Blood for a Roost-Mate: Vampire Bats Echo a Tiny Favor Economy
Vampire bats regurgitate blood to feed starving roost-mates, including non-relatives, and remember who helped them, forming a memory-based reciprocity rather than kin-based sharing. Across decades of experiments, donors tend to give back to partners that have fed them before, with 64% of sharing pairs not related and returns about 8.5 times higher than kin-based expectations. Initial low-cost grooming can escalate to food donations, suggesting a cautious audition process that builds partnerships over time. While captivity and lab studies have limits and researchers caution against anthropomorphizing, the evidence supports a small, memory-driven ‘favour economy’ among bats.
