The ocean is dark and full of terrors — including hungry orcas and horny men looking to bang your mum, if you're a baby humpback whale. So it's advisable to keep your voice to a whisper to avoid these predatory eavesdroppers.
A mother-calf pair in Exmouth Gulf. Credit: Fredrik Christiansen
That, at least, is the conclusion of a new study led by Danish and Australian researchers, who tracked eight humpback whale calves and two mothers for nearly 70 hours to understand how Junior signals Mama when he's hungry for some whale milk. Turns out, even though humpback whales are normally loquacious, suckling sessions were initiated quietly. What's more, calves swimming alongside their mothers tended to speak in incredibly faint squeaks and grunts, at volumes many decibels lower than nearby singing males.
Humpback whales, those massive filter feeders reportedly plotting to take over the world, migrate thousands of kilometres in order to rear their young, from high latitude feeding grounds in the Arctic and Antarctic to warm, tropical breeding grounds. After the babies are born, there's a critical window in which calves must pack on a tremendous amount of weight in order to survive the long journey back to cooler waters. They do so by chugging their mothers' milk — lots of it, enough to grow up to a metre per month, according to several estimates.
But how exactly baby humpbacks signal their mothers when it's time to eat has been a mystery.
Seeking answers, researchers visited a humpback whale breeding ground off the coast of Western Australia during August and September 2014, where they outfitted the calves and mothers with multi-sensor tags that allowed them to remotely monitor a wide range of whale chatter and other calf-mother interactions. They found that unlike human babies, humpback calves don't bawl from across the house when they're hungry — instead, they give their mothers a gentle tap or head butt.
The researchers suspect this behaviour helps ensure that snack time doesn't devolve into a nightmarish bloodbath. "Killer whales especially have been reported to have a high success rate in predating on neonatal humpback whale calves in the area," the researchers write, adding that "mechanical stimulation is an inconspicuous way of communicating, allowing the calf to covertly signal its mother of its readiness to suckle".
Even when calves are just swimming alongside their mums, they seem to prefer talking in whispers, the researchers found, chirping at a much lower amplitude than the comparably boisterous adults. In addition to avoiding the attention of predators, these quiet conversations could help mother-calve pairs fly below the radar of predatory menfolk, who are apparently always looking to snatch breeding-age females away for some whale sex.
Of course, these are just some hypotheses that came out of a single study looking at 10 whales in one part of the world, and more data will be needed to confirm what's going on with this covert communication. But understanding how whale families talk to one another doesn't just offer an intriguing point of contrast to our own broken social units. It could help scientists figure out how to protect these massive beasts, whose chatter may be interrupted by ship noise, fishing and other human activity.
Then again, if you're seriously concerned about the impending cetacean takeover, maybe using technology to interrupt these cryptic marine messages isn't a bad thing. Who knows what the whales are really talking about, anyway?