Late within the night, the Antarctic sky flushes pink. The male leopard seal wakes and slips from the ice into the water. There, he’ll spend the night time singing underwater amongst the floating ice floes.
For the subsequent two months he sings each night time. He’ll sing so loudly, the ice round him vibrates. Every music is a sequence of trills and hoots, carried out in a selected sample.
In a world first, we analysed leopard seal songs and located the predictability of their patterns was remarkably just like the nursery rhymes people sing.
We predict it is a deliberate technique. Whereas leopard seals are solitary animals, the males want their name to hold clearly throughout huge stretches of icy ocean, to woo a mate.
Solitary leopard seals need their name to hold.
Ozge Elif Kizil/Anadolu Company by way of Getty Photographs
A season of underwater solos
Leopard seals (Hydrurga leptonyx) are named after their noticed coats. They reside on ice and surrounding waters in Antarctica.
Leopard seals are particularly vocal throughout breeding season, which lasts from late October to early January. A feminine leopard seal sings for just a few hours on the times she is in warmth. However the males are the true showstoppers.
Every night time, the males carry out underwater solos for as much as 13 hours. They dive into the ocean, singing underwater for about two minutes earlier than returning to the water’s floor to breathe and relaxation. This demanding routine continues for weeks.
A male leopard seal weighs about 320 kilograms, however produces surprisingly high-pitched trills, just like these of a tiny cricket.
Inside a leopard seal inhabitants, the sounds themselves don’t range a lot in pitch or length. However the order and sample by which the sounds are produced varies significantly between people.
Our analysis examined these particular person songs. We in contrast them to that of different vocal animals, and to human music.
Tracey Rogers recording leopard seal songs on the ice edge in Japanese Antarctica within the Nineties.
Tracey Rogers UNSW Sydney
Listening to songs from the ocean
The info used within the examine was collected by one writer of this text, Tracey Rogers, within the Nineties.
Rogers rode her quad bike throughout the Antarctic ice to the sting of the ocean and marked 26 particular person male seals with dye as they slept. Then she returned to file their songs at night time.
The brand new analysis concerned analysing these recordings, to higher perceive their construction and patterns. We did this by measuring the “entropy” of their sequences. Entropy measures how predictable or random a sequence is.
We discovered the songs are composed of 5 key “notes” or name varieties. Pay attention to every one beneath.
The researchers marked seals on the ice with an oil-based paint, to forestall identification mix-ups.
Tracey Rogers UNSW Sydney
A remarkably predictable sample
We then in contrast the songs of the male leopard seals with a number of kinds of human music: baroque, classical, romantic and modern, in addition to songs by The Beatles and nursery rhymes.
What stood out was the similarity between the predictability of human nursery rhymes and leopard seal calls. Nursery rhymes are easy, repetitive and simple to recollect — and that’s what we heard within the leopard seal songs.
The vary of “entropy” was just like the 39 nursery rhymes from the Golden Music E-book, a set of phrases and sheet music for traditional kids’s songs, which was first revealed in 1945. It contains classics such:
Twinkle, Twinkle, Little Star
Frère Jacques
Ring Round a Rosy
Baa, Baa, Black Sheep
Humpty Dumpty
Three Blind Mice
Rockabye Child.
For people, the predictable construction of a nursery rhyme melody helps make it easy sufficient for a kid to be taught. For a leopard seal, this predictability might allow the person to be taught its music and hold singing it over a number of days. This consistency is necessary, as a result of modifications in pitch or frequency can create miscommunication.
Like sperm whales, leopard seals can also use music to set themselves other than others and sign their health to breed. The larger construction within the songs helps guarantee listeners precisely obtain the message and establish who’s singing.
Male leopard seals produce high-pitched cricket-like trills.
An evolving music?
Leopard seals sound very totally different to people. However our analysis reveals the complexity and construction of their songs is remarkably just like our personal nursery rhymes.
Communication via music is a quite common animal behaviour. Nonetheless, construction and predictability in mammal music has solely been studied in a handful of species. We all know little or no about what drives it.
Understanding animal communication is necessary. It will possibly enhance conservation efforts and animal welfare, and supply necessary details about animal cognition and evolution.
Know-how has superior quickly since our recordings have been made within the Nineties. In future, we hope to revisit Antarctica to file and examine additional, to higher perceive if new name varieties have emerged, and if patterns of leopard seal music evolve from technology to technology.
