Cetaceans have a bad habit of stranding themselves. Last week a large pod of 65 pilot whales stranded themselves on a beach in Tasmania. Only 11 survived.

When a similar mass stranding occured in 2003, a predator was suspected of having scared the animals onto the beach. Military use of sonar has also been linked - and cleared of causing - whale strandings.
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Narwhals breach.

Now there's another disaster, on a bigger scale: a huge group of about 500 narwhals have trapped themselves in sea ice in Nunavut, in Arctic Canada. The trapped animals are being culled to prevent a more painful death by starvation or suffocation as the ice closes in around them.

Narwhals are Arctic cetaceans, with a fabulous tusk that is the subject of much folklore. Biologists now suspect that the tusk is a sensory organ that helps detect chemicals associated with prey, and ice formation. If it's the latter it sadly hasn't been of much use to the narwhals in Nunavut.