Latest paper suggests there are two kinds social grooming in vampire bats (and some other updates)

A recent paper from our group (Team Vampire 2017) suggests that vampire bats might perform two different kinds of social grooming. First, a focal vampire bat is more likely to start allogrooming a bat next to them right after grooming themselves. Imagine a cat in your lap that is licking itself and then starts licking your hand. We call these events ‘actor-driven allogrooming’ because they are initiated by the actor.

Second, a vampire bat is also more likely to allogroom another bat that is currently self-grooming, like in this video clip I posted on twitter:

We call this ‘receiver-driven allogrooming’ and we suggest it could even be a response to need (i.e. the allogroomer might be actually ‘helping’ the receiver). This interpretation is consistent with the observation that vampire bats are more likely to allogroom a bat that has wetted and disturbed fur (even independent of the recipient’s increased self-grooming). It’s also consistent with the observation that allogrooming a past stranger increases the probability of a new food-sharing bond forming (paper in review).

Why do we classify these separately rather than consider them as two different factors that both make allogrooming more likely? Because actor self-grooming and receiver self-grooming do not combine to make allogrooming even more likely in the next moment. Instead, they conflict: a bat that is grooming itself is actually less likely to do receiver-driven allogrooming. An actor-driven allogroomer is less likely to be influenced by what the other bat is doing.

Our interpretation is that some kinds of allogrooming (the receiver-driven kind) might be responses to the recipient’s need, while other kinds might just be a bat extending its self-grooming to lick the fur or wings of others (and are not some form of targeted helping). Perhaps this is why some studies on primates find that social grooming reduces stress in the recipients, whereas others find that is only beneficial for the actors. The effect might all depend on whether the social grooming is internally motivated or a response to a need.

Sometimes I ask my wife to scratch a spot on my back that I can’t reach, and that is some great ‘receiver-driven allogrooming’ and a helpful response to need. But sometimes our cat likes to lick the salt in my hair, or a dog licks your face, or my wife likes to pick at things on my skin, and that is ‘actor-driven allogrooming’ which is… less helpful.

This project was led by MSc student and Smithsonian Tropical Research Institute intern Hugo Narizano. The PDF of this paper can be found under “Publications”

In other news…

A recent paper on vampire bat-transmitted rabies from Daniel Streicker’s lab analyzed 14 years of rabies virus genetic data from Costa Rica. They found that rabies virus was unexpectedly dispersing into Costa Rica from both the north and south. Costa Rica has had outbreaks of vampire bat rabies on and off since 1985. But rather than rabies being endemic, different lineages of rabies have been repeatedly invading and going extinct.

There were some interesting conceptual papers on animal social network analysis this year: one on using concepts from complexity science, another reviewing the uses of multi-layer networks, and another making the argument for ‘networks within networks’.

Our 2019 Panama field season is drawing to a close this month.

Dr. Angela Freeman has just arrived in Panama from Cornell University. Since 2017, we have been collaborating on a project to look at oxytocin and vasopressin receptors in the brain as a predictor of cooperativeness in bats.

My PhD student Imran Razik is finishing his final behavioral tests tomorrow! Over the last six months, Imran led a team of people–including Lovisa Duck, Dini Aparicio, Bridget Brown, David Girbino, Cynthia Marroquin, Emma Kline, Basti Stockmaier, and Gregg Cohen– that has already collected the times and durations of over 10,700+ grooming interactions and 700+ begging or food-sharing interactions in a captive colony with bats introduced from three sites.

Lab Members Imran Razik, Bridget Brown, Simon Ripperger, Cynthia Marroquin, and I will be presenting at the North American bat meetings in Michigan this month.

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New Course

I’m also now officially a Research Associate at the Smithsonian Tropical Research Institute.

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Can a captive-born vampire bat feed on a live animal?

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.

The chicken coop in construction (and the vampire house in the background)

Jineth and Michelle
The finished coop and chicken pen. Free eggs!

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:e7448

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Lab updates: July 2019

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.

Tropical Behavioral Ecology and Evolution, May 2019

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.

Team Vampire Summer 2019
Left to right: Dini, Bridget, Simon, Basti, Gerry, Imran, David, Cynthia, and Emma

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).

Theresa Chen is in Switzerland working on cooperation in rats in Michael Taborsky’s lab.

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.

Simon and I are finally in the process of publishing our work on developing new cooperative relationships (in review at PNAS), strengthening existing relationships, then tracking associations between previously captive bats released back into the wild (to be submitted this week). We used dynamic network analyses to look at how their captive relationships persisted and changed in the transition from the lab back to the wild.

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.

To extend this work, I am writing an NSF grant with Ian Hamilton and Elizabeth Hobson.

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Lab updates: May 2019

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.

I recently published a paper entitled Challenges with assessing the roles of nepotism and reciprocity in cooperation networks  in the journal Animal Behavior. I should maybe write a separate post about that when I have time…

Rachelle Adams and I are now co-teaching the field course Tropical Behavioral Ecology and Evolution in Panama. I am going to learn a lot about ants!

A few other recent and relevant articles:

Jerry Wilkinson and Danielle Adams recently published an interesting paper on Recurrent evolution of extreme longevity in bats

Observing grooming promotes affiliation in Barbary macaques

Evidence for reconciliation between males and females in wild chacma baboons

A recent paper on the seed dispersal services provided by African fruit bats

On the evolution of human food sharing behavior norms

Popular article in American Scientist on work by Daniel Streicker’s group: Glow-in-the-Dark Vampire Bats Could Help Curtail Rabies

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Feb 2019 updates

Simon Ripperger will be joining our team this summer in Panama. Simon recently published the first paper on his new method for sampling dynamic social networks of whole groups of bats in the field. The paper in Biology Letters is entitled “Proximity sensors on common noctule bats reveal evidence that mothers guide juveniles to roosts but not food and it was featured in the “research highlights” section of Nature.

Cooperation in vampire bats was also recently featured in this UK magazine called Bat News:

I posted a preprint for a manuscript, currently in review, called Development of new food-sharing relationships among nonkin vampire bats and The Journal Coverage Podcast interviewed me for a podcast episode about it. We also talk a tiny bit about preprints and why they are great. Here’s a short video about preprints by organization ASAPbio:

Finally, as I am writing my first big NSF grant, I came across this interesting analysis. This quote sums it up:

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?

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New paper on relatedness and social networks across different bats

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.

An example of social networks in three bats and probably some copyright violations.

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.

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