Whale vocalization

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 and marine seismic surveys.

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.

[citation needed] 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.

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.

[9] 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 base units of the song (sometimes loosely called the "notes") are single uninterrupted emissions of sound that last up to a few seconds.

[citation needed] 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.

[12] Whales occupying the same geographical areas (which can be as large as entire ocean basins) tend to sing similar songs, with only slight variations.

[citation needed] Humpback whales may also make stand-alone sounds that do not form part of a song, particularly during courtship rituals.

[17] Humpback whales have also been found to make a range of other social sounds to communicate such as "grunts", "groans", "thwops", "snorts" and "barks".

[24] 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.

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.

[12] The multiple sounds odontocetes make are produced by passing air through a structure in the head called the phonic lips.

As the air passes through this narrow passage, the phonic lip membranes are sucked together, causing the surrounding tissue to vibrate.

From there, the air may be recycled back into the lower part of the nasal complex, ready to be used for sound creation again, or passed out through the blowhole.

[31] New cranial analysis using computed axial and single photon emission computed tomography scans in 2004 showed, at least in the case of bottlenose dolphins, that air might be supplied to the nasal complex from the lungs, enabling the sound creation process to continue for as long as the dolphin can add air from the lungs.

[36][37] As “arbitrary traits that function as reliable indicators of cultural group membership,” clan identity codas act as symbolic markers that modulate interactions between individuals.

[citation needed] Research by Dr. Christopher Clark of Cornell University conducted using military data showed that whale noises travel for thousands of kilometres.

[47] As well as providing information about song production, the data allows researchers to follow the migratory path of whales throughout the "singing" (mating) season.

An important finding is that whales, in a process called the Lombard effect, adjust their song to compensate for background noise pollution.

[2] Research indicates that ambient noise from boats is doubling with each decade,[47] reducing the range at which whale sounds can be heard.

[47] Environmentalists fear that such boat activity is putting undue stress on the animals as well as making it difficult to find a mate.

[47] In the past decade, many effective automated methods, such as signal processing, data mining, and machine learning techniques have been developed to detect and classify whale vocalizations.

[51][52] After William E. Schevill became an Associate in Physical Oceanography at Woods Hole Oceanographic Institution (WHOI) in Massachusetts in 1943, his first work was under US Naval auspices investigating echolocation of U-boats.

[53] As he later wrote in 1962: "During World War II many people on both sides listened to underwater sounds for military reasons.

"[53] However, it is worthy of note that his wife Barbara Lawrence, Curator of Mammals at the Harvard Museum of Comparative Zoology (MCZ), often co-wrote these documents with him.

As noted upon his death by the Society for the Bibliography of Natural History, "Bill helped defuse a tense moment between the USA and Soviet Union during the Cold War.

The US military suspected that low frequency blips were being used by the Soviets to locate American submarines, whereas Bill showed these were produced by fin whales (Balaenoptera physalus) hunting prey.