Orcinus orca en el Estrecho de Gibraltar, abril 2011. Parte 1

Orcas en el Estrecho de Gibraltar cerca de Barbate, Cádiz,  abril 2011. La llegada de las orcas al Estrecho de Gibraltar coincide con la luna llena del mes de marzo. 

Se han llegado a ver incluso antes, pues su llegada a estas aguas es debido a la llegada y la presencia del tan codiciado atún rojo, que coincide con la luna llena y las altas mareas de marzo

 El atún rojo, del cual se alimentan este grupo de orcas, proviene de las aguas del atlántico norte donde han estado alimentándose para emprender el viaje al mar mediterráneo, concretamente a las islas griegas, donde van a desobar.

Es en el Estrecho de Gibraltar, paso obligado en el viaje del atún rojo hacia el mediterráneo, donde espera su llegada este grupo de orcas para poder alimentarse.

Su peso ronda los dos mil a tres mil quinientos kilos de media, con un alto grado de proteínas en su carne, lo que satisface plenamente el hambre de todo el grupo al completo

 La velocidad del atún rojo en nado puede rondar los más de cincuenta km/hora, es por sí rápido y veloz, por lo que las orcas necesitan de una estrategia en común para poder darle caza.

 

Utilizan varias, una de ellas es el acecho y la persecución, haciéndoles nadar en vano hasta llegar a cansar a la presa. Otra, posiblemente la más sonada, es el aprovechamiento de la pesca de los propios pescadores del lugar. Es el caso de las almadrabas y las pequeñas embarcaciones de los pescadores marroquíes.

En el primer caso necesitan gastar mucha energía para dar caza a un sólo individuo, por lo que las orcas prefieren esperar a que los pescadores hagan todo el trabajo, y así una vez picado el atún en el anzuelo, la orca aprovecha para acecharle la mordida sin poder oponer resistencia alguna.

De esta forma, el grupo consigue ahorrar energía. La orca, se reparte el botín, por lo que de una pieza se alimentan dos o más miembros del grupo

Diferentes especies de orcas

Increíble viaje del Ártico a las Azores

Undated handout photo of a pod of killer whales. One of the whales in this pod, shown here cruising in Admiralty Inlet at the north end of Baffin Island, which spent almost two months foraging in the Arctic before making a beeline for warmer climes. In a remarkable month-long journey the whale swam 5,400 kilometres from northern Baffin Island, down past Greenland, Labrador and Newfoundland.

Photograph by: Handout, Postmedia News

Biologist Cory Matthews knew the chances of spotting killer whales in the Arctic were slim. The odds of getting a satellite tracker onto the sleek predators were even worse.

But Matthews and his colleagues hit the jackpot. Not only did they manage to fit two Arctic killer whales with trackers, but one of them headed off on a remarkable 5,400-kilometre journey.

In just a month, the whale swam from northern Baffin Island, down past Greenland, Labrador and Newfoundland, and headed for the Azores in the mid-Atlantic.

"It was fast and pretty much a straight line," said Matthews, a University of Manitoba PhD student working with scientists from Fisheries and Oceans Canada. He is lead author of their report on the whale's travels published in the current issue of Polar Biology.

It's long been known that killer whales, or orcas, get around, but the study is the first to document such a rapid, long-distance swim.

And it provides new clues about the little-known whales, which appear to be showing up in Canada's Arctic in increasing numbers.

So many of the black-and-white predators have been spotted in recent years that some have suggested they may be invading the Arctic. Orcas been have spotted feasting on belugas and narwhals and also have been known to take down huge bowhead whales.

Even so, Matthews headed north in August 2009 knowing that finding orcas in Arctic waters would not be easy. "We know they are up there," he said. "But it's like a needle in haystack."

But not long after he and his field crew stepped off a Twin Otter at the north end of Baffin Island, the Inuit told them they were in luck. There was a large group of 20 killer whales just off shore.

Within days, Matthews and researcher Stephen Petersen, from Fisheries and Oceans, were out in a boat pointing crossbows at the whales. The crossbows were loaded with high-tech ammunition — darts to extract samples of whale blubber and embed in the whales satellite tracking devices worth $2,500 each.

They got satellite trackers onto two of the orcas before they disappeared under the icy, inky water. The devices, about the size of cellphones, were attached by darts near the whales' distinctive dorsal fins.

One of the trackers stopped working within days, but the other one lasted three months, emitting up to 300 electronic signals a day when the whale surfaced. The signals were picked up by the Argos tracking system, which uses satellites 850 kilometres above the Earth to follow everything from sea turtles to fishing vessels.

After Matthews and the DFO researchers returned to Winnipeg, they could check on the orca's whereabouts simply by logging into the satellite tracking system by computer.

They watched as the whale foraged in the waters northwest of Baffin Island until the temperatures began to plunge in early October. Then, as ice began to form and choke up the waters of Lancaster Sound, the orca took a decisive turn south. It cruised down Baffin Bay past Greenland and along the coast of Labrador and Newfoundland, hitting a top speed of 252 kilometres a day.

"You can't help but look at the track and think that it is amazing that the whale was going so fast and was so directed," Matthews said of the 5,400-kilometre journey. "It seems like it knew where it was going."

When the orca was about 500 kilometres from the Azores, the signal stopped, bringing an abrupt end to an astounding scientific event.

It is not known if the entire group of 20 Arctic orcas made the same trip, but whales are known to travel in groups. It is also anyone's guess where the orca went after the tracker stopped working.

The Arctic-to-Azores trip is believed to be the first documented case of an orca travelling so far in such a short period of time.

Matthews and his group said the "remarkable" swim suggests killer whales have a large range in the Atlantic. Orcas on the Pacific coast are also known to make long journeys, with reports of them swimming from Alaska to California.

It could be that orcas that spend summer in Canada's north and along the east coast congregate in the mid-Atlantic between the Azores and Bermuda in the winter, said Matthews, noting that whalers reported seeing concentrations of orcas in the southern waters in the 1800s.

Hunters, scientists and other northern travellers are spotting more orcas in the Arctic waters, especially in Hudson Bay. Narwhals, belugas and bowhead whales, which are known to take refuge under the ice, seem to be favoured prey. Matthews said the orcas may also be eating fish, but added more work is needed to understand the changing wildlife dynamic in Canada's north.

Researchers say the increase in orca sightings appear to be related to the way the Arctic ice has been retreating in recent years. Orcas tend to steer clear of thick ice.

While climate change is a prime suspect, some have suggested that the increasing number of orcas in the Arctic may be related to the way bowheads have rebounded since the end of commercial whaling.

To get a better read on the situation, federal scientists have anchored undersea microphones near Churchill, Man., and Repulse Bay, Nunavut, to record whale calls. Hunters and northern travellers have been asked to report orca sightings. Matthews and his colleagues are heading back to Baffin Island this summer.

They aim to collect more biopsy samples, which will allow them to determine what the orcas are eating. And they have six more satellite tracking devices ready to load into their crossbows.

Read more: http://www.canada.com/technology/Killer+whale+tracked+making+incredible+journey+from+Arctic+Azores/4896820/story.html#ixzz1OnNUG7Qx

Orcas of Tysfjord

Nadando con orcas en las Galápagos

Diferentes sonidos de orcas

LA BIODIVERSIDAD

"La Naturaleza te hace sentir, vibrar, despertar la curiosidad que hay en uno. También te hacen creer, intuir, iluminar secretos ocultos en su letargo. Un mundo de vida. Una fantasía, un sueño"