Desert long-eared bats - snarling winged gremlins that take scorpion stings to the face and just don't care (vesper bats part VII)

In the previous article we looked at the majority of taxa included within the 'plecotin' group. As discussed therein, while there may be a clade of 'core plecotins', the traditional concept of the group might be paraphyletic. Some plecotins - Idionycteris in particular - might even be outside the clade that includes plecotins and all other vespertilionines. Here we look at a particularly interesting group of vesper bat species that might, or might not, be part of the 'core plecotin' clade: the desert long-eared bats (Otonycteris). What makes desert long-eared bats especially interesting is that, along with being desert-dwelling specialists (as you'd guess by the name), they're ground-foraging gleaners, described as among the most predatory of Palaearctic bats, and well able to prey regularly on scorpions, solifugids and perhaps even on lizards. They also look really, really scary. [Adjacent photo by Charlotte Roemer, from wikipedia].

Occurring throughout arid north Africa and the Arabian Peninsula, and also in central Asia as far east as Pakistan, desert long-eared bats occur in true desert habitats as well as in semi-deserts and oases. They roost in rocky crevices and sometimes in buildings. Like other plecotins, they have proportionally large ears (up to 40 mm long: that's about half of their head + body length). In contrast to Plecotus and similar taxa, their ears are not connected at their bases by a band of skin. These are large vesper bats, with a mass of 18-30 g and a wingspan of 35-40 cm. [Photo below - showing a female O. hemprichi captured in Sinai, Egypt - by P. Benda, from Benda et al. (2008)].

During recent decades most authors have classified all Otonycteris populations as belonging to a single, highly variable species (O. hemprichi) sometimes known as Hemprich's long-eared bat*. However, variations in skull shape have led to the suggestion that this might actually represent a species complex, or at least deserve splitting into several subspecies. Benda & GvoždÃk (2010) examined both morphology and genetics and found that the desert long-eared bats of Africa and the Middle East could be readily distinguished from the central Asian ones, and they concluded that the two should be regarded as separate species. The central Asian species (O. leucophaea) could, in turn, be split into three subspecies.

* Incorrectly spelt 'Hempriche's long-eared bat' in one or two books. The species name is spelt hemprichi by some authors, and hemprichii by others.

Taking scorpion stings to the face and other such acts of badassery

The eyes in these bats always look relatively large, and they have an alert, aggressive demeanour (I'm basing all this on photos: I've never knowingly* seen a live one!). Combined with a pale coat, semi-translucent wing membranes, large ears and impressive teeth, this look makes these bats superficially resemble the much larger, predatory megadermatids (false vampires and ghost bats). Indeed, their low aspect ratio wings and low wing loading led to suggestions that they're most likely ground-feeding gleaners - possibly of small vertebrates (Norberg & Fenton 1988) - long before this behaviour was properly documented. Observations made since show that they land briefly (2-5 seconds) on the ground to catch prey before chewing nosily, taking off and eating the prey in flight: beetle larvae have been found as stomach contents in some studies, demonstrating a ground-gleaning habit beyond doubt. Holderied et al. (2010) confirmed that, like megadermatids, Otonycteris uses prey-generated noises when hunting, sometimes detecting scorpions via their walking sounds. These bats do use quiet echolocation as well.

* I did see many bats while in Morocco, but was never able to identify them.

Desert long-eared bat diet seems to mostly consist of such terrestrial arthropods as scorpions, solifugids, beetles, cockroaches and crickets, making them "the strongest predator among Palearctic insectivorous bats" (Arlettaz et al. 1995, p. 875). They drop right on to their scorpion prey and may be repeatedly stung on the body and face while subduing them: amazingly, this seems to have no effect and the bats display no evidence whatsoever of selecting scorpions based on their size or toxicity (Holderied et al. 2010). The conclusion must be that they're generalist predators of scorpions as a whole. They eat the whole scorpion - sting and all - and more than 70% of their droppings are made up of scorpion remains at some times of the year.

Norberg & Fenton (1988) suggested that Otonycteris might include small vertebrates in its diet on the basis of wing loading, wing shape and body size. Arlettaz et al. (1995) speculated that Otonycteris may well be in the habit of preying occasionally on the bow-fingered gecko species Cyrtodactylus russowi [for much more on bow-fingered geckos see Lamellae, scansor pads, setae and adhesion... and the secondary loss of all of these things (gekkotans part IV)].

The idea of a predatory vesper bat that attacks, kills and consumes venomous scorpions as well as solifugids and (perhaps) lizards is undeniably badass even though - granted - these prey animals might be just a few centimetres long (the gecko in question is 11 cm long) [below is an image I found in the Tet Zoo archives: it depicts the age-old battle between desert long-eared bats and scorpions. For a larger version, look at the Tet Zoo facebook page]. Arlettaz et al. (1995) found scorpions, solifugids and grasshoppers to form the bulk of the desert long-eared bat diet [see their diagram of diet broken down taxonomically, above], but Benda et al. (2008) reported scarabaeid beetles to be more important. However, the data in the latter study came from an oasis where human impact might influence the bat's foraging habits and choice of prey.

Roaming all over the cladogram

It has proved difficult to classify desert long-eared bats, and don't assume that they've always been recovered close to (or within) 'core plecotins'; in fact, several radically different phylogenetic hypotheses have been published. As we saw in the previous article, 'core plecotins' have a cute, short-faced look whereas Otonycteris looks rather more like snarling demon from hell. Based on this most empirical and scientific rigorous of evaluations, I think it can certainly be doubted that Otonycteris is a plecotin. Koopman & Jones (1970) regarded Otonycteris as a nycticein, close to evening bats (Nycticeius), little yellow bats or rhogeëssa bats (Rhogeesa) and house bats (Scotophilus), but karyotypic evidence later suggested an affinity with plecotins (e.g., Qumsiyeh & Bickham 1993).

Hoofer & van den Bussche (2001) found Otonycteris to be well removed from a plecotin clade, and to instead be the sister-taxon to an Antrozous (pallid bats) + Rhogeesa clade. In other words, they found Otonycteris to be part of Antrozoini, a clade we haven't yet discussed in this series (don't worry, it's coming soon). This is really interesting given that pallid bats at least are notable for their robust jaws and teeth and Otonycteris-like habit of ground-gleaning and preying on (relatively) large animals.

Since then, a larger analysis has put Otonycteris back with the plecotins (Roehrs et al. 2010): sometimes within 'core plecotins' and sometimes within a Plecotini + Lasiurini clade. I think it's safe to say that the phylogenetic affinities of these fascinating predatory bats have yet to be resolved, though an affinity with plecotins in the broad sense does seem most widely supported.

So... that's all of the plecotin or plecotin-like bats out of the way. Next: hairy-tailed bats or hoary bats. 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)

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 - -

Arlettaz, R., Dandliker, G., Kasybekov, E., Pillet, J.-M., Rybin, S. & Zima, J. 1995. Feeding habits of the long-eared desert bat, Otonycteris hemprichi (Chiroptera: Vespertilionidae). Journal of Mammalogy 76, 873-876.

Benda, P. & GvoždÃk, V. 2010. Taxonomy of the genus Otonycteris (Chiroptera: Vespertilionidae: Plecotini) as inferred from morphological and mtDNA data. Acta Chiropterologica 12, 83-102.

Benda, P, Dietz, C., Andreas, M., Hotovâý, J., LuÄan, R. K., Maltby, A., Meakin, K., Truscott, J. & Vallo, P. 2008. Bats (Mammalia: Chiroptera) of the Eastern Mediterranean and Middle East. Part 6. Bats of Sinai (Egypt) with some taxonomic, ecological and echolocation data on that fauna. Acta Societas Zoologicae Bohemicae 72, 1-103.

Holderied M, Korine C, & Moritz T (2010). Hemprich's long-eared bat (Otonycteris hemprichii) as a predator of scorpions: whispering echolocation, passive gleaning and prey selection. Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology PMID: 21086132

Hoofer, S. R. & Van Den Bussche, R. A. 2001. Phylogenetic relationships of plecotine bats and allies based on mitochondrial ribosomal sequences. Journal of Mammalogy 82, 131-137.

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. Dallas: Southern Methodist University Press.

Norberg, U. M. & Fenton, M. B. 1988. Carnivorous bats? Biological Journal of the Linnean Society 33, 383-394.

Qumsiyeh, M. B. & Bickham, J. W. 1993. Chromosomes and relationships of long-eared bats of the genera Plecotus and Otonycteris. Journal of Mammalogy 74, 376-382.

Roehrs, Z. P., Lack, J. B. & Van Den Bussche, R. A. 2010. Tribal phylogenetic relationships within Vespertilioninae (Chiroptera: Vespertilionidae) based on mitochondrial and nuclear sequence data. Journal of Mammalogy 91, 1073-1092.