night observation shift.

It was a rare chance to spend time with such beauty. But the attractions were very different from daytime.

In the Canaries' pristine air, the skies were bejewelled above our heads - and not just with stars, it seemed, but with the stuff between the stars.

It lay like floating silk on top of the visible world.

While it drifted over us, we drifted over the ocean. Below, according to our hydrophone, the beaked whales were still from time to time swimming deep, hunting for squid - the single-minded pursuit of food that occupies the majority of the animal kingdom for the majority of the time.

The team takes two-hour shifts during the night, one hour listening to the hydrophone and one watching we don't hit anything.

There are few fishing boats here at any time of day, but there is fishing gear, floating free of constraint on the sea.

Light break

When I surface in mid-morning, we are on the trail of some Cuvier's beaked whales.

Scars were clearly visible on the body of this Cuvier's beaked whale

Having become accustomed to the darker tones of the Blainville's species, the lighter shade of these made a striking contrast.

It makes filming a little easier, too. These you can just glimpse before they break the surface, giving an extra fraction of a second to get the camera in just the right spot.

In our first sighting, we saw five. It lasted, as most do, for less than a minute; and then we set course for where we expected them to surface next, given the trajectory they had been taking.

It was a partial success. Three animals emerged next, and the next time a single one. This was evidently a loosely bound pod, not contracted to dive in unison.

After they dived for the final time, we picked up clicks on the hydrophone that were presumably the same group, once more in the depths to which they are so well adapted, and in which they spend a majority of their existence.

Skipper Richard McLanaghan called an early start this morning.

Yesterday's disappointing outcome, without a single beaked whale sighting, had persuaded him we needed to be on the water by sunrise to give ourselves the best chance of seeing any today.

Jeppe and Nienke over at the land station were also in position before dawn.

In almost comic-book fashion, a dark cloud hung on the cliff as if it had been pinned there; and while we enjoyed crystal-bright sun, rain fell on the land-lubbers just two kilometres away.

We suggested they treated it as just another day in their Scottish base of St Andrews.

But the teamwork between land and sea was working well. And thanks to joined-up sighting, we had our best view of beaked whales yet - a group of three, emerging and dipping their brown forms across our path, just a few hundred metres away.

Claire managed to get her best picture so far of the male's teeth - preposterous protuberances, to be candid, which grow on the outside of its mouth like ornamental hubcaps.

They may serve the same purpose. Of no use whatsoever for eating, the theory is that they have evolved as secondary sexual characteristics - though they also come in useful in fights, judging by the scars many of the whales carry across their backs.

A group of three beaked whales were spotted

It might sound as though all we do is root around randomly looking and listening for whales.

Ollie was keen to show us today that it is much more scientific than that.

If your intention one day is to use acoustic surveys to find how abundant an animal is, you need to know how efficient your acoustic apparatus is at spotting them.

Will you hear one in two, one in 10, or one in 100?

So when the scientists think a sighted whale has embarked on a deep dive, they mark the sighting point on a map and draw a circle around it.

The boat then sets a straight-line course across the circle - a chord, if I remember my secondary school maths correctly - on a randomly-selected path spewed out by the computer.

Reaching the end, we begin another line transect, listening all the time.

The data will be crunched during the winter.

Of course, we have to assume that anything we hear is produced by the same animal we saw at the middle. But given enough sightings and enough soundings, this work could eventually result in a protocol for estimating beaked whale numbers globally - something which at the moment would be pure guesswork.

No breeze

About half past four, the weather began changing for the worse and soon a fair old wind was blowing.

Such conditions make beaked whale spotting nearly impossible, as the ocean surface scatters here and there, distracting the eye and obscuring these low-profile visitors.

We headed back to port with spray coming over the bows, in wind and waves that nearly shook you off the deck.

Clearly, this kind of work is not for everyone. You must enjoy sailing as much as you enjoy science - and a resistance to sea sickness would, I think, be first on the CV.

This morning I made the short trek west from La Restinga to the grandly titled "land station", a high vantage point on the El Hierro cliffs.

Driven up by Nienke, one of the young researchers in charge, I was expecting an impressive research facility.

It turned out to be nothing more than a gravel passing place on a twisting cliff-descending road.

Jeppe Dalgaard at work in his self-build research station

A camping table and chairs completed the look of some bizarre roadside picnic - until computers and binoculars and video cameras and cables mad an appearance, and some serious science began.

Nienke and Jeppe's job is to scan the sea for beaked whales, report any sightings to Song of the Whale as it cruises below, and refine a video-based system that can tell how far away the whales are.

But this morning, it wasn't to work. By any normal standards the sea was calm, in fact idyllic - certainly nothing that would make you reach for the holiday insurance claim form if it turned up outside your room in Hotel Paradise.

But even this small wind and small swell would make beaked whale spotting too difficult, the land station observers and Song of the Whale team agreed at midday.

And looking through the binoculars, I could see why. Whitecaps, ripples, and dark blobs pulled at the eye, each needing a few seconds' attention to make sure it wasn't a whale.

With regrets, we closed the garden party tent and went back to meet Song of the Whale in its harbour.

Liquid refreshment

What does a crew do when it can't go to sea? It does all the things it can't do when it is at sea.

For some, this meant fixing all the frustrating little things that hadn't been working completely right in the previous few days.

As the first signs of evening evolved, engineer Mat Jerram downed tools and suggested going for a run. I cast a cautious eye over the hills but said yes; a week on a 20m yacht doesn't present too many opportunities for exercise.

During the afternoon, we had seen little of Mat except his rear end poking out from whatever cubbyhole he was investigating for signs of trouble.

Now we saw little but his rear end as it disappeared up the dirt track towards the banana plantation at an alarming speed.

The ground is dry here. I left it half of my bodyweight in perspiration, and envied the cacti that had an excuse for inaction.

Since we arrived, video producer John Galliver has been looking for an excuse to use his underwater camera.

Seeing Mat and me in the harbour cooling down from our run presented the perfect opportunity; and you can see the results of Mat's excursion under the quietened hull of Song of the Whale.

We hope for whale-spotting-friendly weather tomorrow.

At midday, we saw our first beaked whale.

I shouldn't sound surprised; it was what we had come for, after all.

But these creatures are so reclusive, and the boat's hydrophones had picked up so few of their characteristic prey-detecting clicks during the time I had been on board, that I had begun to doubt they would appear at all.

Up on Song of the Whale's A-frame, the raised structure designed to make whale-spotting easier, we scanned the sea in our twos and threes and fours.

My first sighting was a white bucket, presumably left floating by a fisherman. To my right, Claire located a log.

But today, we had a secret weapon. Perched on a road that runs like Zorro's trademark down the volcano-pocked face of El Hierro was a "shore station" - actually a car and a tent - where whale-spotters also dwell.

The whale almost crossed our bow

They radioed a sighting. We manoeuvred to the place they had indicated, and waited.

After many minutes, up it came, a dun-coloured shape mistakable for a dolphin at first glance, but not when you took in the yellowed dorsal fin, the tranquil passage and above all, the length.

Identified by Claire and Ollie as a female Blainville's beaked whale - Mesoplodon densirostris if we're being formal - it ducked up and down through the waves a few times before disappearing.

And that could have been it. Beaked whales have a characteristic diving pattern of one deep dive that can last for an hour, followed by several shorter ones - no-one knows why - and if it was headed for the bottom, that was probably all we would see.

Instead, it came up just a few minutes later. As we closed within about 100m, it almost crossed our bow, and this time its distinctive head - not as beak-like as a Cuvier's whale but distinctly unlike any dolphin - was plain to see.

Over a period of perhaps 15 minutes, we had two more sightings before it eventually started its deep dive, down to the kilometre depths where, presumably, a squid lunch awaited.

So they do exist.

Our departure from La Restinga, the charming little port village on the south-eastern tip of El Hierro, came sooner than anticipated.

So much sea - and so little to see

Rather than leaving this morning, as I had expected, Song of the Whale left harbour last night. It was a beautiful moment, with wisps of elfin mist the only thing between us and the stars.

Half an hour after leaving port, the team played out the 400m-long (1,300ft) cable with underwater microphones that is our tentative link to the cetacean world.

Passing up my chance to listen on the night shift - that will come later - I turned in just after midnight.

Waking this morning, and looking over to the fantastically rugged coast of El Hierro on our right, it was as if we had hardly moved.

And, indeed, we hardly had. Beaked whales are not to be pursued; we go where they are known sometimes to turn up, and hope they do.

A night's listening had yielded just a single visitor.

Later on in the day, I took my first watch up on the A-frame, the tall structure just behind the wheel that gives would-be whale-spotters a wider view of the ocean surface.

I spent an hour up there this time; a normal shift on Song of the Whale during daytime is four.

Apart from the occasional shearwater jack-knifing over the sea, there was no sign of life.

THE SONG OF THE WHALE Take a tour of the research vessel

Earlier in the day, a small group of dolphins had flicked out of the water up ahead; but of Cuvier's and Blainville's beaked whales - our main quarry - there was nothing.

I chatted with Claire Lacey, a former Song of the Whale intern who, in her own words, simply never left, and works full time for the International Fund for Animal Welfare (Ifaw).

Many of her friends, she said, wanted to come along on these trips assuming they were "fun fun fun" all the way.

"Once they realise you can't smoke and you can't drink when you're at sea, they become a bit less keen," she said.

Beach parting

Writing on the beach - before the sun went down

On board Song of the Whale, video producer John Galliver and I attempted to set up the kit we use to send back video clips, as the yacht hove to a few hundred metres from shore.

Even the small swell in what was reputed to be a "calm spot" was too much for our satellite link.

The solution was to take John and me to shore in the small inflatable dinghy - which then went back out to the yacht.

Now, the bytes of video are streaming silently up into the sky.

Night is falling, and a huge dark cloud hangs overhead, glowering as if it would fall between boat and shore and maroon us here.

In a sad commentary on modern priorities, we have two laptop computers, a digital camera and a portable satellite dish.

But nothing with which to light a fire or chase off wild beasts.

If no other entries for this diary materialise, gentle reader, remember me well.

"No-one told us about this."

The headline, strapped across the front page of one of the Canary Islands' main newspapers above a picture of a pylon felled by the power of wind, summed up my thoughts exactly.

Song of the Whale is based at La Restinga this summer

My first view of these fabled holiday islands was a glowering skyscape over roiling coastal seas - more like Skegness in February than a sub-tropical archipelago famed for its climate.

Locals were clearly surprised - "once-in-every-five-years weather", as one described it.

All this might have raised concerns had I been here for the sun and sand.

But in the context of spending a week aboard a whale research yacht, the implications were a bit more alarming.

Conditions are a great leveller in the whale-spotting game.

One scientist told me he once spent all but three days of a scheduled 60-day aerial survey sitting at a Greenland landing strip with fog preventing take-off.

Beaked whales are difficult enough to see at the best of times. Would we spot them at all in this gloom?

Would we even be able to get out of port and go to sea?

On a more personal level, every time I venture out into this great natural environment that I spend so much time writing about, I have a suspicion that the hardy beings who spend their lives here see me as a softy Londoner with cappuccino for brains and a stick of organic asparagus where my backbone should be.

Having nearly vomited all over the last research boat I went on - albeit with severe provocation from bouncing Bristol Channel seas and a lobstery smell that seemed to invade the air's very molecules - how would things go out here, in these choppy days that no-one had told me about?

Rays of hope

But sometimes, with the weather as with games of chance, you get the breaks.

And as video producer John Galliver and I made the hop from Gran Canaria to the tiny island of El Hierro, the clouds parted, a sun fit for holidaymakers came through, and - as if the light carried an anaesthetic charge - the sea's fury abated.

Now, after a drive through El Hierro's jagged landscapes - testament to the brutal beauty that volcanoes raise - John and I are on board Song of the Whale in the peace of La Restinga harbour.

This pretty village has been the base for the Ifaw research yacht all summer.

For skipper Richard McLanaghan, La Restinga is ideal, as the elusive beaked whales are "just around the corner" - although one suspects the beach, the bar and the peace here must help.

And tomorrow we sail, to look and listen for the creatures