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.