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Southern right whale moms and calves may whisper to evade orcas

Quiet calls could help the animals keep close without broadcasting their location to predators

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11:00am, July 11, 2019
right whales

WHALE TALES  The vocal repertoire of southern right whales includes quiet calls that may help mothers and calves stay in touch while hiding their location from predators, a study finds.

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Whales are known for belting out sounds in the deep. But they may also whisper. 

Southern right whale moms steer their calves to shallow waters, where newborns are less likely to be picked off by an orca. There, crashing waves mask the occasional quiet calls that the pairs make. That may help the whales stick together without broadcasting their location to predators, researchers report July 11 in the Journal of Experimental Biology.

While most whale calls are meant to be long-range, “this shows us that whales have a sort of intimate communication as well,” says Mia Nielsen, a behavioral biologist at Aarhus University in Denmark. “It’s only meant for the whale right next to you.”

Nielsen and colleagues tagged nine momma whales with audio recorders and sensors to measure motion and water pressure, and also recorded ambient noise in the nearshore environment. When the whales were submerged, below the noisy waves, the scientists could pick up the hushed calls, soft enough to fade into the background noise roughly 200 meters away.

Hush sound

Southern right whales can make a racket with loud grunts or gunshot-like sounds. But sometimes they communicate quietly with whispers that sound like a mooing cow, as in this audio clip.

Audio: M.L.K. Nielsen et al/Journal of Experimental Biology; Image: Michaël CATANZARITI/Wikimedia Commons 2019

An orca, or killer whale, “would have to get quite close in the big ocean to be able to detect them,” says biologist Peter Tyack at the University of St. Andrews in Scotland. Tyack was not involved with the study, but collaborates with one of the coauthors on other projects.

The whispers were associated with times when the whales were moving, rather than when mothers were stationary and possibly suckling their calves. Using hushed tones could make it harder for the pair to reunite if separated. But the observed whales tended to stay close to one another, about one body length apart, the team found.

Eavesdropping biologists have generally focused on the loud noises animals make, Tyack says. “There may be a repertoire among the calls of lots of animals that are specifically designed only to be audible to a partner who's close by,” he says.

Citations

M.L.K. Nielsen et al. Acoustic crypsis in southern right whale mother–calf pairs: infrequent, low-output calls to avoid predation? Journal of Experimental Biology. Published online July 11, 2019. doi: 10.1242/jeb.190728.

Further Reading

S. Perkins. ‘Spying on Whales’ dives into the story of true leviathans. Science News. Vol. 194, July 7, 2018, p. 29.

H. Thompson. See (and hear) the stunning diversity of bowhead whales’ songs. Science News. Vol. 193, May 12, 2018, p. 48.

M. Rosen. Pygmy blue whales deepen their moans. Science News. Vol. 189, June 25, 2016, p. 13.

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