Two animals sing sweetly to one another, exchanging a series cheeps, trills and chirps. You might think you're hearing two birds if you close your eyes. You would be wrong. This is actually the vocal repertoire of two Alston's singing mice (Scotinomys Teguina), tiny rodents that live in Central America's cloud forests. They communicate with their companions by singing passionately.
Researchers were able to hear their sounds, but they are often far beyond our hearing range. Their elusive calls disprove a common assumption that songbirds are the only animal that sings. You might be surprised to learn that more animals sing to each other than you think. Which species does it? Are they singing to find mates, mark territory, or simply because they like it?
We must first understand what distinguishes a song and other sounds. There is no definitive answer. At its simplest, they describe a song as a series of tones that can be repeated over time to create something we would call a melody. This is according to Brian Farrell, a Harvard University professor of biology who spends part of his research on animal sounds in nature. Farrell explained that "all songs can be described as sounds but not all sounds can be considered songs." Live Science was also informed by Farrell. This means that a dog's bark, or a frog's croak, or a cicada's high-pitched tom, are not sounds we would consider song-like.
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Farrell stated that songwriting requires a certain amount of composition. This ability is enhanced by the ability to improvise. Farrell said that singing animals often learn their vocalizations from parents rather than being born with it. This flexibility is believed to be what underpins the ability to improvise.
This definition is subjective and human. Charles Snowdon, a primatologist who studies the communication and music-related relationships of animals and humans, said that singing is just a shorthand for us to use to describe a subset of animal signals. This definition allows us to see the hidden divas in the natural world.
Take the Mexican free-tailed bat Tadarida brasiliensis, which attempts to draw females' attention during mating season by playing a high-pitched song (so high that people need special audio equipment to hear it). Things get interesting when a male bat catches the attention of a potential mate. According to Animal Behaviour's 2013 study, the male bat quickly changes his song to include a variety sequences to keep the female interested long enough to allow mating to begin. These sequences can be quickly rearranged by the bats to find what the female prefers, a true example of spontaneous improvisation under stress.
Gibbons are among the best primates singers, challenging humans. Although gibbons are not all capable of singing, those who do sing can produce complex arias. They often alternate long, hooping cries with short bursts using vocal mechanisms that researchers discovered are also common in opera singers. They also have unique compositions that are context dependent. For example, researchers have found that predator alerts from some gibbon species use a unique arrangement for sounds that is not used in regular calls. Experts believe that gibbon mates sing duets, which can help strengthen social bonds and demarcate territory from other mating couples.
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However, these primates aren’t the only ones who enjoy singing along. Alston's singing mice can also sing duets and do so very politely. They emit a rapid stream of chirping that can be almost 100 notes long, but studies have shown that the songs of one animal will never interrupt the other's. Each mouse actually pauses for a split-second after its companion finishes, before it starts its song. Neuroscientists are studying the neural basis for this pausing ability to find out more about the evolutionary roots human conversation.
Long compositions can be made by whales, which are unique to each pod. (Image credit to Paul Souders via Getty Images.
The haunting melodies of Megaptera Novaeangliae, the humpback whale (Megaptera megaptera), are the perfect accompaniment to any conversation about singing. Roger Payne, an American biologist, captured the attention of the public in 1970 when he recorded the first vinyl recordings of whale songs and distributed them widely. Farrell stated that the songs had such an impact that they were credited with helping to create momentum against whaling in the 1970s.
Payne's recordings also revealed, for the first-time, that whale crooning was composed of distinct and repeated motifs. Farrell stated that Payne was "really the first to realize that these 20-minute utterances of whales are actually compositions." Researchers have found that whale pods can sing unique songs that can be used for identification and other species of whales, such as killer whales (Orcinus Orca) or belugas, (Delphinapterus Leucas).
What are you singing about?
These are only a few of the singing species on Earth. There may be more, depending on how you define wild melodies. Why do singing animals sing rather than bark, bleat, or buzz? Farrell explained that animals who share the same acoustic space have to compete for bandwidth to be heard. It turns out that singing has the advantage of being able transmit over long distances and able to convey lots of information in its long sequences. This is useful when you use it to mark territory, warn others about predators, or to woo a mate using impressive vocal feats like the free-tailed bats.
Do animals sing for the pure joy of it, or are there other functions? There are no easy answers. Farrell stated that we know that animals have emotions and play. He said that these two facts are well-established and that there is a lot of literature on them. There is increasing evidence that animals respond emotionally to music.
Researchers have examined the effects of Mozart's music on mice. They have discovered that the music lowers mice's blood pressure, which is usually correlated with calm feelings. Snowdon, who had already made such important discoveries, decided to take it one step further. He began working with David Teie, a cellist, 13 years ago to see if their relationship would be stable if they created music specifically for animals. The pair hypothesized that animals would respond more to music that contained frequencies in their vocal and audible ranges. They also suggested that they use a familiar tempo, based on their heartbeats or patterns of vocalizations.
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The vocal abilities of free-tailed bats are impressive. (Image credit to Auscape/Universal Images Group via Getty Images.
Snowdon and Teie conducted two studies. They studied cats and a monkey species called cotton-top tamarin (Saguinus Oedipus) and measured their responses to experimental animal ballads they had written. They composed two distinct tunes for the tamarins. One was composed of sharp, staccato beats to evoke monkeys' agitated chatter, and another one is piercing and whistling. They composed a series of high-pitched, slidable notes for cats. The background beat was set to a tempo that matched the speed of a cat's purr. Both cases elicited a response to the music.
Their 2009 study on tamarins was published in the journal Biology Letters. It showed that the tunes they play could either calm or excite them. In Applied Animal Behaviour Science's 2015 study, the cats were more interested in the speakers that were playing their unique tunes than they were in regular music.
Snowdon stated, "This shows that music has an emotional component and that we can manipulate these emotions to change animals' behavior." Snowdon stated that a different group of researchers tested Snowdon's and Teie’s cat music in a real-world setting at a vet clinic. They found that cats were calmer when they played cat music than listening to human music or silent.
Snowdon stated that the fact that songs can have an effect on animals has led to some people considering that music's emotional effects may have deeper evolutionary roots than we realize. This could help shed light on how music affects humans. This is an area of ongoing research. Can we infer that animals sing for pleasure? Farrell believes that animal song may have an emotional component, although this is beyond the scope of our current research capabilities. He said that it is difficult to prove, adding that "the most intriguing questions are the most difficult to test."
It's hard to believe that animal songs can't contain emotion and joy. Think of the gibbon's playful howl, the singing mouse and the whale's soulful song. That's another mystery.
Original publication on Live Science
