Mothers respond to biological pup calls with heart rate changes in Japanese house bats, Pipistrellus abramus

Maternal care is essential for offspring survival in mammals, especially in colonial species where mothers must recognize their own young among many. In the Japanese house bat, Pipistrellus abramus, mothers identify their pups using acoustic cues, particularly isolation calls (ICs) produced by newborns. However, the physiological mechanisms underlying such maternal recognition remain largely unknown. Here, we investigated maternal emotional responses of mother bats to pup calls by measuring heart rate (HR) changes during controlled playback experiments. We recorded ICs from 2-day-old pups and echolocation calls (ECs) from 30-day-old pups, then presented these sounds to mothers after their pups had become independent. HR significantly increased in response to calls from the mothers own pups--both ICs and ECs--but not to calls from non-family pups. Among all stimuli, ECs from their own older pups evoked the largest HR increase, indicating strong physiological arousal and suggesting sustained maternal responsiveness despite developmental changes in call structure. In contrast, ECs from an unfamiliar adult also induced HR elevation, possibly reflecting general social arousal rather than maternal recognition. These findings demonstrate that P. abramus mothers exhibit selective physiological arousal to their own pups vocalizations, and that HR provides a sensitive physiological index of maternal motivation and recognition based on dynamic acoustic information.