Perhaps you’ve heard about the wayward humpback whales, a mother and calf, who had become disoriented and began swimming inland towards Sacramento, California. They were traveling down the Sacramento River, causing a lot of grief to the Coast Guard and to marine biologists trying to think of a way to get the pair turned rightways.
Luckily, yesterday the two whales started swimming out to sea again after rescue crews lured them away by playing whale songs in the direction they wanted them to swim. This same ruse was successfully used in 1985 to divert another humpback who had swum around the area for almost a month before being lured back to sea.
An interesting story, and I thought would be a good opportunity to talk a bit about some of the cool properties of whale song.
Continued under the fold…..
Whale song is the colloquial term for the repetitive sounds that certain types of whales make to communicate with each other. This type of communication evolved due to the limited ability of other sensory abilities (sight, smell, etc)to perform as well in water as on land. On the other hand, sound, and particularly low-frequency sound, has the potential to travel miles in water while preserving the qualities of the information with high fidelity. The speed of sound in water is in fact four times what it in through air. The echos of this transmitted sound can also be utilized by some dolphins and whales to locate objects in space.
The type of sound and method of production of whale song varies between ‘toothed’ and ‘baleen’ whales. Toothed whales create high-frequency clicks and squeals (you’ve probably heard dolphins make these sounds) while baleen whales produce the low-frequency mournful-sounding rumblings. The toothed whales use clicks for echolocation and force air through “phonic lips,” which are located in the whale eqivalent of the sinuses, and this sound is focused through a fluid-filled organ in the whales head called a ‘melon’ or out the blowhole. Why its called a melon, I’m not quite sure…unless it has to do with the shape of the organ which might be described as vaguely melon-shaped.
Baleen whales use a different mechanism to produce sound, and what that is we aren’t exactly sure, although they do have a layrnx but no vocal chords. They produce mostly low-frequency sounds, below 5000 Hz (which is towards the lower end of human hearing range) and much of it in the 20-200 Hz range. Songs can last half-an hour or more, and are predominantly produced by males in breeding zones. Humpback whale song has a predictable structure: the base “notes” of the song are very low-frequency bursts of sound lasting several seconds which may be frequency or amplitude modulated.
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 will repeat the same song, which last up to 30 or so minutes, over and over again over the course of hours or even days. This “Russian doll” hierarchy of sounds has captured the imagination of scientists.
In addition to the “mating song” there’s also a “feeding song”; this is the song that the whale rescue team used to lure the wayward calf and mom back to sea recently. This song is a 5-10 second sound of stable frequency, repeated. Likely this evolved due to the cooperative nature of Humpback whales’ feeding patterns (some swim underneath schools of fish and lunge up).
I also wrote a post about the inner ear and cochlea of whales (its huge!), check that out here if you like.