– The fact that we have managed to follow her for a whole year is quite special. It gives a unique insight into a whale’s life and migration, says Audun Rikardsen. He is a professor at the Department of Arctic and Marine Biology at UiT Norway’s Arctic University. For many years, he has researched whales, among other things. When the humpback whale started arriving on the coast of Troms, about ten years ago – right outside people’s living rooms – it provided an excellent opportunity to find out more about this large animal. – The humpback whale makes the world’s longest migration of all mammals, but we previously had very little knowledge about this migration. The humpback whales love herring, and eat plenty in the sea off northern Norway before they travel to the Caribbean to mate. Photo: Audun Rikardsen That’s why they started tagging whales with satellite transmitters. Although such transmitters usually fall off within six months, the researchers still had a dream of being able to follow an individual throughout the long journey. And the humpback whale “Theresia” delivered. She carried the satellite transmitter with her all 18,000 kilometers from northern Norway to the Caribbean and back again – a journey that takes almost a whole year. With this, researchers have for the first time been able to follow and document this journey. – It’s absolutely fantastic, says an enthusiastic Rikardsen, who can say that the researchers had a couple of surprises along the way. In the last ten years, the humpback whale has come very close when it has lived in the sea outside Nord-Troms. Photo: Audun Rikardsen Sex holiday to the Caribbean Humpback whales are among the world’s largest mammals. An adult individual can be around 15 meters long and weigh 40 tonnes. The whales mainly live in Arctic regions, but occasionally they make the long trip to warmer waters – and then for reproductive purposes. – The vast majority go on a sex holiday to the Caribbean, laughs Rikardsen, – or they go to give birth and breastfeed. They normally leave around Christmas or early January, in order to make it to the high season in April/May. Audun Rikardsen, professor at the Department of Arctic and Marine Biology at UiT Norway’s Arctic University. He found it very exciting to follow “Theresia’s” journey, including through satellite tracking. Photo: ODD ARNE OLDERBAKK / news The researchers began following “Theresia” at the beginning of January 2019. But unlike many others, she took the longest to turn her nose south. She spent a lot of time outside northern Norway eating huge amounts of herring. When she finally left, a couple of weeks overtime, it was at breakneck speed. “Theresia” swam so fast that the researchers were unsure whether she would use too much energy and not make the entire journey. Photo: Audun Rikardsen The high speed was enough to make up for the delay so that she would reach the Caribbean high season to do her errand, explains the researcher. But time was actually too short for “Theresia”, because suddenly she slowed down in the middle of the North Atlantic and gave birth to a little companion. – We didn’t know she was pregnant, so that was a big bonus. This also explained why she had taken so much time to eat before leaving. As the humpback whale does not eat while it is south, it is important to ensure enough energy for the entire journey. And “Theresia” ate for two, after all. – Those who are going to breastfeed will probably want to make sure they have extra energy. This is how it is with many animals, that you put on weight and often get an extra appetite before birth, says researcher Audun Rikardsen. Photo: Audun Rikardsen The mother whale adapted For the researchers, it was exciting to record how the new mother adapted to the speed when she now had a calf to take care of – because the rest of the journey to the Caribbean went at a more leisurely pace. This gave the researchers, for the first time, insight into how a humpback whale adapts on its journey, based on different circumstances. They also found it interesting that “Theresia” actually chose to continue all the way to the Caribbean when she strictly had no need to go there anymore. She had already given birth. – We believe that the reason why “Theresia” continued the journey was simply to teach the calf the route, until the day it has to fend for itself, says Audun Rikardsen. “Theresia” and her calf swam together from the Caribbean, up to the Barents Sea and back to Skjervøy. Photo: Audun Rikardsen On her own tail The road ahead for “Theresia” and the calf went north again. The researchers followed them past Iceland and then on up to the Barents Sea. Much of the journey went so far out to sea that the waters are not owned or regulated by any nation. Having this kind of detailed knowledge about how and where the whales travel is important in terms of being able to protect them from activity in the sea. – The whales are vulnerable, so it is important to take into account where they are. – In addition, it is important to map the areas the whale uses to see if this changes as the temperature rises. Professor Audun Rikardsen describes the humpback whales’ stay outside northern Norway as a “pit-stop” where they must fatten up before the journey south. Photo: Audun Rikardsen After “Theresia” had been in the Barents Sea for a short period, she returned to the place where the researchers first met her – Skjervøy in North Troms. “Theresia” was one of the first humpback whales Rikardsen encountered in autumn 2020. Now she and the calf had returned to take a “pit-stop” consisting of plenty of herring eating, before they were to turn their noses south again. – The calf also follows the mother on the next round, because then it has learned both ways, says the researcher at UiT. – It will be their last journey together, because down there she mates and releases the calf. Then the calf is on its own tail. The calf of “Theresia” has to fend for itself after the mother has taken it on one last trip to the Caribbean. Photo: Audun Rikardsen / Audun Rikardsen
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For the first time, researchers have followed a humpback whale for a whole year – from the Arctic to the Caribbean and back – news Trøndelag
