The dolphins are coming!
Bottlenose dolphins and orcas are increasingly finding their way to Danish waters. At the same time, we want to build gigantic offshore wind farms. Do we have room for both more marine mammals and more wind farms?
One consequence of climate change is that more and more animals, normally not considered native to Denmark, are now swimming around in our waters. Danes have thus spotted humpback whales, orcas, sperm whales, minke whales, white-beaked dolphins and bottlenose dolphins.
Are these animals Danish now? And if they are, what are the implications then? Magnus Wahlberg, a biologist and whale expert at SDU's Marine Biological Research Station, answers:
- In the first instance, we say that for an animal species to be considered Danish, it must breed in Denmark. If it does, it must be managed according to Danish law; whether it should be protected, whether it should be given special consideration, etc. But there may also be other species that travel through Denmark on their way from wintering to breeding grounds – some birds and perhaps also some whales - we also have a duty to protect them.
What are we dealing with out there?
The following marine mammals breed in Denmark - and can therefore be considered native to Denmark: harbor seals, gray seals, harbor porpoises and perhaps also white-beaked dolphins. We know the seals and porpoises from straits and belts, while the white-nosed dolphin primarily lives in the North Sea and Kattegat, where humans don't come very often.
In recent years, there have been so many sightings of orcas and bottlenose dolphins in Danish waters that we should investigate whether they are just passing visitors or whether they are Danish species, says Magnus Wahlberg.
- If bottlenose dolphins and orcas are to be considered native to Denmark, the impact will be huge on nature conservation in our oceans and waters. These animals live out at sea, where we want to build huge offshore wind farms in the name of the green transition, and there are legal requirements to take these animals into account. We need to know what we're dealing with out there, he says.
Dolphins are not just dolphins
The dolphin family includes 40 species, living in both fresh and salt water. Examples of dolphin species are bottlenose dolphins, orcas and pilot whales.
Orcas could become the largest predator in Denmark
Magnus Wahlberg and his colleagues are currently interested in finding out more about the orcas that periodically appear in the Danish waters, Kattegat and Skagerrak. This involves getting close enough to one of them to take a skin biopsy for DNA analysis.
- We can compare this DNA analysis with DNA from groups living in the Shetland Islands or off the coast of Norway, for example. If there is a match, we will conclude that the animal belongs to that group and that it is just a visitor to Denmark. If there is no match, we may have found a member of a group that turns out to be native to Denmark, he says.
In addition to DNA samples, the researchers also use profile photos of the orcas’ fins and recordings of their sound production to find out which groups they belong to.
If the orca is native to Denmark, it will be Denmark's largest predator.
Meet the researcher
Magnus Wahlberg is an associate professor at the Department of Biology. His research is supported by SDU Climate Cluster, the Carlsberg Foundation, the Danish Ministry of Higher Education and Science, Human Frontiers and the US Department of Defense.