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13 mai 2017 6 13 /05 /mai /2017 06:53

L'essentiel est invisible pour les yeux. Antoine de St Exupéry.

Les baleines franches de l'Atlantique Nord (baleines des basques, Eubalaena glacialis) n'étaient plus que quelques dizaines d'individus quand elle furent officiellement protégées, en 1935. Depuis lors, leur population augmente lentement (300 au début de ce siècle, 500 aujourd'hui). Elles sont surtout observées près des zones urbaines. Or, certaines d'entre elles disparaissent pendant des années (8 ans, 14 ans...) puis réapparaissent avec un baleineau, alors que les scientifiques les croyaient mortes depuis longtemps. Leurs itinéraires et activités sont inconnus pendant ces périodes. La dynamique d'éloignement vis - à - vis des zones urbaines induit, qui plus est, l'existence d'une population additionnelle invisible et inconnue...

https://www.theatlantic.com/science/archive/2017/05/whale-moms/526494/

The Atlantic Daily, hier.  Elizabeth Preston. The mystery of off – the – grids whale moms. Some right whales disappear for years, only to reemerge in strange places with a baby.

Thick fog sat over Cape Cod Bay the morning of April 20, so the survey boat had to work by sound. Every so often, the researchers aboard cut their engine and listened for deep blows to track down surfacing right whales. By mid-afternoon, the fog had lifted, and Marilyn Marx could clearly see markings on one nearby whale that made her excited. “Big white scar!” she called down to the others from the boat’s tower. “Could be 1412!”

Just then, a baby whale popped up next to the massive female. The group on the boat let out a unanimous whoop.

Marx, a scientist at the New England Aquarium in Boston, and the others scrambled to get photographs and skin samples of the mother and calf. Earlier that month, an aerial-survey team had spotted the pair in the area, and the scientists on the water didn’t want to miss their chance to gather data. Unlike most right-whale moms, 1412 hadn’t given birth in the customary calving grounds. Researchers spot most whales in the population every year or two along the eastern coast of North America. She was last glimpsed 14 years ago—in Iceland. No one knows where she spends her time or has her babies.

The mystery mom, and other wanderers like her, stymie researchers’ efforts to monitor them. But they might offer clues that this endangered population is a little better off than it seems.

Scientists estimate that only around 500 North Atlantic right whales are alive today. For the most part, they hug the coast, says the New England Aquarium research scientist Philip Hamilton. In the winter, mothers give birth near Florida and Georgia; in the spring and summer the whales feed around New England and Canada. A network of spotters identifies whales by their unique markings and tracks their movements. At the aquarium, Hamilton curates a catalog of every known whale and its sighting history.

Some scientists have nicknamed North Atlantic right whales the “urban whales” because they live so intimately with human cities. Swimming near the coast, they get tangled in nets and struck by ships. Pollution taints their waters and noise stresses them constantly. But Hamilton estimates that a small number of the animals are what he calls “suburban whales.” They pop up now and then in the usual habitats—but otherwise they stay off the grid. “Those animals have lots of mystery about them,” Hamilton says. “We don’t know where they call home most of the time.”

Perhaps the daughters of suburban moms also swim off the beaten path.

1412 is one of those whales. “She’s been always a favorite of mine,” Hamilton says, rattling off her strange sighting history: 1984, off the coast of New Hampshire, with a calf. Eleven years later, east of Greenland. In 1997, New Hampshire again, with another calf.* 2003, Reykjavik, where an Icelandic whale-watch company got the last photo of her. The long gaps between her sightings are highly unusual. Adding to her intrigue, 1412 is covered in scars. But the scars don’t match the usual patterns from fishing lines and nets, Hamilton says; her wounds may have come from ice.

The reappearance of 1412 this year was especially exciting because of the calf swimming with her. It was a bad winter for whale babies: Only three were born at the calving grounds. In an average year there would be more like 14, Hamilton says. Then, at the end of April, there was more good news: A fifth calf appeared up north. This calf’s mother was another mysterious whale, number 1515. She hadn’t shown up since 2009 and was presumed dead. 1515 has used the calving grounds in the past, Hamilton says, but in between babies she “fully disappears.”

It’s possible that most suburban whales stray only slightly from where scientists usually look. On the other hand, one right whale in the catalog has turned up in the Azores, west of Portugal; another swam to one of the northernmost fjords of Norway. Right whales aren’t known to be very social, so Hamilton says it’s unclear what the whales sacrifice by traveling apart from the group. But they might gain more by being farther away from humans. If suburban whales aren’t where we can spot them, then by definition they must be farther from our noise, ships, and other threats.

Furthermore, right whales’ food sources along the eastern seaboard have been dramatically shifting, probably due to global warming. Whales that swim in unusual places might know about other, better places to find food, Hamilton says. During a reproductive crash in the late 1990s, he notes, at least half of right-whale babies came from suburban moms.

Calves stay with their mothers for about a year. It’s hard to track the young of off-the-grid moms after, Hamilton says, but at least some have integrated with the urban whales. Female calves, when they grow up and have their own young, tend to take those calves to the same habitats where their mothers took them. Hamilton recalls one whale mom who calved up north, then brought her female calf all the way to Florida in July, a trip that’s “unheard of” for the heat-averse whales. He suspects the mother was seizing her only chance to show her daughter the right place to have babies. Perhaps the daughters of suburban moms also swim off the beaten path.

In another six months or so, researchers at Trent University in Ontario will have genetic information from the skin samples they took from 1412 and her calf. They’ve sampled more than 300 mother-calf pairs, Hamilton says, and stumbled across something surprising in the DNA: Many of the calves weren’t fathered by any whale in the catalog. In addition to mystery moms, there seem to be mystery dads who have never been seen at all. There might even be a few dozen of them. And if there are missing males, there could be missing females, too.

The population may be larger than we think,” Hamilton says. For such a threatened species, learning that dozens more animals are living secret lives somewhere in the ocean “would be huge.”


 

 


 


 

 

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