16 Apr 2018

16 Apr 18 - Atlantic Odyssey - Day Eighteen: At Sea From Tristan Da Cunha To St Helena - Some More Strap-toothed Beaked Whales

I thought the previous day had been very quiet when I only saw five Seabirds. Today my personal total was only four Seabirds: with singles of Bulwer's Petrel, a Storm-petrel sp., Red-billed Tropicbird & a Tern sp. However, it was an excellent day overall for Cetaceans & other sealife.
Red-billed Tropicbird: This was distant & looking into the harsh light of the setting sun
On a couple of times during the Odyssey cruise, the Plancius had stopped for a few minutes to release a monitoring buoy & today we stopped to release another buoy. There are a number of nations that have released these monitoring buoys in recent years across all the oceans as part of scientific studies into the oceans and the motion of the oceans. There are over 3000 monitoring buoys currently in operation. They are planned to be released at exact pre-defined positions. Once released they submerge to preset depths, record a number of important properties of the ocean at the selected depth, before returning to the surface to broadcast the gathered information. This pattern is repeated as they drift with the ocean currents and thus provide important real time monitoring across all the oceans.
Monitoring buoy
There were some impressive clouds today
After a couple of days of not seeing any Cetaceans, they were back today. One of the highlights was a small pod of six Strap-toothed Beaked Whales. Unlike the Strap-toothed Beaked Whales seen on 8 Apr, these were better performers for the cameras, although I only managed to photograph five of the individuals.
Strap-toothed Beaked Whale: The initial view of the first individual
Strap-toothed Beaked Whale: A close up of the fin from the last photo showing it is pale coloured (in line with the fin of one of the Strap-toothed Beaked Whale from the 8 Apr)
Strap-toothed Beaked Whale: This second individual has a more strongly marked fin
Strap-toothed Beaked Whale: A closer crop from the last photo shows it has a more obviously marked pale fin again suggesting it is a Strap-toothed Beaked Whale
Strap-toothed Beaked Whale: More of the back & dorsal fin showing a couple of dark diatoms near the waterline
Strap-toothed Beaked Whale: A final shot of this second individual
I seem to remember looking at the above photos with the camera already zoomed into the central image. As I scrolled between my photos, the camera remained zoomed in. Just afterwards Hans showed me one of his photos with the Sharp-toothed Beaked Whale head on view. I was really impressed as it is often so difficult to photograph the beaks of Beaked Whales. What I was not expecting when I checked the photos on my laptop that evening was to see the full frame image from the previous two photos. A good reason never to delete photos when they are on the back of the camera & zoomed in.
Strap-toothed Beaked Whale: Wow. One of my more surprising photos from the Odyssey. There were three individuals in the last photo, not one. I will focus on each individual in turn
Focusing first on the left hand individual, which I think is a female as I cannot see a white tusk sticking up from the base of the beak.
Strap-toothed Beaked Whale: Close crop of the left hand third individual. The distinctive black face & white beak is diagnostic for Strap-toothed Beaked Whales. Typically, the lower face would be a paler grey, but none of my photos show that area. I can't see a white tusk sticking up from the beak so I think this individual must be a female
Strap-toothed Beaked Whale: Another shot of the left hand third individual showing the start of the grey back behind the bulky black melon
Strap-toothed Beaked Whale: Another shot of the left hand third individual showing its pale grey back contrasting with the black face & melon. There is a dark diatom on the side close to the waterline & a distinctive vertical black line behind the melon
Strap-toothed Beaked Whale: A final photo of the left hand third individual (a minute later) as it passes the tip of the fin of another individual
Now focusing on the right hand of the three individuals, which I think is also a female as I cannot see a white tusk. [Marijke has subsequently commented that there is a tooth visible in this photo sticking up from the base of the bill, but it is blackish coloured. This would make it a male. She confirmed that Hans has also got photographs of this individual & showing the tooth. I had overlooked it as I had been looking for a white tooth (or tusk). One tooth for males erupts from the beak & pushes up out of the beak to form a pair of tusks. In Strap-toothed Beaked Whales this pair of teeth can eventually curve over the beak on old males & wrap around it to make it very hard for the male to open their beaks more than a small amount. They still appear to be able to feed so presumably they are able to open the beaks just wide enough to suck in their food. One of those bizarre evolution traits where it looks like they have evolved beyond a sensible point. The Marine Mammals of the World second edition book doesn't say a lot about tooth colouration, but it shows photos with white teeth. I've no idea why this tooth is discoloured. The problem is so little is known about most species of Beaked Whales.]
Strap-toothed Beaked Whale: Close crop of the right hand fourth individual. There is a blackish tooth (tusk) so that would make this a male
Strap-toothed Beaked Whale: Even closer crop showing the blackish tooth just sticking above the line of the forehead which makes this a male
Strap-toothed Beaked Whale: Another shot of the right hand fourth individual which also shows the start of a grey back, but a less obvious melon
Strap-toothed Beaked Whale: A shot of the right hand fourth individual showing the variation in the grey of its back & the black melon, which doesn't look as bulky as on the left hand individual
Strap-toothed Beaked Whale: A fifth individual which has a smaller white beak & a less extensive black melon. Presumably this is an immature individual
Strap-toothed Beaked Whale: Fifth individual. A bit more of the beak & melon
Strap-toothed Beaked Whale: Following Marijke's comments about that the fourth individual was a male with a blackish tooth, then I've looked again at this fifth individual & now believe it is an immature male as I can see a blackish tooth (the bump in the forehead shape) indicating it is a male
Strap-toothed Beaked Whale: More of the fifth individual. Unfortunately, I don't have an image of its dorsal fin
It was really exciting to be able to get such great photographs of this distinctive species. Especially as the Strap-toothed Beaked Whales on 8 Apr had not preformed that well for us.

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