Sperm Whales
Vega
Hugh and Annie
Fri 15 Apr 2016 14:13
Dominica is a Sperm Whale hot spot. We know this firstly because we had a meal at the Anchorage Hotel where we were moored and from where they do whale watching and secondly because my brother researches points of interest for the places we visit. We’re in Martinique now, Jim. On the table next to us at the Anchorage Hotel was a couple from Australia together with their guide for the week who is taking a group out each day to swim with the Sperm Whales. At this point our interest overwhelmed us and we engaged them in conversation. Aren’t sperm whales the ones with teeth and that sank the Pequod? Oh yes, they said, but there are no recorded incidents of them ever attacking anyone (other than sinking the ship that the Moby Dick story is based on I thought). And besides, the Australian couple regularly swam with Killer Whales and there is no record of them ever having attacked anyone either. Hmm, maybe no-one that survived to tell the tale. I recall a synchronised attempt to tip over the dinghy of the film crew filming the David Attenborough series about the Antarctic, as if the crew were seals on a block of ice.
Anyway, it seems that conditions off Dominica and Martinique are particularly good for the Sperm Whales and those who wish to swim with them. The water is very deep close inshore and there is a layer of ocean 2000ft (two thousand!) below the surface that is also particularly good for the giant squid that the whales feed on. Now, as I have learnt from the film Deep Blue, 400ft is about the deepest free divers can go before there isn’t enough oxygen in their blood to sustain life. How were even our intrepid Australians going to get down to the whales? But no, you wait for them to surface, jump in the water ahead of them and photograph them as they swim by. In order to do this you need directional hydrophones to listen out for them and pin point where they are. The whales operate in a highly organised social group led by the dominant bull. When they are socialising they tend to stick together and that is the best time to swim with them. When they are down with the squid the bull will decide when it is time to surface and then signal this by making a noise like two metal bars being banged together. On hearing this the group rises to the surface and it is the sound of the metal bars that the swimmers listen out for and home in on prior to looking for the spouts on the surface.
The following day, as we were sailing across to Martinique I spent 7 hours fruitlessly scanning the sea for the whales and wishing I had remembered to bring the directional hydrophones. I had time to think. You really should read the book Leviathan to get an inkling of just how intelligent and exquisitely adapted to their environment the whales are. However, it seems to me there is one major flaw. If you were a Sperm Whale carousing along 2000ft below the surface, locating, stunning and munching away at your squid, it might be a tad inconvenient to then have to come all the way back up to the surface for a few gulps of air. Particularly if Ahab is waiting for you. Maybe it’s vanity and they like being photographed by bonkers Australian swimmers. I would be miffed if this was the case seeing as they go to such lengths to make sure that Yacht Vega is nowhere in the vicinity when they surface. Whatever, it occurs to me with my smattering of ecology that an awful lot of energy must be spent repeatedly going up and down to and from great depth. In evolutionary terms animals only put energy into things that increase their chance of survival - or rather balance their energy expenditure across behaviours that optimise their chances of survival and passing on their genes to the next generation. And yes, I know that for a whale breathing is quite a good survival technique, but why not evolve a way that allows you to remain below the surface? After all frogs do it and during their early foetal development mammals have gills from their fishy origins. So why not evolve to keep the gill genes switched on and retain gills into maturity? Presumably because for a mammal it isn’t sufficiently advantageous to do so but at first glance it does seem a bit odd. This is a question for my evolutionary biology friends of which I have at least one.