When it comes to epic migrations, birds are likely the first animals to spring to mind.
But bats also complete incredible journeys, with some species able to travel thousands of miles across North America, Europe, and Africa.
Scientists have previously struggled to observe these migrations, meaning they’ve remained an enigma.
To combat this issue, researchers from the Max Planck Institute of Animal Behaviour have turned to ultra-lightweight intelligent sensors.
This has allowed them to study common noctule bats on their spring migration across Europe for the first time.
Their analysis reveals that these bats use an unusual strategy to travel hundreds of miles at night – they surf the wind.
‘They were riding storm fronts, using the support of warm tailwinds,’ said Edward Hurme, first author of the study.
‘It was known that birds use wind support during migration, and now we see that bats do too.’
Noctule bats use an unusual strategy to travel hundreds of miles at night – they surf the wind
When it comes to epic migrations, birds are likely the first animals to spring to mind. But bats also complete incredible journeys, with some species able to travel thousands of miles across North America, Europe, and Africa
The ultra-lightweight intelligent sensors weigh just five per cent of the bat’s total body mass, and are able to transmit data back to the scientits via a novel long-range network.
‘The tags communicate with us from wherever the bats are because they have coverage across Europe much like a cell phone network,’ said Timm Wild, senior author of the study.
In total, the team attached tags to 71 bats in Switzerland – focusing exclusively on females, who spend summers in northern Europe and winters in more southerly locations.
The tags collected data for up to four weeks as the bats migrated northeast.
Surprisingly, the researchers found that the bats did not use a specific migration corridor.
‘We had assumed that bats were following a unified path, but we now see they are moving all over the landscape in a general northeast direction,’ said Dina Dechmann, senior author of the study.
The tags showed that some bats migrated almost 250 miles (400km) in a single night, stopping frequently to feed.
‘Unlike migratory birds, bats don’t gain weight in preparation for migration,’ Ms Dechmann explained.
The ultra-lightweight intelligent sensors weigh just five per cent of the bat’s total body mass, and are able to transmit data back to the scientits via a novel long-range network
‘They need to refuel every night, so their migration has a hopping pattern rather than a straight shot.’
On certain nights, the team saw an ‘explosion’ of departures, which they describe as ‘like bat fireworks’.
The explosions could be explained by changes in the weather – with bats leaving on nights just before incoming storms.
The sensors showed that bats used less energy flying on these nights, confirming that they were ‘surfing’ on the storm fronts.
In this study, the team foused on a portion of the total migration of noctule bats, which they estimate to be around 994-miles (1,600km).
‘We are still far from observing the complete yearly cycle of long-distance bat migration,’ said Mr Hurme.
‘The behavior is still a black box, but at least we have a tool that has shed some light.’
Beyond learning more about bats, the researchers hope the findings will help to prevent deadly collisions during bat migrations.
‘Before this study, we didn’t know what triggered bats to start migrating,’ said Mr Hurme.
‘More studies like this will pave the way for a system to forecast bat migration.
‘We can be stewards of bats, helping wind farms to turn off their turbines on nights when bats are streaming through.
‘This is just a small glimpse of what we will find if we all keep working to open that black box.’
