At 50-feet long, adult humpback whales are so large they have no natural predators. But the same can't be said for their babies, which are some 15-feet long at birth. These blubbery creatures are tasty meal for killer whales, who separate the calves from their mothers before chowing down. But according to a new study, mother and baby humpbacks have a surprising technique to stay safe: they whisper.
As Valerie Dekimpe at Agence France-Presse reports, researchers attached special suction cup tags to eight calves and two humpback mothers to record the whales for 24 hours while they swam in their wintering grounds of Exmouth Gulf in Western Australia. The researchers found that the babies and their mama whales emitted faint squeaks and grunts that could only be heard about 330 feet away while communicating. The vocalizations were 40 decibels lower than male whales, whose calls can be detected kilometers away. They described the results of the study in the journal Functional Ecology.
The project came about as an effort to better understand how the babies survive their early migration. “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 Simone Videsen, researcher at Aarhus University in Denmark and an author of the study. “This migration is very demanding for young calves. They travel 5,000 miles across open water in rough seas and with strong winds. Knowing more about their suckling will help us understand what could disrupt this critical behavior, so we can target conservation efforts more effectively.”
According to Dekimpe, the whispering serves several purposes. Not only does it hide the presence of the calf from killer whales lurking nearby, it could also keep the mother and baby hidden from randy male humpbacks, who often seek mates and interrupt important nursing time. Videsen tells Nell GreenfieldBoyce at NPR that if an orca does catch the quiet sounds, however, it uses the noise as a homing beacon for dinner.
So why do the baby whales make noise at all? The recordings show that the calves only make the vocalizations while swimming, which may be a way of helping their mothers keep track of them, especially in murky waters like those of Exmouth Gulf.
The discovery of the whispers suggests that whales could be more impacted by human activity in the oceans than previously thought. “From our research, we have learned that mother-calf pairs are likely to be sensitive to increases in ship noise,” Videsen says in the press release. “Because mother and calf communicate in whispers, shipping noise could easily mask these quiet calls.” Just last year, a study of humpbacks in the North Atlantic showed that noise from ship traffic significantly impaired the whales’ foraging technique and behavior.
This latest find further underscores the importance of quieting human impact on the environment. Perhaps we could a lesson from the whales and operate in whispers.