They say that love makes your heart beat faster. Now, researchers have found that some mum\u2019s hearts quicken when they hear their young calling.\u00a0<\/p>\n
The mums are Japanese house bats (Pipistrellus abramus), a social bunch that gather in communal maternity roosts to raise their young. At dusk, the mums head to out to forage, returning later to feed their youngsters milk, before snuggling down for the day.\u00a0<\/p>\n
Each mum can have up to four pups, and there can be dozens of families in a roost. Imagine then, trying to locate your own youngsters in a dark, cramped cr\u00e8che full of hangry babies.\u00a0<\/p>\n
Not easy, but each pup has its own distinct isolation call, which the mother can recognise. Intrigued, researchers wondered how these calls were affecting the mothers\u2019 physiology.\u00a0<\/p>\n
So, they captured four pregnant females and recorded the calls of their youngsters as they grew up. This included isolation calls, made by the pups at 2 days old, and echolocation calls, made by the pups at a month old. Then they played the sounds back to the mothers. The results are reported in\u00a0Frontiers<\/a>.<\/p>\n The mums were fitted with ECG monitors to record their heart activity. Their heart rates increased when they heard calls from their own pups, but not when they listened to the calls of other mothers\u2019 youngsters.<\/p>\n \u201cThe fact that the mother\u2019s strong heart rate increases in response to her own pup\u2019s call suggests that these vocalizations instantly physiologically prime the mother to engage in maternal behaviour,\u201d says Kazuki Yoshino-Hashizawa from Doshisha Univeristy.\u00a0<\/p>\n Isolation calls from newborn pups typically signal distress, so it makes sense that the mothers\u2019 arousal would increase. More surprising was their reaction to the echolocation calls of older pups. One explanation for this is that the mothers were simply more familiar with these more recent calls.<\/p>\n Researchers have found bat communication to be surprisingly rich. The winged mammals use calls to recognise one another, attract mates, defend food and roosting spots and protest against unwanted advances. Mother greater sac-winged bats even\u00a0adjust the pitch and timbre of their calls<\/a>\u00a0when interacting with their pups, much like human parents use \u2018motherese\u2019 or \u2018baby talk\u2019.\u00a0<\/p>\n What we don\u2019t know is how the change in heart rate\u00a0feels\u00a0to the mother bat. \u201cWhile measuring overall heart rate allows us to gauge the intensity of physiological arousal, it cannot distinguish between positive emotions, such as maternal motivation, and negative ones, such as stress or alarm,\u201d says Yoshino-Hashizawa.\u00a0<\/p>\n So perhaps the mums\u2019 hearts are racing with love. Or maybe they\u2019re thinking,\u00a0Oh no, not dinner time again!\u00a0<\/p>\n