Bats resolve conflicting sensory information for individual recognition

Recognizing conspecifics individually is paramount in shaping animal societies,¹^,²^,³^,⁴^,⁵^,⁶^,⁷^,⁸ and vocal signals can play an important role in this process.⁹^,¹⁰^,¹¹^,¹² Humans¹³ and some other species¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸ identify individuals by integrating information from different sensory modalities. This ability can facilitate stable relationships, kin recognition, and cooperative interactions.⁵^,⁶^,⁷^,⁸ Studies of individual recognition in wild animals remain rare.¹⁹^,²⁰^,²¹ Here, we present experimental evidence that wild greater sac-winged bats, Saccopteryx bilineata, a species with stable social groups, high roost fidelity, and a preference for well-lit day-roosts,²²^,²³ recognize individual group members. In many species,²⁴^,²⁵^,²⁶^,²⁷^,²⁸^,²⁹ including bats,³⁰^,³¹^,³²^,³³^,³⁴ individuals produce distress calls when physically constrained by a predator. We show that distress calls of S. bilineata encode individual signatures. Further, we conducted playback experiments at the day-roosts to test for individual recognition. We used a violation-of-expectation paradigm in which the subject is presented with information for individual identification aligning or conflicting with one another.¹⁷ When individual recognition occurs, the subject may show heightened attention to conflicting information¹⁷^,¹⁹^,²¹ or the plausible association.¹⁸^,³⁵^,³⁶ Remarkably, roosting bats only approached the source of a distress call under plausible conditions-when the supposed caller was absent from the roost. When confronted with an impossibility-the supposed caller was in the roost and its voice simultaneously came from elsewhere-bats ignored the playback entirely. This striking ability to detect and reject such inconsistencies reveals a high level of cognitive sophistication, as these bats reconcile what they see or smell with what they hear to assess the reality of a situation.