Dolphin Club MIYAKEJIMA

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Dolphins that live in the coastal waters of Mikura Island

	Japanese name	ミナミバンドウイルカ南坂東海豚 (Minami Bandou Iruka) or ミナミハンドウイルカ南半道海豚 (Minami Handou Iruka)
	Scientific name	Tursiops aduncus
	English name	Indo-Pacific Bottlenose Dolphin
	Chinese name	印度太平洋宽吻海豚 or 印太平洋瓶鼻海豚
Taxonomic position
Artiodactyls　　Cetacea　Delphinidae
Recently, it has been discovered that dolphins and whales are closely related to camels and cows, especially hippos. This species was thought to be the same species as the bottlenose dolphin that can be seen in aquariums (and was once seen), but in 2000 it was determined to be a different species.
Where Indo-Pacific bottlenose dolphins live
They are found in the Indian Ocean to the western Pacific Ocean, and although they occasionally migrate from the coast of Mikurajima to the surrounding islands, they tend to live in coastal areas.In contrast, bottlenose dolphins migrate long distances offshore.
Physical characteristics
	They are slightly smaller than bottlenose dolphins, with a body length of about 2.7m. On the other hand, bottlenose dolphins can grow to a maximum of 3.8m. Also, compared to bottlenose dolphins, their snouts (the beak-like part) are longer and thinner, and the curve at the rear end of their dorsal fins is smaller and their shape tends to be closer to triangular. As Indo-Pacific bottlenose dolphins grow, a spotted pattern appears on their abdomen.
The sounds made by dolphins
Indo-Pacific bottlenose dolphins make a variety of sounds. The sounds that sound like "click, click..." and "beep" are called clicks, and are emitted into the sea from a protruding part on their forehead. By picking up the sound that hits an object and bouncing back and analyzing it with their lower jaw, it is said that they can determine what the object is and how far away it is. This is called echolocation. The sound that sounds like a whistling "pew" is called a whistle, and is thought to be used by dolphins to communicate with each other.
Dolphin Skin
	Although you cannot touch the dolphins during the dolphin swim, I will share a little about it, drawing on my experiences as an aquarium curator. When they are born, they may have some hair remaining at the base of their snout, but after this falls out, Indo-Pacific bottlenose dolphins have no hair at all. Sometimes the pores become inflamed. Is that "acne"? Their skin is very smooth and quite elastic. As they get older, the skin becomes slightly more saggy, but... Sometimes, a kind of grime caused by skin metabolism appears on their skin, and when you rub it off in captivity, they sometimes seem to feel very good. Skin wounds remain white for a long time even after they have healed, and can be used to identify individual dolphins.
About Dolphins Swimming
The bottlenose dolphin, which is considered to be a closely related species, can swim at a speed of about 30km per hour, dive for a few minutes, and dive to a depth of more than 500m.
Eating habits
This data is from a time when they were not yet distinguished from bottlenose dolphins, but they appear to eat a variety of fish (both those that humans normally eat and those that we don't), squid, octopus, shrimp, etc.
Vision
Their eyesight is about 0.1 in human terms. However, they seem to have excellent eyesight even in the dark ocean. They can see well in front and diagonally behind, so they may be able to make eye contact even when they are behind a dolphin. As for color, they seem to be able to distinguish between light and dark colors, but it is not yet known whether they can distinguish between colors such as blue, red, and yellow.
About dolphin growth
	The gestation period is about one year, and babies about one meter long are born. When they are born, they still have fetal marks, a remnant of being inside the womb. For about a year and a half after birth, they grow while receiving breast milk from their mother. (In captivity, there have been instances where they continued to peck at their mother's nipples until they were six years old...) Until they are about three years old, they spend their time very close to their mother or a female who acts as her substitute (a babysitter), and they grow up with the help of the water currents that these individuals create to help them swim. Females reach maturity at about six years old, and males at about ten years old, and they have a lifespan of about 30 to 40 years.
Written by Nobuhisa Ueda
○参考文献
加藤暁音他　「いるかいないか」　御蔵島観光協会　2010年
村山司・中原史生・森恭一編著　「イルカ・クジラ学」　東海大学出版会　2002年
村山司編著　「鯨類学」　東海大学出版会　2008年
村山司　「イルカ」　中公新書　2009年
村山司・森阪匡通　編著　「ケトスの知恵」東海大学出版会　2012年

Dolphin Club Miyakejima　
1813-1, Ako, Miyake-mura Miyakejima, Tokyo, 100-1212, Japan　
TEL＆FAX　04994-8-5010　
E-ｍａｉｌ　dcmiyakeis@gmail.com