MAMMAL NAMES | Birds of the Night:

The Myriad Illuminating Names of Ireland's Bats

Our investigations of the names of Irish mammals over the last number of months have thus far looked at those of the mustelids and rodents, mammals that can be found in many of the earthly domains on the island, from the fields and woods to the rivers and streams. However, this month it is time to turn our eyes to the sky and look at the many names of the only mammals to truly inhabit this aerial kingdom – the bats. There are an incredible array of names for bats, their English, Irish, and scientific names, along with more archaic terms for them, combining to shine a spotlight on many different aspects of the form and nature of these winged wonders that dart through the darkness each night throughout the island of Ireland.

It is perhaps best to simply begin with the term ‘bat’ itself, a name that appears to have fascinating origins. The word ‘bat’ seems to be an altered form of the Middle English word bakke which dates from the early fourteenth century, and which is probably related to the Old Swedish term natbakka and the Old Danish natbakkae, which mean ‘night bat’, as well as the Old Norse term for ‘bat’, leðrblaka, that literally means ‘leather flapper’. And these terms can ultimately be traced to the term blak– in Proto-Germanic, itself thought to derive from a Proto-Indo-European root bhlag–, meaning ‘to strike’, and, if this is correct, the original sense of the word ‘bat’ was likely ‘flapper’. As for how the ‘k’ sound in bakke turned into the ‘t’ sound in ‘bat’, this is unknown, but it may possibly be due to this word becoming mixed up with the Latin word blatta, meaning ‘moth’ or ‘nocturnal insect’.

A reference to the flapping wings of the bat can also be detected in some of the more archaic terms for these aerial maestros. For instance, the word in Old English for ‘bat’ was hreremus, derived from the word hreran, meaning ‘to shake’. Similarly, ‘rattle-mouse’ was once a term used in English for the bat, as was the term ‘flitter-mouse’ and its variants ‘flicker-mouse’ and ‘flinder-mouse’, which all seem to copy the German word for ‘bat’, fledermaus, that derives from the word fledaron in Old High German, meaning ‘to flutter’.

The English name ‘bat’ itself, then, and many other terms for this little mammal, refer to what is undeniably its most characteristic feature, the wing, and this is also true of one of the Irish names for the bat. While the word often used for ‘bat’ in Irish is ialtóg, another name is sciathán leathair, meaning ‘leather wing’.

Of course, the name for the bats’ order is also derived from the wing. This name, Chiroptera, refers to the specific nature of the wing in these mammals which is formed from the elongated fingers of the hand, the possible evolution of which was outlined in an earlier post. Thus, ‘Chiroptera’ derives from the Greek words chiros and pteron, meaning ‘hand’ and ‘wing’, respectively. Indeed, pteron also turns up in the name of another group of flying animals that would have once darkened the skies of Ireland, albeit millions of years before the bats first evolved – the pterosaurs (‘wing lizards’) and their best-known member, the pterodactyl (‘wing finger’).

In fact, as noted in the earlier post, apart from the bats and pterosaurs, there is only one other vertebrate group ever to have evolved true powered flight – the birds – and this point leads us to a more poetic term for the bats.

Although the bats are second only to the rodents among the mammals in terms of species numbers, with the order Chiroptera comprised of over 1,100 species, they are still overwhelmingly outnumbered by the birds, who can claim around 10,000 living species. By the time the bats first evolved, over 50 million years ago, birds had already ruled the air for millions of years, the skies having been left to them alone with the extinction of the pterosaurs at the end of the Age of Dinosaurs around 66 million years ago. Thus, sharing a world with the dominant birds who mostly hunted during the day, the bats probably evolved to hunt at night to avoid the attentions of avian raptors and to take advantage of the plentiful food source in the form of the many flying insects that appear after the sun sets. So, this seems to be how the bats became, as they are sometimes referred to, the ‘birds of the night’.

The general names for the bats are very interesting and evocative, then, and this is a trend that continues when it comes to the various names that have been given to the nine native bat species resident in Ireland.

When it comes to the bats of Ireland, a general observer could be forgiven for seeing them all as pretty much the same – a bat is a bat. It is easy to come to such a conclusion, especially seeing as they only come out at night so are less familiar to people than day-dwelling mammals, while their individual forms are hard to make out not only due to darkness but to the speed at which they fly through the air. Certainly, the bats of Ireland are all very similar in some respects, such as their size, with the largest only reaching 15–20 grams in weight and the smallest about 5–8 grams, and they all have the characteristic skin-wings of their order. However, when we look closer it becomes clear that there are some dramatic differences between the individual species, and these are well reflected in their names.

Take the brown long-eared bat, for instance, one of the island’s most common bats, which is widespread across the mainland and can also be found hunting in the dark on many offshore islands. As its English name suggests, this bat’s most distinctive feature is its ears, which are far longer than those of any other bat in Ireland and more like those of a rabbit or a gremlin, as can be seen in the cover picture above. Thus, it is unsurprising that this bat’s scientific and Irish names also derive from these impressively outsized lugs.

The scientific name for this bat is Plecotus auritus, the genus name being derived from two Greek words, pleko, meaning ‘twist’ or ‘fold’, and otos, meaning ‘of the ear’, while the species name, auritus, is from Latin and simply means ‘eared’. The Irish name, ialtóg fhad-chluasach, is quite similar to the English one and just means ‘long-eared bat’.

These ears are fundamental to this little 7–12-gram bat’s life as their large size, combined with superb hearing, amplify the low sounds produced by the beating of insects’ wings, allowing these bats to zero in on their prey.

But if the brown long-eared bat has super ears, another bat in Ireland has a super nose. This is the lesser horseshoe bat, which is found only in the west of the island in the counties along the coast, and whose seemingly strange name is a direct reference to the form of its spectacular schnozz. Unlike the other bats on the island, the nose of this 6–9-gram bat is very complicated in structure, having a series of what are called nose leaves which form a triangular shape above the nostrils and arc into a horseshoe shape below them, hence the name.

And, in a similar manner to the situation with the brown long-eared bat, the scientific and Irish names of this bat are also related to its most characteristic feature. The scientific name is Rhinolophus hipposideros, which comes from the Greek, with rhinos meaning ‘of the nose’, lophos ‘a crest’, hippos ‘horse’, and sideros ‘iron’. The Irish names, in turn, are ialtóg crúshrónach, the ‘horseshoe-nosed bat’, and crú-ialtóg beag, the ‘small horseshoe-bat’.

Also, just like the brown long-eared bat again, this biological super-structure is extremely useful when this bat is on the hunt for tasty insects like daddy-longlegs or moths or flies to snaffle, the nose leaves allowing them to modulate the ultrasound beams they emit from their nostrils to detect prey, concentrating them into a narrower, focused beam or a much more diffuse ‘sonic glow’.

The ultrasound frequencies the lesser horsehoe bat uses are far higher than those emitted by any other bat in Ireland, which is another thing that marks them out as different. But the ultrasound frequencies of some of the other bats on the island are also very important in telling one form from another, as is reflected in the names of some of Ireland’s most common bats – the pipistrelles.

The common pipistrelle and the soprano pipistrelle are probably Ireland’s most widespread and plentiful bats, although, despite its name, the former may be less abundant than the latter. However, for a long time up until recent decades, no one realised that the soprano pipistrelle was a separate species at all and its members were thought to belong to the ranks of the common pipistrelle. But then genetic evidence revealed that what was once thought to be the common pipistrelle was actually two species.

As you might expect, these two species are almost impossible to tell apart from each other and there are only very minor physical differences, the soprano pipistrelle being very slightly smaller than the 5–8-gram common pipistrelle so likely holding the title of ‘Ireland’s smallest bat’. Indeed, this lesser size is reflected in the soprano pipistrelle’s species name, Pipistrellus pygmaeus, with pygmaeus meaning ‘pygmy’, while the common pipistrelle retains the name Pipistrellus pipistrellus which once referred to them both. However, there is another way that these closely related bats can be distinguished from each other, as is revealed by a closer look at their names.

The genus name for these bats, Pipistrellus, probably comes from the verb pipio in Latin, meaning ‘I squeak’, while the ending –ellus also comes from the Latin and just means ‘small’. Pipistrellus, then, means ‘little squeaker’, but it is now clear that these little bats do not squeak in the very same way and this explains the English name for the soprano pipistrelle. While the common pipistrelle emits ultrasounds at a frequency of 45 kilohertz, the soprano pipistrelle emits them at a higher frequency of 55 kilohertz, hence the soprano reference; the soprano being the singer with the highest-pitched voice in us humans, the word itself deriving from the Italian sopra, meaning ‘above’.

And it has been suggested that an appropriate Irish name for the soprano pipistrelle would also include this soprano reference. While the common pipistrelle is referred to in Irish as ialtóg fheascrach, or the ‘bat of the evening’, it is thought that the soprano pipistrelle should be called ialtóg fheascrach sopránach.

Of course, it has recently become clear that not only are the common pipistrelle and the soprano pipistrelle separate species, but that there is a third species of pipistrelle on the island – the slightly larger Nathusius’s pipistrelle. This bat is one of the most recent arrivals in Ireland, having been first recorded only just over 20 years ago, in 1996. But though it is still not as abundant as its pipistrelle relatives on the island, it appears to have spread to more areas since it was first identified here, and its spread in general is thought to be related to global warming.

In any case, its name is not as evocative of its nature as is that of the soprano pipistrelle, with the scientific name, Pipistrellus nathusii, and the Irish name, ialtóg Nathusius, meaning the very same thing as the English name, with Nathusius simply being the nineteenth century naturalist that this bat is named after.

Indeed, many of the other bats in Ireland have names of this type, as you have Natterer’s bat, Daubenton’s bat, and Leisler’s bat, and these are all named in honour of naturalists and biologists from the eighteenth and nineteenth centuries. These names, then, tell us who these bats are named to honour, but they do not reveal much about the bats themselves, so we must look to their scientific and Irish names for greater enlightenment.

Well, when we look at the names of the first two it is immediately clear that they are closely related as they both belong to the genus Myotis. This name, Myotis, comes from two Greek words, mys, meaning ‘mouse’, and otos, meaning ‘of the ear’, as we already saw in the case of the brown long-eared bat. The members of Myotis, then, are the ‘mouse-eared bats’.

And while the species names of these two bats follow the pattern of the English names, being Myotis nattereri and Myotis daubentonii, respectively, and the same can be said for the Irish name of the former, which is ialtóg Natterer, the Irish name of the latter is much more illuminating. The Irish name for Daubenton’s bat is ialtóg uisce, or the ‘water bat’, and this is presumably a reference to the distinctive way this little bat flies; low over still or slow-flowing water.

And before we move on to Leisler’s bat, we might stay with the mouse-eared bats for a moment, as they can claim one more species on the island which has the most revealing names of them all. This is the whiskered bat, so named as this rare little bat possesses long, fine whiskers sprouting from the corners of its mouth and its lips. This feature is also at the root of its species name, Myotis mystacinus, mystacinus deriving from the Greek word mystakos, meaning ‘of the moustache’. The whiskered bat’s scientific name, then, ultimately translates as the ‘mouse-eared moustached one’.

The Irish name also refers to the hair of this bat, but it is not the whiskers but the coat, this name being ialtóg giobach, or the ‘shaggy bat’, and it does indeed have shaggy fur.

This leads us nicely back to Leisler’s bat, as it is sometimes referred to as the ‘hairy-armed bat’. And before we look more closely at its other names we should also be aware that this bat can claim a title on the island that no other form can, that of ‘Ireland’s largest bat’, tipping the scales at up to a mighty 20 grams.

And though the species name and Irish name of this bat are not so grand as this honorific, cleaving as they do very closely to the usual English name of Leisler’s bat – being Nyctalus leisleri and ialtóg Leisler, respectively – the genus name, Nyctalus is much more interesting in its makeup. Nyctalus is a mixture of the Greek word for ‘night’, nyx, and the Latin word for ‘wing’, ala, so this translates into the quite poetic ‘night wing’.

This ‘night-winged bat of Leisler’, then, neatly returns us to that most poetic term for the bats. By now it should be clear that these little denizens of the dark in Ireland are, like the avian rulers of the day, very diverse in form and behaviour, range and habitat. In myriad different ways these moonlight maestros dominate the dark skies of Ireland, truly deserving their description as birds of the night.