This is the family tree for vampire bats at Organization for Bat Conservation. This was a bit difficult to construct for a couple of reasons. The math for estimating kinship analyses from genetic markers assumes large wild populations with zero inbreeding (exactly the opposite of what we have here). For this reason, reliable pedigree reconstruction in a small or inbred population with genetic markers is supposed to be difficult to impossible. However, in addition to 30 polymorphic markers, I knew several other pieces of information to help me along: allele frequencies from some wild vampire bats, known mothers, all potential fathers, and the dates of births as well as male castrations, which reduced the possible fathers to even smaller subsets.
The genetic data revealed two cases of mistaken maternity due to alloparental nursing. In both cases, the female bat Mina had a pup but also nursed another female’s pup at the same time. There was one case of incest: Gelfling had an offspring with his own daughter. In the wild, this is typically prevented by dispersal of one or both sexes from the colony. For bat species where the dominant male typically remains in the group longer than the the time it takes a female to reach reproductive maturity, then the females will typically disperse to avoid mating with their fathers. But in most polygynous bats, including vampire bats, the dominant male is overthrown frequently and it is therefore the males that disperse. This incest avoidance pattern is common across mammals, and explains a big chunk of mammalian dispersal behavior and social structure. But incest might be common and have some benefits in some mammal species . In at least one bat species, females appear to sometimes choose to mate with their own father or grandfather, a behavior called intra-lineage polygyny.
Despite some inbreeding, it seems at first glance to me (looking at this chart and the relatedness estimates) that the female bats were still avoiding inbreeding overall, and that inbreeding occurred less than expected by chance even before the males were being castrated. For example, many of the females mated with the dominant male named “The Count” except for Mya, Veronica, and Countess– all females that were somewhat related to him according to genetic data. Many of the females mated with Gelfling who was also very unrelated to all of them. But I need to run a math simulation to check this intuition. I’m interested to see if there is evidence that females can indeed recognize individuals that are related to them through self- or familial phenotype matching via smell (MHC) or perhaps even voice similarity.
It’s unclear to what extent female vampires have control over their matings. All the mating I’ve seen in common vampires appeared “coercive” in nature (e.g. the female is fighting off the male and the two might even fall to the floor with biting and screeching). Note that I would be very biased to noticing these kinds of dramatic coercive matings. So I really have no idea if male courtship exists in this species or what it might look like. I have seen what looks like courtship behavior in white-winged vampire bats suggesting an important role of female choice. These guys flash their white-wings tips and maybe even sing to females (this is based on anecdotal observations of some more complex calls that I only observed when males and females were placed together).
Recent papers of interest:
- No Short-Term Contingency Between Grooming and Food Tolerance in Barbary Macaques
- Acoustic-GPS tracking of bats: a cool new way of studying bats
- Ecology important for psychology of cooperation
- an argument that cooperative breeding probably doesn’t have the cognitive consequences that people sometimes assume
- Is reciprocity caused by “tit for tat” or “follow your friends”?
My next post will be about a recent trip to Thailand looking at bat pollination and the bat lure, dimethyl disulfide, a floral scent compound found in many bat-pollinated flowers.