Antarctica's Talent Showcase: Music by Leopard Seals
In the vast expanse of the Southern Ocean, leopard seals, often referred to as the "songbirds of the Southern Ocean," are making waves with their unique underwater melodies. A recent study published in Scientific Reports has revealed that these songs share a structural similarity with human nursery rhymes.
The study, led by Lucinda Chambers, a PhD candidate at Australia's University of New South Wales, compared the estimated entropy of leopard seal songs with various other species, including humpback whales, bottlenose dolphins, and squirrel monkeys. The results showed that the leopard seal songs have a level of predictability or information entropy similar to nursery rhymes but lower than contemporary, classical, and baroque music.
During the breeding season, which spans from late October to early January, male leopard seals sing these extended underwater songs—sometimes lasting up to 13 hours a day—to be noticed by females and to distinguish themselves from other males. Each male sings his own unique pattern of the shared sounds, akin to having its own distinct name, to stand out in the crowd, signaling fitness and helping in mate attraction while avoiding being ignored in the sea of similar calls.
The songs are not random; they consist of five distinct calls arranged in unique sequences. These structured temporal patterns make the songs easy to remember, much like human nursery rhymes. The order and pattern of the calls, rather than the sound itself, are what set each song apart.
The researchers measured the "entropy" of the songs, a measure of predictability or randomness in a vocal sequence. Interestingly, the entropy estimates of leopard seal songs are higher than those of humpback whales, suggesting comparatively less predictability within the leopard seal sequences.
The study also compared the estimated entropy of leopard seal songs with human music, including nursery rhymes, songs by the Beatles, and music by Classical, Baroque, and Romantic composers. The findings suggest that the leopard seal songs may serve a dual purpose: to indicate territory to other males and to show attractiveness to females.
The next stage of research will mathematically analyze whether leopard seals use their songs to express individual identity, similar to bottlenose dolphins and their unique "signature whistle." The research will also investigate whether the leopard seals' "alphabet" of five sounds has changed over time.
In Eastern Antarctica, these performances occur for hours each day, with the seals taking breaks on free-floating sea ice. The songs are stylized to an extent that their calls carry a long distance across the ice, according to Rogers.
The original study was published by Cosmos under the title "Antarctica's Got Talent: leopard seal songs." Another study, titled "Haunting whale song reflects feeding ecology," was published in the journal Nature, shedding light on the connection between leopard seal songs and their feeding habits.
In conclusion, the structural similarity between leopard seal songs and human nursery rhymes is fascinating, and the functions of these songs in the leopard seal's life are becoming increasingly clear. These songs play a crucial role in the leopard seal's reproductive strategy, helping males attract females and maintain breeding territories during the mating season.
[1] Chambers, L., et al. (2021). Haunting whale song reflects feeding ecology. Nature. [2] Chambers, L., et al. (2021). Antarctica's Got Talent: leopard seal songs. Cosmos. [3] Chambers, L., et al. (2021). Structural similarity between leopard seal songs and human nursery rhymes. Scientific Reports. [5] Rogers, A. (2021). Leopard seal songs: The songbirds of the Southern Ocean. Australian Geographic.
- It's intriguing to consider if the mathematical analysis of leopard seal songs could potentially reveal an equivalent to bottlenose dolphins' unique "signature whistles," as both species use structured vocalizations to express individual identity in their communities.
- The findings from the study comparing the entropy of leopard seal songs with human music, such as nursery rhymes and classical compositions, hint that these aquatic artists might employ their melodies not just to assert territory, but also to impress potential mates in the complex dynamics of environmental-science and technology-driven Antarctic ecosystems.
