Acoustic-GPS pilot tests with frog-eating bats

I just arrived in Panama and I’m very excited to be here.

I recently joined a collaboration between Rachel Page’s lab in Gamboa, Panama and Yossi Yovel’s lab in Tel Aviv Israel. Rachel studies the fringe-lipped or frog-eating bat, Trachops cirrhosus, a bat that eavesdrops on the mating signals of its prey, frogs and katydids. This system is a classic story in behavioral ecology, and an important model for understanding the evolution of behavioral and cognitive traits under both natural and sexual selection. Mike Ryan has long studied the dilemma faced by male túngara frogs – to attract mates the male frogs must call conspicuously, but the types of male frog calls that are more attractive to female frogs are also more attractive to the bats. Rachel and her lab have used controlled experiments to study the bat side of this story. She has showed that the bats can (1) rapidly alter associations about prey cue and quality, (2) adaptively switch between social and asocial learning strategies, and (3) learn from each other in such a way that information can be quickly spread via cultural transmission.

Yossi has developed miniaturized tracking devices (<4 g) that can be mounted on wild bats. These sophisticated tags contain a tiny GPS coupled with miniaturized ultrasonic microphones. They measure several behaviors that are crucial for describing foraging strategy, including the bat’s own biosonar signals and the signals of nearby conspecifics. The device will also record the vocalizations of frogs being targeted, and it will even record the chewing sounds after a successful bat attack.

This month, we are testing how well these tags work with Trachops. Thanks to Rachel, we know a great amount about information use and decision-making by these bats on a small scale. Hopefully, Yossi’s tags will tell use more about foraging trajectories and strategies in the bat’s natural habitat on a much larger scale.

I am also still writing up and submitting my last manuscripts from my PhD vampire work (on use of contact calls) and hope to be finished with that this summer as well.

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Does neocortex size predict social grooming in bats?

The social brain hypothesis predicts that species with larger neocortex volume for their body size should possess more social complexity [1].

Does this apply to bats? It’s not really clear. Wilkinson [2] found that relative cortex volume did not correlate with colony size, but it was greater among those bats with stable social groups. Colony size is a poor measure of social complexity in bats, because a “colony” is not necessarily a measure of a social group or network.

Social grooming is a good measure of social complexity and bonding in primates, and it also occurs in bats [3-5]. Undergraduate Lauren Leffer and I did a study comparing social grooming rates of bats at the Organization for Bat Conservation in Bloomfield Hills, Michigan [3]. We scored the presence or absence of social grooming in 7,800 samples of an equal number of male and female bats of five species (rough average mass): Desmodus rotundus (30 g),  Artibeus jamaicensis (45 g), Carollia perspicillata (20 g), Eidolon helvum (300 g), and Rousettus aegyptiacus (150 g). One advantage of our approach is that all the bats were housed under similar captive conditions with no external parasites (so differences in social grooming are more likely to be driven by social factors rather than environmental ones). Even better, all the bats we watched had an equal and fixed association which also removes group stability as a factor.

I recently examined whether relative neocortex volume was correlated with observed rates. I first regressed previously published measures of body size (g) and neocortex volume (mm-cubed) [6-7], then extracted regression residuals for neocortex size, and tested whether these predicted social grooming rates using both log and rank transformations (social grooming rates were very zero-inflated).

Our tiny sample of five bats suggested that residual neocortex size is likely to predict social grooming rates (log-transformed: R2=0.75, F(1,3)=8.86, p=0.0588; rank: R2=0.77, F(1,3)=10.46, p=0.0481). The plot to the left shows the social grooming rates by rank.

This suggests to me that, even though social grooming is rare in bats (0.1–0.5% of time in the non-vampires), it may still be a useful measure of social complexity, as it is in primates. While we cannot draw strong conclusions from such a small sample, I think this provides some motivation for doing more comparative studies on social grooming in more bats.

References

  1. Dunbar R, Schultz S. 2007. Evolution in the social brain. Science. (PDF)
  2. Wilkinson GS. 2003. Social and vocal complexity in bats. In: de Waal FB, Tyack PL, editors. Animal Social Complexity: Intelligence, Culture and Individualized Societies. Cambridge, MA: Harvard University Press. p. 322-341. (PDF)
  3. Carter and Leffer. In prep.
  4. Carter G, Wilkinson G. 2013. Cooperation and conflict in the social lives of bats. In: Adams, R, Pedersen, S (eds). Bat Evolution, Ecology, and Conservation. Springer Science Press. pg 225-242. (PDF)
  5. Carter G, Wilkinson G. 2013. Food sharing in vampire bats: reciprocal help predicts donations more than relatedness or harassment. Proceedings B. (link)
  6. Baron G, Stephan H, Frahm HD. 1996. Comparative neurobiology in Chiroptera. Basel: Birkhäuser Verlag.
  7. Pitnick S, Jones KE, Wilkinson GS. 2006. Mating system and brain size in bats. Proceedings B. (PDF)
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The best popular science books? My picks.

One of the most frequently read posts on this website was my review of E.O. Wilson’s ambitious but flawed book Social Conquest of the Earth. But there are many more popular science books that I really love! So that’s what I”m writing about here.

Most popular science books have clear and enjoyable writing that explains some field or topic to a lay audience, but the best of them also have their own novel and exciting scientific ideas. Popular science books written by  some particular authors (e.g. Steven Pinker, Richard Dawkins, Bernd Heinrich, Jonathan Weiner, Carl Sagan) are guaranteed to be worth your time,  but many others are hit-or-miss. So if you’re looking for books to read, here are my top 5  recommendations.

1. The Selfish Gene by Richard Dawkins. The book is about how to think clearly about adaptation. Probably the most important book on evolution since Darwin. It might fundamentally reshape how you think about almost everything. Every biologist should read it. Here’s a 4-min off-the-cuff version.

2. The Blank Slate by Steven Pinker. Pinker is the best science writer, and here he covers some of the most controversial topics in academia. Are humans blank slates? Of course not. But Pinker does more than argue these points; he insightfully probes and dissects how the idea of the myth of the blank slate (and two other similar notions) have influenced science, our society, and what we think about many controversial social issues. Everyone should read this book. Here’s a taste from a TED talk.

3. Winter World by Bernd Heinrich. This book is about how organisms survive in the wintertime. There are a lot of “Wow, I-didn’t-know-that-cool-nature-fact!” books out there. In my opinion, this one is probably the best. For a more in-depth book on a narrower topic, read also The Mind of the Raven. The author is a fascinating individual: one of the greatest animal behaviorists and naturalists alive today, and he also “set American national records for any age in the standard ultramarathon distances of 100 kilometers, 200 kilometers, 100 miles, and longest distance run in 24 hours” [156 miles]. Quote from wikipedia.

4. Thinking Fast and Slow by Daniel Kahneman. This guy got a Nobel Prize for the work he summarizes here. There has been a recent wave of books on behavioral economics, how humans decide, what makes people happy, etc. This one is written by the guy who invented the field, so it’s no surprise that it’s the best by a large margin. A 2.5-min trailer here.

5. How the Mind Works by Steven Pinker. The best science writer tackles the most difficult topic. And another short video.

Here are some other great popular science books by category…

Biology

  • Mind of the Raven. Corvids are way smarter than most people realize.
  • The Ancestor’s Tale. A book about evolution focusing on the organisms.
  • The Extended Phenotype. This is a good philosophical biology book.
  • The Beak of the Finch. This is a book about field studies documenting evolutionary change. Won a Pulitzer Price.
  • Summer World. Sequel to Winter World. It’s almost as good.
  • A Sand County Almanac. The classic book on conservation and ecology.
  • Mother Nature is Trying to Kill You. I’m probably biased because I’m in this book. But this is a very funny and enjoyable read.
  • Endless Forms Most Beautiful. About evo-devo
  • Dark Banquet. Stories about vampire bats!
  • The Forest Unseen. Excellent nature writing, about a tiny patch of woods and all that happens there.

Statistics (non-technical beginner books)

  • Intuitive Biostatistics. the most important statistical concepts for biologists explained very clearly.
  • R in Action. I learned how to use R using this book. It was perfect for me.
  • Mont Carlo Simulation and Resampling Methods for Social Sciences. This might be really pushing it for non-technical, but this book is amazing. When a statistics book is written for social scientists, it often means it’s very easy to understand (always a good thing).

Psychology

  • The Better Angels of Our Nature. Wow. Steven Pinker’s latest masterpiece: a book about the history of violence. It will make you appreciate how good life is today. Read this book if you like big ideas, convincingly argued, that will change how you see the world.
  • Incognito. Great book on the brain. Great writer.
  • The Stuff of Thought. The best part of this book is about how people use indirect speech to negotiate social relationships. The chapter on swearing is pretty amazing too.
  • The Language Instinct. This and the last are more Steven Pinker, I didn’t even think I was interested in language until I read this.
  • Why Everyone Else is a Hypocrite. This is a very funny and very smart book on what evolutionary psychology looks like at it’s very best.
  • Predictably Irrational. Lots of experiments. Fun to read.
  • The Folly of Fools. Triver’s book on self-deception. Very enjoyable reading.
  • Stumbling on Happiness. A good book on the psychology of happiness.
  • Social— I’m listening to this one right now as an audiobook. So far, so good.

Cooperation

  • The Origins of Virtue. About evolution of cooperation. A bit outdated now, but still great.
  • Just Babies. A recent book on development of moral sense in children
  • The Moral Molecule. A book about oxytocin
  • The Altruism Equation. About history of a social evolution theory

Books on being a scientist

  • Unweaving the Rainbow.  This book starts with this classic line: “We are going to die, and that makes us the lucky ones.”
  • The Pleasure of Finding Things Out. Great stories by Richard Feynman. Every scientist loves Feynman.
  • 101 Theory Drive. This is a great book about what being a mad scientist is like. Forget all that “sociology of science” stuff, I think this is the best sociological book on scientists. You will learn a bit of neuroscience, but also you will learn about the role of obsession, insanity, and delusional ambition.
  • Time, Love, Memory.  A book about behavioral genetics that reads like a thrilling novel. Very good.

Some good popular science essay compilations

  • This Will Make you Smarter
  • This Explains Everything
  • A Devil’s Chaplain
  • Oxford Book of Science Writing
  • What if? [by the xkcd guy. Everything he does is pure gold. I haven’t actually read this book but I follow the essays online.]

A few other delightful nonfiction books

  • Desert Solitaire by Edward Abbey
  • Pilgrim at Tinker Creek by Annie Dillard
  • The Way of Zen by Alan Watts
  • The Moral Landscape by Sam Harris
  • Waking Up by Sam Harris
  • The Giving Tree by Shel Silverstein. I think this must be the greatest pound-per-pound book about real altruism– a controversial children’s book with only 650 words. There are many interpretations. It is a simple story about a tree that gets happiness from giving, and a boy who only takes and takes. What is most interesting to me is the way we react to this stark and truly unconditional altruism. Is it beautiful and inspiring? Or it is alienating and unhealthy? Even though it is stated repeatedly that the tree is happy, many (most) readers choose to believe that the tree is just self-deluded and they instead find the whole thing increasingly unsettling as the book goes on. (“But how can it be happy if it’s just giving the whole time?”) Readers also become very upset at the boy character for his selfishness, his exploitation, and for his lack of appreciation and reciprocity. What does this tell us about our own human nature? Reading this book is a personal psychological experiment on inequity aversion and our ability to even imagine being an entity that thrives on altruism.

If you have your own recommendations for me and others, feel free to post them in the comments.

And here are some recent and relevant papers…

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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).

Directions 

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

Abstract:

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: http://rsbl.royalsocietypublishing.org/content/11/2/20140959

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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