What Dolphin Moms Whistle

We may never know if mother bottlenose dolphins think their babies are cute. But according to a new study, they do whistle at their calves frequently following birth--apparently to help the youngsters tell their moms from other females.

What do they whistle? Their names, of course. "But wait," you say. "Dolphins don't have names." Not so fast. According to another recent study, they do.

Not Just Whistling Dixie

Researchers have known for years that individual bottlenose dolphins (and members of many other dolphin species, too) emit unique signature whistles using the nasal passages beneath their blowholes (hear one). But until recently, no one knew whether the whistles actually convey identifying information, like the sounds that make up our names do.

To find out, a team of scientists synthesized a series of bottlenose dolphins' signature whistles, then called out to other dolphins through an underwater speaker system. The synthesized whistles lacked any features of an individual dolphin's voice--the same way a computer-generated version of your name would lack any features of your voice. Yet the dolphins often turned to listen when they heard the synthesized versions of their kin's whistles, and largely ignored the whistles of unknown dolphins.

No one's claiming that such signature whistles are equivalent to "Chuck" and "Edna." But the research suggests that dolphins do more than just recognize the tone of a familiar voice. They identify and respond to signature sound patterns even when a stranger whistles them. What's more, we now know that mother dolphins whistle their signature sound patterns--their "names"--to their babies following birth. In fact, they whistle them ten times more often than normal during a calf's early days, when it's most likely to get lost.

Not Just Whistling Names

That alone is probably enough to make you marvel at dolphins. But communication skills aren't the only thing the loquacious cetaceans have going for them. Among their other endearing traits:

• Superb swimming. Bottlenose dolphins, like the ones in the study, have been clocked at close to 20 mph (32 km/h). Other species are even faster--including killer whales (yes, killer whales are dolphins), which top out at 30 mph (50 km/h). Many dolphins are acrobats, too. Spinner dolphins often leap from the water and do flips and barrel rolls before landing in a splashy belly flop (see it).
• Social skills. Dolphins travel in pods that range in size from just a handful to superpods of more than 1,000. They sometimes swim in circles around injured pod members to protect them from further harm--or even support a hurt friend at the surface to keep him from drowning. They also hunt together, circling schools of fish to feast on or driving them to shallow water where they're easier to catch.
• Mammalian mothering. The word "dolphin" comes from the ancient Greek delphis, meaning "womb." That's fitting, since mother dolphins carry their young for a year or more, then nurse them for another six months to two years.
• Fish-eating grins. Bottlenose dolphins, and other species, have upturned mouths that look like a permanent smile. Inside their distinctive beaks, however, are dozens of needlelike teeth designed for slicing up fish. Beaks and teeth are actually the best way to tell a dolphin from a porpoise. Dolphins generally have longer snouts and conical teeth. Porpoises have flatter snouts and spadelike teeth.