Science

The humpback whale is the most acoustically complex animal

Today, there are some 15,000 humpback whales (Megaptera novaeangliae) in the world, named for the hump they have on their dorsal fin. By the mid-20th century, however, this figure was much lower. In 1966, the population of individuals of this type was less than two thousand.

That is why conservation and observation is necessary among experts in marine biology to prevent it from becoming an animal in danger of extinction again. That is precisely why scientists are now trying to study their behaviour through sounds.

To this end, researchers from the University of Extremadura, specifically in the area of Ecology in the Department of Plant Biology, Ecology and Earth Sciences, together with scientists from the UK’s Institute for Acoustic Research, have analysed recordings of many hours of humpback whales spread throughout the world: Alaska (14), North Atlantic (4), Caribbean (26), Hawaii (21), Indian Ocean (10), North Pacific (23) and South Pacific (16).

Daniel Patón, professor at the University of Extremadura, explains that these observations have allowed them to know, among other aspects, that these animals have a total of 47 formants or fundamental frequencies of emission.

Humpback whale (Megaptera novaeangliae). (Photo: UEx)

“The number of formants depends on the anatomical structure of each species. For example, the human being has 4 or 5 frequencies, the deer has 7 and a nightingale could have between 10 or 12 formants. In the humpback whales we have seen almost fifty, so we can say that this species is the most complex animal in the world, acoustically speaking, to date.

The sounds studied are also equivalent to an acoustic fingerprint that also allows us to establish population differences and observe the evolution of the animal itself.

In this regard, the study has determined that the oldest populations of humpback whales are those of the Indian Ocean, specifically the Gulf of Oman. As Patón points out, “these are the only ones that do not migrate”.

They have also been able to verify that the most recent populations of this species, which is mainly piscivorous, are found on the East Coast of the Pacific. In Hawaii, populations of different origins come together during reproduction. In Alaska only wintering appears.

In order to find these results, the researchers have first of all built up a database of the formants obtained from the listeners of these audios. Subsequently, these sounds have been contrasted across 16 selected mathematical distances. As Patón pointed out, “the most appropriate one for measuring the kinship index by means of multivariate analysis” has been used.

All this has allowed us to know their customs of migration, grouping and courtship, as well as which populations are more archaic. The reliability of these population acoustic tests is supported by the fact that it coincides with recent research using DNA.

“The results obtained are exactly the same as those obtained with genetic techniques. This shows the reliability of the sounds and the method used for this work”, has specified the scientist Daniel Patón. (Source: University of Extremadura)

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