Why do we wish to identify individual humpback whales?
Whales are difficult animals to study. They are widespread across large expanses of ocean and spend most of their time underwater. In order to develop effective conservation strategies for whales, it is of crucial importance to be able to identify important areas for the whales as well as monitoring changes in their distribution and habitat-use over time. To be able to answer such questions, knowing the identity of individual whales and being able to distinguish individuals in a group is of critical importance.
One way to learn more about whales and their migrations is to attach satellite tags or radio transmitters to the skin of the animals but this is both difficult and expensive. Studying whales with animal-borne instrumentation can therefore often only be used to study a limited number of animals under a relatively short time period. Fortunately, we can learn a lot about whales by using a simpler method; photo-identification.
When humpbacks dive, they usually lift their tail flukes, showing the underside of the tail. Each fluke has a unique pattern of black and white pigmentation and scars and not two whales in the world look exactly the same. In the 1970’s, researchers discovered that there was enough variation in the natural markings of humpback whale tail flukes to distinguish between individuals. After this discovery, fluke photographs began to be collected from all over the world.
Once individual humpbacks have been photographed and identified, they can be added to a photo identification catalogue. As photos of new individuals, and resightings of already known individuals, are added, it is possible to combine the sightings so that they tell us a story of where and when the whales spend their time.
Photo-identification is a powerful tool that can be used to study migration destinations, habitat preferences and small-scale movements within an area. It can also be used to study social bonds, age and sexual maturity, site-fidelity (tendency to return to the same area) and is a widely-used technique to estimate the number of whales in a population.