12 Jul 2018

16 Apr 18 - Atlantic Odyssey - Day Eighteen: At Sea From Tristan Da Cunha To St Helena - Surfboard

About 45 minutes before the excellent Strap-toothed Beaked Whale sighting in the afternoon, we saw another Cetacean. This was another learning experience for me. It was on its own & quietly logging (i.e. hanging around still) at the surface. All the Cetaceans we had run into so far on the Odyssey had been actively swimming, diving & resurfacing or were even more active Dolphins. It was likely to be a Tick for me as this wasn't a behaviour I was familiar with. It was a small Dolphin sized Cetacean.
Surfboard: All I saw initially was a fin
Surfboard: This was followed by a view of most of the body in front of the fin. The wet tail is reflecting a lot of sunlight
Surfboard: Another view showing the pale spots were changing between photos confirming this was down to reflected light
Surfboard: Note the bulging head, flat appearance & the dorsal fin isn't reflecting much light now
Surfboard: A closer view of the head
Surfboard: A closer crop of the last photo confirming there is a large notch in the dorsal fin
This was quickly called as a Surfboard by Marijke & Hans. Marijke said that Dwarf Sperm Whales & the closely related Pygmy Sperm Whales are often nicknamed as Surfboards due to their appearance as upturned surfboards. The two species look & act very similar. Both are prone to logging on the surface & quietly sinking when they are ready to hunt again or are disturbed. Due to their inactivity on the surface, a day with really calm seas is needed to stand much chance of seeing them. Dwarf Sperm Whales are up to 2.7 metres and Pygmy Sperm Whales tend to be a bit larger at 2.7 - 3.8 metres. Therefore, they are approximately the size of a Bottle-nosed Dolphin, but they are much harder to see due to the inactive behaviour. Dwarf Sperm Whales have a fairly large flat head & a flat back with a fairly prominent dorsal fin. The rear body tapers rapidly & is strongly angled downwards. It is hard to see the rear body & tail as they tend to sink, rather than fluke like the vastly bigger Sperm Whale. Dwarf Sperm Whales have a larger, more erect & pointed dorsal fin whereas, Pygmy Sperm Whales have a lower & more rounded fin. Based on the dorsal fin shape this was my first Dwarf Sperm Whale. It was good to speak to Glenn Overington about this Cetacean sighting as Glenn found the first UK record of Dwarf Sperm Whale in Mounts Bay in Autumn 2011.
Dwarf Sperm Whale: After spending sometime stationary on the surface, it quietly sunk below the water line
Dwarf Sperm Whale: Nearly gone
Marijke said there was a suspicion about them among some Cetacean watchers & we should refer to them as Surfboards, rather than calling them by their proper names: suggesting we would be pushing our luck in finding others if we used their proper names too soon. Despite having a rationale scientific background, I don't believe in commenting on the lack of punctures I've had on a foreign trip for the same reason. We still blame Birding mate, Keith Turner, for his rash comments on the final day about how lucky we had been with only 1 puncture in the month in Kenya in 1987: the next puncture was within the hour, with a final one about two hours later. I was happy to stick with Surfboards when discussing what we would like to see on future calm days or calling a potential future candidate.
Dwarf Sperm Whale: That's just about it. I had seen in previous Odyssey reports there were a number of good Cetaceans we could potentially bump into on the trip, but while I was clearly keen to see as many Cetaceans as possible, I wasn't as optimistic I would see them. So I was really pleased to have seen my first Dwarf Sperm Whale. Whereas, I was fairly confident we would connect with just about all the potential new Seabirds
Dwarf Sperm Whales have a potentially large range and occur in all the Tropical oceans as far South as South African & Australia and as far North as Spain & Japan and tend to occur offshore. Pygmy Sperm Whales have a similar range, but they seem to prefer temperate seas so they have occurred a bit further North as far as Scotland. They occur both around the continental shelf, as well as, in deep waters. Not a lot is known about their feeding habits & diet, but both appear to have similar diets of Cephalopods i.e. Squid, Octopus, as well as, other seafood like fish etc.

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