Wednesday, 18 September 2019

The Bats of Tar Lakes


On the 16th September, a bat walk was held at Tar Lakes, with a great turnout of people keen to see what wildlife the night sky had to offer. 14 of the UK’s 18 bat species can be found in Oxfordshire – the county’s woodland and hedgerow habitats make it a great place to see a range of different species. The group hoped to collect information on what sort of bats are using the lakes and their surrounding habitats, and find out a bit more about these elusive nocturnal creatures. Using bat detectors that lower the bat’s ultrasonic calls to the range of human hearing, the participants listened in on a number of different bat species as they made their way around the lake complex. Here is what we saw;



Common and soprano pipistrelles

Common pipistrelles Pipistrellus pipistrellus were the most frequently heard bat on the walk. This small species can be found in woodland and urban habitats, making use of holes in trees and buildings to roost in. Their calls sound like fast slaps as they pass by, at a frequency around 45kHz.

A soprano pipistrelle Pipistrellus pygmaeus was first bat species spotted on the walk, foraging over a patch of scrub habitat. This species looks and sounds similar to the common pipistrelle, however their calls are pitches higher at 55kHz – as their name would suggest!

Both of these bats were seen flying over scrub and hedgerow habitats, where their insect prey was most abundant – ‘feeding buzzes’ were heard on the detectors as the bats honed in on their prey. Hedgerows are incredibly important for bats, due to their use as navigational tools as they commute from roosting to foraging grounds.


Common Pipistrelle in flight
A common pipistrelle bat © Paul van Hoof


Noctule

Noctules Nyctalus noctula are one of the larger bats we have in Oxfordshire – they are associated with woodland habitat, and can occasionally be heard without detectors by children and adults with good hearing, due to their calls sometimes being just low enough for humans to hear at around 20kHz. Noctules were heard several times on the walk, but despite their large size, the group could not spot them in the air as they few rapidly around!
 
Image result for Noctule
Noctule © Branko Karapandza

Daubenton’s bat

A bat that is commonly associated with water habitats is the Daubenton’s bat Myotis daubentonii – this species is seen trawling across rivers and lake with its large hairy feet, catching the midges that hover above the surface. Using high-powered torches, we were treated to a few sightings of this bat foraging across the lake.

Daubenton's bat © Paul van Hoof


Mystery myotids

Bats that are part of the Myotid genus, such as Natterer's bats and Bechstein's bats, are very hard to tell apart using only a bat detector due to their similar sounding calls – they can even be challenging to identify when in the hand! Their rattling call was heard a few times briefly above the hedgerows bordering the lakes, perhaps commuting between roosting and foraging sites.

Other nightlife

The group also spotted some other wildlife whilst on the walk – several common newts and toads were encountered on the northern path around the lake, which narrowly avoided being trodden on at times! A surprisingly large number of devil's coach horse beetle were also seen, with their long black bodies and scorpion-like poses spotted in the grass.

Many thanks to the Oxford Bat Group for lending us their bat detectors for the evening – for more information on the work they’re doing across the county, visit their website - http://www.oxfordshirebats.org/

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