Yay, more vesper bats! The groups we’ve looked at so far have – in anatomical terms – been pretty conservative. This time round we’re looking at a really remarkable group; as is so often the case, their familiarity (relative to so many others of the world’s bats) means that we tend to forget or ignore how remarkable they are. Ordinarily, you might balk at the idea of a mammal whose ears are longer than the combined length of its head and body. Yet this is exactly what we have in the long-eared bats (or, in the Plecotus species at least). Yes, welcome to the world of… yeah, long-eared bats, or plecotins…
This small group of vesper bat genera are alike in – by now I think it’s obvious – possessing proportionally enormous ears that are often joined at their bases. The auditory bullae are also unusually large, large glands (termed pararhinal glands) tend to be present on the snout and face, and the premolars are reduced in size (and sometimes absent). This reduction and occasional absence of premolars once led some authors (Tate 1942) to regard plecotins as myotines (that is, as especially close relatives of the mouse-eared or myotis bats). However, molecular phylogenies tend to find them as the ‘most basal’ lineage within Vespertilioninae, the vesper bat clade that also includes serotines, pipistrelles and noctules (e.g., Volleth & Heller 1994, Roehrs et al. 2010). [Composite image above shows - l to r - P. sardus (by Mauro Mucedda, from wikipedia), skull of the Ethiopian long-eared bat P. balensis (from Kruskop & Lavrenchenko (2000)), and Western barbastelle Barbastella barbastellus].
Morphological and molecular studies find ‘core plecotins’ to be monophyletic
(e.g., Leniec et al. 1987, Frost & Timm 1992, Bogdanowicz et al. 1998) – the adjacent cladogram (from Tumlison & Douglas (1992)) shows a possible phylogeny for the taxa involved. But the monophyly of all taxa conventionally allied with Plecotus has never been established; indeed, there are some indications that they form a paraphyletic assemblage to some of the remainder of Vespertilioninae (Volleth & Heller 1994, Hoofer & Van Den Bussche 2003, Roehrs et al. 2010, Agnarsson et al. 2011), in particular to the hairy-tailed bats or lasiurins.
Here in Europe, the familiar long-eared bats are those included in Plecotus. About 11 species are currently recognised (Spitzenberger et al. 2006) (for discussion of some of the more recently named European ones, see Hidden in plain sight: discovering cryptic vesper bats in the European biota); they occur from the Canary Islands and Cape Verde Islands in the west all the way to Japan in the east, occurring across Eurasia as well as in coastal north Africa.
American long-eared bats
A small group of American vesper bats with long ears were often included within Plecotus but are now generally classified on their own as Corynorhinus. They’re known as the American long-eared bats, big-eared bats or lump-nosed bats. They do look much like the Plecotus species, but have a longer, more dorsally convex rostrum, a more bulbous cranium and a narrower, more blade-like tragus. The adjacent drawing shows the head of Townsend’s big-eared bat C. townsendii, specifically the Ozark subspecies C. t. ingens. Note the huge, bulbous pararhinal glands. The same species is shown in flight below [image by US Bureau of Land Management, from wikipedia].
Like Plecotus bats, American long-eared bats often hover and they’re able to pick arthropod prey off foliage and the walls of buildings. Fossils identified as Corynorhinus are known from the Late Miocene, Pliocene and Early Pleistocene of Europe (Topál 1989, Spitzenberger et al. 2006); Plecotus itself is known from the Early Pliocene onwards, but its lineage presumably extends back to the Miocene as well (Topál 1989). Plecotins as a whole seem to go back to the Early Oligocene if Quinetia misonnei from Belgium has been correctly identified (Horáček 2001).
Allen’s big-eared bat and the Spotted bat
The southwestern US and Mexico are inhabited by another big-eared vesper bat once included within Plecotus: Allen’s big-eared bat or the Lappet-eared bat Idionycteris phyllotis (in contrast to many of the species I’m covering in this series, there are loads of photos of it online). A denizen of wooded mountainous areas, it possesses paired fleshy lappets that project over the forehead from the bases of the ears. Allen’s big-eared bat shares osteological characters with Plecotus and the Spotted bat or Pinto bat Euderma maculatum (these include a postorbital expansion of the zygomatic arch, an anteriorly rounded auditory bulla and single-rooted lower fourth premolar), and morphology-based analyses have found Idionycteris and Euderma to be sister-taxa, with Plecotus, Corynorhinus and Barbastella successively more distant (Tumlison & Douglas 1992). Despite this strong anatomical similarity, DNA-based phylogenies have found Allen’s big-eared bat to be the sister-taxon to the enormous clade that includes unambiguous plecotins and all other vespertilionines (Roehrs et al. 2010).
The remarkable Spotted bat or Pinto bat is another American member of this big-eared vesper bat group. Unknown until 1890, its presence was only confirmed in Canada, Oregon and Colorado in 1980 and it’s been described by some authors as North America’s rarest mammal (Nowak 1999). Its colouration is really striking: the ground colour of the body fur is reddish brown to black, the underside is white, and there are three large white spots on its dorsal side – one on each shoulder, and one over the small of the back. The painting of this bat below is by Carel Brest van Kempen (of Rigor Vitae) and appears here with permission.
Unlike other Plecotus-like bats, the Spotted bat seems not to be a slow-flying gleaner, but a fast-flying, high-level hunter. A mummified specimen, carbon-dated to about 9100 years old (and hence to the early Holocene), has been discovered in a cave in Grand Canyon National Park, Arizona (Mead & Mikesic 2001). It has all its fur and wing membranes preserved.
Barbastelles: short-eared long-eared bats?
The barbastelles (Barbastella) are also similar to Plecotus and likely closely related to them [adjacent photo of B. barbastellus from Corsica Nature]. Barbastelle ears are nowhere near as long as those of Plecotus or Corynorhinus, but they’re very large: so large that the small eyes are surrounded by the ear’s bases. Because some chromosomal studies have found barbastelles to be closer to Plecotus and Corynorhinus, or to Plecotus and Otonycteris, than to other plecotins, the possibility exists that barbastelle ears are reduced relative to their ancestral state (Qumsiyeh & Bickham 1993, Volleth & Heller 1994). Alternatively, gigantic ears evolved at least twice among plecotins.
Barbastelles have very long fur and are typically very dark, being dark brown or black (a very unusual colour for a bat, despite what cartoons show). The hairs are ‘frosted’, with yellowish or creamish tips. Hair extends onto the wing and tail membranes and the face is extremely short and flat. Those pararhinal glands on the snout are particularly large, as they are in Corynorhinus. Despite their affinity to Plecotus, barbastelles (like the Spotted bat) seem to be aerial hawkers, though they may also practise some gleaning. They seem to be specialist predators of moths and are reportedly very cold-tolerant.
The best-known barbastelle is the mostly European B. barbastellus. A second species, B. leucomelas, supposedly occurs across Asia from the Caucasus to Japan and central China, and has also been reported from the Sinai Peninsula and Eritrea. A third species, B. beijingensis, was named from China in 2007 (Zhang et al. 2007). It’s larger than the other barbastelles and with more prominent canines and upper fourth premolars. Recently it’s been suggested that B. leucomelas is actually at least two species and that the name B. leucomelas should be restricted to the barbastelles of the Sinai Peninsula and its surrounds (Zhang et al. 2007, Benda et al. 2008); the remainder should be known as B. darjelingensis (Benda & Mlíkovský 2008). Barbastelles were recently reported from Laos and Vietnam (the species status of these populations is uncertain, but they might be B. darjelingensis) (Kruskop & Shchinov 2010). It might be that barbastelles are present – but so far overlooked – throughout the Asian tropics.
Tropical long-eared bats or African long-eared bats – not really long-eared bats at all
There’s also a group of endemic African bats with long ears: the Laephotis species, sometimes called tropical long-eared bats or African long-eared bats. Until recently I had assumed that they were morphologically very similar to Plecotus and kin, in part because a particularly well known writer and artist specialising on African mammals makes this appears so in his published work… but it ain’t the case. Laephotis bats much resemble the North American Histiotus species (we’ll get to them later) and have often been classified together with them in a ‘histiotine’ group. However, it’s now evident that the two aren’t close at all: Histiotus is most likely a serotine while Laephotis seems to be part of the hypsugine clade, probably being closest to the African Neoromicia species (Stadelmann et al. 2004, Roehrs et al. 2010, Agnarsson et al. 2011).
This means that any similarities between African long-eared bats and true, plecotin long-eared bats are convergent. That’s ok, since Laephotis doesn’t look much like plecotins in detail: as you can see from my drawing here of L. namibensis, the muzzle is longer, the eyes look smaller, and the ears lack a midline connection and are altogether different from those of plecotins.
Little is known about African long-eared bats: they’ve most often been reported from savannah habitats, high-altitude grassland or scrubland (typically roosting under bark). The populations of more arid habitats are often quite pale-furred. The fact that some specimens have been observed above or close to standing water led Stanley & Kock (2004) to suggest that members of this group might be regular drinkers: I have no idea how common drinking is in bats, but I don’t think anybody does… at least, not for obscure species like these. While four species are currently recognised (all of which were named in the 20th century: two in 1971), there has been considerable confusion as to which species some populations belong, and morphometric studies have failed to convincingly separate L. namibensis and L. wintoni (Kearney & Seamark 2005).
Ok, you could argue that Laephotis shouldn’t have been discussed here but elsewhere in the series. But anyway, that’s most – but not all – of the plecotins/plecotin-type vesper bats out of the way. Coming next: desert long-eared bats… the ones that look scary.
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)
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 – -
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