Maui's dolphins: biology

Few to see, but easy to identify

Unlike common dolphins, Maui's don't have a sickle-shaped dorsal fin; they have a rounded dorsal fin shaped like a "Mickey Mouse" ear.

They have distinctive black markings notably a black face, flippers, dorsal fin, and tail combined with a grey body and a white underbelly - features that help them stand out against the blue-green of the sea.

Maui's have a gently sloping snout unlike the "bottlenose" snout of common dolphins. Smaller than humans, Maui adults are normally 1.2 - 1.4 metres long (baby Maui's are very large - 50 - 60 cms - in proportion to their mothers), weigh about 50 kg, and are known to live up to 20 years.

Diet
Maui's dolphins spend most of their time making short dives (90 seconds or so) to find fish on the sea floor. They also find fish and squid in mid water and sometimes feed near the surface.

Like other dolphins, Maui's use echolocation to find their food. Water is better at transmitting sound than light. Dolphins rely much less on their eyes than people and use sound as a means of navigating, finding food and communicating.

They make high frequency sonar clicks which bounce off anything in the water. This is known as echolocation. The dolphin interprets the echoes to understand their surroundings and the size and position of objects in the water such as fish, boats and other dolphins. Maui's dolphin clicks can be quite loud - the maximum level recorded being 163 decibels - about as loud as a rock concert.

But remember that dolphin sounds are ultrasonic, so in fact, a person would hear nothing. The clicks are very short and are emitted in series that range from a few dozen to several thousand.

Behaviour
Feeding takes up a lot of the Maui's time. They also play, for example with seaweed, chase each other, blow bubbles, fight and jump (although not as frequently as some other dolphin species). Maui's dolphins do not pair for life but mate frequently.

Slow to reproduce
Maui's dolphins are only breeding fast enough to replace the numbers of dolphins that are dying naturally. Females reach sexual maturity at 7-9 years and give birth about every 2-4 years. This slow birth rate means that Maui's dolphins are struggling to recover from human induced deaths.