Spinner Dolphins

Spinner Dolphin (Stenella longirostris)

Other name: Long-snouted dolphin
Max. Length: 240 centimeters
Max. Weight: 77 kilograms
a value: 0.0696
b value: 2.612
Frequency: Common; found in the Indo-Pacific Ocean

Cocos island houses several types of dolphins and identifying each species may become difficult, as for a layman’s eye, they almost look the same. In order to guide you in the easy identification of a spinner dolphin, we suggest you initially focus your sight on their beak.

Of all the dolphin species in Cocos island, the spinner dolphin has one of the longest beak, hence, it is also referred to as the long-snouted dolphin. You can easily notice this characteristic as their relatively long snout stands in contrast to its small and slender body. Speaking of their body, they have a 3-color combination which consist of dark grey on the upper portion, light grey in its mid-body and white towards the belly. Another easy identifying mark is their dorsal fins which has a triangular shape.

Acrobatics is synonymous with Spinner Dolphins

If you wonder why they are called spinner dolphins, then might as well focus on the way they swim. While traveling near the surface is almost a mandate to all dolphins where they need to breathe in fresh air, spinner dolphin has a unique behavior where it has become the basis of its nomenclature.

Most, if not all, dolphins has the ability to jump out of the water. Spinner dolphins doesn’t just jump. They also spin their body when they leap out of the water as if they are doing an acrobatic somersault. In some cases, a spinner dolphin can do multiple somersaults in just a single leap which easily beats any human record in an Olympic platform diving. But let us remind you that spinning is just limited only when they are leaping out of the water and not when they are swimming in a horizontal position like a torpedo.

To Sleep or Not to Sleep

As far as spinner dolphins is concerned, the way hours of the night is not a time for sleeping like what we humans do. Instead, they are highly active and go hunting offshore. They dive to greater depths in search for the favorite meal like squids and small pelagic fish.

During daytime, where most of your interaction with this particular species will occur, you can see them near the shore and swimming in a relatively calm and relax state. One of their downtime during morning is sleeping. But how?

Since they need to breathe in fresh air once in a while, they need to stay close to the surface. During their nap time, their brain is not completely on a relax mode. Instead, they alternately use their left and right brain allowing certain body functions to continue. In short, they continue to swim while sleeping. A good indicator for a sleeping dolphin is they are not jumping or spinning. So please do not engage for an interaction when you see a dolphin that is swimming slowly and calmly. Otherwise, you will be disturbing their beauty rest.

Mating: Size doesn’t matter, Frequency does

In the wild, passing on the genes for the next generation is very important for the survival of their species. But what if the male reproductive organ is very small like the thickness of a pencil and only a few centimeters long. This is the dilemma of spinner dolphins.

Lucky enough for spinner dolphins, they have adopted to this predicament in several ways. One method for a mating pair is to face each other belly to belly. This guarantees maximum penetration and transfer of genetic material. But for a female spinner dolphin, it does not end there. It will mate with several males in a single day increasing the chances of their eggs to be fertilized and ensuring the existence of their next generation.

Reference

Sealife Base: www.sealifebase.org

Wikipedia: www.wikipedia.org

NOAA Fisheries: www.fisheries.noaa.gov

Video courtesy from JohnDownerProd