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What's new. What's hot. What they're saying. |
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Nature: Big Sounds & Bird Songs
Discover magazine recently profiled biologist Ted Cranford, who for decades has been to trying to figure out how toothed whales and dolphins make their sounds. It's a "non-trivial" question, we're informed, meaning that the answer is "both significant and hard to get." Cranford was the first to start using advanced imaging technologies (such as CT scans) on marine mammals (don't call whales fish!), and recently he even managed to pull off what colleagues called impossible -- a scan of a sperm whale, the largest of the toothed whales. A washed-up whale carcass gave him his subject, although performing the scan involved transporting a frozen 600-pound head through the California desert without thawing, and keeping it both cold and motionless during the several days required for the scan inside one of the US Navy's supersized machines. (His solution -- putting the head inside a massive cardboard tube, usually used for casting concrete pillars, and filling the empty space with expanding polyurethane foam.) The scan revealed "one of the weirdest noses in the animal kingdom," including a unique structure called "phonic lips." Exceptional nose design is necessary for creating the sperm whale's distinctive clicks, which each last only 1/10,000 of a second but can be heard for 15 miles. These can temporarily deafen a nearby swimmer, and if they were produced in open air (instead of underwater) they would be "louder than a jumbo jet taking off." Also, whales can adjust an internal lens organ to focus the sounds into a narrow beam. Cranford hypothesizes that sperm whales can use intense, focused sound to stun nearby prey (schools of little fishes and squid), and that the males also use their powerful sound to impress nearby females. Explore Discover magazine, Dec. 2003 [no free access to archives] Read Ted Cranford's bio page at his Whale Science site (w/scan images of "phonic lips") Hear sperm whale clicks at WhaleSongs.org
Bret Whitney is more likely to be soaking wet from sweat than sea water. He travels the world's jungles and other remote places to identify species of birds. When the birds are hard to see, Whitney's presence on a research team is even more valuable, because of his remarkable ears. A recent issue of Popular Science describes Whitney's work, and his ability to distinguish thousands of species' calls, including some that no one (even Whitney himself) has ever actually seen. (He's able to mimic quite of few of them himself.) This "birdsong virtuoso" has probably identified more new species of birds than anyone on the planet, contributing to a changing consensus about the total number of bird species. Once thought to be around 6,000, scientists today believe the actual number may be over 10,000. Whitney argues that the number might actually be closer to 50,000, by splitting species that, evidenced by differences in songs, should actually be considered distinct species. (For example, there are already more than a dozen "look-alike" flycatchers, not known to interbreed, and distinguishable only by song.) In 1999, Whitney's keen ears were called in to investigate the claim that the long-lost ivory-billed woodpecker still survived in the Louisiana swamps. The spectacular "Lord God" bird has been thought extinct for at least 50 years, but what may have been its distinctive double-rap TOK! TOK! was caught on tape. Despite everyone's hopes that the Lord God bird still lives, Whitney identified the taped sounds as merely automatic gunfire in the distance. Whitney found his interest in birds at age 4, after his grandmother gave him a set of bird identification flash cards, which he promptly memorized while in bed recovering from measles and mumps. (He still can recall from memory the descriptive text on each one.) At age 6 he began sneaking up on birds for closer study. Now he does it for a living, working with Field Guides Inc. to take others on trips for the birds. Read "The Man with 10,000 Bird Songs in his Head" in Popular Science, Dec. 2003 (w/photos, graphics of bird song "sheet music" sonograms) Browse Field Guides' worldwide array of birding tours and find out when you can join Whitney's next trip Listen to Birder.com's bird song gallery Find our more about birds and birding at the American Ornithologists' Union
The South American ovenbird is known for the duets of its mating pairs. According to a recent Science Update from the journal Nature, "when a male and female strike up a song, the male begins by singing roughly six notes per second and gradually upping the tempo. Instead of keeping up with her partner, the female punctuates his beat with one of her own." The result is a "most appealing rhythm," according to researchers Rodrigo Laje of Argentina and Gabriel Mindlin of Univ. of California -- San Diego. Appeal aside, what causes the interaction? Is it conscious patterning? Is it music? The researchers essentially say "no." Their study of recordings reveals that the birds songs behave like non-linear oscillators, which can create complex patterns naturally. The relative rate of male and female notes tend to come in simple ratios; for example one female note for each three male notes (1:3) is very common, but other ratios (1:4, 2:7, 3:10) also appear. Rather than actually counting beats to create their syncopated rhythms, the birds can just let their singing muscles vibrate naturally, and the interaction of the two "oscillators" can cause them to get locked together, jumping between fixed ratios. Huh? Maybe it's just easier to pretend it's music. Read the Nature article, "Songbird duets resonate to beat" |
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