Eclipse and The Pips

, 29 September 2015
Eclipse and The Pips
Nathusius' pipistrelle / Roger Jones

By Michael Blencowe

People and Wildlife Officer

Back when I was a lad you knew where you stood when it came to pipistrelles.

Even without a bat detector I could hazard a guess that the small bats I saw flittering and diving around my suburban garden were common pipistrelles (Pipistrellus pipistrellus). Then, in the late ‘90s, bat experts announced that my pipistrelles could actually be one of two species.

The soprano pipistrelle (Pipistrellus pygmaeus) looks very similar to the common pipistrelle but, as its name suggests, uses higher frequency echolocation to hunt and navigate. With the use of a bat detector you could eavesdrop on the pip's squeaks and differentiate between the common pipistrelle (typically echolocating at 45 kHz) and the high pitched soprano pipistrelle (55 kHz).

Just as I was getting my head ‘round separating the two pipistrelle species I now find out that there’s a new bat on the block; the Nathusius’ pipistrelle (Pipistrellus nathusii). The Nathusius’ is a rare but widespread species which has probably gone largely un-detected in the UK in previous years. However recent advancements in bat detecting technology are giving experts the opportunity to learn more about this species. It is known that the Nathusius’ pipistrelle is strongly migratory, and studies suggest that populations in NE Europe head SW each winter. Bat ringing, like bird ringing, has provided a lot of information on European populations of Nathusius’ but little is known about its migratory habits in the UK.

(Photo: There go the pips. From left-right Nathusius' pipistrelle, soprano pipistrelle and common pipistrelle).

Now a UK-wide Nathusius’ pipistrelle survey is giving us important information about this bat and these results are helping to inform its conservation needs.

On Sunday evening I joined a team at Rye Harbour as they were setting up their research equipment. Daniel Hargreaves, Roger Jones and Sally-Ann Hurry are Sussex based bat experts who are licensed to conduct bat surveys. Daniel, who is leading the survey, has already made a major breakthrough in our understanding of the Nathuisius’ when a bat which he had ringed in Bristol was found 370 miles away in The Netherlands.

Nathusius' pipistrelles are associated with water bodies and Roger and Sally had identified Rye Harbour as a potential ‘hot spot’ for this rare bat. The team had already been trapping here in September and had successfully captured some Nathusius' pipistrelles. On Sunday evening an impressive 'supermoon' rose over Castle Water heading for its starring role in the night's lunar eclipse. The temperature was mild, the breeze dropped and as the sun set noctules, Britain's biggest bats, were acrobatically hunting overhead.

It wasn't long before the first Nathusius' pipistrelles were caught in the Harp Trap. Each bat was carefully weighed and their vital statistics measured and recorded. A lightweight, numbered ring was fitted to each bat's forearm and a small sample of fur was taken. This fur will undergo stable isotope analysis at the University of Exeter to help determine the bat's origin.

(Photo: Pip processsing at Rye Harbour)

At the end of their examination the bats were gently released and they flew back out into the skies of Sussex headed for…who knows where? Hopefully some of the bats ringed on Sunday will be found elsewhere and shed more light onto this tiny bat's incredible migration.

At the end of the evening a total of 13 Nathusius’ pipistrelles had been recorded - the most ever caught at a trapping session in the UK. It’s great to discover that our Rye Harbour reserve which is such an important area for so many other species is also an important site for the Nathuisius’ pipistrelle.

(Photo: Nathusius' pipistrelle at Rye Harbour. Photo by Roger Jones).

Thank you to Daniel, Roger and Sally-Ann for allowing us to join them during their survey and for introducing us to these amazing bats.