This is an exciting time in the world of humpback whale research. New findings are emerging rapidly, often challenging conventional wisdom.
Snorkelers and divers off the coast of Maui often hear the complex, patterned whale vocalizations that are commonly called "songs." Researchers believe these sounds can travel through the water for hundreds, perhaps thousands, of miles. Only males produce these organized "songs," and for many years, it was believed that this singing only occurred in warm water breeding areas, such as Hawai'i.
That belief is being reconsidered, in the face of evidence that North Atlantic male humpback whales sing extensively on their feeding grounds. According to a recent article in "Aquatic Biology," a team of researchers, including Elizabeth Vu of the Northeast Fisheries Science Center, recorded whales in Stellwagen Bank National Marine Sanctuary, an area where North Atlantic humpback whales feed in summer, in 2006 and 2008. They found that song occurred there during all months of their study, except for February 2006 and June 2008.
Songs vary between breeding areas, which is why whales from Hawai‘i may sing a slightly different song than whales in Japan or Mexico.
Photo: Pacific Whale Foundation
It is known that the whales within a given breeding area sing the same unique song, which changes throughout the season. Songs vary between breeding areas, which is why whales from Hawai'i may sing a slightly different song than whales in Japan or Mexico. Science has sought to understand the function that the song plays in the social dynamics of the species.
Maui researcher Jim Darling and his team have theorized that males use the songs to promote association with other males. Darling's team conducted experiments in which they played recorded whale songs from various breeding areas to see if they would attract males. They found that greater numbers of singers were attracted to a song similar to the one of their particular breeding area. Definitive answers demonstrating a likely mutual benefit remain elusive.
Other research has found that singing peaks at night. Is it possible that whales are more likely to mate at night? Do the males cooperate in mating situations? These are questions that researchers hope to answer through further study.
It turns out that females and calves also create sounds while in their breeding areas. Acoustic communication appears to be an important part of mother-calf interaction during the calf's first few months of life, according to researchers Dr. Alison Stimpert, David Mattila and Whitlow Au.
The team carefully placed non-invasive acoustic/behavior tags (DTAGs) on humpback calves in Hawai'i and found a higher sound production rate during active behavior and some unusual and loud noises that were previously undocumented on the breeding grounds. They also found evidence of physical contact between mothers and calves, in the form of rubbing noises, which tended to be more common during periods of rest (17 rubs per hour) than during periods of competition when two or more male escorts were present (10 rubs per hour). This data suggest the presence of two or more escorts has an impact on the interaction between mothers and calves.
Several studies are showing that human-generated noise, called "anthropogenic sound," has an impact on whale songs. A study by researchers Denise Risch, Peter Corkeron, William Ellison, Ursula Siebert and Sofie Van Paris showed that songs by humpback whales decreased in frequency in Stellwagen Bank National Marine Sanctuary when an Ocean Acoustic Waveguide Remote Sensing (OAWRS) experiment was taking place about 120 miles away.
OAWRS produces low-frequency acoustic waves that can travel over considerable distance. This study shows the greatest distance over which anthropogenic sound has been shown to affect the behaviors of baleen whales.
Research frequently identifies new dangers to whales. Pacific Whale Foundation's (PWF) researchers have documented lesions and wounds on the backs of female humpback whales in Australia and Ecuador. Whale mothers spend long periods of time at the surface of the ocean, often with their calves beneath them, and are exposed to more sun as a result. The ozone depletion above Queensland, Australia, may increase the likelihood of such skin maladies for South Pacific whales.
Research can also help protect whales from danger. PWF's study of 2,464 humpback whale sightings from whale watch vessels indicated there is an 8 percent increase in the odds of a surprise encounter with a whale for each one knot increase in vessel speed. It supports the message of PWF's Be Whale Aware program, which urges all vessel operators to reduce their speed during winter and spring when whales are present in Hawai'i.
PWF expanded its study of vessel-whale interactions this winter, stationing a researcher with a theodolite (a surveying instrument with a rotating telescope for measuring horizontal and vertical angles) above Ma'alaea Bay. The study will further document the rate of surprise whale encounters by vessels operating in the area and the reactions of whales and calves to vessels in the area, serving as a ground truth effort to remove any bias of boat-based surprise encounter data.
Sometimes whale research can benefit humans in surprising ways. Using scientific modeling, researchers have found that the small bumps, known as tubercles, along the front edge of a humpback whale's pectoral fins create less drag and more lift when compared to a smooth fin.
Human engineers have borrowed the idea, adding similar bumps to windmill and helicopter blades to improve their efficiency.
Visit the PWF tent at World Whale Day to learn more about ongoing research.
Merrill Kaufman is an education manager for Pacific Whale Foundation.