Analysing the DNA New Zealand bottlenose dolphins inherit from their mothers may help reveal connections between different dolphin populations, and also assist in their conservation.

Compared to other dolphins in New Zealand, the bottlenose are less abundant, more isolated, and have lower rates of reproduction. This means that genetic variation within the populations is likely to be very low.

This is a concern because the ability of a population to adapt to environmental changes is determined by genetic variation.

Auckland researcher Gabriela de Tezanos Pinto has been studying the DNA of bottlenose dolphins living in Doubtful Sound. These dolphins were thought to be completely isolated, and the number that are actively reproducing is believed to be less than 20.

However, recent genetic research indicates some interchange between the Doubtful Sound dolphins and those living in the open sea, Gabriela says. This could mean that oceanic dolphins provide a source of genetic variation for the Doubtful Sound population.

To help in her research, Gabriela has reconstructed DNA sequences from published surveys and asked scientists from around the world to send her samples. The DNA is sourced from mitochondria, which are only inherited from the mother. This means that maternal inheritance patterns can be investigated.

Although bottlenose dolphins live in other parts of the world, the New Zealand populations are special because they have certain unique characteristics.

“The three populations in New Zealand (Northland, Marlborough Sound and Fjordland) are ecologically different from each other, and how they have adapted to different conditions is intriguing.

“For example, the Doubtful Sound dolphins live in a complex environment composed of at least three metres of fresh water on top of the salt water. That is unusual for dolphins as they are used to saltwater environments and the adaptation to a semi-freshwater is special.”