In the footsteps of humpback whales in the icy waters of Antarctica

(On board the ARC Simon Bolivar) In the icy sea of ​​Antarctica, Colombian scientist Andrea Bonilla captures with her camera the tail of a humpback whale, the human equivalent of its fingerprint.

With other scientists, she has been working since 2014 on developing a catalog based on the visual analysis of the caudal fins of these large cetaceans which can measure up to 18 meters long and weigh up to 40 tonnes.

“What we do is follow the story of each individual,” the researcher from American Cornell University explains to AFP aboard the ARC Simon Bolivar, a Colombian navy ship.

His team has identified 70 whales over the years and hopes to find the trace of some of them in order to study their evolution, their movements or even their growth.

“The coloring and patterns of each whale’s (tail) are unique, it’s like a fingerprint, so what we do is look at the different markings that they have, the different scars, and based from this and the coloring, we can know precisely which individual it is,” Andrea Bonilla explains to AFP.

Threatened with extinction for years due to commercial fishing, the mammal has benefited from an international hunting ban since 1985, which has allowed its population to recover.

Today, there are 84,000 humpback whales in the world, according to the International Union for Conservation of Nature’s red list.

A study published at the end of February in the journal Royal Society Open Science, however, revealed that they suffered, in addition to collisions with ships and noise pollution, from the effects of climate change which alters marine ecosystems and the availability of prey.

Continental map

Between 2012 and 2021, the number of humpback whales fell by 20% in the North Pacific, from 33,000 individuals to just over 26,600, according to this study which used the largest dataset of photo-identification ever created for a large marine mammal.

Photographic identification is common in the study of marine mammals, although tail fin identification is used more with humpback whales due to their unique markings and habit of sticking their tails out of the water in plunging.

The species migrates very long distances between warmer breeding areas and food-rich areas in colder regions.

“They take advantage of this large biomass of food that is here (in Antarctica) and, for several months, they just accumulate energy,” explains M^me Bonilla.

From May, “they begin to move back to more tropical areas” and experience a “fasting” period of around six months, she continues.

Inside ARC Simon Bolivar, she uses an image-editing program to crop photos and zoom in on details.

From the photos taken, she also draws on paper the details of the photographed tails.

The objective of Colombian scientists is to constitute a vast catalog of humpback whales in order to compare it to those existing in “other breeding areas” and to consolidate a continental map in order to then implement conservation initiatives.

“If a whale always comes to the same area to breed, it is important to protect these areas. If they disappear or are disturbed, the whale will have no place to go,” warns Andrea Bonilla.