Australasian big-eared bats, and how to (perhaps) single-handedly wipe out an entire species, 1890s-style (vesper bats part X)

About 12 species of big-eared Australasian bats are known as the, err, Australian big-eared bats and New Guinean bats. More formally, they are the Nyctophilus species. They're also known from some of the islands that surround New Guinea (like the Lesser Sundas), and also from New Caledonia (an endemic New Caledonian species, N. nebulosus, was named in 2002). Their presence has also been claimed for Fiji, but the evidence for this (based on specimens stored at the Natural History Museum in London) is inconclusive (J. E. Hill, in Parnaby 2002). Together with the New Guinea big-eared bat or Thomas's big-eared bat Pharotis imogene, these bats have often been given their own 'subfamily' (Nyctophilinae) or 'tribe' (Nyctophilini) (e.g., Tate 1942, Koopman & Jones 1970, McKenna & Bell 1997). I'll be referring to both Nyctophilus and Pharotis as the nyctophilins. Yes, we're now on part X of the vesper bat series: for the other parts, follow the links given below [adjacent photo shows a Mount Missim big-eared bat N. shirleyae, a species named as new in 2009].

The phylogenetic position of Nyctophilini is somewhat controversial, and I've put them in this part of the series simply because they've traditionally been positioned somewhere close to pallid bats and their relatives (Antrozoini) (the next vesper bat clade we'll be looking at). However, Volleth & Tidemann (1991) suggested that they might be part of Vespertilionini, though note that this name was used for a clade that included various vesper bats regarded in the series here as hypsugines, vespertilionins and members of the serotine clade.

As suggested by some of their common names, nyctophilins have particularly large ears. Like the huge ears of plecotins, these are usually joined at their bases by a web of skin across the forehead (this is not the case in the Small-eared nyctophilus N. microtis) [adjacent head illustration of N. gouldi from Parnaby (1992)]. Their ears are also prominently ribbed and very broad - about as broad across the base as they are long, actually. The snout in these bats is quite deep and grades gently into the braincase (recall that, in such vesper bats as woolly bats and myotines there is often a pronounced 'step' between the low snout and globular cranium). Their premolar dentition is reduced, with just one upper and two lowers (Tate 1941).

While vesper bats are generally said to lack nose leaves and other such structures, nyctophilins are the exceptions, since they possess small, horseshoe-shaped nose leaves around their nostrils. Behind the nose leaf, a bilobed convexity rises from the upper surface of the snout. It differs in shape and size among the species and (together with the width of the toothrow across the upper canines and penis anatomy) provides a reliable way of distinguishing some of the species. In N. geoffroyi, for example, the bump is tall and its two lobes are connected by an obvious membrane [see diagram below; from Parnaby (1992)], while in N. bifax the bump is low and the midline membrane is absent (Parnaby 1992).

It was suggested by Tate (1941) that the species within the group could be classified into several species groups, distinguishable via the size of their auditory bullae, ears, snout width and other features. It seems obvious that there are relatively large species with robust snouts and proportionally large auditory bullae and also relatively small species with more gracile snouts and proportionally small auditory bullae. However, as usual there are species that form a range of intermediates and overlaps in the middle and Dobson (1878) even suggested that all the species should be synonymised. That view is certainly not tenable, but a modern phylogenetic evaluation of the group is definitely required: do big, broad-snouted, big-eared species really go together, or might some be more closely related to the small species? And what of all the species named since Tate (1941) was published? Some of the post-1941 species - like N. microdon from New Guinea (named in 1954) - are particularly distinctive. The group was recently reviewed by Parnaby (2009) who named two new species (N. shirleyae and N. corbeni) and suggested the presence of seven 'species groups', one of which housed N. microdon on its own.

Nyctophilins seem to be ecologically flexible, adaptable bats, able to forage in woodland, scrubland and arid habitats, and they've even moved into urban areas. They have a slow, fluttering flight and are highly manoeuvrable, pursuing insects in the open air but also gleaning from vegetation and even the ground. Some Nyctophilus species are even able to take off from the ground with a single leap and downward flap of the wings; in this respect they're somewhat like the Pallid bat (Antrozous pallidus) [adjacent photo of N. gouldi in flight by Terry Reardon; from here].

A Nyctophilus species described from a single fossil skull - N. howensis from Lord Howe Island - might have survived into recent times (or perhaps still be extant), since eyewitness accounts of a large bat on the island seem to match it (Nowak 1999). A supposedly distinctive Nyctophilus-like bat was described from Mount Lamington, Papua New Guinea, in 1968 and named Lamingtona lophorina. However, more recent appraisals have regarded it as a synonym of N. microtis (Hill & Koopman 1981). Other species remain very poorly known. N. heran from Lembata Island, Indonesia, is only known from a single specimen.

The sad, sad tale of Pharotis imogene

A really obscure and apparently very rare vesper bat from New Guinea - the New Guinea big-eared bat or Thomas's big-eared bat Pharotis imogene - is an assumed close relative of the Nyctophilus species. Like those bats, Pharotis has both large ears and a horseshoe-shaped nose leaf (Nowak 1999). Its snout is shorter than that of the Nyctophilus bats and its ears are larger. Not much else is known of it, other than that it inhabits, or inhabited, lowland sclerophyll woodland in Central Province, southeastern Papua New Guinea. Below is what seems to be the only available photo: I borrowed it from here, but you might recognise it from Walker's Mammals of the World (where it's credited to "Howard Hughes through Australian Museum Sydney").

All 45 known specimens were collected in 1890: all are female, and there are suspicions that they represented a single maternity colony. If so, it's plausible that the collector single-handedly wiped out the very last colony. I totally understand the necessity of collecting zoological specimens. We need to do it if we want to document the existence of populations without ambiguity. But I confess to being a little confused as to why someone would proceed to euthanise and take home every single individual from a small colony. Still, it was 1890 I suppose. A clue that all is not lost comes from a possible specimen, also from Central Province, collected in 1985. Unfortunately, this individual was destroyed (I don't know why) in 1992 and never had its identity confirmed.

Nyctophilins remain somewhat enigmatic. Superficially a little like plecotins - and occasionally confused with them in the 1800s - they were later regarded as close to antrozoins, and more recently suggested to be close to the clade that includes serotines, hypsugines and vespertilionins. Behaviourally flexible and morphologically aberrant compared to other vesper bats, they also contain more than their fair share of mysterious species. There are those known from just a few, or even single, specimens, those of uncertain provenance, and those suspected of now being extinct. And if you want to know more, you'll have to get into the primary literature, for it's time for us to move on once more.

For previous Tet Zoo articles in the vesper bats series, see...

• Introducing the second largest mammalian 'family': vesper bats, or vespertilionids
• The vesper bat family tree: of myotines, plecotins, antrozoins, and all those cryptic species (vesper bats part II)
• Bent-winged bats: wide ranges, very weird wings (vesper bats part III)
• Of southern African wing-gland bats, woolly bats, and the ones with tubular nostrils (vesper bats part IV)
• The many, many mouse-eared bats, aka little brown bats, aka Myotis bats (vesper bats part V)
• Long-eared bats proper: Plecotus and other plecotins (vesper bats part VI)
• Desert long-eared bats - snarling winged gremlins that take scorpion stings to the face and just don't care (vesper bats part VII)
• Hairy-tailed bats: a tale of furry tails, red coats, cold tolerance, migration and sleeping out in the open (vesper bats part VIII)
• Robust jaws and a (sometimes) 'greenish' pelt: house bats (vesper bats part IX)

And for previous Tet Zoo articles on bats, see...

• Desmodontines: the amazing vampire bats
• Giant extinct vampire bats: bane of the Pleistocene megafauna
• Camazotz and the age of vampires
• Dark origins: the mysterious evolution of blood-feeding in bats
• A new hypothesis on the evolution of blood-feeding: food source duality involving nectarivory. Catchy, no?
• Oh no, not another giant predatory flightless bat from the future
• The most terrestrial of bats
• I stroked a pipistrelle
• Red bats
• We flightless primates
• Big animalivorous microbats
• Hidden in plain sight: discovering cryptic vesper bats in the European biota
• PROTOBATS: visualising the earliest stages of bat evolution

Refs - -

Dobson, G. E. 1878. Catalogue of the Chiroptera in the Collections of the British Museum. British Museum: London.

Hill, J. E. & Koopman, K. F. 1981. The status of Lamingtona lophorhina McKean and Calaby, 1968 (Chiroptera: Vespertilionidae). Bulletin of the British Museum (Natural History), Zoology Series 41, 275-278.

Koopman, K. F. & Jones, J. K., Jr. 1970. Classification of bats. In Slaughter, B. H. & Walton, D.W. (eds.) About Bats: a Chiropteran Biology Symposium, pp. 22-28. Southern Methodist University Press, Dallas.

McKenna, M. C. & Bell, S. K. 1997. Classification of Mammals: Above the Species Level. Columbia University Press (New York).

Nowak, R. M. 1999. Walker's Mammals of the World, Sixth Edition. The Johns Hopkins University Press, Baltimore and London.

Parnaby, H., 1992. An interim guide to identification of insectivorous bats of south-eastern Australia. Technical Reports of the Australian Museum 8, 1-33.

- . 2002. A new species of long-eared bat (Nyctophilus: Vespertilionidae) from New Caledonia. Australian Mammalogy 23, 115-124.

- . 2009. A taxonomic review of Australian greater long-eared bats previously known as Nyctophilus timoriensis (Chiroptera: Vespertilionidae) and some associated taxa. Australian Zoologist 35, 39-81.

Tate, G. H. H. 1941. Results of the Archbold Expeditions. No. 40. Notes on vespertilionid bats of the subfamilies Miniopterinae, Murininae, Kerivoulinae and Nyctophilinae. Bulletin of the American Museum of Natural History 78, 567-597.

- . 1942. Results of the Archbold expeditions. No. 47. Review of the vespetilionine bats, with special attention to genera and species in the Archbold collection. Bulletin of the American Museum of Natural History 80, 221-297.

Volleth, M., & Tidemann, C. R. (1991). The origin of the Australian Vespertilioninae bats, as indicated by chromosomal studies Zeitschrift für Säugetierkunde, 56, 321-330