Life after Light – Bats along Grantham Canal

It’s very nearly Halloween – what better time to introduce you to the bats which haunt Grantham Canal when darkness falls…

IMG_4159I spent several nights this September cycling along Grantham Canal with an EM3 bat detector connected to a GPS unit, recording the bats in flight between the A1 to the east and Hickling Basin to the west. Bats use echolocation to navigate and hunt and the bat detector converts this ultrasonic sound into something we can hear. The sound emitted by the detector tells you when a bat is there, often which species it is and sometimes even what it is doing.

You might imagine that this is quite a sinister place to be, surrounded by bats on a moonlit night, but there really is nothing to be afraid of! As the detector tapped and pattered away to announce their, I could see bats flying before me in the darkness. But even though I was cycling towards them, they elegantly avoided me every time, never making contact and certainly never tangling in my hair. This is one of the most enduring myths about bats but their fantastic echolocation abilities mean that they can ‘see’ and avoid obstacles on even the darkest of nights.

I recorded at least five species in September, some calls with ‘buzzes’ indicating foraging and some with ‘song flight’ where male soprano pipistrelles emit lower frequency social calls to attract mates. These are just on the edge of human hearing and can be heard without a detector – you may have heard the very high frequency chirrups if you walk outside at dusk in the autumn.

Common Pipistrelle

The Common Pipistrelle is one of the smallest but certainly the commonest bat species in the UK
The Common Pipistrelle is the smallest and the commonest UK species

The common pipistrelle is our most abundant species in the UK, and was encountered throughout the route of the canal, particularly where there are more trees as this species specialises in hunting along ‘edge’ habitat which is typically along hedges, tree lines and other landscape features.

The orange bat symbols in this map indicate the locations where common pipistrelle bats were identified. The A1 which dissects the canal is at the far eastern end with Hickling Basin marking the western extent
The orange bat symbols in this map indicate the locations where common pipistrelle bats were identified. The A1 which dissects the canal is at the far eastern end with Hickling Basin marking the western extent

Soprano Pipistrelle

The soprano pipistrelle is physically similar to the common pipistrelle but a has differences in morphology such as wing veination and face colouring with the much darker face of the common pipistrelle earning it's other name of bandit pipistrelle
The soprano pipistrelle is physically similar to the common pipistrelle but has differences in morphology such as wing veination and face colouring with the much darker face of the common pipistrelle earning it’s other name of bandit pipistrelle

The soprano pipistrelle is very similar morphologically and was not even identified as a separate species until 1992. Now they can be told apart confidently in their hand, and with fair reliability acoustically as the soprano pipistrelle calls at 55 kHz compared with the common pipipstrelle at 45 kHz. In England, the soprano pipistrelle is often found associated with water and so it was no surprise to find them along the canal. An interesting observation however is that there appears to be much more activity to the east, near to larger water bodies. Denton Reservoir lies just beside the canal towards the eastern end and is likely to be an important foraging resource for this species.

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The blue bat symbols in this map indicate the locations where soprano pipistrelle bats were identified. The A1 which dissects the canal is at the far eastern end with Hickling Basin marking the western extent

The vast majority of the recordings related to these two pipistrelle species – the other  bat species were found at much lower frequencies.

The yellow bat symbols in this map indicate the locations where Natterer's bats were identified; black represents whiskered/Brandts; purple represents brown long-eared; and green represents noctule. The A1 which dissects the canal is at the far eastern end with Hickling Basin marking the western extent
The yellow bat symbols in this map indicate the locations where Natterer’s bats were identified; black represents whiskered/Brandts; purple represents brown long-eared; and green represents noctule. The A1 which dissects the canal is at the far eastern end with Hickling Basin marking the western extent

Noctule

The noctule bat is our largest species and tends to fly high and early, often the first bat to appear around sunset and can be seen in the skies as the swifts are still on the wing. Only one noctule was heard during the transects, between Denton and Woolesthorpe and picked up again near Muston. This bat is large and the sky was light meaning I could watch it  flying my way, foraging as it flew to the west. This is a widespread species which favours roosting in trees, but numbers are generally lower than the pipistrelles.

Noctule bat - the largest UK species
Noctule bat – the largest UK species

Brown long-eared bat

Brown long-eared bat is one of our quietest but most charismatic bats. Their large ears make them quite charming to behold, and they are frequently found roosting in barns and other buildings. I only picked up a single instance of this bat, but their very quiet echolocation means they are generally under-recorded.

The brown long-eared bat is named for quite obvious reasons!
The brown long-eared bat is named for quite obvious reasons!

Myotis bats

The myotis bats are considered to be some of the most difficult to identify from sound alone. Daubenton’s bats are the myotis species most frequently associated with water as they specialise in flying low over still waters and taking insects on the wing or from the water’s surface. Natterer’s bat is another myotis species and some of the calls recorded along the canal in September are characteristic of this species. Whiskered and Brandt’s bats are the other two myotis species which are likely to be present in this part of the country. These two bats are very similar to one another and are difficult to separate even in the hand. Some of the calls have the characteristics of one (or both) of these two species. Whilst these species are not commonly associated with aquatic habitats, the canal also boasts hedgerows, copses and grass bank margins which provide great terrestrial habitat as well.

A Daubenton's bat - the myotis species most frequently associated with water. The myotis bats are larger than the pipistrelles but not as big as the noctule.
A Daubenton’s bat – the myotis species most frequently associated with water. The myotis bats are larger than the pipistrelles but not as big as the noctule.

I encountered a whole host of other species whilst cycling along in the afterglow of sunset including barn owls, tawny owls, hares fleeing down the towpath and badgers snuffling in the hedgerows. The canal is stunning in the daytime but at night it comes alive with a whole host of new species – a walk around sunset might reveal creatures which you would not normally be privileged enough  to watch.

Sunset along Grantham Canal

If you are looking to commission bat surveys in the Midlands area, check out Landscape Science Consultancy’s website here!

An olinguito for the UK? The age of discovery is not over yet.

Scientists have just announced the discovery of a new carnivorous mammal in South America, named the olinguito. It is a member of the raccoon family and is the first new carniverous mammal to be discovered in the western hemisphere in 35 years.

Two of the reasons cited for the ability of the olinguito to evade description for so long is its habitat and behaviour – it lives in the cloud forests of Columbia and Ecudor and spends its time in the canopy where the dense mists conceal it, moving only at night. The team leader Kristofer Helgen said that ‘the age of discovery is not over’. Whilst this statement may seem plausible in tropical rainforests where great expanses of inaccessible habitats could conceal new species, you would be forgiven for assuming that the stable of mammals in the UK is… stable! For starters, this is one of the most densely populated places on the planet; then take into account the huge number of amateur naturalists, both past and present who dedicate their time to studying their local patch or favourite taxa; and then there is sad fact that we are really rather poor in mammalian fauna, having exterminated anything which might compete with us hundreds of years ago.

But there is one group of species which can still turn up surprises, even now. Bats share some of the characteristics of the olinguito which have allowed it to remain a mystery until now; that is they emerge at night, concealed by the darkness and move around on a plane above our own. Other characteristics condusive to crypsis include their habit of roosting in crevices and cracks, deep in tree cavities or high in caves, and their communication in ultrasound, so that only the low frequency social calls, or the echolocation of noctules, can be heard without a detector to convert the sound down into our range.

In 1993, it was first suggested that the pipistrelle bat, our most common species, actually comprised two cryptic species, the common and the soprano pipistrelle, the latter so named because the frequency of its echolocation is at a higher pitch than the former. Although these two species are similar, they can be quite easily told apart with characteristics such as wing veination, the presence of a ridge on the nose, the colour of the face and the difference in smell. If these two species were – say – butterflies, it is almost without question that they would have been separated as distinct species many years ago, but our most common bat escaped such detailed scrutiny as recently as 20 years ago.

In 2010, the presence of another cryptic species was discovered, the Alcathoe is a small myotis species alongside the whiskered and Brandt’s bats. This was not a new species – it is well known on the continent – but nobody realised that populations existed in this country as well. Work is still ongoing to establish just how widespread this species is and Philip Brown of Bristol University is asking anybody undertaking trapping work to describe any small myotis bats caught and send the details, along with droppings, to him to try to describe more fully and understand more accurately the status of this species in the UK.

The Nathusius pipsistrelle is a species which was previously thought to be a migratory vagrant but was first confirmed breeding in the UK in 1997 and its range within the UK has expanded year on year, partly as a result of increased survey effort but also believed to be a response to climate change as identified in this paper by Lundy et al. from 2010. This is a highly mobile species which is easily able to adapt to changing conditions and its increasing prresence in the UK is consistant with a continental scale change in range. The Bat Conservation Trust (BCT) run a Nathusius pipistrelle monitoring scheme in september every year – this is the month when the UK population is at its peak when bats arrive from the continent. If you would like to get involved with the surveys, you can find out more and sign up here.

There are a number of other species which are currently recorded as vagrants in the UK but it is possible that some of these may be resident now or may become so in the future as a result of climate change. These include the Kuhl’s pipistrelle and the parti-coloured bat – you can find out more about them in this factsheet from the BCT.

Bats are studied mainly through their echolocation using bat detctors, by observing them in flight when emerging from or re-entering a roost or commuting and foraging in the wider environment. This generally requires specialist kit to determine which species is being observed and despite the abundance of volunteers and professionals, the proportion of the population who would be able to identify bats, compared with those who could identify common butterflies and garden birds, is very low. Even more rarely are bat workers able to catch and inspect the bats they study, and even then it is possible that unusual bats may be regarded an unusual specimen of a known species rather than something otherwise unknown such as the Alcathoe.

The increasing ease with which DNA samples can be analysed may help to identify new cryptic species or confirm the presence of continental species within the UK which the progression of climate change may encourage.

Since 1993, we have identified two new species of pipistrelle to be resident in this country and there is the possibility of a fourth species joining the line-up in the near future. South America may have a new species of carnivorous mammal, but the best bet for the next new British discovery has to be within the bat world.