Seals are taking advantage of offshore wind farms to forage for food, satellite tracking has shown.
Data from tagging harbour and grey seals on the British and Dutch coasts of the North Sea revealed that 11 harbour seals visited two active wind farms off the German and UK coasts.
At both sites, the GPS tracking showed several worked their way through the area in a grid-like pattern, travelling in straight lines between individual turbines where they appeared to focus their hunt for prey.
Seals also tracked the path of subsea pipelines, with two seals in the Netherlands encountering a section of pipeline and following it on multiple trips for days at a time, the research published in the journal Current Biology showed.
In north-east Netherlands, four out of 96 seals visited Alpha Ventus, a windfarm off the coast of Germany, while Seven out of 22 seals tagged in south-east England went into the Sheringham Shoal wind farm.
One seal visited Sheringham Shoal, an the 88-turbine windfarm 11 to 14 miles off the Norfolk coast, 13 times and on each of the trips that was tracked moved through the area in a grid-like way, the research led by the University of St Andrews showed.
Man-made structures in the sea create “artificial reefs” which lead to localised increases in the number of fish and crustaceans.
But It is not clear if the presence of the turbines actually increases the amount of prey available to seals, or simply concentrates them in a new, man-made location where they are particularly vulnerable to being eaten, the scientists said.
“I was shocked when I first saw the stunning grid pattern of a seal track around Sheringham Shoal,” said Deborah Russell, of the University of St Andrews.
“You could see that the individual appeared to travel in straight lines between turbines, as if he was checking them out for potential prey and then stopping to forage at certain ones.
“Only a small proportion of our study seals utilised wind farms or pipelines. At present these structures cover a small proportion of the extent of the at-sea distribution of seals.”
“As wind farms become more extensive, many more seals will likely be affected.”
The scientists said both wind farms were newly built and more seals may come to use them for finding food over time, particularly if the artificial reefs at the base of the turbines are not yet fully established.
More research is needed to assess the impact of offshore wind farms, which are becoming more widespread in the North Sea, and to resolve the uncertainty as to whether the structures increase the amount of wildlife or just concentrate it in one area.
This will help assess whether the wind farms need to be designed and managed to limit them becoming “ecological traps” for prey species or to maximise the benefits for top predators such as seals, the researchers said.
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