Saint-Paul (France) (AFP) – After traveling thousands of kilometers, many humpback whales choose Reunion Island to give birth to their calves. For scientists, this is an opportunity to collect valuable data. But also to raise public awareness, because the growth of whaling tourism puts pressure on cetaceans.
In fins, mask and snorkel, camera in hand, divers get as close as possible to two whales who are putting on a show for the occasion.
One of them advances towards the swimmers and rises towards the surface to point its head above the water. She dives back and lets the swimmers admire her large pectoral fins. Further on, a third cetacean, with its calf, probes a few meters from the group in water at 24°C, heated by the sun.
Reunion, in the Indian Ocean, is a place of choice for observing marine mammals, which come to give birth or mate between June and October.
[Lire aussi: Cinq ans après la dernière attaque, comment La Réunion a éloigné le « risque requin »]
In 2023, 1,271 humpback whales were recorded by the local Cetacean Observation and Identification Group (Globice). «A record»according to the association.
The island is also one of the rare places in the world to allow swimmers to enter the water, including for observing mothers and calves. But the practice is well regulated.
Diving professionals, specialized operators and simple boaters must be trained in a respectful approach. And with the growth of tourism, what was a charter has become a stricter prefectural decree.
On the surface, four boats are positioned several hundred meters from the animals.
For Audrey Cartaud, project manager of the Quietude team at the Center for the Study and Discovery of Marine Turtles (CEDTM) in Reunion, “The boats put enormous pressure on the animals. Some structures go up to five or six rotations per day”.
[Lire aussi: Prévenir les collisions entre les cétacés et les navires dans le sanctuaire Pélagos en Méditerranée]
Listening to the seabed
To enforce the rules – in particular the presence of a maximum of five boats in a zone of 300 meters around the animal – the maritime gendarmerie regularly organizes outings.
« As soon as the sea allows it (…) we are on the water, we carry out patrols on boarding rules, safety weapons and compliance with decrees. And we also have a vocation to provide first aid“, specifies Martin L’Her, from the Port nautical brigade (north-west), from the zodiac which allows him to scan the area.
The CEDTM is not sworn in but its members also travel the sector.
« We work with the gendarmerie. We meet regularly on the water and we ensure that the regulations are respected as best as possible”underlines Jonathan Cotto, project manager within the CEDTM, at the helm of his boat.
[Lire aussi: A l’écoute des profondeurs de l’Antarctique]
For scientists, the passage of whales is an opportunity to collect valuable data. This involves observing on the surface, but also listening to the seabed: the humpback whale is renowned for having the most complex song in the animal kingdom.
Beverley Ecalle, in full wetsuit, is an ethologist for the Abyss association, specializing in the conservation of marine mammals.
“We saw two blasts then we lost sight of them. We stay a little behind to see (…) if the whales have probed and gone elsewhere. This allows us to observe the entire area to see if there are any other whales nearby.” and listen to their songs, she said.
Songs which make it possible to evaluate the periods and levels of whale visitation from one site and from one year to the next “to better understand the movements of individuals between breeding sites”, according to Globice.
[Lire aussi: Comment le chant des baleines aiderait à percer les secrets du fond des océans]
On his boat, Yann Doh, researcher in cetacean bioacoustics, unwinds the hydrophone cable which will allow the precious songs to be collected. “We have 10 meters of cable, we will try to put as much as possible to record under the surface layer which is very disturbed by the waves, by the bubbles, and which will pollute our recording”he emphasizes.
For the scientist, “It’s really the fact of knowing more that will allow us to communicate with the general public, but also to raise people’s awareness”.
© AFP
To go further:
Slight rebound in the population of a highly endangered whale species
In Polynesia, the growth of whale tourism raises fears for the health of cetaceans
Australia: dozens of cetaceans wash up on a beach
Read also on GoodPlanet Mag’:
The Transarctic expedition: the study of the ice aboard Commandant Charcot
“Save the whales”: disinformation mixes with anti-wind power in the United States
Demonstrators demand the release of environmentalist Paul Watson in Paris
