Humpback Calves "Whisper" To Their Moms To Avoid Predators
Every winter, hundreds of humpback whales migrate long distances from their high latitude feeding grounds in the Arctic and Antarctic to warmer tropical regions to breed and give birth. The newborn calves, which consume over 52 gallons of milk on a daily basis, have only a few months to pack on the body fat needed to survive the long trek back to cooler waters in summer. How the babies signal hunger and avoid predators during these formative months has always been a mystery to scientists.
“We know next to nothing about the early life stages of whales in the wild, but they are crucial for the calves’ survival during the long migration to their feeding grounds,” says study lead author Simone Videsen of the University of Aarhus, Denmark. "These early life stages of wild whales are so elusive because they're an aquatic animal. We can't follow them around all the time to see what they're doing."
To investigate, the team, which included scientists from Western Australia's Murdoch University, tracked eight calves and two mothers in the Exmouth Gulf using special recorders that captured their movement and ambient sounds. The temporary tags, stuck onto the babies’ skin using suction cups, fell off within a day, and were therefore, not harmful to their health.
Their findings published in the journal Functional Ecology on April 25, revealed that instead of bawling loudly like their human counterparts, humpback calves signal their hunger by gently nudging their mothers or uttering soft grunts and squeaks. The moms acknowledge the requests by responding with quiet calls. This is very different from the normally loud and eerie adult whale songs which reverberate across the ocean.
The team believes these quiet conversations help whale mothers keep track of their young in murky waters without being overheard by dangerous eavesdroppers. According to Videsen, “Potential predators such as killer whales could listen to their conversations and use that as a cue to locate the calf and predate on it.”
The scientists speculate that the barely audible conversations also keep mate-seeking males at bay, allowing the females to focus on nurturing the newborns before the tough, 5,000-mile, journey back to the feeding grounds in the Antarctic.
The study highlights the importance of keeping the nursery waters shielded from human noise pollution. The scientists assert that activities such as whale watching, shipping and fishing, could mask the quiet communication between the mother and calf, increasing the risk of their separation with potentially fatal consequences for the baby humpbacks. Given that the population of the majestic mammals, that were on the endangered list until 2016, is finally recovering, it is important to ensure that every one of these precious calves survives.
Resources: britishecologicalsociety.org, npr.org,
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The moms acknowledge the requests by responding with quiet calls. This is very different from the normally loud and eerie adult whale songs which reverberate across...