Tuesday, December 16, 2008

Great Dives We'll Never Do #1

We roll off back off the sides of a small RIB (that's a rigid inflatable boat for non-waterfolk) and into the rather frigid north Californian waters. The chilling water initially knocks our breath out of us but as our thick wetsuits do the job the cold abates. We take a minute to orientate ourselves, noting the lights of the boat to one side and the dark silhouette of the cliffs edged against the purple night sky to our other, and descend into the inky seas. Our torches illuminate the darkness and we progress down picking our way between towering kelp fronds. Orange blurs exit our torch lights as we wake the odd Garibaldi or kelpfish and then we hit bottom. We move on through the darkness, working our way slowly on closer to the shallow water nearer the cliffs and our quarry. A tiny hornshark sits on the seabed and a pair of bat rays fly past. Ordinarily we would be happy to spend time with these little elasmobranchs but today we are hunting bigger game. Suddenly a huge grey white shape edges gently through the torchbeam, too big to be framed entirely by a single torch. As more torches align on our elephantine partner the huge frame of Steller's Sea Cow, Hydrodamalis gigas, is revealed.*


8 metres (26 feet) in length, the huge sirenian moves with slow assurance through the water nibbling periodically on the abundant macroalgae. A second animal, smaller but still dwarfing us divers joins it - a suckling calf 10 feet long. As the dive goes on the calf becomes inquisitive, each diver gets the experience of an animal roughly twice their size curiously approaching and even nuzzling them. Occasionally eager to check we pose no threat the mother moves closer. At full size she will be over 4 tons.....perhaps more. Even as we struggle to take in her massive scale and curious gaze other equally gargantuan Steller's sea cows pass us by in the gloom. All to soon our time is up and we head slowly to the surface. As we leave, the mother and calf surface for a breath and briefly spy hop to watch us aboard. Saying a fond farewell and laughing at our luck we slowly retreat being sure to keep our speed down to avoid other sea cows as leave.


I can't comprehend how good this dive would be. Sirenians are tremendous fun to share the water with**. Dugong and Manatees are pretty much completely chilled around humans, generally allowing a close approach and continuing feeding oblivious to nearby divers. Occasionally curious especially when young they tend to be tactile and can bump or nuzzle divers if in the mood. The opportunity to dive with an 8 meter version of such an animal would not be one to miss. But (as I'm sure you have worked out from the post title if nothing else) miss it we must.

The first picture above is a reconstruction of a Hydrodamalis sp. from San Diego Museum of Natural History (the second is an extant Dugon Dugon from Singapore). Steller's sea cow became extinct in 1768 just 27 years after its discovery in the North-West Pacific's Commander Islands. Its population at that time likely numbered just 1500 and exposed to humans for the first time this relict population stood no chance. Now it can only be found like this one...in the Harvard Natural History Museum


But before exposure to humans moving along first the asian pacific and then the american pacific coasts this wonderful beast would have ringed the northern pacific - devouring kelp from Japan to California - if the first Americans truly did boat along the coasts then this could have been a wonderful food source for them - enormous, lumbering, easy to kill and rich in meat and fat. Sadly their wonderful food/fuel took away one*** of our wonder dives.

* I framed this as a night dive due to the black background behind my image of the SDMNH mount - generally I'm not a huge fan of night diving with marine mammals (even huge ones) - marine mammals tend to attract big predators.
** For information about experiences with Dugong/Manatee you can enjoy now without time travel apparatus see:

My post on interacting with an orphaned dugong;
Florida Cracker's post on Florida manatees; and/or
Julie Zickefoose's post on Amazonian manatees.
*** If you enjoyed this I'm open to suggestions for other timetraveling dives (or other nature experiences).

PS - great and fabulously complete website on SSCs here


Julie Zickefoose said...

What an utterly cool post. I was so there with you, the back of my brain saying, "But aren't Steller's sea cows extinct?" And I have stood beneath that very skeleton at the MCZ and wondered and marveled. Now, off to see you with an orphaned dugong.

tai haku said...

Thanks Julie - high praise coming from one who writes posts as beautifully as you.

I've been meaning to write this for ages and to be honest it took your amazonian manatee post to remind me. On the subject of amazonian manatees did you hear about the "new" dwarf species?