Recently I was talking to someone about vampire bats and described them as “super-bats” as in, super-strong, super-fast, super-smart. In this blogpost, I’m going to give just one example of this– a vampire bat’s extraordinary ability to feed on difficult and dangerous prey. Thanks to Ed Hurme for suggesting I write a blogpost about this after a brief discussion we had earlier.
What kinds of animals will a vampire bat feed on? Vampire bats routinely feed on livestock such as cows, horses, goats, pigs, and chicken. And there are many reports of vampires parasitizing more interesting hosts such as humans, sea lions, penguins, tapirs, peccaries, or even raptors. But just how exotic can the prey of vampire bats be?
In the 1970s, researchers placed a surprising variety of animals in large cages with vampire bats to find out. Many of these observations have not been published in papers but they appear in the out-of-print book, Natural History of Vampire Bats (1988) edited by Arthur Greenhall and Uw Schmidt. Greenhall explains that common vampire bats were able to feed on an armadillo, porcupine, cave rat, vole, cottontail rabbit, (larger) fruit-eating bat, crocodile, turtle, ground iguana, boa constrictor, coral snake, and even a tropical rattlesnake.
Several of the encounters in this book sound like a ridiculous (and somewhat sadistic) “vampire vs [species X] cage match” that you might expect to see on some pseudo-educational TV show or youtube. For example, consider Greenhall’s description of a bat placed with a Neotoma sp. cave rat (which is much larger than a vampire bat) and is sometimes found in the same caves:
The rat stoutly defended itself and on one occasion rat and bat engaged in a fist fight, both animals rising on their hindlegs and exchanging blows (Figure 7). Joint attack by vampires against one rat presented an uneven fight, and the rat was bitten on its tail, hindleg, nose, and ear, and finally killed.
In a captive encounter with a slender vine snake, Leptophis sp, Greenhall explains that “the bat dodged several more strikes until the snake stopped, seemingly tired. The bat bit its back and fled...” One of the most intriguing accounts describes a vampire bat facing a snake that would simply eat most bats:
A rat snake, Elaphe sp., a bat predator often found near caves with Desmodus, repeatedly struck at the vampire which skillfully avoided the strikes (Figure 8). After some maneuvering, the bat positioned itself facing the snake’s head, nose to nose. The vampire bat repeatedly licked the rostral scale until wound was made and blood flowed… The snake remained motionless, but flicking its tongue.
These images are stills from video recordings. I would be very interested to see that footage someday.
A few other updates:
- Our work on food sharing was discussed in a “quick guide” on reciprocal altruism in Current Biology.
- I’m giving a talk this Saturday Sept 28 at the Great Lakes Bat Festival in Southfield Michigan.
- By placing guano-stained rags in different locations, I found that we could influence where a lone vampire bat chooses to roost (they prefer roosts tainted with guano). This makes me wonder if the pungent smell of vampire guano helps the bats find roosts.
- I will soon know if my bats have been responding to the intranasal oxytocin I’ve been giving them.
Some interesting recent and relevant papers:
- “Social amoeba farmers carry defensive symbionts to protect and privatize their crops” Nature Communications [so cool it’s hilarious]
- “Wolf Howling Is Mediated by Relationship Quality Rather Than Underlying Emotional Stress” in Current Biology
- “Female Bechstein’s Bats Adjust Their Group Decisions about Communal Roosts to the Level of Conflict of Interests” in Current Biology [I really like this stuff, but I’m still not sure what the term “group decision” means in a group with unstable membership.]
- “Reciprocity explains food sharing in humans and other primates independent of kin selection and tolerated scrounging: a phylogenetic meta-analysis” in Proceedings B [ In my opinion, this author thinks clearly about reciprocity (as occurring within a long-term social bond rather than as a calculated tit-for-tat strategy that requires planning and self-control to avoid defection).]
- “The excuse principle can maintain cooperation through forgivable defection in the Prisoner’s Dilemma game” in Proceedings B [This result was surprisingly clear. Fantastic system they have here.]
- Finally, I somehow came across this funny gem from an article online entitled “What vampire bats can tell you about bond yields“
the more the bats cooperate with one another, the less a single bat gains from cooperating. Quick-witted dear readers will see parallels in the bond market. When you lend money (buying a bond, for example), you have to trust the person you lend to. As your level of trust goes up, you accept lower interest rates, because your risk of loss goes down. This is equivalent to the cooperation in a bat colony.
And I thought I related everything to vampire bat cooperation…