Whales and dolphins are creatures of the water, but as mammals, they also rely on air to breathe, and they face death if they become stranded away from either element.
The plight of three dolphins trapped in the ice off the northeast coast of Newfoundland last week captured the hearts of local residents.
After listening to their cries during the night, a group of fisherman from Seal Cove cut a path through the ice in the bay for the dolphins and even towed one of the animals to safety with a rope. Their rescue efforts drew criticism from at least one whale-rescue expert who said they might have done the dolphins more harm than good.
Is it rare for whales and dolphins to get trapped in the ice along Canada's coasts?
Most whales and dolphins do move farther south or away from the coast during the winter, but there have been a few cases of whales getting trapped in the ice along coasts in the northern part of the country in the past few years.
Earlier this winter, hundreds of narwhals became trapped in the ice near Pond Inlet, Nunavut. The whales were killed on the advice of local elders, who said it would spare them from further suffering and death by drowning as the ice thickened.
A number of other examples have made the news in recent years. In May 2008, 15 to 20 beluga whales were trapped in the sea near Grise Fiord, Nunavut.
In November 2006, 100 to 200 beluga whales became trapped in the Husky Lakes, a string of saltwater lakes and inlets east of Tuktoyaktuk, N.W.T., after a channel connecting the lakes to the Beaufort Sea froze. They, too, could not be freed and were instead culled.
What causes the animals to become trapped in the ice?
Most often, whales and dolphins are stranded in the ice when winds or currents shift suddenly, says Laurie Murison, executive director of the Grand Manan Whale and Seabird Research Station in New Brunswick.
However, human activity that causes a lot of underwater noise might also play a role when the animals are near the edge of the ice, Murison said.
"They may panic and end up in an area where the ice can close in on them," she said.
In the case of the whales trapped in the Husky Lakes in 2006, the animals often liked to feed in the lakes during the summer. The local mayor reported that the Department of Fisheries and Oceans used to help chase away the whales but had stopped doing that four or five years earlier.
What types of whales and dolphins are susceptible?
Species that aren't used to a lot of ice, such as grey whales and many dolphins, might have more difficulty getting out, Murison said.
"They just don't have the ability to find those ice leads [channels of open water] as easily as animals that normally are in ice conditions, like bowheads or narwhals or belugas."
Some species can't swim that far underwater before they need to come up for air, she added.
However, even species that are accustomed to the ice can sometimes become trapped.
What should people do if they find a whale or dolphin stranded in the ice?
It might be possible to rescue the animals depending on the circumstances, but it's important to find experts familiar with the best rescue methods, says Andrew Reid, a co-ordinator the Marine Animal Response Society (MARS) in Nova Scotia.
"Dragging the animal by their tail is something you definitely wouldn't want to do," he said. That method could dislocate the animal's spine or pull them underwater.
Reid said involving boats is always risky.
"Anytime you bring boats near animals, there's always the possibility of hitting them," he said.
He added that frozen seas are also a dangerous place for people.
Tonya Wimmer, president of MARS, said rescuers face risks such as dehydration, hypothermia or even being hurt by the animal itself, depending on the conditions.
"People will do some crazy things to save an animal," she said, adding that they sometimes think of the animal before themselves. "Which is lovely, but we have to make sure people's lives aren't in danger while we do these things."
Where do whales become beached or stranded on land?
Canada's southeastern coasts and waters aren't free of traps for whales and dolphins either, as the animals can also become stranded or beached on land. Occasionally, dozens of animals become beached at once.
Including both live and dead animals, about 30 to 40 beachings are reported along Nova Scotia's coast alone each year, Reid estimated.
However, that is likely an underestimate, he said, as some people who have seen beached animals aren't sure whom to call, and some coastal waters are remote areas where a beached animal will never be found.
Similar incidents take place all over Canada's coastline.
Wimmer said there are no readily available Canada-wide statistics, but her group is currently trying to compile information for her region and make sure people know whom to call when they spot a stranded whale or dolphin.
What types of whales and dolphins become beached?
Species that navigate by sonar and travel in groups, such as pilot whales, are more likely to end up beached in large numbers. Such whales are mostly smaller species, and most have teeth.
However, single baleen whales, which are massive filter feeders, can also become beached occasionally.
What can cause them to beach themselves?
Whales and dolphins that are old, sick or injured often come toward the shore. They might be too tired to swim any longer, said Reid.
Healthy whales can become beached because of a navigational error.
Sometimes, the whales are fooled by a natural geographic trap, such as the one that exists at Welfleet, Mass., in Cape Cod, says Murison.
"They think they're going out to sea, and they actually end up in an ever [increasingly] shallow area," Wimmer said.
Sometimes, the animals just get caught up in feeding.
"A lot of the time, we get animals in Bay of Fundy who end up in rivers," Wimmer said. "A lot of that is, literally, they've followed their stomach and get caught on the really fast drop in tide."
Could humans be sometimes responsible?
Toothed whales also use a form of sonar for navigation, listening for the echo of their own, high-pitched voices to determine how far away they are from shore.
Their hearing and their navigational abilities can be damaged by explosions or other loud underwater noises. In fact, some beached whales show signs of damage in their ears, Murison said.
"Hearing is the most critical sense for whales," she added.
Dolphins and whales, including baleen whales, also rely on their voices and their hearing to communicate with one another.
Environmental groups have expressed concerns that noise pollution from commercial shipping, seismic surveys and sonar technology might be causing an increase in beachings.
A paper published in Nature in October 2003 noted mass strandings have taken place near naval exercises that included the use of military sonar.
The beached whales and dolphins showed symptoms of decompression sickness, or the bends, which affects divers who surface too quickly, the paper said. Researchers have suggested that human-generated underwater noise is causing the animals to dive and surface beyond healthy physical limits.
Some environmental groups, led by the Natural Resources Defense Council, have filed lawsuits against the U.S. navy in recent years in an effort to curb the use of mid-frequency sonar, alleging it disturbs and sometimes kills whales and dolphins.
In November 2008, the U.S. Supreme Court ruled in favour of the navy in one suit. A month later, the navy announced it had reached a deal with the council and other groups to continue research on how sonar affects whales and other marine mammals. However, the navy has not agreed to adopt any additional measures to protect animals when it uses sonar.
What should be done about beached whales and dolphins?
Groups such as MARS have protocols to deal with beached animals but only attempt a rescue if they appear to be healthy.
Wimmer said rescuers check the whale over and look for injuries before attempting a rescue.
"Do they look like they're a nice, fat healthy whale? Do they look like they're skin and bones?" she said.
Baby whales without their mothers aren't usually rescued, as they wouldn't survive on their own, Wimmer said.
If a rescue is attempted, smaller animals, such as dolphins, are placed on a stretcher and carried out to sea. For larger animals such as pilot whales, a tarp is put under the animal and attached to inflatable pontoons used to move the animals away from the shore.
How can whale beachings be prevented?
Reid said efforts have been made to prevent whale and dolphin injuries, which can be caused by getting entangled in fishing gear or collisions with ships. For example, shipping lanes in the Bay of Fundy between Nova Scotia and New Brunswick have been moved to minimize collisions with whales, and different fishing methods are being used to reduce the chance that whales and dolphins will be hurt.
Murison said Canada's Department of Fisheries and Oceans has some guidelines in place for activities that produce a lot of underwater noise, such as blasting, seismic surveys and naval activity. In particular, the department recommends conducting those activities when the tide is low, to reduce the propagation of the noise. If they must be done at high tide, those involved in the activity are asked to look out for whales in the area.