Breeding emperor penguin colonies like this one in Halley Bay can stay in one spot on the ice for eight months, creating a characteristic reddish-brown spot of guano (Image: Thorsten Milse/Robert Harding/Rex Features) The tell-tale colour of faeces can give away a penguin colony (Image: BAS) The Halley Bay colony can be seen in satellite images (Image: BAS)


Looking for penguins? The fastest and easiest way is to spot their poo from space, say researchers.

Peter Fretwell and Philip Trathan of the British Antarctic Survey located 38 emperor penguin colonies on winter sea ice all the way around Antarctica by spotting patches of their faeces, or guano, in satellite images. Ten of the colonies had not been observed before.

Earlier this year, a study forecast that climate change could melt emperor penguins out of house and home by the end of the century. Based on data from the best-studied colony in Adélie Land, Henri Weimerskirch, an ecologist at the Chizé Centre for Biological Studies in France, found there was a one in three chance that 95% of the penguins in the colony would be gone by 2100.

But studying emperor penguin populations is fraught with difficulties: during the Antarctic summer, when most research takes place on the continent, the animals are feeding at sea. During the winter, when it is too cold for humans to work in comfort, they gather in large breeding colonies on the ice that grows out over the coastal sea.

Stained ice

The easiest way to spot the penguins would be to with satellite images, but the birds themselves are too small to show up. So, the researchers realised, poo is the clue. “During the breeding season, the birds stay at a colony for eight months. The ice gets pretty dirty and it’s the guano stains that we can see,” says Fretwell (see image).

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To seek out the characteristic reddish-brown patches of guano, Fretwell and Trathan studied the Landsat Image Mosaic of Antarctica – a seamless cloud-free patchwork of satellite images that were taken of the entire continent between 1999 and 2004 (see image).

Penguin colonies tend to meet up in the same region every year. Of the colonies that researchers were already aware of, six had shifted location and six could not be found. The researchers say that the missing groups may just be too small to see using this method.

The guano-spotting technique will allow researchers to monitor the evolution of colonies across the continent, the researchers say. They now want to use high-resolution satellite images to try to count the number of penguins in each colony.

Journal reference: Global Ecology and Biogeography (DOI: 10.1111/j.1466-8238.2009.00467.x)