04.06.2018 – The dark dolphins

Our trip this morning included a lovely sighting involving a large Tropical whale (Balaenoptera edeni) and her calf, as well as a school of Short-beaked common dolphins (Delphinus delphis).

The dolphins swam very close to our vessel for some time, which allowed us to spot two anomalously all-black individuals. Short-beaked common dolphins can be recognized by the characteristic yellow hourglass pattern on their flanks, which was lacking in these particular animals. This rare anomaly is known as hyper-pigmentation or melanism and is a mutation that involves the excessive production of melanin, a pigment that plays an essential role in the protection of the skin from the suns formidable UV rays. This condition is usually associated with several disadvantages including exposure to predators and prey due to a lack in counter-shading and reduced attractiveness for mating success. These individuals, however, seemed perfectly integrated in the herd with one of the animals even swimming alongside a young calf, which also seemed to have a similar darker body colour, making this all the more interesting. Many animals have been reported to display adaptive melanism, where the condition is heritable and passed on to subsequent generations due to potential benefits such as camouflage during foraging.

These interesting observations this morning were the prelude to a spectacular trip this afternoon, which also happened to be the first tour of our new summer guide, Jan. We had sightings involving Short-beaked common dolphins, Tropical whales, Bottlenose dolphins (Tursiops truncatus) and also saw three young Loggerhead turtles (Caretta caretta) basking at the waters surface. What an eventful start to the new week!

by Paula Thake

Sightings of the day

13:30 Short-beaked common dolphins, Tropical whale

17:00 Bottlenose dolphins, Short-beaked common dolphins, Tropical whale, Loggerhead turtle