Whales use a variety of sounds for communication and sensation.Communication and behavior of whales, R Payne. 1983. Westview Press. The mechanisms used to produce sound vary from one family of cetaceans to another. Marine mammals, including whales, dolphins, and porpoises, are much more dependent on sound than land mammals due to the limited effectiveness of other senses in water. Sight is less effective for marine mammals because of the way particulates in the ocean scatter light. Smell is also limited, as molecules diffuse more slowly in water than in air, which makes smelling less effective. However, the speed of sound is roughly three times greater in water than in the atmosphere at sea level. As sea mammals are so dependent on hearing to communicate and feed, environmentalists and cetologists are concerned that they are being harmed by the increased ambient noise in the world's oceans caused by ships, sonar, marine seismic surveys and offshore wind farms.
The word "song" is used to describe the pattern of regular and predictable sounds made by some species of whales, especially the humpback whale. This is included with or in comparison with music, and male humpback whales have been described as "inveterate composers" of songs that are "'strikingly similar' to human musical traditions".Payne Roger, quoted in: Author(s): Susan Milius. "Music without Borders", p. 253. Source: Science News, Vol. 157, No. 16, (15 April 2000), pp. 252-254. Published by: Society for Science & the Public. This position has been complicated by more recent research, however. It has been suggested that humpback songs communicate male fitness to female whales, although this explanation has been challenged on various grounds.
Types and purpose of vocalization While the complex sounds of the humpback whale (and some blue whales) are believed to be primarily used in sexual selection, there are simpler sounds that are created by other species of whales that have an alternative use and are used all year round. Whale watchers have watched mother whales lift their young towards the surface in a playful motion, while making a noise that resembles cooing in humans. This cooing-like noise made by whales seems designed to relax their young and is one of several distinct everyday noises whales are known to make. Unlike some fish such as sharks, a toothed whale's sense of smell is absent, causing them to rely heavily on echolocation, both for hunting prey and for navigating the ocean under darkness. This requires the whales to produce noise year round to ensure they are able to navigate around any obstacles they may face such as sunken ships or other animals.
It has also been proven that whales are extremely social creatures. The noises that are made throughout the entire year (the main sounds being whistles, clicks, and pulsed calls) are used to communicate with other members of their pod. Each sound a whale makes could mean something different. The clicking noises whales make are used for navigation.
The question of whether whales sometimes sing purely for aesthetic enjoyment, personal satisfaction, or 'for art's sake', is considered by some to be "an untestable question".Entomologist and ecologist Thomas Eisner called it "an untestable question in scientific terms", quoted in: Milius (2000), p. 254
Song of the humpback whale
Interest in whale song was aroused by researchers Katy and Roger Payne as well as Scott McVay after the songs were brought to their attention by a Bermudian named Frank Watlington who was working for the US government at the SOFAR station listening for Russian submarines with underwater hydrophones off the coast of the island. The Paynes released the best-selling Songs of the Humpback Whale in 1970, and the whale songs were quickly incorporated into human music by, among others, singer Judy Collins, as well as George Crumb, Paul Winter, and David Rothenberg.
The humpback whale produces a series of repetitious sounds at varying frequencies known as whale song. Marine biologist Philip Clapham describes the song as "probably the most complex in the animal kingdom."
Male humpback whales perform these vocalizations often during the mating season, and so it was initially believed the purpose of songs is to aid mate selection. However, no evidence was found that links these songs to reprosexuality.
The songs follow a distinct hierarchical structure. The base units of the song (sometimes loosely called the "notes") are single uninterrupted emissions of sound that last up to a few seconds. These sounds vary in frequency from 20 Hz to upward of 24 kHz (the typical human range of hearing is 20 Hz to 20 kHz). The units may be frequency-modulated (i.e., the pitch of the sound may go up or down or stay the same during the note) or amplitude-modulated (get louder or softer). However, the adjustment of bandwidth on a spectrogram representation of the song reveals the essentially pulsed nature of the FM sounds.
A collection of four or six units is known as a sub-phrase, lasting perhaps ten seconds (see also phrase (music)). A collection of two sub-phrases is a phrase. A whale will typically repeat the same phrase over and over for two to four minutes. This is known as a theme. A collection of themes is known as a song. The whale song will last up to 30 or so minutes, and will be repeated over and over again over the course of hours or even days. This "Russian doll" hierarchy of sounds suggests a syntactic structure that is more human-like in its complexity than other forms of animal communication like bird songs, which have only linear structure.
All the whales in an area sing virtually the same song at any point in time and the song is constantly and slowly evolving over time. For example, over the course of a month a particular unit that started as an upsweep (increasing in frequency) might slowly flatten to become a constant note. Another unit may get steadily louder. The pace of evolution of a whale's song also changes—some years the song may change quite rapidly, whereas in other years little variation may be recorded.
Whales occupying the same geographical areas (which can be as large as entire ocean basins) tend to sing similar songs, with only slight variations. Whales from non-overlapping regions sing entirely different songs.
As the song evolves, it appears that old patterns are not revisited. An analysis of 19 years of whale songs found that while general patterns in song could be spotted, the same combination never recurred.
Humpback whales may also make stand-alone sounds that do not form part of a song, particularly during courtship rituals. Finally, humpbacks make a third class of sound called the feeding call. This is a long sound (5 to 10 s duration) of near constant frequency. Humpbacks generally feed cooperatively by gathering in groups, swimming underneath shoals of fish and all lunging up vertically through the fish and out of the water together. Prior to these lunges, whales make their feeding call. The exact purpose of the call is not known.
Some scientists have proposed that humpback whale songs may serve an echolocative purpose, but this has been subject to disagreement.
Other whale sounds Humpback whales have also been found to make a range of other social sounds to communicate such as "grunts", "groans", "thwops", "snorts" and "barks".Cecilia Burke, ''A whale's varied vocabulary', Australian Geographic , AG Online. Retrieved 7 August 2010.
In 2009, researchers found that blue whale song has been deepening in its tonal frequency since the 1960s.McDonald, Mark A., Hildebrand, John A., Mesnick, Sarah. Worldwide decline in tonal frequencies of blue whale songs. Endangered Species Research, Vol. 9 No. 1 23 October 2009. While noise pollution has increased ambient ocean noise by over 12 decibels since the mid-20th century, researcher Mark McDonald indicated that higher pitches would be expected if the whales were straining to be heard.Keim, Brandon. Blue Whale Song Mystery Baffles Scientists. Wired. 2 December 2009.
Killer whales have been observed to produce long range calls that are stereotyped and high frequency travelling distances from as well as short range calls that can travel distances from . Short range calls are reported during social and resting periods while long range are more commonly reported during foraging and feeding.
Most other whales and dolphins produce sounds of varying degrees of complexity. Of particular interest are beluga whales, commonly called "sea canaries", which produce an immense variety of whistles, clicks and pulses. One captive male beluga named NOC (pronounced "no-see") was documented spontaneously imitating the vocal patterns of adult male human speech, which are far lower pitched than normal belugas vocalizations; to achieve these frequencies he deliberately overinflated his vestibular sac, which belugas typically use to keep water out of the blowhole, to control the pressure in his nasal tract.
It was previously thought that most baleen whales make sounds at about 15–20 hertz. However, a team of marine biologists, led by Mary Ann Daher of the Woods Hole Oceanographic Institution, reported in New Scientist in December 2004 that they had been tracking a whale in the North Pacific for 12 years that was "singing" at 52 Hz. Scientists have been unable to explain this phenomenon. For humans 52 Hz is a very low sound; it is audible through human ears as a low moaning sound, while normal whales are inaudibly low. It was not expected that this whale was a new species, more so this whale indicated that a currently known species potentially has a much wider vocal range than previously thought. There is disagreement in the scientific community regarding the uniqueness of the whale's vocalization and whether it is a member of a hybrid whale such as the well documented blue and fin whale hybrids.
Mechanisms of sound production Humans produce voiced sounds by passing air through the larynx. Within the larynx, when the vocal cords are brought close together, the passing air will force them to alternately close and open, separating the continuous airstream into discrete pulses of air that are heard as a vibration. This vibration is further modified by speech organs in the oral and nasal cavities, creating sounds which are used in human speech.
Cetacean sound production differs markedly from this mechanism. The precise mechanism differs in the two suborders of cetaceans: the Odontoceti (toothed whales, including dolphins) and the Mysticeti (baleen whales, including the largest whales such as the blue whale).
Odontocete whales
Odontocetes produce rapid bursts of high-frequency clicks that are thought to be primarily for echolocation. Specialized organs in an odontocete produce collections of clicks and buzzes at frequencies from 0.2 to 150 kHz to obtain sonic information about its environment. Lower frequencies are used for distance echolocation, due to the fact that shorter wavelengths do not travel as far as longer wavelengths underwater. Higher frequencies are more effective at shorter distances, and can reveal more detailed information about a target. Echoes from clicks convey not only the distance to the target, but also the size, shape, speed, and vector of its movement. Additionally, echolocation allows the odontocete to easily discern the difference between objects that are different in material composition, even if visually identical, by their different densities. Individuals also appear to be able to isolate their own echoes during pod feeding activity without interference from other pod members' echolocations.