The narwhal, a marine mammal known best for its single, unicorn-like tusk, may be under threat after aerial surveys showed a decline in its numbers. Hunting and local climate change in the Greenland waters where it usually lives may be to blame, researcher Dr Mads Peter Heide-Joergensen believes.
The monitoring suggests there has been a population fall of 10% over 17 years - and this may be an underestimate. Details are outlined in a zoological journal called Marine Mammal Science.
The 2001 survey, repeated four times, covered an area of 840 sq km and counted 360 narwhals. The 2002 survey, repeated seven times covered an area of 2,208 sq km and counted 566 narwhals. When compared with the results of surveys conducted in 1985 and 1986, the estimates show a 10% decline over the 17-year period.
However, Dr Heide-Joergensen said the decline could be much bigger because the 80s studies did not correct for perception bias, which is designed to take account of the fact that some whales may be present at the surface and not seen by the observers."
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