The science of counting whales

Photo / Mark Mitchell

This post originally appeared on Sciblogs.

Good friends of mine have recently returned from an expedition to the Auckland Islands, a couple of days sail south of Bluff, where they were researching Southern right whales. In the long dark winter months while we are flat out hibernating, quaffing red wine and laying down a bit of winter fat, Port Ross turns into a veritable whale orgy. This used to happen in harbours and bays all around New Zealand but intensive whaling in the 19th century quickly put a stop to that sort of carry on.

One of the tasks facing the research team was to count the whales in the bay. Sounds easy enough...that is until you start to consider the logistics. There are a LOT of whales to count (this year there were around 200 in a bay that is about the size of Wellington Harbour). They spend much of their time underwater and even when they're at the surface, not much pokes out. And, well they all kind of look the same (grey, whaley looking etc.). Perhaps now you can understand why the counting of whales has become a bit of a science in itself.

Expedition leader Dr William Rayment explained the process to me. The first step is to build an identification catalogue of all of the whales encountered. Despite looking similar to the untrained eye, on closer inspection each whale has unique patterns of callosities on their head and body. Callosities are clusters of unusual wee crustaceans called cyamids that congregate around rough skin patches on the whale, and surprisingly, their patterns don't change much at all over time. Once a whale is sighted, it is approached by the researchers in a small boat, and photos are taken to add to the catalogue. If this individual is encountered again, be it on the same expedition or years later in a distant location, a photo match with the catalogued picture will enable this individual to be identified.

On this latest 3 week voyage, Dr Rayment and his team spent each day attempting to photograph all the whales in the bay, and are now working to match those photos with photos in the catalogue that they have been building over the last four years. Dr Rayment is working with the Department of Conservation to photograph whales visiting the New Zealand mainland, and also has contacts in Australia, so it is likely that a picture will begin to emerge about the migration patterns of this species that appears to be making a remarkable recovery from the brink of extinction.

The more visits the research team make to the Auckland Islands, the better their ability will be to accurately estimate the total number of Southern right whales that spend time in New Zealand's waters. Because they are able to track individual whales over time, the researchers also hope to gain valuable information about how often the females have calves, their survival rates, and how much each animal moves around. These kinds of information can also be gained by DNA matching, but that is a more invasive technique that requires small biopsies of skin to be collected on each whale sighting.

Dr Rebecca McLeod is a marine ecologist at the University of Otago. View her work and that of 30 other scientists and science writers at Sciblogs, New Zealand's largest science blogging network.