Two creatures sing softly to each other, exchanging a series of trills, peeps and chirps. If you close your eyes and listen, you might think you hear two birds. But you would be wrong. In fact, it is the vocal repertoire of a pair of Alston’s Singing Mice (Scotinomys teguina), small rodents found in the cloud forests of Central America and which communicate by singing passionately with their companions.
Their sounds are mostly outside of our audible range, so the researchers revealed their sweet symphonies by recording their vocalizations at a frequency we can hear. But their elusive appeals also refute a commonly held assumption: that songbirds are the only animals, other than humans, that sing. In fact, more animals sing to each other than you might think. So what species do it? And do they sing only to find mates and mark their territory – or maybe also, like us, just because they like it?
First, we need to understand what separates a song from other sounds. Few researchers claim to have a definitive answer. But at the simplest level, they define a song as a sequence of tones, which can be repeated over a period of time into something that looks like what we would call a melody, explained Brian Farrell, professor of biology at the Harvard University which devotes part of its research to the study of animal sounds in the natural world. Put simply, “all songs are sounds, but not all sounds are songs,” Farrell told Live Science. By this definition, a dog‘s bark, a frog‘s croak or a cicadaThe high-pitched thrums are not sounds that we would necessarily think of as songs.
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To take it a step further, you could say that a song involves a certain degree of composition, which is facilitated by an ability to improvise, Farrell said. Interestingly, song animals are often also the ones who learn their vocalizations from their parents, rather than being born with the ability; this flexible learning is believed to underlie the ability to improvise, he said.
This definition is highly subjective, human. But singing is a “shorthand way for us to talk about a certain subset of animal signals that we find very musical,” said Charles Snowdon, primatologist and emeritus professor of psychology at the University of Wisconsin-Madison who studies the way animals communicate and animals relate to music. When we apply this definition, we begin to discover the hidden divas of the natural world.
Take the free tail mexican bat (Tadarida brasiliensis), which tries to get the attention of females during mating season with a high-pitched melody (so high-pitched, in fact, that humans have to hook up with special audio equipment to hear it). When a male bat manages to capture the interest of a potential mate, things get interesting. Quickly, he improved his single song to incorporate a variety of sequences, apparently to keep the female intrigued long enough for mating to begin, according to a 2013 study in the journal Animal Behavior. Bats can quickly rearrange these sequences to guess what the female likes, a real case of improvisation under pressure.
Meanwhile, gibbons challenge humans as being among the most sublime singers from the world of primates. Not all species of gibbons sing, but those that produce complex tunes that typically intersect with long calls and shorter bursts of sound – using vocal mechanisms the researchers have discovered are common among opera singers, too much. Their compositions also depend on the context: researchers have found that predator alerts of certain gibbon species have a unique arrangement of sounds not heard in regular calls, for example. In addition, fellow gibbons are also known to duets sung, which, according to experts, contributes to strengthen the social bond and delimit the territory of the other mating pairs.
Related: Why do birds sing the same song over and over again?
However, these primates aren’t the only animals that love to sing. Alston’s singing mice also sing duets, and they do so very courteously. Animals typically emit a rapid stream of twittering (their songs can contain almost 100 notes), but studies show that one animal’s songs will never, ever interrupt another. In fact, each mouse pauses for a fraction of a second after its mate finishes, before starting its own song. Neuroscientists have been studying the neural basis for this pausing ability, to see what it might tell us about the evolutionary roots of human conversation, which can also be based on taking turns.
Meanwhile, no conversation about vocals would be complete without the haunting melodies of the humpback whale (Megaptera novaeangliae). In 1970, the American biologist Roger Payne captured the public’s imagination by producing the first recordings of whale songs on vinyl and distributed them everywhere. The heartwarming songs had such an impact, in fact, that they are credited with helping to boost the anti-whaling momentum in the 1970s, which ultimately resulted in a almost global moratorium, Farrell said.
Payne’s recordings also showed, for the first time, that whale song was made up of distinctive and repetitive patterns. Payne “was really the first person to find out that these 20-minute whale-watching utterances are actually compositions,” Farrell said. Since then, researchers have found that groups of whales have unique songs that can be used to identify them and that other whale species, including killer whales (Orcinus orca) and belugas (Delphinapterus leucas), also sings.
What is there to sing?
These are just a handful of the singing species on the planet, and depending on how we define the wild animal melodies, there can be many more. But why to do do animals that sing sing rather than bark, bleat or buzz? In addition to competing for territory, mates, and food, animals that inhabit the same acoustic space must effectively “compete for bandwidth” to be heard, Farrell said. It turns out that singing has the advantage of transmitting over long distances and being able to carry a lot of information in its long stretches. It’s useful when you use it to demarcate a territory, alert others to predators, or woo a mate with impressive vocal prowess, as free-tailed bats do.
But beyond these functional roles, are there any animals that sing just for fun? Here there are no hard and fast answers. But we know animals play and have “emotional lives,” Farrell said. “These two things are established, and there is a great deal of literature about them,” he said. And there is also growing evidence that animals have an emotional response to music.
For example, researchers studied the impact of Mozart’s compositions on mice, which can hear the highest frequency tones in music, and they found that music lowered the arterial pressure, which is generally correlated with feelings of calm. To build on such discoveries, Snowdon decided to take it a step further: 13 years ago, he began working with a cellist named David Teie, to determine if this relationship would hold if they composed music specially for animals. They hypothesized that animals would be even more likely to respond to music if it contained frequencies within their vocal and audible ranges, as well as a familiar tempo based on their heartbeat or model of vocalizations.
Related: What kind of music do animals like?
In two separate studies, Snowdon and Teie decided to study cats and a species of monkey called the cotton-headed tamarin (Saguinus oedipus) and measure the creatures’ responses to a series of experimental animal ballads that Snowdon and Teie had composed. First, for the tamarins, they composed two distinctive tunes: one composed of high-pitched, jerky beats that evoke the restless chatter of a monkey; and another shrill, whistling melody. For the cats, they composed a sequence of sharp and slippery notes on a background which corresponded to the tempo of a purr. In both cases, the specially composed music elicited a response.
Their 2009 study on tamarinds, published in the journal Biology letters, showed that they could be successful in calming or arousing the monkeys depending on the tune they played. Meanwhile, in a 2015 study in Applied Sciences of Animal Behavior, their cat songs aroused the interest of felines, who were more likely to approach and rub against the speakers playing their unusual songs – a sign of contentment and delight – than the speakers playing regular tunes.
“It shows that there is an emotional component to music and that if we manipulate those emotional factors we can change the behavior of animals,” Snowdon said. In fact, when a separate group of researchers tested Snowdon and Teie’s cat compositions in an actual veterinary clinic setting, “they found that playing cat music kept the animals calmer during a veterinary examination as human music or silence “. said Snowdon.
The fact that songs composed can have this effect on animals has led some to consider that the emotional impact of music may have evolutionary roots deeper than we realize, which could shed light on its profound effect on humans, Snowdon said. This is an area of ongoing research. In the meantime, can we conclude that animals sing only for fun? Farrell is inclined to think there is an emotional component to animal song, but that is beyond our current research capacity to confirm, he said, adding that “the more interesting questions are the most difficult to test. “.
Thinking of the playful cry of the gibbon, the empathetic chatter of the singing mouse, and the moving melody of the whale, it’s hard to believe that there is no emotion and joy woven into the songs of animals. But that’s a mystery for another day.
Originally posted on Live Science.