Using DNA to uncover vampire bat diet

There’s an article on getting DNA from vampire bat feces in Science Magazine here.

When I was an undergraduate at Cornell University, I worked on that topic for my undergraduate honors thesis. I extracted and sequenced DNA from the crap of vampire bats that fed on chicken blood. I was pretty excited after it finally worked after about 3 years without success. It was really cool to see another team finally doing what I wanted to do and apply this method to vampire bats living in places like the Amazon where they might be feeding on their original wild prey. See my previous post on this topic.

This team found that the vampires they caught were all still feeding on domestic animals though. It’s a neat study nonetheless.


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Recent Updates

Micah Miles

Micah in the field holding a whiptail

My defense talk is April 8th 2-3pm. See my previous post below.

I recently analyzed my playback data and found that vampire bats are more attracted to the calls of high donors vs low donors of similar sex and low relatedness. More soon…

Micah Miles (right) was one of the undergraduate assistants who helped me with my research on vampire bats. She was recently accepted into graduate school at University of Georgia to study effects of urbanization and climate change on salamander populations in the southern Appalachians. Congrats Micah!

Micah also informed me that a discussion on vampire bat food sharing was on the “front page of reddit”. I’m not really too familiar with reddit, but apparently it’s a popular website. The site says its “the front page of the internet” and vampire bat food sharing was on the front page of reddit, so I guess that means food-sharing in vampire bats was on the front page of the internet. So that’s neat.

I also just discovered this from almost 2 years ago: Vampires’ gift of ‘blood honey’

Some recent papers of interest:

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Dissertation defense talk date and time

happyI submitted my dissertation to my doctoral committee. If interested, you can read my submitted draft here (note: this link is temporary until my official approved dissertation is published by the school). There are 4 chapters: 1) my reciprocity review paper, 2) my study on predictors of vampire bat food sharing, 3) a study on oxytocin and food sharing, and 4) my contingency test on social bond stability. These last two are not published yet. There are also a few studies I did that did not make it into the dissertation, because I’m still writing them up. The first is a study on kinship, social bonds and the production and perception of contact calls. Another is on testing the limits of helping behavior among kin and non-kin by forcing donors to feed others across a cage barrier. There’s also two short studies I did with undergraduate Lauren Leffer, one on vampire bats’ use of scent cues to find roosting spots, and another on comparing social grooming across different bat species.

My actual defense (not open to the public) is the morning of April 9th, 9am until noon. But my public defense talk will be 2:00pm -3:00pm Wednesday April 8th in 1103 BRB (Bioscience Research Building, University of Maryland, College Park).


There are a few options. First, you can pay to park in one of the numbered metered spots in the Regents Parking Garage next to the Biology-Psychology Bldg (which is where the talk will be) or the Union Lane Garage. It’s $3/hour or $15 for the day. You can pay with credit card at a central meter. To get other directions, search google maps or use these.

From the Regents Parking Garage: you will know you are at the correct exit if there are trees, a fence and large practice fields to your right (the right of the parking garage). Once you have exited the parking garage, proceed past some dumpsters on your right up the path in between the Biology-Psychology Building and the Plant Science Building (red brick wall). Make a right once you have reached the top of the stairs and proceed to the front of the Biology-Psychology Building. There are picnic tables and benches in front of it. Enter the doorway on the far left-hand side of the building, or go inside then left until you enter a newer-looking building. You will enter a large atrium with a high ceiling. If you walk straight back towards the inner courtyard (away from the entrance). You will see 1103 on the left along a curved wall with a glass-walled handicap ramp, and across from a staircase.

From the Union Lane Garage: follow the signs to the Stamp Student Union, which is on Campus Drive. If you are standing at Campus Drive facing the front entrance of the Stamp Student Union (the entrance along Campus Drive), the Biology-Psychology building is located to your right. Head down the sidewalk running along Campus Drive (which goes downhill) and you will see the Biology-Psychology building to your left. There are picnic tables and benches in front of it. Enter the doorway on the far left-hand side of the building, or go inside then left until you enter a newer-looking building. You will enter a large atrium with a high ceiling. If you walk straight back towards the inner courtyard (away from the entrance). You will see 1103 on the left along a curved wall with a glass-walled handicap ramp, and across from a staircase.

Click for larger image
Click for larger image


Or you can park off campus for free and walk onto campus.




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New reciprocity experiment with rats

Norway rats reciprocate help according to the quality of help they received


Direct reciprocity, according to the decision rule ‘help someone who has helped you before’, reflects cooperation based on the principle of postponed benefits. A predominant factor influencing Homo sapiens‘ motivation to reciprocate is an individ­ual’s perceived benefit resulting from the value of received help. But hitherto it has been unclear whether other species also base their decision to cooperate on the quality of received help. Previous experiments have demonstrated that Norway rats, Rattus norvegicus, cooperate using direct reciprocity decision rules in a variant of the iterated Prisoner’s Dilemma, where they preferentially help cooperators instead of defectors. But, as the quality of obtained benefits has not been varied, it is yet unclear whether rats use the value of received help as decision criterion to pay help back. Here, we tested whether rats distinguish between different cooperators depending purely on the quality of their help. Our data show that a rat’s propensity to reciprocate help is, indeed, adjusted to the perceived quality of the partner’s previous help. When cooperating with two conspecific partners expending the same effort, rats apparently rely on obtained benefit to adjust their level of returned help.

Biology Letters paper:

Cool study. I could not get vampire bats to even cooperate in isolated dyads. They were too freaked out. Maybe rats are better than bats at being lab rats.

Other recent and relevant papers:

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Studying bat pollination in Thailand

My friend Alyssa Stewart studies bat pollination in Thailand. I visited her this December to help* her with one of her dissertation chapters and to do a small study of our own. Alyssa is studying just how good the flower-visiting bats are as pollinators in Thailand. The most common flower-visiting bats there are: Eonycteris spelaea (the dawn bat), two species of  Macroglossus, two species of Cynopterus, and a small Roussettus.

Macroglossus sobrinus (from wikipedia)

From the plant’s perspective, the value of a bat depends on how often it visits the flowers, how much pollen it can carry, and how effectively it carries that pollen to another flower of the same species, rather than to a different species or to the bat’s stomach (I have always thought that pollen placed on a bat’s body should taste pretty bad to dissuade the bats from eating it, which is the first thing I wanted to study, but we shelved that idea).

So Alyssa has been studying these bats and their pollination of several flowers including the genera Parkia (seen below), Durio, Ceiba (silk cotton tree), Musa (banana), Oroxylum, and Sonneratia.

Merlin Tuttle has some great photos from Thailand of Eonycteris visiting flowers here. Including this gem:

I tried to take this same picture of Eonycteris visiting a Parkia flower and this is my version, which is just as good as you can see:IMG_3573

Over evolutionary time, flowers have switched from birds to bats more often than vice versa, because bats are often better pollinators due to their fur holding more pollen. Even though bats often drink more nectar, many plants are willing to pay that cost in exchange for the excellent pollination services of bats.

Eonycteris with pollen on its face after feeding on a flower

Eonycteris with pollen on its face after feeding on a flower


Most work on bat-flower mutualism has focused on neotropical bats and flowers. Alyssa’s work highlights many of the similarities and differences between the Old World and New World bat-flower mutualisms. For one, the paleotropical bats don’t have sophisticated echolocation like their neotropical cousins that are capable of hovering and feeding precisely from each flower like a hummingbird. Like in this video:

The paleotropical bats instead crash-land on the flowers, often getting the pollen on their face, body, and wings. Like these videos of Dawn bats feeding on banana flowers (warning the video has music but its nice music):

Actually, these flower-visiting bats do have a very primitive form of echolocation first discovered by Ed Gould and recently studied in much greater detail by Arjan Boonman, Yossi Yovel, and Sara Bumrungsri. The bats somehow click their wings to produce biosonar, which helps them avoid obstacles but it is not very precise or high resolution. This primitive echolocation helps the Dawn Bat navigate in the pitch black of the caves where it roosts. I actually tried getting some recordings of these clicks myself. They were quite difficult to record or differentiate from background noise, and they would really only make them under absolute darkness, just as described in the study. It is astonishing how great the night-vision of these fruit bats was. It’s described further in the supplement to the Boonman et al. paper. Anyway, back to the flowers…

Alyssa’s test flight chamber

Alyssa hanging flowers in the flight chamber. She only fell off this table once while I was there. The infrared light and camera is seen on the right.

Alyssa hanging flowers in the flight chamber. She only fell off this table once while I was there. The infrared light and camera is seen on the right.

Alyssa’s prediction was that each flower species would place its pollen on different parts of the bats’ bodies such that the bat would be better at delivering pollen to the same species rather than to different species. So her experiment was to catch a bat, fast it so that it would be hungry, and then release it in a room with a male flower. After the bat visited the male flower, she would unveil a female flower. Hopefully, the bat would visit both flowers so that she could count how many pollen grains were transferred. Usually, the bat just flew around the room freaked out, but if we were lucky, it visited both flowers within 30 minutes.

Alyssa prepares Ceiba flowers for her tests

Alyssa prepares Ceiba flowers for her tests

Alyssa tested different bats under several conditions: sometimes the bat would transfer pollen from a male to a female of the same species. Other times, it would transfer pollen between flowers of two different species. Her prediction was that pollen transfer within species would be greater than between species (making the bats very efficient pollinators). This seemed to be the case so far while I was there, and the difference was quite dramatic.

Collecting pollen from the bats
Collecting pollen from the bats

The other small study we did was to see whether Eonycteris was attracted to the scent of dimethyl disulfide (DMDS), an odorous compound found in many neotropical bat flowers (it smells terrible!).

A team from Germany found that DMDS is intensely and innately attractive to flower-visiting bats in the neotropics. When I worked with captive flower-visiting bats of the species Glossophaga soricina, I walked into a room with a tiny amount DMDS in a test tube and they all started hovering over to me and sticking their heads inside the tube. And these are bats that have never smelled odor this in their life.

DMDS acts as a powerful bat lure in the scent bouquets of many bat-pollinated flowers. And at first, it seemed like it was a general aspect of the bat pollination syndrome, along with pale petals that open at night. However, a later study found that DMDS was not found in many bat-pollinated flowers of West Africa. Most remarkable is the case of the silk-cotton tree (Ceiba pentandra), which is pollinated by bats on both the hemispheres. C. pentandra flowers possess a substantial amount of DMDS in Central America, but the later study found that the same species of flower contained no detectable DMDS in West Africa. In Thailand, we did not detect a strong sulphurous odor in C. pentandra. In fact, they smelled pretty nice. Finally, another study found that Cynopterus sphinx— a fruit bat that often feeds on flowers– was not attracted to DMDS.

To me, all this suggested that DMDS as a bat lure evolved only in the neotropics and is therefore probably unattractive to palaeotropical flower-visiting bats. So we tested the most common nectar bat in Thailand, Eonycteris spelaea, with choices of four Ceiba pentandra flowers, where one random flower was scented with DMDS. Rather than preferring the DMDS-treated flower, 21 of 22 bats chose an untreated flower. So they actually appeared to avoid it. In stark contrast, when I conducted the same test with the neotropical bat Glossophaga soricina, they were more than ten times more likely to visit the DMDS-treated flower first. This result suggested to me that the role of DMDS in bat pollination syndromes may be limited to the New World tropics.

At times, our trip was filled with great peril as when Alyssa almost beheaded herself  in her desperate attempt to cut down flowers high in a tree by tenuously balancing heavy plant shears loosely attached to a long pole, attached to another long pole (what could go wrong). I was supposed to be helping that day but decided to stay behind in the air-conditioned lab with my computer working on my dissertation (that may have happened a few* times). The shears came down and luckily only nicked her lip between her nose and mouth requiring only a few stitches, but she then had to wear a bandage that made her look like she had a ridiculous Adolf Hitler moustache, and I had to try really hard not to laugh while talking to her about serious stuff (I could not even smirk). It is remarkable though how much a Hitler moustache changes someone’s appearance. I also had to suppress my urge to ask to take a funny photo for my blog. So really that was difficult for both of us.

We submitted our DMDS study, leaving out the minor detail that we conducted our behavioral tests in a laundry basket (“an experimental cage”). I look forward to Alyssa’s study on pollen transfer. When I left Thailand, she was heading north to Bangkok to find Durian flowers in bloom to finish off her study. A huge thanks to Alyssa for a great time and for showing us Thailand and it’s bats. We had a lot of fun.

Alyssa showing Ceiba to Michelle

Alyssa showing Ceiba to Michelle (who may have just woken up).


Ceiba pollen

The only big disappointment was not finding stalk-eyed flies for our lab. My confessional is that, on the last four days, when we could have been looking for flies around mosquito-infested streams, Michelle and I instead decided to visit the rock climber’s beach paradise of Railay, where huge overhanging limestone cliffs strewn with stalactites and bat caves come straight out of the seaside beaches. These were some of the best days of my life. The climbing was amazing.



Taphozous melanopogon, I believe

Taphozous melanopogon, I believe




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Ancestry chart for the vampire bats at Organization for Bat Conservation

Screen shot 2015-01-11 at 12.14.33 PM
Click image for larger view.

This is the family tree for vampire bats at Organization for Bat Conservation. This was a bit difficult to construct for a couple of reasons. The math for estimating kinship analyses from genetic markers assumes large wild populations with zero inbreeding (exactly the opposite of what we have here). For this reason, reliable pedigree reconstruction in a small or inbred population with genetic markers is supposed to be difficult to impossible. However, in addition to 30 polymorphic markers, I knew several other pieces of information to help me along: allele frequencies from some wild vampire bats, known mothers, all potential fathers, and the dates of births as well as male castrations, which reduced the possible fathers to even smaller subsets.

The genetic data revealed two cases of mistaken maternity due to alloparental nursing. In both cases, the female bat Mina had a pup but also nursed another female’s pup at the same time. There was one case of incest: Gelfling had an offspring with his own daughter. In the wild, this is typically prevented by dispersal of one or both sexes from the colony. For bat species where the dominant male typically remains in the group longer than the the time it takes a female to reach reproductive maturity, then the females will typically disperse to avoid mating with their fathers. But in most polygynous bats, including vampire bats, the dominant male is overthrown frequently and it is therefore the males that disperse. This incest avoidance pattern is common across mammals, and explains a big chunk of mammalian dispersal behavior and social structure. But incest might be common and have some benefits in some mammal species . In at least one bat species, females appear to sometimes choose to mate with their own father or grandfather, a behavior called intra-lineage polygyny.

Despite some inbreeding, it seems at first glance to me (looking at this chart and the relatedness estimates) that the female bats were still avoiding inbreeding overall, and that inbreeding occurred less than expected by chance even before the males were being castrated. For example, many of the females mated with the dominant male named “The Count” except for Mya, Veronica, and Countess– all females that were somewhat related to him according to genetic data. Many of the females mated with Gelfling who was also very unrelated to all of them. But I need to run a math simulation to check this intuition. I’m interested to see if there is evidence that females can indeed recognize individuals that are related to them through self- or familial phenotype matching via smell (MHC) or perhaps even voice similarity.

It’s unclear to what extent female vampires have control over their matings. All the mating I’ve seen in common vampires appeared “coercive” in nature (e.g. the female is fighting off the male and the two might even fall to the floor with biting and screeching). Note that I would be very biased to noticing these kinds of dramatic coercive matings. So I really have no idea if male courtship exists in this species or what it might look like. I have seen what looks like courtship behavior in white-winged vampire bats suggesting an important role of female choice. These guys flash their white-wings tips and maybe even sing to females (this is based on anecdotal observations of some more complex calls that I only observed when males and females were placed together).

Recent papers of interest:

My next post will be about a recent trip to Thailand looking at bat pollination and the bat lure, dimethyl disulfide, a floral scent compound found in many bat-pollinated flowers.



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In the news

Cute story on vampire bats on the BBC Earth News website.

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