In polar waters, you can listen to the song of the leopard seals. These songs, based on a repertoire of 5 sounds, have been analyzed by scientists. And it emerged that they have a structure similar to that of the nursery rhymes for children.
In the Antarctic seas, in the period of the loves of the leopard seals, just put a hydrophone in the water to listen to the songs of the males of Foca Leopardo. These great pinnipians, over 3 m long, are predators at the apex of the food chain (Cacciano fish, penguins and despite the accidents with humans are rare, one of them was fatal: in 2003 the biologist Kirsty Brown was dragged in depth while he was snorkeling). Lucinda Chambers, of the University of New South Wales in Sydney, and colleagues studied the structure of the songs of the males of Foca Leopardo. These animals have a repertoire of 5 sounds, which you can listen to below, which combine by creating sequences. The researchers found that the structure of the songs of the males of Foca Leopardo resembles the structure of the nursery rhymes for children, who have the characteristic of being repetitive and easy to remember. A deepening on Evidence Network n ° 396 is dedicated to research. Lucinda Chambers told us about the study and behavior of these animals.
On what occasions do the leopard seals “sing”?
The males of Foca Leopardo sing during the reproductive season (late October – early February). The singing consists in immersing under water, singing a sequence of about 10 sounds, and then return to the surface to breathe. They repeat this cycle over and over again for many hours. We observed the females to issue some of the same sounds, but do not perform this cycle.
What is the function of singing?
We believe that the main purpose is to woo females. However, it can also be used to defend the territory from rival males or to advertise their physical form (how large and strong are!)
Do leopard seals have a common repertoire of sounds?
The five sounds that make up their “repertoire” are a acute double trill, a serious double trill, a medium single trill, a serious descending trill and a “siren” with a single trill. They combine these sounds in a complex sequence to create singing.
The song of each male is thought to be unique, as if it were his signature.
It is our theory, we are working to prove it.
How did you analyze the structure of the songs?
The sounds are identical for all seals, but the patterns change from seal to seal. The duration of the songs is also variable. We have estimated a characteristic called “entropy”, which tells us how random or predictable the patterns are.
And what does the similarity with nursery rhymes consist of?
We compared this entropy value with similar values calculated for other animals, including Tursiopi and megattere, as well as with human musical genres such as classical, baroque music and nursery rhymes. Comparing the value with the human one, that of the leopard seals was more similar to that of the nursery rhymes. The melody of a nursery rhyme must be predictable enough to be learned by a child. In the same way, the singing of the leopard seal must be sufficiently predictable to be learned from the seal, but complex enough to allow the individual to differentiate his song from that of others.
