The Curious Secrets of Sperm Whales

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By Wade Hughes

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They are the world’s largest toothed predators.  Large bulls can, today reach lengths of 20 metres, and weights of around 50 tonnes or so, although numerous reports from 18th and 19th Century whale ship logs recount capture of bulls of 25 metres or more.

 

Sperm whales (Physeter macrocephalus), and as far as we know only sperm whales, are capable of taking on and overwhelming the ferocious and aggressive creature of the deep, the giant squid – and in order to feed they do so regularly, taking squid, large and small, in waters up to 3000 metres deep. Some estimates of their annual food intake are similar to the amount of biomass the human race plunders from the oceans each year.  They also snap up fish, rays and some octopus.

 

Yet, on the surface, they appear to be “timid and inoffensive” as the first comprehensive observer and recorder of sperm whale behavior and biology, Thomas Beale[i], described in 1839.  It was also Beale who considered sperm whales to be a “curious secret”.

 

As a present day observer, it is possible to see that Beale was correct in both of these observations.  Sperm whales are shrouded in curious secrets; and they can also be curious, as well as secretive.

 

After six summers of entering the water and swimming with these distant cousins, we have come to realize that another 19th century observer got it right too.  French zoologist René Lesson declared in exasperation “What an impenetrable veil covers our knowledge of cetacea! Groping in the dark, we advance in a field strewn with thorns“.

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And so it is today.  Preeminent contemporary researcher Hal Whitehead describes sperm whales more as “surfacers” than “divers” because they spend so much time in the depths and only return to the surface for short intervals.  As mammals they must breathe, so they typically spend eight to 12 minutes an hour doing that.  In addition, they spend time on the surface socializing, giving birth and sometimes apparently just laying about.  But for the remainder, they are down deep and dark, hunting and … well, there’s that field of thorns again.

 

So, more than with any other animals that I’ve photographed or observed, each fleeting encounter with a sperm whale, as it swims briefly up into the light and then recedes inexorably into the darkness, evokes a sense of privilege at being allowed a glimpse of their behaviour.

 

Each encounter yields another fragment of insight and familiarity – and releases a fresh surge of unanswered questions.  Last year, a 15 metre long bull diverted from its path to swim slowly and directly towards me.  It cruised to a stop less than a metre from me – so close that I was concerned we would touch.

 

Using some method of buoyancy control that we don’t understand, it rotated its body into a vertical position alongside me, flukes down, head up.  Then it revolved slowly in front of my face.  First its left eye stared at me, then its massive throat and jaw slid past, and then its right eye locked with mine.  It hung there motionless.  Was it a threat?  An investigation of a potential snack?  An invitation to touch?  We do know that sperm whales participate in highly tactile activities; rubbing, bumping, gently mouthing each other in rollicking melees known as marguerites – so-called because, heads in and tails radiating outwards in a roughly circular formation, they resemble the petals of a daisy … some daisy!  But would a sperm whale welcome physical contact with another species?  More thorns.

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There is debate about whether physical contact in an encounter such as this is appropriate or not.  My own view is that it is not, on two grounds.  Firstly, these are wild whales and I feel that touching them would breach their wildness.  It might also give them a first class fright and 50 tonnes of startled whale could do some damage, even inadvertently.  But I know one world-class authority on cetacea that holds a different view.  Her argument is that if an animal makes the first initial approach, then a proportional response is appropriate, just as it is with humans or any other tactile creature.  A gentle inquiry solicits an equally gentle response.  A hand extended begets physical contact through a handshake.  The relationship has begun to take shape.  Whales, she contends, are no different.

 

Equally, there is plenty of debate about whether the visible presence of an observer in the water changes the behaviour of the observed.  It’s a difficult to remain undetected in broad daylight in the open ocean when in the presence of an animal that can detect and intercept darting squid and fish using the animal world’s most powerful echo-location.  I think that in some cases, our presence does temporarily modify their behaviour.  Some whales will swim up to us, or swim or dive away from us.  Others won’t deviate an inch.  Sometimes we see contrasting behaviour from the same whale on the same day.

 

But some days we see extraordinary behaviour!

 

Last northern summer, a young male sperm whale surfaced with a large squid firmly clamped in its jaws.  It is rare to see sperm whales with squid near the surface.  The whale appeared to have taken the squid head on with the squid’s swimming fins hanging symmetrically down each side of the whale’s jaws.  The width of the squids body, fin tip to fin tip was estimated to 1.5 to two metres.  The whale was around six to seven meters long and carried extensive scarring and marking on its skin, some circular lesions presumably caused by the suckers of large squid.  The attack on this squid probably occurred in the last moments of the whale’s hunt in the deep, just before it began its long haul to the surface, the squids extended tentacles and hooked suckers jammed in the whale’s throat.

 

After swimming on or near the surface for about ten minutes with the squid held in its jaws, the whale sank slowly on its side, and then on its back, convulsively chewing and snatching at the squid’s carcass.  The method of consumption resulted in considerable wastage of the whale’s food.  From a review of the photographs, a number of scientists[ii] consider that the squid is most likely the Dana octopus squid (Taningia danae)[iii], a species that grows to substantial size and weight.

 

So as our last whale of the season descended out of sight, pursued by strings of frantic sardines feeding on sinking shreds of squid, it left in its wake answers to some intriguing questions as it retreated again into the abyssal fields strewn with Lesson’s thorns.

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  1. The Natural History of the Sperm Whale; Thomas Beale, Surgeon:
    John Van Voorst, 1 Paternoster Row, London; 1839
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