By Victoria Gill
Science and nature reporter, BBC News
Orcas avoid being overheard by their prey by hunting in "stealth mode", according to researchers.
The scientists wanted to know how orcas, commonly known as killer whales, communicate when hunting mammals, which can hear their distinctive calls.
The researchers thought the predators might switch to very high frequency whistles to co-ordinate the hunt.
But the orcas actually go completely silent and are somehow still able to form organised hunting groups.
Volker Deecke from the University of St Andrews in Scotland and Rüdiger Riesch from North Carolina State University in Raleigh, US, carried out the study, which was published in the journal Behavioural Ecology and Sociobiology.
They used hydrophones - underwater microphones - to listen to and record orcas communicating with each other. The team could even hear crunching sounds when the animals were eating their prey.
The researchers focused on transient orcas, in the Pacific Ocean off the coast of Canada and Alaska. These tend to live in smaller social groups and to move around more than resident orcas.
Some scientists believe that the two are distinct sub-species.
"The most striking difference between the two is their diet," explained Dr Deecke.
Residents eat fish, whereas transients hunt and eat marine mammals, including seals and porpoises.
Dr Deecke added: "In the 40 years that these animals have been studied, scientists have never seen a resident eat a mammal and never seen a transient eat a fish."
Hunting trip
Resident orcas hunt for salmon using echolocation. The orcas click, producing waves of sound that travel through the water and bounce off the fish, allowing the predator to sense its location.
"But all marine mammals have excellent underwater hearing," explained Dr Deecke.
"If if a killer whale swam along clicking like mad, all the seals and porpoises would think - here comes a predators, let's get away."
But the transient orcas' solution surprised the researchers.
"They go into stealth mode - completely silent," said Dr Deecke. "This raises the question: how are they communicating?"
It seems that orcas can carry out complex, co-ordinated mammal-hunting trips without "talking to each other" at all.
"To cover a wider area, they fan out occasionally - travelling hundreds of metres, even kilometres apart, and they come back together again," said Dr Deecke.
Only once they catch their prey, does the noise - whistling and pulsing calls - begin.
"It's a bit like us at a dinner party," said Dr Deecke. "They communicate while they eat then gradually wander off and go quiet again."
The orcas are unlikely to be able to see each other from these distances. Glaciers that descend into the sea on the Alaskan coast give the ocean the consistency of milk.
Dr Deecke thinks that the orcas might "rehearse" their hunting routines, to learn the position of each group member.
"They tend to be very predictable," he said. "I often know exactly where they are going to surface."
How they manage this level of co-ordination is not clear. And the scientists plan to continue their research by fitting sound recording and satellite tracking tags to individual orcas to follow their behaviour much more closely.
Dr Deecke said: "It seems like there's no way for them to communicate without their prey being able to eavesdrop."
http://news.bbc.co.uk/earth/hi/earth_news/newsid_9409000/9409694.stm
vrijdag 4 maart 2011
zaterdag 22 januari 2011
Vancouver Aquarium researchers have discovered a unique pack of killer whales that are plundering massive grey whales with hunting methods never seen before.
Dr. Lance Barrett-Lennard says the newly discovered group of over 150 transient killer whales return to ambush grey whales every spring near Unimak Island, Alaska, as the whales migrate north to the Bering Sea.
It has long been known killer whales, or orcas, can take down pretty much any size sea mammal, Barrett-Lennard says. But this specific group has developed a unique set of strategies, including stashing carcasses of calve and yearling whales on the ocean floor and returning 24 hours later to devour the prey.
“The most surprising thing was the storing of carcasses at a consistent depth so they could return to feed,” Barrett-Lennard said.
Sitting in a small fishing boat in stormy seas, Barrett-Lennard observed groups of about 40 orcas “hang out in the background,” as packs of four to six killers attempted to separate mothers and calves.
The attackers ram mother whales and constrain them by grabbing on flukes or the tail, in battles that can last about 45 minutes. Some mothers fight so ferociously within the first 20 seconds, thrashing their tales and ramming the orcas, that the killers give up.
When a mother is separated though, almost every time, a brutally efficient death by drowning awaits the younger whale. In one hour the killers will send an eight tonne, 15-metre long yearling to the bottom.
“It’s awesome, but hard to watch,” Barret-Lennard said. “These killer whales are so good at what they do. I find myself cheering for the grey whales.”
The attack pack of four killers gets first dibs on the carcass, “but the whole mob” will return the next day and continue to feed, which is a pattern never observed in any other group of orcas, Barrett-Lennard said.
Barrett-Lennard found that this group of killer whales feeds almost exclusively on the grey whales for extended periods. The finding indicates they’ve picked up on the grey whales’ annual migration patterns and know when and where to hunt them in the perfect strategic location.
In fact, Barrett-Lennard and his colleagues predicted they would see killer whales hunting grey whales at the “choke point” of the northern migration route, off the shallow black sand beaches and crashing white surf that borders Unimak Island, the easternmost of the Aleutian Islands.
Transient killer whales are one of three distinct types of orca in the northeastern Pacific Ocean. Resident orcas eat fish and make a lot of noise during the hunt, unlike stealthy transients. Another new report says mysterious offshore orcas, which are difficult to find and study, actually feed on Pacific sleeper sharks.
Dr. Lance Barrett-Lennard says the newly discovered group of over 150 transient killer whales return to ambush grey whales every spring near Unimak Island, Alaska, as the whales migrate north to the Bering Sea.
It has long been known killer whales, or orcas, can take down pretty much any size sea mammal, Barrett-Lennard says. But this specific group has developed a unique set of strategies, including stashing carcasses of calve and yearling whales on the ocean floor and returning 24 hours later to devour the prey.
“The most surprising thing was the storing of carcasses at a consistent depth so they could return to feed,” Barrett-Lennard said.
Sitting in a small fishing boat in stormy seas, Barrett-Lennard observed groups of about 40 orcas “hang out in the background,” as packs of four to six killers attempted to separate mothers and calves.
The attackers ram mother whales and constrain them by grabbing on flukes or the tail, in battles that can last about 45 minutes. Some mothers fight so ferociously within the first 20 seconds, thrashing their tales and ramming the orcas, that the killers give up.
When a mother is separated though, almost every time, a brutally efficient death by drowning awaits the younger whale. In one hour the killers will send an eight tonne, 15-metre long yearling to the bottom.
“It’s awesome, but hard to watch,” Barret-Lennard said. “These killer whales are so good at what they do. I find myself cheering for the grey whales.”
The attack pack of four killers gets first dibs on the carcass, “but the whole mob” will return the next day and continue to feed, which is a pattern never observed in any other group of orcas, Barrett-Lennard said.
Barrett-Lennard found that this group of killer whales feeds almost exclusively on the grey whales for extended periods. The finding indicates they’ve picked up on the grey whales’ annual migration patterns and know when and where to hunt them in the perfect strategic location.
In fact, Barrett-Lennard and his colleagues predicted they would see killer whales hunting grey whales at the “choke point” of the northern migration route, off the shallow black sand beaches and crashing white surf that borders Unimak Island, the easternmost of the Aleutian Islands.
Transient killer whales are one of three distinct types of orca in the northeastern Pacific Ocean. Resident orcas eat fish and make a lot of noise during the hunt, unlike stealthy transients. Another new report says mysterious offshore orcas, which are difficult to find and study, actually feed on Pacific sleeper sharks.
Orcas squirrel away their food
VANCOUVER Who knew squirrels and killer whales had so much in common?
Experts have discovered that killer whales in Alaskan waters store leftovers from their kill and return later to feed.
The research team, led by killer whale expert Lance Barrett-Lennard, found 150 transient killer whales gathered every May off Alaska’s Aleutian Islands, preying on gray whales heading to the Bering Sea feeding grounds.
While the whales gorged on their kill right away, the orcas also went back to their sunken kill over several days.
Barrett-Lennard says it’s the first time any whales have been documented storing food for the future.
Transient killer whales are loners, so Barrett-Lennard says it was mind-boggling to see so many of them in one place.
The Canadian Press
VANCOUVER Who knew squirrels and killer whales had so much in common?
Experts have discovered that killer whales in Alaskan waters store leftovers from their kill and return later to feed.
The research team, led by killer whale expert Lance Barrett-Lennard, found 150 transient killer whales gathered every May off Alaska’s Aleutian Islands, preying on gray whales heading to the Bering Sea feeding grounds.
While the whales gorged on their kill right away, the orcas also went back to their sunken kill over several days.
Barrett-Lennard says it’s the first time any whales have been documented storing food for the future.
Transient killer whales are loners, so Barrett-Lennard says it was mind-boggling to see so many of them in one place.
The Canadian Press
vrijdag 25 juni 2010
They're not just priceless, whales are smarter than previously thought
Whales, it seems, could be worth more alive than dead, with the first peer-reviewed assessment of whale tourism's global value predicting the $US2.1 billion ($2.3 billion) industry could easily grow by 10 per cent each year over the next decade.
Some 13 million eco-tourists paid to see the animals in their natural element last year, generating 13,000 jobs for people across hundreds of coastal regions worldwide, the study found.
''We can have our whales and still benefit from them, without killing them,'' said the study's co-author, Ussif Rashid Sumaila, a researcher at the University of British Columbia.
The study coincides with a decision on Thursday by the 88-nation International Whaling Commission meeting in Morocco, to adopt a ''five-year strategic plan'' to explore both the economic benefits and ecological risks of whale-watching.
The move comes as some scientists say the marine mammals are not only smarter than previously thought but also share several attributes once claimed as exclusively human.
Self-awareness, suffering and a social culture along with high mental abilities are a hallmark of cetaceans, an order grouping more than 80 whales, dolphins and porpoises.
''We now know from field studies that a lot of the large whales exhibit some of the most complex behaviour in the animal kingdom,'' said Lori Marino, a neurobiologist at Emory University in Atlanta, Georgia.
A decade ago, Dr Marino conducted an experiment with bottlenose dolphins in which she placed a small mark on their body and had the mammals look at themselves in a mirror.
By the way the dolphins reacted to the image and then looked at the spot, it was clear that they had a sense of self-identity, Dr Marino determined.
For Georges Chapouthier, a neurobiologist and director of the Emotion Centre at Pierre and Marie Curie University in Paris, self-awareness means that dolphin and whales, along with some higher primates, can experience not just pain but also suffering.
Unlike nociception - a basic nerve response to harmful stimuli found in all animals - or lower-order pain, ''suffering supposes a certain level of cognitive functioning,'' he said.
''It is difficult to define what that level is, but there's a lot of data now to suggest some higher mammals have it, including great apes, dolphins and, most likely, whales.''
As for intelligence, cetaceans are second only to humans in brain size, once body weight is taken into account.
More telling than volume, though, are cerebral areas which specialise in cognition and emotional processing - and the likelihood that this evolution was partly driven by social interaction, according to several peer-reviewed studies.
Some scientists suggest this interaction can be described as culture, a notion usually reserved for humans.
''Evidence is growing that for at least some cetacean species, culture is both sophisticated and important,'' said Hal Whitehead, a professor at Dalhousie University in Nova Scotia.
If culture is learnt behaviour passed across generations that is different from one community to the next, then humpback whales, to cite one example, are rather cultured indeed.
'At any time during the winter breeding season, all the males in any ocean sing more or less the same elaborate song, but this communal song evolves over months and years,'' Professor Whitehead noted in a study in the journal Biological Conservation.
Scientists have also observed orcas, or killer whales, learning from other orcas from a geographically separate group how to steal fish from longlines used by commercial fishing boats.
Two orca communities that rarely intermingle despite sharing the same waters off the coast of Vancouver Island, meanwhile, have learnt to divide their natural bounty: and one group eats fish and the other mammals, especially seals, Professor Whitehead reported.
Such findings are disturbing factors in the calculus of conservation.
''If we wipe out a subgroup, it is more than killing a certain number of individuals. It could actually wipe out an entire culture,'' Dr Marino said.
Some 13 million eco-tourists paid to see the animals in their natural element last year, generating 13,000 jobs for people across hundreds of coastal regions worldwide, the study found.
''We can have our whales and still benefit from them, without killing them,'' said the study's co-author, Ussif Rashid Sumaila, a researcher at the University of British Columbia.
The study coincides with a decision on Thursday by the 88-nation International Whaling Commission meeting in Morocco, to adopt a ''five-year strategic plan'' to explore both the economic benefits and ecological risks of whale-watching.
The move comes as some scientists say the marine mammals are not only smarter than previously thought but also share several attributes once claimed as exclusively human.
Self-awareness, suffering and a social culture along with high mental abilities are a hallmark of cetaceans, an order grouping more than 80 whales, dolphins and porpoises.
''We now know from field studies that a lot of the large whales exhibit some of the most complex behaviour in the animal kingdom,'' said Lori Marino, a neurobiologist at Emory University in Atlanta, Georgia.
A decade ago, Dr Marino conducted an experiment with bottlenose dolphins in which she placed a small mark on their body and had the mammals look at themselves in a mirror.
By the way the dolphins reacted to the image and then looked at the spot, it was clear that they had a sense of self-identity, Dr Marino determined.
For Georges Chapouthier, a neurobiologist and director of the Emotion Centre at Pierre and Marie Curie University in Paris, self-awareness means that dolphin and whales, along with some higher primates, can experience not just pain but also suffering.
Unlike nociception - a basic nerve response to harmful stimuli found in all animals - or lower-order pain, ''suffering supposes a certain level of cognitive functioning,'' he said.
''It is difficult to define what that level is, but there's a lot of data now to suggest some higher mammals have it, including great apes, dolphins and, most likely, whales.''
As for intelligence, cetaceans are second only to humans in brain size, once body weight is taken into account.
More telling than volume, though, are cerebral areas which specialise in cognition and emotional processing - and the likelihood that this evolution was partly driven by social interaction, according to several peer-reviewed studies.
Some scientists suggest this interaction can be described as culture, a notion usually reserved for humans.
''Evidence is growing that for at least some cetacean species, culture is both sophisticated and important,'' said Hal Whitehead, a professor at Dalhousie University in Nova Scotia.
If culture is learnt behaviour passed across generations that is different from one community to the next, then humpback whales, to cite one example, are rather cultured indeed.
'At any time during the winter breeding season, all the males in any ocean sing more or less the same elaborate song, but this communal song evolves over months and years,'' Professor Whitehead noted in a study in the journal Biological Conservation.
Scientists have also observed orcas, or killer whales, learning from other orcas from a geographically separate group how to steal fish from longlines used by commercial fishing boats.
Two orca communities that rarely intermingle despite sharing the same waters off the coast of Vancouver Island, meanwhile, have learnt to divide their natural bounty: and one group eats fish and the other mammals, especially seals, Professor Whitehead reported.
Such findings are disturbing factors in the calculus of conservation.
''If we wipe out a subgroup, it is more than killing a certain number of individuals. It could actually wipe out an entire culture,'' Dr Marino said.
donderdag 24 juni 2010
Orca doing well, wellwishers name her Morgan
The orca, or killer whale, rescued in the Wadden Sea on Wednesday evening is recovering well at the Dolfinarium in Harderwijk, news agency ANP reports.
The orca has been named Morgan. 'It is a Scottish Celtic name and we chose it because she may well come from the north of Scotland,' a spokesman said. 'We are pleased with her progress so far.'
The orca has been named Morgan. 'It is a Scottish Celtic name and we chose it because she may well come from the north of Scotland,' a spokesman said. 'We are pleased with her progress so far.'
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