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Sperm whales

A sperm whale raises its tail flukes as it begins a dive. Colin Munro Photography

I turned around and saw him about one hundred rods directly ahead of us, coming down with twice his ordinary speed of around 24 knots, and it appeared with tenfold fury and vengeance in his aspect. The surf flew in all directions about him with the continual violent thrashing of his tail. His head about half out of the water, and in that way he came upon us, and again struck the ship.” So wrote Owen Chase, First Mate, in his 1821 account of the sinking of the whaling ship the Essex.

A sperm whale raises its tail flukes as it begins a dive. Colin Munro Photography

A sperm whale raises its tail flukes as it begins a dive.

The whale in question was a cachalot, or sperm whale.  Probably the best known whale; the whale in Herman Melville’s Moby Dick (which was actually based on the sinking of the Essex). The sperm whale, Physeter macrocephalus, is the largest toothed whale, and indeed the largest toothed predator that has ever lived.  Males average 16 metres in length and over 40 tonnes in weight (females are significantly smaller); some may exceed 20 metres and 50 tonnes.  They are the sole extant (living) species in the family Physeteridae, though fossils of several extinct species have been found.  Sperm whales look like no other whale; their massive head and relatively tiny lower jaw coupled with their huge size renders them unmistakable when seen underwater.  However that is not how they are commonly seen.  The best view most of us get of a sperm whale is of them resting almost motionless on the surface, between dives, with only the top of their back and their blowhole visible, followed by the rise of the tail flukes as it descends beneath the surface.

The blow hole and wrinkled skin of a sperm whale resting on the surface. Colin Munro Photography

The blow hole and wrinkled skin of a sperm whale resting on the surface

As sperm whales are air breathing mammals it is tempting to think of them as animals that live at the surface, diving occasionally to hunt.  Not so.  When feeding they will spend 8-10 minutes on the surface breathing, replenishing their oxygen supplies.  In contrast they will spend 35-50 minutes underwater searching for prey.

The low, bushy, forward-directed, blow of a sperm whale is almost unmistakable. Colin Munro Photography

The low, bushy, forward-directed, blow of a sperm whale is almost unmistakable

Studies indicate that sperm whales will spend 70-95% of their time in these foraging cycles so, in terms of where they spend most of their time, these are creatures that inhabit the ocean depths and surface only briefly to breathe.

Unlike most other great whales, the sperm whale does not venture into polar waters to feed, preferring tropical and temperate seas (adult males will venture in to high latitudes).  But even in the tropics it inhabits a cold world.  At a thousand metres depth, well within the normal foraging range of sperm whales, the temperature is only 4-8 degrees centigrade.  It is also a world of almost total darkness.  At 200 metres depth, even in the open ocean the light levels are less than 1/1000th of those at the surface.  At a thousand metres one enters the aphotic zone (the midnight zone) where no sunlight penetrates.  But that does not mean it is a world devoid of light.  It is a world full of bioluminescence. Light produced by chemical reactions within living organisms.  It has been estimated that that 90% of the animals that live below 1000 metres are capable of bioluminecence; glowing, flashing or pulsing green, red, but or white.  This includes many of the prey species of sperm whales. Although they do also consume fish, cephalopods (octopus, cuttlefish and squid) are by far the greatest portion of their diet.  Famously they predate on giant squid and the even larger colossal squid (which may be longer than a full grown sperm whale and is the largest known invertebrate) but they also consume a wide variety of other cephalopod species.  This includes the wonderfully named vampire squid (Vampyroteuthis infernalis is its scientific name, which translates as ‘vampire squid from hell).  Neither a vampire nor a squid it occupies a cephalopod Order all of its own, the Vampyromorphida.

There are a few spots in the oceans renowned for sperm whale sightings.  These are mostly along the edges of underwater canyons and steep drop-offs, where shallow coastal seabeds plunge sharply to hundreds or thousands of metres.  Off the Kaikoura peninsula of New Zealand is possibly the best known area, followed by the Azores islands (where volcanic seamounts rise up from deep water).  The images of mine in this blog were all take off Vesteralen, northern Norway, where a complex of deep canyons direct the seabed offshore from the Lofoten Islands and Vesteralen archipelago. It appears sperm whales hunt along these canyons, thus time spent cruising along the margins of the canyons is often rewarded by sightings of sperm whales as these surface between foraging dives to expel carbon dioxide and replenish their oxygen supplies.

 

 

 

Orcas and Common Seals: Summer in Norway and Scotland

A curious common seal, Shiant Islands, Hebrides, Scotland. Copyright Colin Munro

I’ve spent most of this summer sailing along the coast off Western Scotland and Norway, with a brief swing by the Faroe Islands. I think this includes some of the most dramatic scenery in the World and some of the best marine wildlife.  From the wild remoteness of St. Kilda to the sheer majesty of Troll Fjord there is little that betters the coastline of the northeast Atlantic.  The one downside is that internet has been working only intermittently and then at a glacially slow speed.  However it has been a great trip for marine mammals, with regular sightings of grey and common seals, harbour porpoise, common and bottlenose dolphins and even the occasional orca and sperm whale.  So whilst siting in a bar in Bergen on a chilly and rainy August evening I thought I’d take the opportunity to upload a few images of orcas (Orcinus orca) and common seals (Phoca vitulina).

Male orca cruising off the Lofoten Islands, Norway. copyright Colin Munro

Male orca cruising off the Lofoten Islands, Norway

We were lucky with around the Lofoten Islands, where a small family group of orcas altered course to swim alongside us for a few minutes, rather like overgrown dolphins (which is exactly what orcas are).

 

A female orca (or killer whale) Orcinus orca, cruising along near the Lofoten Islands, Norway.

A female orca (or killer whale) Orcinus orca, cruising along near the Lofoten Islands, Norway.

The western isles are always good for seals, with common seals pupping whilst we were there.  We had particularly good sightings around the Shiant Islands and The Isle of Skye, where both common seals and grey seals (Halichoerus grypus) occur together.

A curious common seal, Shiant Islands, Hebrides, Scotland. Copyright Colin Munro

A curious common seal, Shiant Islands, Hebrides, Scotland.

Very often they would pop up behind our Zodiac, always at a safe distance, but curious as to what we were doing.

A common seal cruises with its eyes and nostrils just above the water. Dunvegan, Isle of Skye, Scotland. Copyright Colin Munro. www.colinmunroimages.com Colin Munro Photography

A common seal cruises with its eyes and nostrils just above the water. Dunvegan, Isle of Skye, Scotland.

With only the tops of their heads, eyes and nostrils visible, seals can be tricky to spot. A glance in their direction frequently results in a loud splash as they duck dive out of sight, rather like inquisitive but shy children.

Common seals playing on rocks, Shiant Isles, Hebrides, Scotland.  Harbor seals, copyright Colin Munro www.colinmunroimages.com

Common seals playing on rocks, Shiant Isles, Hebrides, Scotland.

Basking on the rocks they were often quite playful.

Female common seal or harbour seal, Phoca vitulina,  dozing on the rocks, Dunvegan, Isle of Skye. Copyright Colin Munro Colin Munro Photography www.colinmunroimages.com

Female common seal or harbour seal, Phoca vitulina, dozing on the rocks, Dunvegan, Isle of Skye

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