21 Apr 2018

21 Apr 18 - Atlantic Odyssey - Day Twenty Three: Clymene Dolphins

The first full day at sea on the crossing between St Helena & Ascension Island had started well for Cetaceans with a small party of Sperm Whales & a party of around fifteen Short-finned Pilot Whales before breakfast. This was followed by a brief appearance of a small party of False Killer Whales while most people were still finishing their breakfast. The morning continued with another party of eight Sperm Whales in late morning which were in no hurry to dive & allowed us to have prolonged & close views. Soon after that a distant Orca put in a brief appearance off the port side, but too distant & brief for photos. It all quietened down for Cetaceans for several hours until late afternoon when we picked up a distant pod of at least fifteen Dolphins on the starboard side. Unfortunately, they were hunting & didn't want to come & check out the Plancius. The photos aren't any better than record shots as they didn't come closer than a half mile. However, the photos did allow them to be identified as my first Clymene Dolphins.
Clymene Dolphin: It is just about possible to see the three coluration tones on the right hand most exposed individual. The odd pale marking on the central individual is presumably splashing water or an effect of the harsh crop
Clymene Dolphins are one of the Spinner Dolphin group & are also known as Short-billed Spinner Dolphin. They are a small Dolphin with a maximum size of only 1.9 metres & thus are only about 80% of the size of a Striped Dolphin or one of the Atlantic populations of Short-beaked Common Dolphin. They have similarly markings to the Atlantic population of Spinner Dolphins, which also have a similar range in the Atlantic. Clymene Dolphins occur in the tropical & subtropical Atlantic, Caribbean & Gulf of Mexico, in a broad band from Brazil to New Jersey in the US & from Mauritania to Angola & are typically a deep-water oceanic Dolphin. The key features are they are similar to the larger Spinner Dolphins, more robust in shape & having a shorter & stockier beak and an erect & only slightly falcate dorsal fin. The colouration is a dark grey uppersides, light grey sides & a white belly, with the dark grey dipping into the light grey under the eye & below the dorsal fin. There may also be a dark band running along the rear flanks which Spinner Dolphins do not show. The main separation from the Atlantic population of Spinner Dolphins is Spinner Dolphins are a bit larger (between intermediate in size between a Clymene Dolphin & Short-beaked Common Dolphin), are slimmer with an extremely long & thinner beak and the dorsal fin is either slightly falcate or erect & triangular in shape.
Clymene Dolphin: Showing the dark flank stripe
Clymene Dolphin
Clymene Dolphin: The short beaks are visible on these individuals
Clymene Dolphin
Overall, it had been another long, but brilliant day on the Atlantic Odyssey with five Cetaceans species seen & two new Cetaceans for my list: False Killer Whale & Clymene Dolphin.