Tetrapod Zoology

i-92b006251b3dcffe6fa86d468f7f8af0-vampire-bat.jpg

I am fascinated by bats, and I wish I knew more about them. And among the most fascinating of bats are one of the few groups that all people around the world have heard of: the vampires….

Various non-sanguivorous bats are regarded as vampires by various people in various parts of the world, but true vampires – the only truly sanguivorous bats and indeed only sanguivorous mammals – are unique to the American tropics. Though often classified in their own microbat family, Desmodontidae, it is universally agreed today that vampires are part of the American leaf-nosed bat family Phyllostomidae*. Although separate ‘family’ status for vampires was championed by some workers as recently as the 1980s (e.g., Corbet & Hill 1980), inclusion of vampires among phyllostomids isn’t a new idea: this is what Paul Gervais (1816-1879) thought as early as 1854, as did John Edward Gray (1800-1875) and several other 19th century mammalogists. Among phyllostomids, recent phylogenetic studies have mostly agreed that desmodontines are basal members of the group, and in fact one of the first lineages to diverge (Wetterer et al. 2000, Jones et al. 2002).

* Not Phyllostomatidae, as it used to sometimes be written.

i-20a9192c541a982bdd88f7a3f741bd74-vampire white-winged.jpg

There are three living vampire species: the reasonably large and widespread Common vampire Desmodus rotundus, the small, poorly known and rare White-winged vampire Diaemus youngi (only discovered in 1893), and the Hairy-legged vampire Diphylla ecaudata, the only species that has ever been recorded as far north as the USA. The White-winged and Hairy-legged species are mostly bird predators, while the Common vampire is mostly a mammal predator [adjacent image of White-winged vampire from here].

Vampire bats are fascinating for a whole host of reasons, and not just for the sanguivory. For their size, vampires are phenomenally strong, and able to carry up to a third of their weight and fly after consuming their own body weight in blood. They are reportedly far harder to euthanize with the chest-squeeze method than is normal for bats. They are long-lived, reaching 19 years or so both in captivity and in the wild. They are particularly agile compared to other bats and among the most terrestrially capable of all bats. Their large, powerfully muscled thumbs enable them to spring up from the ground – they are the only bats capable of ‘flight-initiating vertical jumps’ (Schutt et al. 1997) – and they are also unique among bats in being able to gallop (Riskin & Hermandon 2005). Bats appear to have lost the ability to run early on in their evolution, meaning that vampires have evolved running quite independently from all other mammals.

i-e5a9102a3fb0b5b94cd5b5b9bc949d5a-vampteeth.jpg

Needless to say, vampires are anatomically specialized. They have a particularly short muzzle that lacks a nose leaf, a peculiarity given that most other phyllostomids possess one. Pit organs in the nose are sensitive to infrared radiation and help them to locate capillaries just under the skin. Their upper incisors and canines are large and projecting, and both Common and White-winged vampires only have one pair of upper incisors (the Hairy-legged vampire has two pairs) [pic of teeth from here]. These teeth lack enamel and are shear-like with sharp cutting edges; they appear to be kept sharp by constant contact with the smaller lower incisors and canines. Vampires use their upper jaw teeth to shave away a small area of fur or feathers, and to then make a small, shallow incision. Using the long, pointed tongue they lap at the wound, the special grooves on the side helping capillary action (the tongue’s upper surface remains free of blood) and the enzyme desmokinase preventing clotting. Desmokinase actually doesn’t work on all sorts of blood: it does the job for cattle, horse and people, but not for the blood of sheep and dogs.

The lower incisors are widely spaced (to allow passage of the tongue during feeding) and bilobed, apparently to help the bat grip to the skin of a prey animal. The Hairy-legged vampire has a peculiar fan-shaped, multi-lobed lower incisor which recalls the similar incisors of the colugos. I don’t know if its function has been determined (in colugos it’s supposed to be a grooming tool). Molars are absent in the Common vampire, giving this bat the lowest tooth count (20) of any bat. The White-winged vampire has large glands at the corners of its mouth that can emit jets of a nauseating fluid (!).

Vampires are small, with the biggest individuals reaching 90 mm in head and body length, 350 mm in wingspan, and at most 50 g in weight. Their wing and leg bones have peculiar longitudinal grooves that help anchor their hypertrophied limb muscles. They have a T-shaped stomach that has a large secondary pouch, and during feeding it swells considerably: a bat drinks between 0.5 and 1.4 times its own weight in blood. Even while still feeding (a feeding bout lasts for between 10 and 60 minutes) the bat starts to urinate in order to get rid of the excess water and nitrogen contained within blood (blood is about 90% water). Accordingly their kidneys are highly specialized. Vampires are tailless and have a strongly reduced uropatagium (the membrane between the legs). The calcar – an ankle bone unique to bats that normally helps support the trailing margin of the uropatagium – is either absent or reduced to a tiny spur.

i-e83a4d440470b9818b2376b79c21f70c-vampire cornell.jpg

Because blood is pretty much pure protein, vampires have no fat reserves and hence are highly sensitive to cold. They also have a fast metabolism and will starve after three days without food. Common vampires unable to get a meal for themselves are now known, remarkably, to practice reciprocal altruism: they have a ‘buddy system’ where hungry bats beg blood from their roost-mates (usually, but not always, a related individual), and they apparently help those that have helped them in the past (Wilkinson 1984). Regurgitated blood is also fed to juveniles pretty much as soon as they’re born, and then periodically during the pup’s first year (yes, baby bats are called pups). The single pup is not only proportionally enormous (representing 20% of the mother’s weight at birth), it is also cared for for a much longer time than any other bat and is only weaned when about 9-10 months old. Juveniles take a year or two before they can feed properly on their own, and juveniles will use the same wound sites as their mothers and presumably follow her as she hunts and feeds (Wilkinson 2001) [adjacent image from here].

Vampires are highly sensitive to dehydration – in fact they dehydrate by way of evaporation faster than any other mammal – and they roost in areas where humidity is at or approaching 100%. These physiological factors are debilitating if vampires aren’t able to keep warm and suitably well hydrated.

It’s perhaps worth noting by the way that myths about humanoid vampires do not come from the bats: if anything it’s the other way round, with European myths and ideas about humanoid vampires being transferred to the American bats in the 1750s. At this time people thought that various bats from the Old World and elsewhere were blood-feeders, and in fact the view that the false vampires, ghost bats and yellow-winged bats of tropical Africa, Asia and Australasia were blood-feeders persisted until well into the 19th century. While people knew that certain bats were in the habit of attacking livestock and drinking blood, they seem to have assumed that it was one of the large, scary looking species that was responsible. Some explorers and naturalists had noted as early as the 1760s that the true vampires were the small desmodontines, but this was widely overlooked until much later. The history of the discovery of vampire bats and their sanguivorous habits is a fascinating and lengthy story, best reviewed in David Brown’s excellent Vampiro: the Vampire Bat in Fact and Fantasy (Brown 1994).

And one more thing on vampire lore and legend: apparently (and ironically), bats were never incorporated into Old World vampire mythology until Bram Stocker did so in his 1897 book (Altringham 2003).

Lots more to come. Have you ever wondered how a behaviour as remarkable as sanguivory may have evolved? (though, for inspiration, you might like to check the previous articles on blood-feeding in birds here and here).

Refs – -

Altringham, J. D. 2003. British Bats. HarperCollins, London.

Brown, D. E. 1994. Vampiro: the Vampire Bat in Fact and Fantasy. High-Lonesome Books (Silver City, New Mexico).

Corbet, G. B. & Hill, J. E. 1980. A World List of Mammalian Species. British Museum (Natural History), London.

Jones, K. E., Purvis, A., MacLarnon, A., Bininda-Emonds, O. R. P. & Simmons, N. B. 2002. A phylogenetic supertree of the bats (Mammalia: Chiroptera). Biological Reviews 77, 223-259.

Schutt, W. A., Altenbach, J. S., Chang, Y. H., Cullinane, D. M., Hermanson, J. W., Muradali, F. & Bertram, J. E. A. 1997. The dynamics of flight-initiated jumps in the common vampire bat Desmodus rotundus. The Journal of Experimental Biology 200, 3003-3012.

Riskin, D. K. & Hermanson, J. W. 2005. Independent evolution of running in vampire bats. Nature 434, 292.

Wetterer, A. L., Rockman, M. V. & Simmons, N. B. 2000. Phylogeny of phyllostomid bats (Mammalia: Chiroptera): data from diverse morphological systems, sex chromosomes, and restriction sites. Bulletin of the American Museum of Natural History 248, 1-200.

Wilkinson, G. S. 1984. Reciprocal food sharing in the vampire bat. Nature 308, 181-184.

Wilkinson, J. 2001. Bat blood donors: feeding and sharing in vampire bat colonies. In MacDonald, D. (ed) The New Encyclopedia of Mammals. Oxford University Press (Oxford), pp. 766-767.

Comments

  1. #1 Matt Hodgkinson
    February 8, 2007

    You might be interested in this article we published in BMC Biology: http://www.biomedcentral.com/1741-7007/4/18/

    It’s about how vampire bats can locate their prey again by remembering the sound of their prey’s breathing.

  2. #2 Cameron
    February 8, 2007

    Hmm, how do you think the stories about various Old World bats drinking blood got started? Did these stories start after the vampire bat was known, or did they exist before? Were they based on freak sanguivorical occurance, perhaps tying in to the next post?

    I’m enjoying the posts Darren, excellent work as always.

    -Cameron

  3. #3 Jim Lemire
    February 9, 2007

    Great posts. I’ve relly enjoyed this site since I found it (via Pharyngula). I’ve taken the liberty of linking to many of your posts on the Attleboro (MA) High School AP Biology blog (http://attleborobio.blogspot.com/) to give the students something different to explore. Hopefully some of the students will wander over this way…

  4. #4 Poseidon
    February 9, 2007

    At last!

    Thank you again for tying biology into myth; it’s one of the main reasons I come back here every day. As long as you keep writing about the cultural and mythological implications of zoology, I’ll always be a faithful reader.

  5. #5 Tommy Tyrberg
    February 9, 2007

    It seems to me that Desmodus stocki must have been more resistant to dehydration than the extant species. It has been found in Big Bend, and not even caves are very humid in that area. As a matter of fact they are so dry that Wetmore thought the mummified remains of Gymnogyps found there were subrecent though they are actually late Pleistocene.

  6. #6 Darren Naish
    February 10, 2007

    Tommy, I absolutely agree with you. The next post I have planned discusses D. stocki and the other fossil vampires. It should be ready by tonight.

  7. #7 Sordes
    February 10, 2007

    The terrestrial locomotion of vampire bats is really interesting, although I think the adaptions for terrestrial lifestyle of the enigmatic New-Zealand bats Mystacina tuberculata and Mystacina robusta (R.I.P) with all their highly unusual anatomical adaptions are even more interesting.

  8. #8 Steve Bodio
    February 10, 2007

    Nice drawing of stocki feeding from a ground sloth in Brown..

  9. #9 Tristram Brelstaff
    February 10, 2007

    Nothing to do with vampires, but I have just watched the first 10 minutes of the new ITV series ‘Primeval’. It looks just up your street: a sort of Walking With Dinosaurs meets Torchwood. It is repeated on Sunday afternoon at 4:40pm. I look forward to your review!

  10. #10 Darren Naish
    February 10, 2007

    Thanks Tristram. I learnt from a friend this evening that I’d missed it (and I’ll probably miss it again tomorrow as I’m out all day). I have to say, though, that I try to avoid watching ITV (and I sort of lost interest in Torchwood about half way through the series). I do appreciate the heads-up.

  11. #11 Tristram Brelstaff
    February 11, 2007

    The first episode featured three Permian reptiles loose in the Forest of Dean: Gorgonopsis, Coelurosauravus jaeckeli, and a large herbivore which someone mentioned as being related to tortoises. The Radio Times has an article on the program. The trailer for the second episode indicates that will feature giant insects.

  12. #12 David Marjanovi?
    February 12, 2007

    and a large herbivore which someone mentioned as being related to tortoises.

    Must have been a pareiasaur.

    And unlike Haeckel, Jaekel lacks a c, even though it’s not logical.

  13. #13 Nathan Myers
    February 13, 2007

    Aren’t Heckyl and Jeckyl cartoon crows? Hmm, crows…

  14. #14 patrick
    February 15, 2007

    Actually, other bats (some flying foxes) are capable of terrestrial galloping but it is extremely unrefined and awkward–slow and barely effective. The Desmodus gallop is really only notable for its speed and its distinct aerial phase. Flying foxes are also excellent swimmers. 19 years is not that long for a bat to live in captivity–many individuals have lived over 30 years.

  15. #15 Darren Naish
    February 16, 2007

    Thanks for your comment Patrick. It’s true that vampires are not particularly long-lived given bat longevity in general; the point I suppose is that they are still surprisingly long-lived for such small mammals (most people assume – based on rodents – that any mammal less than a few kg only lives for two or three years). As for running, other than vampires no bat exhibits a gait that can be defined as a run.

  16. #16 McKenna Hicks
    October 7, 2007

    looking 4 pet bat can u help me

  17. #17 alex
    February 6, 2008

    are vampires real

  18. #18 CUJO
    February 7, 2008

    Bats are cute, but I strongly recommend against owning one as a pet. Fruit bats are endangered and a protected species, and I have a hard time picturing someone being able to feed a caged microbat all the insects it needs in but one night. On top of that, bats don’t like to be disturbed during the day and too much stress taxes its energy reserves and can kill it. I cannot picture the avera. If you want a pet bat, set up a batbox in your backyard and then watch for it at dusk on summer nights. Give it a name, and then leave it the hell alone.

    I did see a video on youtube of a woman with a pet bat once, apparently it was something of a town celebrity, but I think a situation like that is the exception rather than the rule.

  19. #19 dave Godfrey
    February 7, 2008

    Raising orphaned bats is often done by hand. Richard Morecroft an Australian newsreader did it once, and then released the bat into the wild. It wasn’t easy. (The book is called “Raising Archie” if your interested).

    If you want a flying pet stick to birds. Many parrots will outlive you.

  20. #20 Lily
    March 22, 2008

    idk if vampires are real… but there are ppl out there that drink blood… like me….

  21. #21 noelia
    April 3, 2008

    so there really are no humanoid bats?? could that ever happen though?? is it true that are carniverous ppl in Africa? how did this whole sanguivory thing begin?

  22. #22 noelia
    April 3, 2008

    how did sanguivory begin? are there really no human vampires? wat would happen to someone who started drinking blood?

  23. #23 Hai~Ren
    November 23, 2008

    There’s a very interesting article that describes some of the unique traits of Diphylla and Diaemus. (Click on my name)

  24. #24 David Marjanovi?
    November 23, 2008

    are there really no human vampires?

    WTF? No.

    wat would happen to someone who started drinking blood?

    Well, nothing. Blood has no magic properties or anything. :-|

    If you tried to live only off blood, however, and actually found enough of it, your kidneys might not cope, you’d be at constant risk of starving, and you’d get a craving for sugar. Vampire bats have very powerful kidneys, and they share blood with each other to avoid having to “eat” constantly.

  25. #25 David Marjanovi?
    November 23, 2008

    …and if you had actually read the post, you’d know all of that already!

  26. #26 lawrence
    July 30, 2009

    html:/837lawrence/herrera/hindi mo no/
    /vampirebats/levitate?/?/

  27. #27 Tanjung
    May 21, 2010

    I’m a college student of Gadjah Mada University in Indonesia from Faculty of Biology. I need help about excretion system of Common Vampire Bat ( Desmodus rotundus )for my assignment. i’ve search for this info in web, but i didn’t found the info that i need. Maybe Mr. Darren Naish or anyone in this forum have the info or a link to website that contain this info?
    Thank you before and sorry that my English is not good enough,^^

  28. #28 Daniel
    May 21, 2010

    Tanjung: Google “Desmodus rotundus kidney OR excretory OR renal” (without the quotes), then drill down the results. Read the bibliographies in those papers and try to read the citations you find interesting.

    It seems you can also find some interesting results using http://highwire.org/cgi/search

  29. #29 LeeB
    May 21, 2010

    Tanjung,

    I had a quick look and these papers might be useful.

    McFarland and Wimsatt 1969; Renal function and its relation to the ecology of the vampire bat, Desmodus rotundus.
    Comp. Biochem. Physiol 28 p. 985-1006.
    Busch, C. 1988; Consumption of blood, renal function and utilisation of free water by the vampire bat Desmodus rotundus. Comp. Biochem. Physiol. 90A p. 141-146.
    Morton and Richards 1981; The flow of excess dietary water through the common vampire bat during feeding.
    Comp. Biochem. Physiol. A. 69(3)p. 511-515.

    LeeB.

  30. #30 DDeden
    August 5, 2011

    How Vampire Bats Find Veins
    Heat-sensing protein channels allow to find the best place to sink their
    teeth into the prey
    Jessica P Johnson 4.8.11
    Researchers have discovered an IR-sensing protein channel that allows
    vampire bats to identify the hottest part of the animal ‹ veins close to
    the skin’s surface that carry 38°C blood, and presumably the best spot for
    feeding.

The site is undergoing maintenance presently. Commenting has been disabled. Please check back later!