Antrozoins: pallid bats, Van Gelder's bat, Rhogeessa... Baeodon!! (vesper bats part XI)


Vesper bats. Well done with sticking with it all so far - I have lots of non-bat stuff I want to cover, but (for reasons soon to be explained) I need to get this series finished. With this article - part XI in the series (XI) - we are not at the end. But we are at the beginning of the end. Look at the cladogram below to see where we are, and follow the links below if you want to know what happened before. We arrive now at Antrozoini...

The Pallid bat or Desert bat Antrozous pallidus of western North America and Cuba is a large (wingspan 37-41 cm; mass 20-35 g), fairly scary-looking, big-eared vesper bat with proportionally large eyes, a square-shaped muzzle and creamy or yellowish dorsal fur [image above by Anne-Marie, formerly of the apparently defunct Pondering Pikaia]. It superficially resembles the Old World desert long-eared bats (Otonycteris), though this resemblance most likely represents convergence. Semi-circular ridges surround each nostril and its snout glands produce a skunk-like odour.

Like some megadermatids (false vampires and ghost bats), it flies low to the ground (from 50 cm to 2.5 m up), searching for low-flying or grounded insects, arachnids, rodents and lizards, and (in another parallel with megadermatids), it may use passive acoustic cues to find prey rather than echolocation. It may alight on the ground when capturing prey; its pelvic and hindlimb bones are said to be especially robust and hence to reflect this behaviour, though I don't know if this has been properly demonstrated. It's a desert specialist and can go for a month without drinking (all water coming from prey animals); also notable is the large amount of co-operation recorded among females: "Female roost mates have been observed helping each other through labor and helping to locate lost young" (Graham 2002).

The Pallid bat is not a phylogenetic singleton: it seems to be closely related to the peculiar Van Gelder's bat Bauerus dubiaquercus of Mexico, Belize, Honduras, Guatemala, El Salvador and Costa Rica. In fact, Bauerus has been included in the genus Antrozous by some. While both are somewhat similar, Bauerus is darker with smaller ears; the two also differ substantially in skull shape and tooth morphology. In real contrast to Antrozous, Bauerus is a tropical forest bat, inferred from head and wing shape to be a pursuit predator of insects. In contrast to Antrozous, there's no indication from the pelvic skeleton that it might alight on the ground when hunting (though both the thumb and foot are long and robust). [Drawing of Bauerus below from Emmons (1997)].


Van Gelder's bat was named in 1959 and remains poorly known. Its memorable species name - which means something like 'doubt oak' - is said on wikipedia to denote the fact that collector Oakes A. Plimpton (then of the American Museum of Natural History) was sceptical of this bat's distinction as a new species. That's such a nice story that I wish it were true but, in fact, the 'dubia-' bit of the name honours the other collector, Richard G. Zweifel (and, in German, 'zweifel' means doubt) [thanks to Dartian for corrections: see comments below]. The generic name honours Harry J, Bauer, the sponsor of the expedition that led to the discovery of the bat (Engstrom et al. 1987).

Antrozous and Bauerus are so distinctive relative to most other vesper bats that they've conventionally been given their own 'subfamily': Antrozoinae. Some authors have gone even further and have suggested that this deserves to be promoted to 'family': Antrozoidae (Simmons 1998, Simmons & Geisler 1998). In fact these authors also argued that antrozoids were likely not vesper bats at all, but a distinct lineage more closely related to molossids (the free-tailed bats or mastiff bats). However, genetic data shows that these bats belong within the vespertilionine radiation (Teeling et al. 2005, Miller-Butterworth et al. 2007, Roehrs et al. 2010), in which case their small clade should be termed Antrozoini [Pallid bat below by M. Siders, from wikipedia].


Fossils of Antrozous are known as far back as the Middle Miocene: some of these have been identified as the living Pallid bat (indicating a pretty surprising duration for a single species) while others have only been labelled as Antrozous sp. (Czaplewski 1993, Czaplewski et al. 2008). Anzanycteris anzensis from the Pliocene of California has been identified as an antrozoin by some authors (White 1969, McKenna & Bell 1997).

A particularly large fossil vesper bat from the Early Miocene of Florida - Karstala silva - possesses a lower molar tooth character (that is, a "groove alongside an inclined lingual cingulid") unique to Antrozous and Bauerus. However, in other characters it resembles the hairy-tailed bats (Lasiurus) while in humeral shape it differs strongly from antrozoines and hairy-tailed bats. Its affinities remain uncertain (Czaplewski & Morgan 2000). With an estimated mass of 20-22 g - similar to a Hoary bat L. cinereus or European serotine Eptesicus serotinus - it's North America's largest known fossil bat (Czaplewski & Morgan 2000).

Another North American fossil vesper bat - Simonycteris stocki from the Pliocene of Arizona - is also somewhat similar to Antrozous, but it's similar to serotines as well: based only on a skull fragment with teeth, it can't (yet) be identified precisely (Czaplewski 1993).

Little yellow bats: where the cryptic species are


The little yellow bats or rhogeëssa bats (Rhogeessa) primarily occur in Mexico, but are also found throughout Central America as well as in Bolivia, Venezuela, Colombia, Brazil and Trinidad. As suggested by the name, they're typically small (between 3 and 10 g) and often yellowish-brown dorsally. 11 species are currently recognised. Molecular studies have shown that populations that look just about identical are highly divergent in genetics, and indeed this is one of the first bat groups in which so-called cryptic species were discovered (Baker 1984). [The adjacent yellow bat belongs to a new species, the name of which was up for auction in 2008. I don't know how this panned out (lots of species names have been put up for auction in recent years)].

They aren't all "just about identical", however; several of the species can be distinguished based on measurements of the toothrow, finger bones and so on, and large sagittal and occipital crests give some of the species a pronounced raised area at the back of the skull. Little yellow bats have fairly large, robust teeth: the lower jaw has a robust appearance with a particularly deep 'chin' region [skull diagrams below from Baker (1984)].


The wing membranes of these bats are said to be unusually thick for bats of this size (Roots & Baker 1998, Vonhof 2000): it would be interesting to know if this correlated with any particular facet of behaviour. They have broad, naked interfemoral membranes. Males possess large, strongly smelling glands on the dorsal surfaces of the lower parts of the ears: as is the case for many vesper bat taxa, females are bigger than males (Audet et al. 1993). Little yellow bats are typically associated with humid, well vegetated lowland habitats, but populations of R. minutilla have been reported from semi-arid thorn forests. Czaplewski et al. (2005) suggested that this species - one of the world's smallest mammals - might have become isolated as a relict during the late Pleistocene. Numerous fossils of Rhogeessa are known from the Pleistocene of Venezuela, though it hasn't been possible to work out whether they represent new species or are referable to modern ones (Czaplewski et al. 2005).



Within Rhogeessa sensu lato, R. alleni has long been regarded as the 'most divergent' in terms of morphology and hence worthy of its own 'subgenus', Baeodon Miller, 1906. Genetics confirms this distinction, but shows that R. gracilis should be included in Baeodon too (Baird et al. 2008) [in the adjacent montage, B. alleni is on the left and R. hussoni is on the right. Both images are from Professor Paul's Guide to Mammals].

Hoofer & Van Den Bussche (2003) regarded Baeodon as properly (viz, 'generically') distinct from Rhogeessa and included both taxa within Antrozoini. In their large molecular analysis of vesper bats, Roehrs et al. (2010) found Rhogeessa to form a clade with both Antrozous and Bauerus, but the position of Baeodon was less well resolved: in some trees compiled from nuclear DNA data, Baeodon was the sister-taxon to the hairy-tailed bats (Lasiurus). However, the authors noted that this position was likely incorrect.


Tomopeas: get out, the party's over, you ain't no vesper bat

Having mentioned molossids, it's worth discussing another bat once thought by many bat workers to be somehow intermediate between this group and Vespertilionidae.

It's the Blunt-eared bat Tomopeas ravus, a tiny (3 g) Peruvian bat of arid habitats, often included among the vesper bats even though a list of anatomical features (including an overhanging upper lip, tubular nostrils, tail-tip that extends beyond the edge of the uropatagium, and fused seventh cervical and first dorsal vertebra) are more reminiscent of molossids (Miller 1907, Davis 1970). Despite this obvious early evidence for non-vespertilionid status, most authors continued to treat Tomopeas as a vesper bat, albeit one deserving of its own 'subfamily' (Tomopeatinae). However, Davis (1970) did suggest that it might best be given its own 'family' positioned in between Vespertilionidae and Molossidae.

Molecular studies eventually confirmed that Tomopeas is indeed a molossid, and in fact one of the 'most basal' members of the group (Sudman et al. 1994). This recovered position is consistent with the hypothesis that vesper bats and molossids are sister-taxa, since it seems logical that primitive members of both groups might exhibit symplesiomorphies (shared primitive characters).

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

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

Refs - -

Audet, D., Engstrom, M. D. & Fenton, M. B. 1993. Morphology, karyology, and echolocation calls of Rhogeesa (Chiroptera: Vespertilionidae) from the Yucatán Peninsula. Journal of Mammalogy 74, 498-502.

Baird, A. B., Hillis, D. M., Patton, J. C. & Bickham, J. W. 2008. Evolutionary history of the genus Rhogeessa (Chiroptera: Vespertilionidae) as revealed by mitochondrial DNA sequences. Journal of Mammalogy 89, 744-754.

Baker, R. J. (1984). Mammalian sympatric, cryptic species: a new species of Rhogeessa (Chiroptera: Vespertilionidae). Systematic Zoology, 32, 178-183

Czaplewski, N. J. 1993. Late Tertiary bats (Mammalia, Chiroptera) from the southwestern United States. The Southwestern Naturalist 38, 111-118.

- ., Morgan, G. S. & McLeod, S. A. 2008. Chiroptera. In Janis, C. M., Gunnell, G. F. & Uhen, M. D. (eds) Evolution of Tertiary Mammals of North America Volume 2: Small Mammals, Xenarthrans, and Marine Mammals. Cambridge University Press, pp. 174-197.

- ., Rincón, A. D. & Morgan, G. S. 2005. Fossil bat (Mammalia: Chiroptera) remains from Inciarte Tar Pit, Sierra de Perijá, Venezuela. Caribbean Journal of Science 41, 768-781.

- . & Morgan, G. S. 2000. A new vespertilionid bat (Mammalia: Chiroptera) from the Early Miocene (Hemingfordian) of Florida, USA. Journal of Vertebrate Paleontology 20, 736-742.

Davis, W. B. 1970. Tomopeas ravus Miller (Chiroptera).

Emmons, L. H. 1999. Neotropical Rainforest Mammals: A Field Guide (Second Edition). University of Chicago Press (Chicago & London).

Engstrom, M. D., Lee, T. E. & Wilson, D. E. 1987. Bauerus dubiaquercus. Mammalian Species 282, 1-3.

Graham, G. L. 2002. Bats of the World. St. Martins Press (New York).

Hoofer, S. R. & Van Den Bussche, R. A. 2003. Molecular phylogenetics of the chiropteran family Vespertilionidae. Acta Chiropterologica 5, supplement, 1-63.

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

Miller, G. S. 1907. The families and genera of bats. Bulletin of the United States National Museum 57, 1-282.

Miller-Butterworth, C. M., Murphy, W. J., O'Brien, S. J., Jacobs, D. S., Springer, M. S. & Teeling, E. C. 2007. A family matter: conclusive resolution of the taxonomic position of the long-fingered bats, Miniopterus. Molecular Biology and Evolution 24, 1553-1561

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.

Roots, E. H. & Baker, R. J. 1998. Rhogeëssa genowaysi. Mammalian Species 589, 1-3.

Simmons, N. B. 1998. A reappraisal of interfamilial relationships of bats. In Kunz, T. H. & Racey, P. (eds) Bat biology and Conservation, pp. 3-26. Smithsonian Institution Press, Washington, D.C.

Simmons, N. B. & Geisler, J. H. 1998. Phylogenetic relationships of Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx to extant bat lineages, with comments n the evolution of echolocation and foraging strategies in Microchiroptera. Bulletin of the American Museum of Natural History 235, 1-182.

Sudman, P. D., Barkley, L. J. & Hafner, M. S. 1994. Familial affinity of Tomopeas ravus (Chiroptera) based on protein electrophoretic and cytochrome B sequence data. Journal of Mammalogy 75, 365-377.

Teeling, E. C., Springer, M. S., Madsen, O., Bates, P., O'Brien, S. J. & Murphy, W. J. 2005. A molecular phylogeny for bats illuminates biogeography and the fossil record. Science 307. 580-584.

Vonhof, M. J. 2000. Rhogeessa tumida. Mammalian Species 633, 1-3.

White, J. A. 1969. Late Cenozoic bats (subfamily Nyctophylinae) from the Anza-Borrego Desert of California. University of Kansas Museum of Natural History Miscellaneous Publications 51, 275-282.


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The Pallid bat or Desert bat Antrozous pallidus of western North America and Cuba [...] [is] a desert specialist

Cuba isn't exactly known for its deserts; any idea what kind of habitat the pallid bat prefers there?

the 'dubious' bit of the name honours the other collector

Sorry, but that's not quite correct; the name is indeed meant to honour both collectors - Van Gelder says so in the paper (1959:2). So yes, it is an esoteric pun (Zweifel + Oakes).

in German, 'zweifel' means doubtful or dubious

Not quite; the noun Zweifel means 'doubt', whereas the adjective for 'doubtful'/'dubious' is zweifelhaft.


Van Gelder, R.G. 1959. Results of the Puritan-American Museum of Natural History Expedition to Western Mexico. 8, A new Antrozous (Mammalia, Vespertilionidae) from the Tres MarÃas Islands, Nayarit, Mexico. American Museum Novitates 1973, 1-14.

Interesting. Part XI, a record for tet zoo. Why so many bat post. Tell Mark Witton he needs to update his flickr site.

I think that Mark is too busy these days (with paying work and his pterosaur book project) to knock up stuff for fun. Alas, happens to all of us.

Little yellow bats have fairly large, robust teeth: the lower jaw has a robust appearance with a particularly deep 'chin' region

Lies quite a bit behind where the chin would be; looks like it contains the roots of the canines.

By David MarjanoviÄ (not verified) on 11 Apr 2011 #permalink

You may well be right: I was using 'chin' in the sense of 'ventral convexity near/at dentary symphysis' (and I think this is fair enough, especially given the quote marks).


Fossils of Antrozous are known as far back as the Middle Miocene: some of these have been identified as the living Pallid bat (indicating a pretty surprising duration for a single species)

Other lines of evidence would seem to agree with the idea that A. pallidus is a very old species. Weyandt et al. (2007) found high degrees of molecular difference between various pallid bat populations in North America, suggesting deep intraspecific divergences; some results imply lineage splits taking place in, if not in the Miocene, then quite possibly in the Pliocene (more than 3 MYA). Their data also imply that this bat has rather limited dispersal capabilites and/or tendencies (which makes the fact that it has been able to spread across the sea to Cuba all the more surprising).


an esoteric pun

I should have written 'joke' instead, as it wasn't really a pun. Oh well.


Weyandt, S.E. & Van Den Bussche, R.A. 2007. Phylogeographic structuring and volant mammals: the case of the pallid bat (Antrozous pallidus). Journal of Biogeography 34, 1233-1245.

"I have lots of non-bat stuff I want to cover, but (for reasons soon to be explained) I need to get this series finished."

Nice foreshadowing, but I don't see anything in this post about why you need to finish. Guess I'll haul out the ol' tenterhooks to wait on for your next installment.

Antrozous is also reported to go after scorpions, although it's not a scorpion specialist. I have no idea whether it's immune to scorpion venom or not.

By heteromeles (not verified) on 11 Apr 2011 #permalink

A certain comparative physiologist of my acquaintance in grad school kept a pallid bat that he used to carry around in his shirt pocket.
Man that thing's cage smelled weird.

By Sven DiMilo (not verified) on 11 Apr 2011 #permalink

I've seen Pallids hunt on the ground and heard an interesting hunting vocalization as they do so. I've also found them in heavily wooded areas. They do emit a skunky odor but not to an unpleasant degree.
I'm sad to point out that the bat held with its wings uncomfortably outstreched (above) appears underfed. Being of a scientific bent need not mean being unfeeling.

Their data also imply that this bat has rather limited dispersal capabilites and/or tendencies (which makes the fact that it has been able to spread across the sea to Cuba all the more surprising).

Three million years are a long time.

By David MarjanoviÄ (not verified) on 11 Apr 2011 #permalink

Thanks, everyone, for comments. Some responses...

The Cuban pallid bats (representing the subspecies A. p. koopmani*) are very poorly known - as of 2007 only four individuals had been found, and not at roost sites. Accordingly it's been described as the rarest Cuban bat, and the most endangered (Mancina et al. 2007). Fossils show that it's been on the island since the Pleistocene at least. There's little available information on habitat, but one of the specimens was discovered "in the Guamuaya mountainous region" (Mancina et al. 2007).

* Originally named as a species (A. koopmani Orr & Silva Taboada, 1960).

Pallid bats and scorpions (comment 7): yes, they attack and eat scorpions (there are various pictures of this in the literature), but I didn't want to over-do it following the theme of the desert long-eared bat article.

The underfed Rhogeessa bat shown in the photo (comment 9) is the holotype of a new species and I assume that the photo shows it as captured in the field. Its poor condition was therefore not caused by the biologists who captured and/or photographed it.

Refs - -

Mancina, C. A., Echenique-DÃaz, L. M., Tejedor, A., GarcÃa, L., Daniel-Ãlvarez, A. & Ortega-Huerta, M. A. 2007. Endemics under threat: an assessment of the conservation status of Cuban bats. Hystrix 18, 3-15.

Orr, R. T. & Silva Taboada, G. 1960. A new species of bat of the genus Antrozous from Cuba. Proceedings of the Biological Society of Washington 73, 83-86.