|
Seals learn songs to detect orcas
13th November 2002
NewScientist.com news service
Harbour seals in British Columbia have learnt to trust the local killer whales, new research reveals. The calls of unfamiliar killer whales sent the seals diving for safety, but they were unperturbed by the songs of their friendly fish-eating neighbours.
The local killer whales live in family groups, stay in one region, and because they eat only fish, pose no threat to seals in the same waters.
But there is another population of killer whale that roams the Pacific coast of North America. These "transients" have a range of hundreds of kilometres and hunt in small groups. They feed on mammals and are particularly fond of harbour seals.
The two types of killer whale look very similar but sound very different. When researchers played recordings of the calls of the mammal-munching whales from speakers slung beneath a boat, the seals disappeared underwater.
"You would be hard-pressed to see a seal on the dark bottom. But a seal at the surface would be beautifully back-lit, so it's a bad place to be if you're being hunted by a predator," explains Volker Deecke, of St Andrews University, Scotland, and the Vancouver Aquarium Marine Science Centre, who led the work.
The seals were also scared by the calls of fish-eating killer whales that live 600 kilometres away in Alaska. But they did not react when the chatter of the local killer whales was broadcast.
This suggests that the seals associate all unfamiliar killer whale calls with danger, and have memorised the noises that their harmless neighbours make. A resident population may have as many as 50 unique calls, so the learning capacity of the seals is impressive, says Deecke.
But although this knowledge will help avoid false alarms, it will not keep the seals completely safe. When hunting, mammal-eaters swim silently so as not to scare away their prey.
Journal reference: Nature (DOI:10.1038/nature01030)
Top
|
