Studies Shed New Light on Blue Whales and Their Calls

Using a variety of new approaches, scientists at Scripps Institution of Oceanography at UC San Diego are forging a new understanding of the largest mammals on Earth.

In one recently published study on blue whales, Scripps researchers used a combination of techniques to show for the first time that blue whale calls can be tied to specific behavior and gender classifications. In a separate study, researchers used recordings of blue whale songs to determine the animal's population distributions worldwide.

While the specific function of songs and calls produced by whales remains a mystery to a large degree, the sounds are thought to mediate social interactions between the animals.

The first study, led by Scripps postdoctoral researcher Erin Oleson and Scripps scientist John Hildebrand, describes the behavioral context of calls produced by eastern North Pacific blue whales. Few researchers have attempted to link sound production with specific behaviors or environmental conditions to attempt to determine the significance of whale calls.

“This is the first study that has been able to study the calls by directly observing the animal while it is calling and gathering key information such as depth and body orientation-getting a sense of what the animal is doing underwater,” said Oleson. “Once you understand the context of specific types of sounds, then you can use those sounds to infer something about what they are doing when you are not there to actually see them doing it.”

Using a blend of approaches that included attaching miniature acoustic recording tags to whales, Oleson and her colleagues were able to find clear patterns tied to whale behavior, sex type and group size with specific call types. The tags included the National Geographic “Crittercam,” an integrated video-camcorder and data-logging system, and the “B-probe,” an electronic data-logging tag attached to the animal via suction cup. Those data were supplemented with analysis of whale tissue samples and visual observations from ships.

The researchers found that only males produced sounds known as “AB” calls while “D” calls were heard from both sexes, typically during foraging. The researchers note in the paper, published in the January 25 issue of the Marine Ecology Progress Series journal, that the sex bias evident in AB callers suggests that those calls probably play a role in reproduction.

Oleson hopes such call and behavior information will eventually be used for better understanding whale habitats and calculating species abundances.

The second study, published in a recent issue of the Journal of Cetacean Research Management, describes the first attempt at determining worldwide blue whale populations by analyzing nuances of their songs.

Hildebrand and his colleagues used acoustic recordings from around the world, including data from his own instrument deployments and recordings from other scientists and the U.S. Navy, to create a new map that geographically categorizes blue whale species types into nine regions around the world based on their song “dialects.”

While certain regional designations are concentrated in areas close to one coastal area, such as the map's “type 1” classification primarily off the North American coast, others, such as “type 4,” are spread over broad areas, in this case throughout the Northern Pacific Ocean.

The blue whale saw its numbers dwindle dangerously before whaling moratoria were enacted. Now the new study may become a tool for representing its true population stocks. The paper suggests that the stock structures of blue whales, traditionally based on International Whaling Commission boundaries, should instead be reconstructed based on song, which would more accurately represent their true population distributions.

“By listening to the animals, you can tell something about the areas in which they are interacting to breed and that's important to know for managing and conserving the animals,” said Hildebrand, who coauthored the paper with Mark McDonald of Whale Acoustics and Sarah Mesnick of the Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration.

Source: University of California, San Diego

Related stories:

Hunted, rammed, poisoned, whales may die from heartbreak too
More than two decades after the start of a leaky moratorium on whale hunting, the most majestic of sea mammals have made little headway in recovering their once robust populations, say experts.
Research tracks whales by listening to sounds
Researchers have developed a new tool to help them study endangered whales – autonomous hydrophones that can be deployed in the ocean to record the unique clicks, pulses and calls of different whale species. Those efforts are leading to some surprising findings, including the discovery by a team of researchers of rare right whales swimming in the Gulf of Alaska.
Warning buoys for right whales installed along Massachusetts Bay
Endangered North Atlantic right whales are safer along Massachusetts Bay's busy shipping lanes this spring, thanks to a new system of smart buoys. The buoys recognize whales' distinctive calls and route the information to a public Web site and a marine warning system, giving ships the chance to avoid deadly collisions.
Fin whales' big gulp
Some baleen whales, in their powerful feeding lunges, gulp a volume of water equal to a school bus, according to new calculations by biologists at the University of British Columbia and the University of California, Berkeley.
Secrets in rare cartography
Whales were the economic drivers of the 1850s. So important was this resource that the founder of the U.S. Oceanographic Office, Matthew Fontaine Maury, created a map showing the worldwide distribution of sperm and right whales in 1851.
Group calls for ban on dolphin therapy
A British conservation group wants a ban on dolphin-assisted therapy, arguing there is no proof it helps the sick and disabled.
Mariners urged to look out for whales
The U.S. Coast Guard has warned mariners to take care to avoid hitting whales, after three whales were killed off the California coast.
Third blue whale found dead in California
Sharks gnawed at its carcass Saturday as the third blue whale to die off California in two weeks was towed to a beach for examination.

News discussion:

General Science news