28 Apr 2018

28 Apr 18 - Atlantic Odyssey - Day Thirty: Two More Turtle Species

Another early morning start on the Plancius wondering what would be seen during the day. The early morning Clymene Dolphins & Pantropical Spotted Dolphins had got things off to a good start. It was another hot & sunny day. With only a couple of days before we reached the Cape Verde Islands, there was anticipation of an increase in Seabirds as we were now closer to Cape Verde, than Ascension Island. However, we would be in deep water until we were very close to the islands. In the end, the day turned out to be similar to the previous day for Seabirds with a few Bulwer's Petrels, Cory's Shearwaters, Red-footed Boobies, Long-tailed Skuas & Arctic Terns. Around half the Seabirds seen were Leach's Storm-petrels. The highlight was my only Pomarine Skua of the Odyssey. There was also a Storm-petrel sp. that I didn't get to photograph. It could have been a Band-rumped Storm-petrel or my first Cape Verde Storm-petrel. Cape Verde Storm-petrels have been recently split off from Band-rumped Storm-petrel & without photos, it would have been tricky to be sure.
Three more of the good company from the Odyssey: Chris Gladwin, Chris Keher & Mark Newsome
With the Birding being uninspiring again, it was down to the sea to provide the main interest to keep us on the decks. Fortunately, the sea came up trumps with Sea Turtles. The Sea Turtles were tricky to get onto as they are so low in the water that they needed to be much closer than a hundred metres to stand a chance of seeing them. But at that distance, when they realised they were right next to the Plancius, their immediate thought was to dive & try & get away from us. Therefore, even when we were lucky to see a Sea Turtle it was generally diving by the time it was level with the bridge wings. You also needed to be close to the finder, as there wasn't time to move closer to an observer, as they were already thinking of diving as they were spotted. We saw two Loggerhead Turtles & an Olive Ridley's Turtle in the morning. Fortunately, I managed to see & photograph both species. Just getting to see a Sea Turtle was tough, given the brevity of views but we generally needed to get photos to confirm the identification. A useful identification chart can be downloaded from the Sea Turtle.org website.
Loggerhead Turtle: The shell is not circular, but is longer than it is wide. They have five or 6 costal scutes (which are the segments along the side of the upper shell). I seem to remember Marijke saying that Loggerhead Turtles were very prone to having Barnacle encrustaceans on their shells
Loggerhead Turtle: The first coastal scute touches the nuchal scute (which is the narrow segment on the shell immediately behind the head). Unfortunately, my photos do not show either of the key features associated with the scutes, but other people managed to get better photos allowing Marijke to confirm the identification of both Turtle species seen
Olive Ridley Turtle: This was the smallest Sea Turtle we saw & had this distinctive shaped shell which was far more rounded than the other Sea Turtles we saw. The shape was still noticeable even when it was underwater
Olive Ridley Turtle: The only other Sea Turtle with a similar shell shape is Kemp's Ridley Turtle, but that is restricted to the Gulf of Mexico & Atlantic coast of the US. Olive Ridley's Turtles occur in the Pacific and Indian Oceans & South Atlantic (& just into the North Atlantic as we crossed the Equator the previous day)
Olive Ridley Turtle: It was great to see it pop its head out of the water for a breather. They have six or more costal scutes
Olive Ridley Turtle
Olive Ridley Turtle: Having got its breath, it was quickly off
With just seven species of Sea Turtles in the world, we had managed to see four species on the Atlantic Odyssey & today's species were both Ticks. There was a realistic chance of seeing a Hawksbill Turtle on either the Odyssey or the follow-on West African Pelagic. However, we were unlucky not to see one. But we had seen more Sea Turtles species than any of the previous Odyssey trips, so I can't complain too much about not seeing a Hawksbill Turtle.
Marine rubbish: Fishing float
Marine rubbish: Oil barrel
It was depressing that we were still two days sailing before we reached the Cape Verde Islands & we hadn't seen any ships since we left Ascension Island two days earlier. But even this far out in the Atlantic, we still encountered evidence of human rubbish.