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There she blows? Unlocking the mysteries of deep ocean cetaceans

Researchers use genetic tools to reveal new insights into populations of the secretive Gray’s beaked whale throughout the waters of New Zealand and across to West Australia.

Kirsten Thompson from the University of Exeter, in collaboration with the University of Auckland and Oregon State University, has recently published in the journal Heredity. In this new study, robust genetic tools were employed to reveal novel information about the genetic diversity and population structure of the deep ocean cetacean, the Gray’s beaked whale (Mesoplodon grayi).

Understanding the genetic structure of a population is critical to its conservation and management. Using samples taken from stranded animals that were collected over a 22 year period, this research aimed to assess genetic diversity and the extent to which a genetic population divergence may exist between whales on the east and west coasts of New Zealand, and across to West Australia.

All beaked whale species remain somewhat of a mystery with regards to their appearance and behaviour. Many species are only known from a handful or records, and there are very few publications describing their populations. The Gray’s beaked whale is almost never sighted at sea, yet strangely strands fairly regularly around the coast of New Zealand. Like other beaked whales this species is thought to be a deep-diver, living in small groups along continental shelf edges foraging on squid and small fish. Interestingly, in contrast to other whales, the results of this study have revealed high levels of genetic diversity in Gray’s beaked whales in this region and a lack of genetic structure. This suggests these whales move freely with unimpeded gene flow between the east and west coasts of New Zealand.

Kirsten Thompson said: "Gray's beaked whales are so rarely seen alive that we know nothing of their basic biology - where they feed, aggregate, breed or their social system. Through the use of molecular genetics and the long-term collection of tissue from strandings we are beginning to gain some fascinating insights into their life history. Surprisingly, we found high levels of gene flow across a 6500 km distance and a historically large population size. It seems the whales move freely throughout the abundant deep ocean habitat in the waters of New Zealand."

The data generated in this study, implies that Gray’s beaked whales have existed in a historically increasing population, and that the rarity in live sightings is likely due to their cryptic behaviour and offshore distributions. With this in mind, conservation strategies aimed at protecting Gray’s beaked whales in New Zealand and Australian waters can approach the management of this population as a single unit. This study provides an extremely valuable and exciting source of data regarding the health of the Gray’s beaked whale population, and highlights the value of genetic tools and long term stranding collections for the study of species which are often elusive, long-lived and slow-breeding.

Article written by Lauren Laing, Biosciences Press Gang.

Date: 16 March 2016

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