I am hoping to develop some new long-term field sites for future work on vampire bats.
On March 27, I traveled with Austin Garrido, Rob Mies (director of the Organization for Bat Conservation), his daughter Georgia Mies, and labmates May Dixon, Rachel Crisp, Katharina Eggert, Hugo Narizano, and Julia Vrtilek to Lake Bayano, a two-hour drive from our lab in Gamboa, Panama. This is closer than our other field site which is five hours away. On a previous trip, I had seen several stable roosting groups of vampire bats (Desmodus rotundus) in Pueblo Nuevo Cave along with other bats including Natalus mexicanus roosting individually, Carollia perspicillata roosting in small groups, and large mixed aggregations of Pteronotus gymnonotus and, I think, Pteronotus parnelli.
We saw the same species on this trip. At least 3-4 female groups of vampire bats were located in the first part of the cave that is easily accessible from the entrance. These are groups I hope to track in the future using proximity loggers. See the video below with high-definition infrared footage shot by Rob Mies, which allowed me to count the bats.
There are apparently about five cattle pastures in the surrounding area. That night, during the new moon, we set mist-nets around corralled cattle at the closest pasture hoping to catch and band a sample of vampire bats and perhaps even see some of those same marked individuals back in the cave. A large mark-recapture study could even help us estimate the vampire bat population size.
That night, we caught only 25 vampires bats in our nets. Three escaped from the hand or net being before being processed (a female and two bats of unknown sex). Interestingly, only 5 of 24 vampire bats we netted at the cattle pasture were female. One of these female vampires was a yearling, not fully grown. The captures were spread pretty evenly throughout the night, but the highest density of captures seemed to be between 1:45 and 4:00 am. We recaptured two of the bats we banded. The last bat we caught was around 4:30 am and we took down nets around 5 am.
The next day, I saw one of the banded males back in the cave. The three original female groups were still there. Hopefully, this will be a second site that Simon Ripperger and I will study social foraging in vampire bats. I had valuable discussions with the cattle farmers. They agreed to gather the farmers together at some point when we return in order to discuss what work we would like to do there in the future.
A big special thanks to Austin Garrido for organizing logistics, to May Dixon for help with all-night mist-netting, and to Rob Mies for footage.