In 2016 and 2017, we captured female vampire bats and then released them back into the wild almost two years later to track their wild association networks. During their time in captivity, 12 of the females gave birth to pups. Would these captive-born bats be able to survive in the wild?
Jineth Berrío-Martínez conducted an experiment on whether the captive-born bats could feed on a live chicken (alone or with the presence of their mother).
First, we decided to buy a bunch of chickens to use as hosts. My wife Michelle, who is a farmer, helped us build a chicken coop that was secure against predators.
Each day, Jineth would isolate a chicken and a vampire bat and film the feeding. Some of the results were unclear and unexpected. For example the mothers never fed on the chickens (see the paper for more information), but we did answer the main question: yes captive born bats can feed on a live animal.
Jineth tried a number of different setups in a series of pilot trials before finding one that worked well. The vampire bat had to be able to access the chicken but also get away from it. The example below shows a cage that a vampire bat could enter and exit but not the chicken. We used a different setup in the actual tests (see the videos below) where the bat could hide in roost box.
Here is a video showing a captive-born bat feeding on a live animal for the first time.
We had previously found that younger bats are far more exploratory and more likely to crawl and jump on top of novel objects, and we observed that this was equally true when feeding on novel live animals! Overall, it seemed that the young vampire bats could feed on a live animal, but they were not particularly good at it when compared to some wild-caught vampire bats. We could not compare them with their mothers however, because none of the mothers even tried to feed on the chicken. Instead, they hid in their roost box the whole night.
Sam Kaiser also did an experiment testing whether captive-born or wild-born bats prefer cold blood (which is what we give them in captivity) or warm blood (which is what they would feed on in the wild). It turns out that the vampire bats don’t really care much at all about the blood temperature when the blood is in a feeder spout. This might seem a bit surprising because vampire bats use heat to find blood near the skin, but it’s not too surprising to consider that vampire bats use many different cues (echolocation, olfaction, vision, etc) and they probably learn to use different cues in different contexts.
Study: Berrío-Martínez J, Kaiser S, Nowak M, Page RA, Carter GG. 2019. The role of past experience in development of feeding behavior in common vampire bats. PeerJ 7:e7448https://doi.org/10.7717/peerj.7448
At the end of May, Rachelle Adams and I finished teaching the course “Tropical Behavioral Ecology and Evolution” in Panama. Each student worked on an individual research project and also wrote a blog post about another student’s project.
In June, students Imran Razik, Bridget Brown, and David Girbino were joined by Cynthia Marroquin and Emma Kline. Simon Ripperger and Hanna Wesier also joined up with us from Germany. Dineilys Aparicio is helping us as an intern.
Imran is continuing work on cooperative relationships in vampire bats by looking at variation in urinary oxytocin as a predictor of grooming and food-sharing. Bridget is studying if bats use olfaction to select roosting sites. David is looking at how “first impressions’ between vampire bats as strangers might predict their relationship development. He is also helping us look at individuality in the echolocation calls (a student project led by Amy Luo). Cynthia is looking at individual variation in metabolic rate in bats. Emma is looking at the effects of proximity loggers on bat behavior. Simon is tracking social networks in the wild. Hanna is testing a mobile bat-mounted ECG to measure heart rates.
Basti is continuing his work on sickness behavior in vampire bats. This week at the The Animal Behavior Society Meeting, he is giving a talk on Wednesday entitled Effects of sickness on social networks depend on the type of behaviour, measure, and relationship. His manuscript for this work is currently in revision for Journal of Animal Ecology. At this same meeting, I’m giving a talk on how vampire bats maintain their cooperative relationships from the lab to the field (Friday, after the lunch break).
A paper by Ivar Vleut, myself, and Rodrigo Medellin entitled Movement ecology of the carnivorous woolly false vampire bat (Chrotopterus auritus) in southern Mexico was recently accepted at PLOS One and should be out shortly.
Simon did some great work on developing sites for tracking social roosting and foraging networks. Check out this 30-second clip of some footage he took by staying up all night in a cattle pasture with an infrared video camera. It shows vampire bats competing with each other over wound sites on cattle.
This year we are studying a captive colony. Two of these were bats we captured in December 2015, studied in captivity from 2016-2017, released and studied in the wild in 2017, and now re-captured and being studied again in 2019! During this time, we have seen how these bat interact with more than 30 unfamiliar individuals over the course of about 17 months. Getting many repeated measures in the social or cooperative behavior of individuals across different contexts is key to understanding why some individuals are more ‘generous’ in their grooming and food-sharing.
PhD student Imran Razik was awarded both a Short-term Fellowship from the Smithsonian Tropical Research Institute and a Student Research Grant from the Animal Behavior Society. He will be studying urinary oxytocin as a predictor of variation in grooming and food-sharing between both old (familiar) and new (unfamiliar) individuals.
MSc student Bridget Brown was awarded a Critical Difference to Women Scholarship. She used this money to fund her travel to Panama where she is studying possible chemical cues for roost-finding in bats.
This summer, PhD Student Theresa Chen will be working with Michael Taborsky at the University of Bern, Switzerland, working on information used by rats to make decisions to cooperate.
Imran, Bridget, and Gerry will be at the Smithsonian Tropical Research Institute in Panama. We will be working with Simon Ripperger, Sebastian Stockmaier, Hanna Weiser, and Rachel Page on vampire bat social networks.
The work of two of our past interns, Jineth Berrío-Martínez and Sam Kaiser, entitled The role of past experience in the development of feeding behavior in common vampire bats was recently accepted with minor revisions in the journal PeerJ.
We find that the effort researchers waste in writing proposals may be comparable to the total scientific value of the research that the funding supports…
Although I would add to this idea that writing proposals is not always a wasted effort because it is also an intellectually creative, worthwhile, and fun thing to do on its own. The basic problem is that so many good ideas are not funded and are therefore never made public. Maybe we should publish proposals: “This is what I would do in my lab with a million dollars.” Then if someone else “steals” your research project idea, they could cite your proposal to say “this is where I got this idea” or the author of the proposal would be an author on the paper that actually carried it out. This could encourage more sharing of ideas and data?
Last year, I attended a symposium hosted by Peter Kappeler at the German Primate Center on the topic of “social complexity”. A bunch of evolutionary and behavioral ecologists from different backgrounds got together to argue about stuff like ‘How should we define social complexity?’, ‘Is the brain size of a species a good of measure of social complexity? (or anything at all?) and “Why does Germany have so much more science funding than us?”
This was actually one of the best conferences I attended, I met a bunch of people whose work I’d read, and I started useful collaborations, including one with a Msc student working on neophobia, who convinced me that bats reacting to novel objects was actually interesting and helped me write this paper. With others from Damien Farine’s lab, I wrote my opinion about the conference here.
What’s more socially complex: a bee or a chimp? (Answer: vampire bat). Biologists tend to define social complexity in such as way that their animal is one of the ‘complex ones’. One possible solution to this that I liked for talking about social complexity was the terms proposed by Dieter Lukas and Tim Clutton-Brock: “organizational complexity” (exemplified by cooperative breeders and eusocial insects which have a division of reproduction and labor) and “relational complexity” (exemplified by animals with individualized relationships like some primates, elephants, and of course vampire bats). They published evidence for these distinct dimensions of complexity in mammals here. Others suggested other frameworks.*
The invited speakers were asked to write up their talks as papers for this special issue in Behavioral Ecology and Sociobiology. I gave a talk about vampire bats and I contributed to an invited talk/paper on social complexity across bats, led by Jerry Wilkinson.
Here’s the link to that paper, Kinship, association, and social complexity in bats (if that link doesn’t work look under “publications” above). The basic idea is that comparing social networks across species is actually quite difficult and rarely done because different studies measure ‘groups’ and ‘associations’ differently across species. But bat researchers tend to do the same thing: we individually mark bats, then observe which bats are in a roost across different days, and when we mark them, we collect a tissue sample to estimate their genetic relatedness. Several people have done this over several years. So Jerry gathered all the data together from different researchers that have done long-term studies** and we did the same basic social network analyses in each species to see if anything interesting came up.
To be honest, there wasn’t anything too surprising if you know the social and genetic structures of these different bat species, but it was quite nice to put it all together in one place and to measure all these species using the same metrics. For some species, it did change my picture of their social structures as being a bit more ‘messy’ that I thought. I also noticed was that we actually had different conclusions about relatedness and association for some species than previous published analyses, suggesting that the details of how you measure relatedness and association can determine what you conclude. Another lesson was that the link between relatedness and association can depend a lot on what your null model accounts for. This is something Damien has often written about. For example, if two individuals are always seen together but always in the same roost, then do they actually prefer roosting near each other or do they just prefer the same roost and they don’t actually care about each other? It’s actually easier to infer social structure for animals that switch roosts and move around because you can account for spatial effects. Another example is that a null model that does not account for time effects could lead to the idea that two individuals are highly associated simply because they both died in the first year of the study. Social networks are inherently correlational, and it’s quite easy to draw the wrong conclusions if you don’t think about and correct for these kinds of biases.
Another nice thing that you don’t see in the paper is that we ran all the same analyses in both Matlab (‘Socprog’ by Hal Whitehead) and R (‘asnipe’ by Damien Farine) to test if both packages gave the same results and if not, why not. Given all the possible ways to do things, not all of the analyses we did ended up in the paper, and I think there’s a lot more that could possibly be tested. For example, if we could get reliable maternity data, perhaps we could test for evidence of within-group maternal inheritance of associations (if you’re reading this and want to see if this analysis is feasible, feel free to email me).
*_One could also look at animal social complexity not as just understood by us biologists but more from the perspective of mathematicians who study ‘complexity science’. Liz Hobson and others at the amazing and lovely Santa Fe Institute wrote a paper on this (preprint here).
** Jerry Wilkinson had data on evening bats in the USA. Wilkinson and Kisi Bohn’s had data on greater-spear nosed bats in Trinidad. Mirjam Knörnschild, Linus Günther, Barbara Caspers, Martina Nagy, and Frieder Mayer provided data on sac-winged bats and proboscis bats in Costa Rica. Gloriana Chaverri had data on disc-winged bats in Costa Rica. Gerald Kerth had data on Bechstein’s bats in Germany. Jorge Ortega had data on Jamaican fruit bats kin Mexico. Krista Patriquin had data on Northern long-eared bats in Canada. Bryan Arnold (Pallid bats) and Dina Dechmann (Lophostoma silvicolum, the bats that live in active termite nests) also contributed data but were not included in the study because the data were too sparse to estimate good networks. Victoria Flores and Rachel Page will soon be adding the frog-eating bat to this comparative dataset.
Nov 8 Seminar: “Wireless tracking sensor network give novel insights into the (social) life of bats” by Simon Ripperger. (1:00–2:00pm, Room 110, Orton Hall, The Ohio State University). Simon is visiting my lab this fall and joining us this spring to track wild vampire bat social networks (and vampire bat-cattle networks).
Kin selection and allocare in sperm whales. “babysitting rates were correlated with relatedness (rs = 0.4, P < 0.05), and allonurses were, on average, closer maternal relatives of the calves they nursed than were available females who were not allonurses (Δr = 0.14, P = 0.054).”
Social bonds facilitate cooperative resource sharing in wild chimpanzees.”The strongest predictor of sharing across food types was the presence of enduring and mutually preferred grooming partners, more than harassment, direct signalling, or trade. Moreover, urinary oxytocin levels were higher after the sharing of both individually and jointly acquired resources compared with controls.”
Resource Ephemerality Drives Social Foraging in Bats. “Miniature GPS-microphone tags allow monitoring wild bats’ movement and interactions. Bats foraging on ephemeral resources move in groups in variable movement patterns. Bats foraging on predictable resources move alone and in fixed movement patterns.”
By-product group benefits of non-kin resource-sharing in vampire “Our study focuses on the contrast in the group estimates between sharing and non-sharing populations. For constant ecological resources, sharing behaviour can increase the sustainable population size, increase the total resource stored in the population, and reduce the average resource required per individual, compared to a non-sharing population.” I do not agree that this group-based modeling approach makes the correct assumptions.
I’ve always been incredibly curious about the natural world and how it works, especially the animal kingdom. As a kid I would spend hours peeking under rocks, watching documentaries, and reading through wildlife encyclopedias. My entire childhood was focused around biological exploration, be it outside or in a book, so when I finally found out what “zoology” was in fifth grade, it immediately resonated with me, and it was then that I decided to become a zoologist. Although it was a vague plan at the time, my motivation only strengthened as I got older, ultimately leading me to apply for my bachelor’s degree in zoology at SUNY Oswego.
At university, I immediately jumped into a two-year long laboratory position as research assistant to Dr. Julien Bachelier, an evolutionary biologist and plant systematist. Following this, I began an animal ecology research assistantship to diversify my skillset in the field, first aiding in a study on the behavioral responses of white-footed mice and Northern short-tailed shrews to predation threat. The next year, I collaborated on a project which led to my first publication on same-sex courtship behaviors in fruit flies. Shortly thereafter, I travelled to Costa Rica with my research advisor, Dr. Maria Sagot, to help study the importance of group vocal behavior on roost-finding efficiency in Spix’s disc-winged bat. After Costa Rica, I worked for two months at the Bronx Zoo in New York City, and while it was fun, it helped me realize just how much I valued the intellectual rigor of research. So, when I returned to university, I was confident in my scientific and professional goals. I became a teaching assistant for a mammalogy course, which I found very rewarding, and I further conducted an independent undergraduate thesis on seasonal changes in beaver activity and the impact of beaver presence on diversity at an artificial pond ecosystem.
Understanding animal behavior at its core has always been my greatest passion, so I’m not surprised to find myself excitedly starting my PhD in Evolution, Ecology, and Organismal Biology. I also look forward to working with Dr. Gerry Carter, and my plan is to follow up on his most recent work and look more closely at the formation and stability of vampire bat social bonds. Overall, I hope I can make significant contributions to the fields of behavioral ecology and biology, and one day pay it forward to the next generation of young curious naturalists who find themselves endlessly reading, watching documentaries, or peeking under rocks.
Imran Razik is a recipient of the Ohio State University Graduate Enrichment Fellowship. he is conducting experiments in Panama on whether oxytocin explains individual variation in how vampire bats respond to new group members.