Hello! I’m Gerald Carter – a postdoctoral researcher at the Smithsonian Tropical Research Institute. I’m interested in the adaptive design of cooperative relationships. How do cooperative animals choose, maintain, and regulate their social relationships?
Background: The evolution of cooperation is a central theme of biology. Cooperative traits pose an evolutionary puzzle because non-cooperative traits should exploit the public good of cooperation. Biologists have largely resolved this puzzle with three key ideas. First, natural selection favors altruism that is sufficiently beneficial to close kin. Second, helping behavior can be evolutionarily stable even among non-kin, if interactions are repeated and giving help is conditional on receiving it. Third, cooperators can ensure mutual benefit by choosing or avoiding partners based on the supply, demand, and relative returns of alternative partners.
The problem: The exact mechanisms that enforce cooperation have only been demonstrated in organisms that are easy to manipulate in the lab and possess simple cognition (or lack it entirely, like plants, microbes, and fungi). In more complex vertebrate societies (like our own), the mechanisms stabilizing cooperation are controversial, because a large gap remains between evolutionary models and our understanding of the psychological mechanisms that underlie social decision-making. Most notably, some animals form stable social bonds that appear analogous to friendship, but we don’t understand the development or adaptive design of these complex relationships (or even of human friendship for that matter). Testing for cooperative strategies, like reciprocity, among bonded partners requires an experimental model organism that forms long-term bonds and performs natural, frequent, and costly helping behaviors that can be monitored, measured, and manipulated over long time-periods.
For testing how animals make decisions about forming and maintaining cooperative relationships, vampire bats (pictured left on my shoulder ) are a uniquely tractable experimental model. Vampires are long-lived (30+ years) obligate blood-feeders on a tight energy budget—they can starve to death after just 2-3 nights of unsuccessful hunting. They regurgitate food to multiple kin and non-kin, and these decisions are based on past social experience. Reciprocal donation rates are eight times more important than genetic kinship for predicting food-sharing rates. Non-kin bonds might act as form of “social bet-hedging” – relying exclusively on a few kin donors is too risky.
Vampire bat food sharing gives us a great window into the design of social relationships. It has fitness consequences in nature, it can be induced, measured, and manipulated in captivity, and it affects other social behaviors like clustering for warmth, contact calling and allogrooming. It is possible to manipulate cooperative decisions via intranasal oxytocin and by preventing sharing in specific pairs. My goal is to test theories of how animals make cooperative investments by manipulating food-sharing relationships. See my blog and publications for more information.
What I’m working on now:
- Do vampire bats perform reciprocity?
- How do new food-sharing bonds develop?
- Do vampire bat contact calls convey kinship?
- How do social bonds function outside the roost?
- Do bonded partners share wounds?
- Is riskier helping more nepotistic?
- Is kin discrimination easier to detect than reciprocity?
- How does sickness effect allogrooming in vampire bats?
- Is guano a cue to roost-finding in vampire bats?
- What is the social structure of the frog-eating bat?