Whale communication and culture
One of the most compelling fields in whale biology is the study of communication and culture. Odontocetes, or toothed whales such as dolphins and sperm whales, propagate sound waves to echolocate, allowing them to detect objects and organisms with sonar. Mysticetes, or baleen whales, have vocal folds, or cords, that allow them to generate the loudest biological sounds on earth. Some cetologists have found that these sounds also indicate the presence of cultural lineages. Groups of killer whales maintain their own vocal dialects, despite interaction with other orcas. Dolphins appear to possess some of the core properties of grammar and syntax, fundamental to human language.
For much of the twentieth century, the typical lab of a whale biologist was about six meters above the open sea. On the flensing deck of factory whaling ships, cetologists examined blubber thickness, stomach contents, gonads, and earwax layers. They learned a lot about dead whales: what they had eaten and when they had become sexually mature. The layers of wax provided an indication of age.
World War II interrupted these studies and the business of whaling. German whale chasers were employed to hunt Allied submarines, and enormous Japanese whaling ships transported miniature submarines across the Pacific to attack Pearl Harbor. The suspension of the hunt likely saved many whales in the Southern Hemisphere, at least for a while. Yet the extensive use of depth charges and bombs in the north probably killed many thousands of cetaceans.
It wasn't until after the war that a few biologists probed the ocean and began to listen to the whales themselves. The cetologist William Schevill made the first hydrophone recordings of cetaceans in the wild in the 1950s. At the Woods Hole Oceanographic Institution in Massachusetts, he described the calls of more than 30 marine mammal species, from sperm whales to blue whales, dolphins, and seals. Schevill's knowledge of these underwater sounds was so extensive that he helped defuse a tense moment between the US and Soviet Union during the Cold War. Constant low-frequency blips had been detected in the oceans, and the American military suspected that the Soviets might be using these sounds to locate US submarines. Schevill and his colleague William Watkins found the source: fin whales produce trains of blips for about fifteen minutes, followed by a two- or three-minute pause when they surface to breathe.
As it turned out, these sounds were being used for detection, but fin whales were not considered a national threat. (This didn’t stop the military from using whales as target practice at the time.) Often feeding beneath the euphotic zone, the surface of the ocean where light is dense enough for photosynthesis, whales use sound to locate prey. Male humpbacks sing for months on their breeding grounds, and beyond. Whales also rumble, grunt, and gurgle—using their voices to attract mates, stay in touch with their offspring, and navigate the shelves, seamounts, and islands in the ocean.
In the dark world of the ocean, whales depend on sound for orientation. Lacking an external ear, they detect sound waves via a fat pad between mandible and middle ear. Sperm whales and most odontocetes echolocate—they emit sounds that enable them to detect distances and shapes. This ability is important for predators of the deep sea, where light is greatly reduced. Only 1 per cent of surface light travels to a depth of 100 meters; at 600 meters the sun's illumination equals that of starlight. It remains unclear whether baleen whales, filter feeders, have this ability. The cetologist Peter Beamish has tested the navigational skills of humpback whales in the dark. After building a maze in a Newfoundland bay for a humpback rescued from a fishing net, he blindfolded the whale with rubber drain plungers. Before being set free, the humpback managed to navigate the maze.
Poets love the idea that whales see the world through their own vocalizations. The Australian poet Les Murray writes of the sperm whale, "My every long shaped cry reestablishes the world . . . " To the American poet Amy Clampitt, great whales
. . . devise the ringing calculus
of icebergs, compute the density of ships
as pure experience of hearing . . .
Whale culture and dialect
In 1967, the biologist Roger Payne began to record and analyze the sounds of humpbacks off Bermuda. Working from hundreds of hours of tape recordings taken on the breeding ground, Payne and Scott McVay contended that the sounds they heard were more than idle chatter. They described the sounds as notes ‘uttered in succession . . . to form a recognizable sequence or pattern in time’; in other words, they were songs with discrete themes. All the whales in a breeding group appeared to sing the same songs, over and over again.
Studies by biologist Hal Whitehead show that sperm whale matrilineal groups, or clans, appear to have distinct cultures and dialects. Some of these clans are itinerant, traveling great distances in short periods of time; others appear to be sedentary, remaining in one place for days. Whitehead transcribes the variation in vocalizations between clans. Group A: "Click-Click-Click-Click-Click," Group G "Click-Click-Click-Click-pause-Click," Group T "Click-Click-pause-Click-Click." Melville it is not, but these codas are preserved across the ocean and over time, each repertoire "a group property." Cultural inheritance in sperm whales is not only observed in their clicks and pauses but also in the variation in foraging patterns, synchronized dives, even defecation rates. To Whitehead, clan identity is similar to nationality in humans:
like being a Slovenian, [clan membership] means not only being a member of a group with distinctive ways of communicating and behaving, but also knowing that one is a member of that group, which is different from other groups. Like humans in multicultural settings, sperm whales seem to show affinity for their own clan.
Sperm whales may define themselves, if they define themselves, by what they are not. Membership in a dominant clan can increase the chances of survival and of reproduction.
Humpback whales also show evidence of cultural transmission. In any year, whales sing identical songs in Hawaii and Mexico, breeding areas that are 4,500 kilometers apart. How do they manage this? Perhaps they hear the songs across long distances or learn them during the summer months, when different groups gather in the north to feed. More remarkable than the geographic consistency is the change in calls over time. Slight variations in the songs occur each year. But, as with evolution, these changes can make huge leaps in a short time. The Australian biologist Mike Noad and colleagues found evidence of a ‘cultural revolution’ in the Southern Hemisphere. In 1996 two male humpbacks from the Indian Ocean arrived in the Pacific with a new song. Within two years, all the Pacific males had changed their tune, picking up the migrants’ songs.
Why did they switch? A preference for novelty, perhaps, though this notion seems to be contradicted by the observation that all whales in a particular area sing the same song in a given year. Although the cause of this dramatic change is still unclear, our knowledge that cetacean cultures persist and change over time—and that culture is not the unique domain of humans—is likely to revolutionize our perception of these mammals.
Threats: Ocean Noise
Whales, and our understanding of their calls, are under a new threat. A dependency on sound makes whales vulnerable to the rising level of noise in the ocean. The number of cargo ships has tripled in the past 75 years, with bigger ships plying the seas each year. Bio-acoustician Chris Clark describes these chronic sounds as a "smog of human-generated acoustic noise.” Fishermen add to this noise, employing depth finders and acoustical gear in their search for fish. The constant noise, which can impact whales' ability to hunt and reproduce, is punctuated by intense pulses from seismic air guns, used to map oil and gas deposits along the shelf. Some of the loudest sounds produced by humans, the pulses reach across entire oceans and may be responsible for recent strandings and deaths of beaked whales in Mexico.
Naval exercises using high-decibel midfrequency sonar for antisubmarine training can also harm whales. Mass strandings of beaked whales have occurred around the world after military tests. In 2000, 13 beaked whales and two minkes stranded in the Bahamas after the US Navy deployed midfrequency sonar. Four of the whales had unusual hemorrhages near their ears. In 2002, 14 beaked whales were stranded in the Canary Islands after a test. Ten of them had gas bubbles in their blood vessels, evidence of decompression sickness. The whales may have reacted to the ear-splitting noises by surfacing too quickly, disoriented by the sonar. Given that symptoms of the bends have never been found in these deep-diving whales, it is also possible that the noises caused the bubbles to form in the bloodstream of vulnerable whales.
There is evidence that cetaceans attempt to avoid noise and increase breathing rates in the laboratory, a sign of stress. In the acoustic smog of the modern ocean, there may be nowhere for dolphins and whales to go. Noise can also affect communication. Humpback whales change their songs in the presence of active sonar, extending their calls to compensate for the acoustic interference on their breeding grounds.
Fidelity to feeding grounds and breeding areas allows whales to exploit areas of high productivity and gather to reproduce. Commercial whalers focused on these areas, often to the point of extirpation, while also hunting adjacent stocks, which limited the opportunity for repopulation. As a result, many historical feeding and breeding grounds are now gone, the cultural memory of the habitat lost. Northern right whales no longer calve in the Bay of Biscay or feed off the British Isles. Fin whales were extirpated from the feeding and calving grounds along the Straits of Gibraltar in the 1920s. Blue whales were hunted to extinction off the coast of Japan by the 1940s. Humpbacks have been extinct off South Georgia in the South Atlantic since 1915. The unique attributes of these whale populations - their dialects, intricate knowledge of local waters, and behaviors - are gone forever.
- Clapham, P.J., A. Aguilar, A., and L. T. Hatch. 2007. Determining spatial and temporal scales for the management of cetaceans: lessons from whaling. Marine Mammal Science, doi: 10.1111/j.1748-7692.2007.00175.x.
- Cox, T. M., et al. 2006. Understanding the impacts of anthropogenic sound on beaked whales. Journal of Cetacean Research and Management, 7:177–187.
- Noad, M., et al. 2002. Cultural revolution in whale songs. Nature, 408:537.
- Norris, S 2006. Creatures of culture: making the case for cultural systems in whales and dolphins. BioScience, 52:9–14.
- Payne, R. S., and S. McVay. 1971. Songs of humpback whales. Science, 173:585–597.
- Right Whale Listening Network at the Cornell Lab of Ornithology
- Whitehead, H. 2003. Sperm Whales: Social Evolution in the Ocean. Chicago: University of Chicago Press.