<p>Roosting animals face frequent threats from intruders, including predators, competitors, and parasites, and have evolved a range of strategies to mitigate these risks. Here, we report the first evidence of drumming behavior in roosting bats, a form of vibrational signaling used in other mammals as an antipredator defense. Through observational and experimental data on <i>Thyroptera tricolor</i>, we describe the biomechanics of drumming—rapid forelimb extensions against the roost substrate—and identify the contexts in which it occurs. Drumming was most commonly triggered by interspecific intrusions, especially by novel objects near the roost entrance, and was rare during conspecific encounters. In controlled trials simulating predator presence, over half of tested individuals engaged in drumming, with significant variation in duration and intensity. We found no sex differences in this behavior, but individual repeatability was high, suggesting stable inter-individual differences. Drumming was sometimes paired with vocalizations, though the behaviors occurred independently as well. Given the structural constraints of the species’ tubular roosts and limited escape options, we propose that drumming functions as a context-specific defense strategy to deter predators and alert group members. Our findings reveal a previously undocumented antipredator behavior in bats and highlight the adaptive value of vibrational signaling in species occupying confined, exposed refuges.</p>