Posted by: Rob Viens | March 2, 2014

Breaching the Subject of Sperm Whales

The next 10 days found the Beagle surveying the east coast of Tierra del Fuego.  As the ship worked on completing its mission in the Atlantic, Darwin was taken by one of the most awesome sights to grace the ocean – breaching whales.   And these were no “little” orcas – they were the world’s largest toothed predators – sperm whales:

“During this week a complete survey has been made of the East coast of Tierra del Fuego. We landed only once, which was at the mouth of what was formerly supposed to be St Sebastians Channel, it now turns out only to be a large wild bay. — The country here is part of Patagonia, open & without trees; further to the South, we have the same sort of transition of the two countries which is to be observed in the Straits of Magellan. The scenery has in consequence a pretty, broken & park-like appearance. — In St Sebastian bay, there was a curious spectacle of very many Spermaceti Whales, some of which were jumping straight up out of the water; every part of the body was visible excepting the fin of the tail. As they fell sideways into the water, the noise was as loud as a distant great gun. — By the middle of the day we were, after very fortunate weather, at anchor in Thetis Bay, between C St Vincent & Diego.” (Feb 14-21)

Sperm whale (from Wikipedia Commons)

Sperm whale

Sperm whale breaching (from the blog Ten pages (or More))

sperm whale breaching

As already noted, the ” Spermaceti Whales” that Darwin refers to are sperm whales (Physeter macrocephalus). These cetaceans are just plain big.  Along with being the largest tooted whales, they also have the largest brains in the animal kingdom (averaging about 17 pounds (~8 kg)) and can dive deeper and hold their breadth longer than any other mammal (~3 km and 90 minutes respectively). Males have been found up to about 67 feet (~20 m) long and with weights up to about 63 tons.  So you can see why Darwin was so impressed as he watched these whales shooting out of the water and crashing back down into the sea with a thundering boom.  I have seen humpbacks doing a full-body breach in Alaska, and it is a sight to behold. I can only imagine how impressive the even larger sperm whale would be.

The sperm whale is named for its spermaceti organ which takes up a large portion of the head that is filled with a large volume of fats and waxes called spermaceti.  It was this material that whalers where most interested in harvesting as “whale oil”. (They were so focused on the spermaceti that they referred to the large melon in the whale’s head as “junk”. Though the ambergris found in the stomach was coveted for perfumes.) Several hypotheses have been proposed for the function of the organ, including a role in buoyancy. However, evidence seems to suggest that the most likely function of the spermaceti is for echolocation- amplifying the “signal” as sound waves move from seawater into the higher density fluid, and making the whales more effective at hunting their prey.

Cross section of a sperm whale’s head showing the spermaceti organ (from Wikipedia Commons):

Sperm whale head

Amidst the majestic whales, the crew continued to work over the next few days, however, the weather created both treacherous conditions and becalmed seas that made the work difficult:

“Upon going on shore, we found a party of Fuegians; or the foot Patagonians, fine tall men with Guanaco mantle. — The wigwam was also covered with the skin of the same animal. — It is a complete puzzle to every-one, how these men with nothing more than their slight arrows, manage to kill such strong wary animals.” (Feb 14-21)

“As soon as the Ship doubled C. St Diego she got into a very great & dangerous tide rip. The Ship pitched very heavily; in a weak vessel it would almost have been sufficient to have jerked out her Masts. We soon got out of these uncomfortable straits; where a strong tide, great swell, & a bottom so uneven as to vary from 16 to 60 fathoms & then to 5, almost always cause a great bubbling sea. — In the evening, it fell a complete calm, & the long Southerly swell set us far too close to the West end of Staten land.” (Feb 22)

“What a great useless animal a ship is, without wind; here the swell was setting us right on shore & in the morning we found ourselves at the East end of the island about 30 miles further from our destination, than on the day before. — Staten land is one of the most desolate places; it is the mere backbone of a mountain forming a ridge in the ocean. Its outline is peaked, castellated & most rugged.” (Feb 23)

A reminder of some of the places Darwin mentions in his diary:

Tierra del Fuego Map

Staten Island has remained largely uninhabited since it was first “discovered” by the Dutch in 1615.  Over the years it has seem some minor use, including as a base of operations for sealing, a prison, and the home of the “Lighthouse at the end of the world” (Faro del fin del mundo). Today there is a small outpost of the Argentinean navy located on the island, which is otherwise uninhabited by humans.

When the winds picked up again, the Beagle would leave the deserted island and head west to revisit some old sites from last summer… (RJV)


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