Hi everyone, it’s LTV Rob here! I’ve been off the island for just over 4 weeks now and am missing it a lot, so I thought I’d give you an update of the project I carried out whilst there.
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| Abseiling into caves for seal monitoring gave me an opportunity to check out potential sites for bat roosts. |
One
of the animal groups on Skomer that really intrigued me from the outset were bats.
With no trees on the island, there appears to be little suitable roosting
habitat – so are there bats there? The most recent survey of the island was conducted
in 2014, but this was only at The Farm so I was keen to look at activity across
the island.
I
used an SD1 recorder for the study.
These amazing bits of kit can be pre-programmed to record at certain times of
day. During active hours, the recorders ‘listen’ for sounds of certain
frequencies. When it identifies what it thinks is a bat it records a sound-bite
which can then be downloaded later. These recordings are viewed on spectrograms
which are visual representations of the calls. Each species has a unique call shape
which allows us to tell them apart.
If you visited the island from July to
September, you might have noticed my bat detector setup – it looked a bit like
some sort of NASA Moon lander! The microphone was tied to an old tripod which
meant I could set it up at different locations on the island – The Farm, Moorey
Mere, North Pond, North Haven, North Haven Slip, on the main track towards the
courtyard and overlooking The Lantern, a large cave system on the very east of
the island. I left the recorder for several days at each site and then collected
it in to see what we’d got…
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| The bat detector set up at the Farm |
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| The detector enjoyed some nice views of Middleholm from the 'Lantern' (and strong winds too!) |
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Over
the 7 recording sites, 380 bat recordings were obtained. 6 species were
identified with confidence: Common Pipistrelle, Soprano Pipistrelle, Leislers,
Noctule, Serotine and Greater Horseshoes. Barbastelle and Grey Long-eared bats
were also suspected. This is a good result for Skomer as it suggests that bat
diversity is stable. Activity varied between sites for each species, which
suggests that species are utilising different areas of the island.
Perhaps the most
exciting finding is that of Greater Horseshoe bats! This rare cave-roosting species
has declined nationally by over 90% in the last 100 years and is restricted largely
to a few populations
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in
south-west England and Wales. This is partly due to the intensive use of
pesticides which are reducing prey availability. 58 recordings of Greater
Horseshoes were taken across the island, which is higher activity than was seen
in 2014 – this could suggest that Greater Horseshoe numbers are on the rise on
Skomer, which is very encouraging. Islands like Skomer, which is pesticide
free, are evidently a natural stronghold for them!
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| Greater Horseshoe bat (source: Bat Conservation Trust 2010) |
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| A spectrogram of the Greater Horseshoe...no other species call at 80kHz so I knew immediately what it was! |
This project
highlighted that there is high bat activity on Skomer and that species activity
varied between different habitats on the island. More work is needed to
understand how each species is using the island so watch this space! In the
meantime, next time you visit Skomer think about these flying mammals which are
hidden away during the day and come out to join the Manx Shearwaters after
dark…
Thank
you for reading my batty ramblings!
Rob (Skomer LTV 2019)
