Humpback whales are only one of many species that undertake some mammoth migrations from one part of the ocean to another, and as noted in my previous blog, researchers in the Azores are making headway in trying to map out some of these routes as these volcanic islands, sitting pretty in the deep waters of the north Atlantic, are frequented by a huge number of species at different times of the year.
As a species, sperm whales can be found throughout the north Atlantic however the different sexes exhibit a different distribution and social structure. The stable female groups remain in low latitudes (closer to the equator) year round whilst male sperm whales are thought to follow a seasonal shift in latitude although, in truth very little is known about the movements of male sperm whales in the north Atlantic.
In the northern hemisphere, males are thought to leave the maternal group when they reach sexual maturity and head northwards allowing males to feed in cold-water (and hence productive) habitats such as areas in northern Norway. Males are then thought to return south to breeding grounds from the age of approximately 27 years. Some have suggested that the distance travelled during the male sperm whale migration might increase with age however there is still much to learn as both frequency and duration of these migrations remains uncertain – for example it is believed that these migrations might not occur on an annual basis.
Migration between ‘grounds’, such as Norway and the Azores, has in the past been commonly accepted because the whaling industry tended to find large quantities of sperm whales in both areas but only now are researchers from the Azores, Andenes and Tromso able to track individual whales and learn more about their movements over time.
Several photo-id catalogues exist for male sperm whales in the north Atlantic with the largest collections held for the Azores (310 individuals) and Andenes (375 individuals) and Tromsø (84 individuals) in Norway and collaboration between researchers began as far back as 1990. In that time (almost 25 years) there have been 6 matches between individuals in Andenes and Tromso – which is not wholly unexpected as they are only approx. 25 nm apart – with three of these having been sighted in multiple years. However, an additional six photo-id matches have been made from the Azores to Norway (a much greater distance at ~2400 nm) and in all cases the “first” photograph was in the Azores. This is important as it may indicate that the males photographed in Azores are mainly younger animals who are moving north once they’re reached sexual maturity.
Although it is believed that sperm whales use the whole of the Atlantic basin, interestingly no photo-id matches were made to collections from Iceland, Nova Scotia, Greenland, Dominica, Guadeloupe, Gulf of Mexico or the Mediterranean. Clearly there is more to learn about male sperm whale movements in the north Atlantic and thanks to the efforts of a few dedicated people we’re finding out more all the time.
Research like this proves that multinational collaboration is essential when working with animals that cover large distances and importantly it also underlines the importance of photo-identification as a non-invasive tool in whale and dolphin research. These findings also show the value of data collected from whale watching vessels and the importance of collaboration between groups when investigating biology at an ocean basin scale.
“It is hoped that with the addition of more images from around the Atlantic, further insight might be gained into the movements of these widely ranging animals.” – Lisa Steiner, Whale Watch Azores.