They fly by night

Originally published October 2015

Hello Everyone! The seasons are changing, the leaves are on the turn, the Equinox has passed and the time of Mabon is upon us. Blackberries are being crumbled, Elderberries fermented and Sloes pricked (with a thorn off the bush, naturally!). The Swallows are on the wing, autumnal Murmerations are darkening the skies and even the vociferous Wood Pigeons are sounding a little lacklustre.

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It is not fashionable to read newspapers these days but I find it a very rewarding pastime when looking for trends in the coverage of ecological issues. The Nature Notes, Environment and Letters sections of that old stalwart, The Times, are highlighting three main areas at present, over-zealous foragers clearing the woodlands of fungi, the loss of species, both nationally and globally, and Butterflies and Moths. All three of these topics are relevant to our corner of the world and have been covered in previous scribbles, no doubt to surface again in future articles. Just to add that our Quarry Wood Moth event, held in July and featured in last month’s Crowhurst News was an astounding success. Lorna captured the occasion with an array of fabulous photos which gave us an idea of just how stunning Moths are, especially when seen close-up. The good news is that Ralph and his amazing light trap will be returning to our little reserve next year.

Now, just to show that I really do believe in the Circle of Life, let us have a quick look at one the most voracious predators of our nocturnal Lepidoptera, those most misunderstood of animals, Bats. As the last songbird of the evening bids us farewell for the night, the air becomes the domain of small, dark silhouettes flitting around like young schoolchildren released into the playground. Those of us with keen ears can often pick up some of the sounds they make, though the vast majority of them are out of our hearing sensitivity. Bats are the only mammals that are able to achieve true flight. They belong to the Order Chiropetera and the Greek scholars amongst you will have translated this to hand-wings, an accurate, if rather pedantic, description of their physiology. They are a phenomenally successful Order with an estimated 1,116 different species worldwide; representing a fifth of all mammal species on the planet. This distribution is reflected at our national level as the eighteen species resident in the UK constitute about a quarter of our mammal species.

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It will not surprise anyone to know that all the bats we have in this country are Microbats known as the Microchiropterans. The Megachiropterans, or Megabats, are found in the Tropics and Sub-tropics only.  Unlike the name of their taxonomic Order, these monikers are not as literal or helpful as a method of categorising bats.
Some Megabats are actually smaller than many Microbats and vice versa, although the former group does includes the largest of the bat species, the Grey-headed Flying Foxes (Pteropus poliocephalus) of Australia.1384862664_7f833ed3bb_z
The Hog-nosed bat or Bumblebee Bat (Craseonycteris thonglongyai) found in Thailand and Myanmar is not only the smallest bat, but also the smallest mammal in the world and, weighing in at less than two grams, is a Microbat in every sense of the word.

The mega/micro differentiation actually alludes to the bats method of feeding. The Megabats are vegetarian, living off fruit, nectar and pollen. Some of the smaller bats in this group feed in the same way that Humming Birds do and are responsible, or at least partly-responsible, for pollinating many hundreds of plants including Guava, Mango and Banana. Bat pollination, known as Chiropterophily has a close link with all you lovers of Mexican theme nights as the Agave plant, used to make Tequila, is on this list also. In the case of the Agave, our species thought it best to interfere and has cloned the plant in order that it can be harvested before the flower appears. Clearly this did not benefit the bats, and as disease has killed off many of the crops due to lack of genetic fitness, it has not benefitted the farmers either!

Microbats are carnivorous. The group includes fish eaters, frog eaters and the infamous Vampire Bats that feed exclusively on the blood of cattle. However most of them are insectivorous and can eat up to half their body weight in a single night. This is quite a feat considering that the bats catch their prey on the wing without the benefit of light. In his 1986 book, The Blind Watchmaker, the biologist and author, Richard Dawkins, compares the solution to this problem to those an engineer might consider. The obvious answer is some kind of radar or, in the absence of radio waves, sonar. 5507572209_bb754ef8f1_zDawkins describes how a bat’s skull, with its seemingly gargoyle-like features, is in fact a finely-crafted instrument enabling the animal to direct ultrasound pulses in whatever direction it chooses. By sending out a continuous stream of pulses or clicks that bounce off objects around it and return to the bat it can build up a picture of the world around it. As the bat locates the prey the number of clicks increases to around 200 a second in order to build up a more accurate picture so it can close in and capture it. In this way, thousands of our moths and numerous other insects meet their end each night. As in every area of taxonomy this relatively simple method of subdividing bats is becoming more complicated with the current studies in genetics. Scientists are busy creating even more categories within the Mega and Micro groups. However that is a story for another time!

All of the eighteen resident species have been recorded in Sussex, however the bats we are most likely to see are the Brown long-eared Bat (Plecotus auritus), the Common pipistrelle (Pipistrellus pipistrellus), the Soprano pipistrelle (Pipistrellus pygmaeus) and the Serotine (Eptesicus serotinus). The best way to identify them is by using a bat detector. Some species emit quite distinct sounds, whereas others can be identified by the frequency range and repetition rate of calls only.

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The conservation status of bats is high. In the UK all species and their roosts are protected by law. It is important to remember that, after hibernation, they return to the same roosts every year and that these sites are protected all the year round, not just when the bats are in residence. Bats, like their chief prey, moths, are in vogue. Moth and bat events are organised up and down the country, as wildlife groups encourage public interest. I am just waiting for a deluge of bat-related articles in the Times Letter section!
Could it be that bat detectors will replace metal detectors as the piece of kit hobbyists are most likely to have in the corner of their shed? belagoingbattyAll this despite the fact the Night Flyers have endured centuries of bad publicity in folk-lore and literature.
They have been associated with death and graveyards long before Bram Stoker wrote a certain novel which led to the, now familiar, sight of Bela Lugosi and Christopher Lee morphing into rather unconvincing bats in order to gain access to the bed chamber of some troubled maiden. The Bard refers to bats by their archaic name Reremouse, and, as with many creatures of the night, gives them a somewhat rough time as they are skinned for witches spells and slaughtered for their leathery wings.

Oct 2015 - 3 witchesEye of newt, and toe of frog,
Wool of bat, and tongue of dog,

Macbeth

Some war with reremice for their leathern wings
To make my small elves coats, and some keep back
Midsummer Night’s Dream

Perhaps we should consider a bat event of our own on Midsummer, if only to re-address the balance of opinion? Have fun on All Hallows and do enjoy your bat-shaped sweets and cakes!
Put me right at pgcrow@yahoo.com

Paul Johnson

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Img 1: Middleton Murmeration by Stephen Cole, used under Creative Commons License 2.0; Img 2-3-4 Quarry Wood photography by Lorna Neville; Img 5: Flight of the Despised by Lemuel Cantos, used under CC2.0; Img 6: Bats heading east at sunset by Pip Wilson, used under CC2.0; Img 7: Grey headed flying fox by Duncan PJ, used under CC2.0; Img 8: Pallid Bat and skull (Antrozous pallidus) by Hilary Andrews, used under CC2.0; Img 9: Plecotus auritus by Ján Svetlík, used under CC2.0; Img 10: Pipistrellus pipistrellus by Emili V. López Álvarez used under CC2.0; Img 11: Pipsqueak [pipistellus pygmaeus] by Bill Tyne, used under CC2.0; Img 12: Eptesicus serotinus by Paulo Alves, used under CC2.0

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