Blue whales are changing their tune. That’s what new recordings of these huge mammals indicate. This changing behavior is described in an article in the journal Endangered Species Research. Why it’s happening is unknown. But one theory says they’re singing in lower tones today because the species is coming back. Stand on the beach in San Diego and it’s unusual but not unheard of to see a spouting blue whale. The eastern Pacific is one of a handful of areas where blue whales migrate and feed. Just a couple of blocks from here is the office of John Hildebrand. He’s a professor at the Scripps Institution of Oceanography, and he studies the sounds of dolphins and whales. Hildebrand co-wrote the article, mentioned above, on the songs of male blue whales. He said the males sing in order to warn away other males and to attract females. But their song has been changing. “They’ve been shifting the frequency, they’ve been shifting the pitch, to be lower each year,” said Hildebrand. “And that shift in pitch has resulted in song that is now about 30 percent lower than it was in the 1960s.” Hildebrand said this change in register is happening in blue whale colonies all over the world. But why? The theory of Hildebrand and his
co-authors is tied to the good news that blue whales are coming back from the brink of extinction. Blue whale hunting was internationally banned in 1966. But Hildebrand said prior to that whaling had reduced the number of these creatures to dangerously low levels. “Worldwide in the early sixties there probably would have been, you know, a few thousand,” he said. Those low numbers meant much lower densities of blue whales, and fewer females who could hear a male’s come-hither song. Hildebrand said, for males in that situation, “There’s a push to have the sound go to higher frequency so that more of the girls can hear it.” In other words, in the sixties the girls were so far away the guys had to shout to be heard. But now that blue whales are more numerous, Hildebrand speculates that males have abandoned the tenor register and returned to singing bass, because it makes them sound bigger and more attractive to females. He said males of many species use lower tones to attract mates. “In fact, human females, if you put some headphones on and play a bunch of males voices and you tell them to pick out the sexy voice, do they pick the weak little voice or do they pick the big booming voice? Right? I mean you know the answer,” Hildebrand said. No one disputes the finding that blue whale song has gone down in pitch. But Hildebrand’s theory of why it’s happened has raised some doubts and some eyebrows. “It’s a great anthropomorphism to suggest
that the whales have thought this through and have to modify their behavior,” said whale expert Richard Ellis of New York’s Natural History Museum. “I really don’t think that the whales, for all their big brains and everything else, I really don’t think the whales think about this,” said Ellis. Still, Hildebrand said blue whales are conformist when it comes to behavior. And if a few males realize they can utter deep sexy tones and still be heard by the females, other males are likely to follow suit. news from kpbs.org – The blue whale (Balaenoptera musculus) is a marine mammal belonging to the suborder of baleen whales (called Mysticeti). At up to 32.9 metres (108 ft) in length and 172 metric tons (190 short tons) or more in weight, it is the largest animal ever known to have existed.Long and slender, the blue whale’s body can be various shades of bluish-grey dorsally and somewhat lighter underneath.There are at least three distinct subspecies: B. m. musculus of the North Atlantic and North Pacific, B. m. intermedia of the Southern Ocean and B. m. brevicauda (also known as the pygmy blue whale) found in the Indian Ocean and South Pacific Ocean. B. m. indica, found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of small crustaceans known as krill. Blue whales were abundant in nearly all the oceans until the beginning of the twentieth century. For over 40 years, they were hunted almost
to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide, located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate. Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000). There remain only much smaller (around 2,000) concentrations in each of the North-East Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere. Vocalizations. Estimates made by Cummings and Thompson (1971) suggest that source level of sounds made by blue whales are between 155 and 188 decibels when measured relative to a reference pressure of one micropascal at one metre. All blue whale groups make calls at a fundamental frequency of between 10 and 40 Hz; the lowest frequency sound a human can typically perceive is 20 Hz. Blue whale calls last between ten and thirty seconds. Blue whales off the coast of Sri Lanka have been repeatedly recorded making “songs” of four notes duration lasting about two minutes each, reminiscent of the well-known humpback whale songs. Researchers believe that as this phenomenon has not been seen in any other populations, it may be unique to the B. m. brevicauda (Pygmy) subspecies. The reason for vocalization is unknown.
Richardson et al. (1995) discuss six possible reasons: 1. Maintenance of inter-individual distance, 2. Species and individual recognition, 3. Contextual information transmission (e.g., feeding, alarm, courtship), 4. Maintenance of social organization (e.g., contact calls between females and males), 5. Location of topographic features, 6. Location of prey resources.Whale song is the sound made by whales to communicate.The word “song” is used to describe the pattern of regular and predictable sounds made by some species of whales, notably 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”. The mechanisms used to produce sound vary from one family of cetaceans to another. Marine mammals, such as whales, dolphins, and porpoises, are much more dependent on sound for communication and sensation than are land mammals, because other senses are of limited effectiveness in water. Sight is less effective for marine mammals because of the way water absorbs light. Smell also is limited, as molecules diffuse more slowly in water than in air, which makes smelling less effective. In addition, the speed of sound is roughly four times greater in water than in the atmosphere at sea level. Because 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 and marine seismic surveys.
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