Tiny Bat ‒ Big Impact on Offshore Wind Farms

A tiny bat, ringed in the UK, found in Netherlands, 600 kilometres (as the bat flies) from where it was ringed, has provided the first record of a bat crossing the sea from the UK to mainland Europe!

Bat experts in the Netherlands and the UK are working together to learn more about this remarkable journey and its implications for bat conservation and offshore wind farms.

Bat Conservation Trust believes that the tiny bat, a Nathusius’ pipistrelle, which typically weighs around 6-15g and is about the size of a human thumb, flew from Blagdon, near Bristol, in the South West of the UK across the country and over the North Sea before settling in a farm building in the Netherlands about ½ km from the coast: a direct journey of 596 kilometres (370 miles).

The bat was found on 23rd December 2013 by Teddy Dolstra, from the Friesland Mammal Working Group who regularly monitors bats roosting at the site.

The exact location of where the bat was found is Hoarnesstreek 2,Pietersbierum, Franekeradeel, Holland.

Sadly, the animal had already died, but because it was carrying a miniature identity ring, he was able to discover that the remarkable creature had been found previously in the UK. This could be the proof that these little bats do successfully migrate across the North Sea.

The movements of Nathusius’ pipistrelles both around the UK and between the UK and the continent, are currently a mystery. They are elusive creatures, and are too small to carry devices such as satellite trackers used to monitor bird migration. In some areas, like Blagdon, several male bats have been found, but females are either absent or scarce and are believed to visit only on their migration route elsewhere.

On the continent some migration routes are well known and it is established these tiny bats can travel very long distances over land. There are several records of them bats landing on oil platforms or boats in the North Sea but this is an exciting find, showing that the bat not only made its way from one side of England to the other, but then crossed the sea.

Daniel Hargreaves, who ringed the bat back in 2010, says of the discovery: “We have hypothesised for a long time about the migration of bats to and from the UK but it’s very difficult to prove. This finding was a great surprise and is helping us to understand the huge journeys these bats can make. We have only ringed 34 bats at Blagdon lake so to receive a record like this is astonishing; it’s incredible to think that this little bat has flown a distance of at least 600km, avoiding hazards like roads and wind turbines, and for it to safely cross the sea is remarkable.”

Lisa Worledge, Bat Conservation Trust: “The timings of peaks in Nathusius’ pipistrelle recordings in spring and autumn, as well as records from North Sea oil platforms, have long suggested that some of these bats migrate. This discovery provides the first direct evidence that a British bat migrates over the sea between the UK and continental Europe.”

Dr Fiona Mathews, University of Exeter: “Nathusius’ pipistrelle is one of the species most at risk from land-based wind turbines throughout Europe. We now urgently need to identify the migration routes they use to cross the sea between the UK and continental Europe: offshore wind farms in the wrong place could be very bad news. In the autumn, we installed bat detectors on board Britany Ferries crossing to and from South-West England. We are analysing the data to find out when and where bats are recorded at sea and clearly now need to extend these surveys to include The North Sea.” 

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Press release, January 21, 2014; Image: nathusius