Counting Penguins From Space
Satellite images can tell us how many of the portly birds grace the planet
Penguins. The very word puts a smile on most faces. Clearly, we need them; their future is important. And counting them is no mean business. In the vast icy expanses at the bottom of the planet, counting them 1–2–3, like you would ducks in a pond, is not practical. So Michelle LaRue’s research team at the University of Canterbury in New Zealand decided to get a bird’s eye view — or rather, an alien’s eye view.
The research group pored over satellite imagery of Antarctica, the home of the emperor penguin — the largest and the famous-est among the penguins. And now they know how many emperor penguins exist. I will divulge the sacred number after I tell you how they got to it.
Spotting our monochromatic friends in snowy-white Antarctica is akin to finding a needle in a haystack. The scientists needed bread crumbs to follow — or penguin footprints. In this case they had to make do with penguin droppings, called ‘guano’. This is visible as brown stains on the snow, as in the picture bellow, allowing the scientists to close in on penguin hotspots.
Now the researchers could zoom into these spots to begin the counting. They used a technique called ‘supervised image classification’. The idea is to classify parts of the image based on what’s in them. In this case, the white barrenness of the continent works in our favour. A typical penguin hotspot would have penguins, guano, snow, and some shadow.
The scientists ‘supervised’ the classification by marking parts of the image as ‘penguin’, ‘guano’, ‘snow’, or ‘shadow’. And then the algorithm did its work poring through satellite images from around the snowy continent, and churned out the number of ‘penguin pixels’ in Antarctica. Assuming each pixel, or a given area, has the same number of penguins, we get the magic number: the penguin population.
Do we?
Satellite images are obtained over multiple days. Do penguins maintain the same distances on all days? LaRue’s team decided to check their own assumption with further research. They found that the number of penguins in a pixel — the ‘penguin index’ — can vary dramatically based on the weather conditions. Why? The answer is incredibly cute. When it’s cold and windy, penguins tend to huddle together to stay warm. This shoots up the penguin index and our love for penguins.
For the scientists, this means they have to factor in weather conditions into their census calculations. A tedious task. But when they do, they land with the magic number…
Around 595,000 emperor penguins in existence. We know where they are. We can find them. And, hopefully, protect them.
More penguin knowledge
- Read more about the first penguin census:
An Emperor Penguin Population Estimate: The First Global, Synoptic Survey of a Species from Space - And the penguin index:
Quantifying the causes and consequences of variation in satellite-derived population indices: a case study of emperor penguins - Learn about the delightful penguin huddles:
The Warmth of Penguin Huddles
