Scientists have been studying penguins for over a century now, starting with some of the expeditions during the Heroic Age of Antarctic Exploration. This research covers several areas, including behavioral traits, population sizes, and susceptibility to diseases. One aspect that has interested many scientists is the effects of tourism and climate change on penguin populations. This involves collecting accurate counts of colonies over time; however, counting colonies with tens or hundreds of thousands of penguins can be challenging.

Scientists have used several methods of determining penguin populations. Some colonies are relatively small, and so even decades ago, scientists could determine the number of adult penguins in a colony by standing on a hill with a good view, counting the number of nests, and then multiplying by two (penguins are usually counted by nesting pairs, as it's often the case that one penguin in a pair is nesting and the other is out at sea). On my first trip to Antarctica in 2013, we had a scientist on board whose job was to count penguins. I remember him standing at each of the landing sites and using a handheld tally counter to tick off each nest. In the end, we visited several colonies that had a combined total of 7,911 nesting pairs of penguins. It was really interesting to see him work! He and his colleagues would then enter the numbers from each colony into a database, which would keep track of the populations from year to year. They would cross-reference this data with how many visits tourist ships made to the landing sites to attempt to determine how much of an impact tourism may have on the populations.

This method worked great for smaller colonies, but this becomes much more difficult for larger colonies. In Saint Andrews Bay on the island of South Georgia, there is a colony of 150,000 king penguins. Imagine being tasked with counting those! Similarly, at Cape Adare, there is a colony of 338,000 Adélie penguins. It would be impossible to count colonies of this size without any technology, so different methods had to be adopted.

One method involves estimating the size of large colonies. If a scientist can approximate the density of a penguin colony, and they can calculate or estimate the size of the nesting area, then they can get a decent idea of the sizes of a larger colony. Basically, density * area = population. While these densities change from colony to colony, there is some data available. Adélie penguin colonies tend to have an average density of 0.62 breeding pairs per square meter. King penguins tend to have an average density of 1 breeding pair per square meter. And when emperor penguins huddle closely together to keep warm in the middle of the winter, there can be up to 21 penguins per square meter!

So if we had satellite imagery of an Adélie penguin colony on the Antarctic Peninsula that had an area of 1250 square meters, the population would be approximately 0.62*1250 = 775 breeding pairs. If we surveyed a site in South Georgia and saw that a king penguin colony occupied approximately 5000 square meters, the population would be approximately 1*5000 = 5000 breeding pairs. And if we were in the Weddell Sea and we observed a group of emperor penguins huddling in a circle with diameter 2 meters, then the huddle would contain approximately 21*π*(2)^2 ≈ 264 penguins.

One last note: as satellite imagery has improved, it has become possible to count individual penguins in satellite photos. Eventually, the imagery may be so good that doing counts in person will become obsolete.

Sample Problems

1. In the first image below, estimate the population of the leftmost area of the Adélie penguin colony given the fact that the area is approximately circular in shape with a radius of 8.8 meters.

2. In the first image below, estimate the population of the middle area of the Adélie penguin colony given the fact that the area is approximately circular in shape with a radius of 7.6 meters.

3. In the first image below, estimate the population of the rightmost area of the Adélie penguin colony given the fact that the area is approximately rectangular in shape with dimensions 19 x 26 meters.

4. Count the number of penguins in each area of the colony to check your answers. Yes, I want you to actually count them one by one. You may want to print the image or use an app and mark them as you go to keep track.

5. In the second image, use the scaling information to estimate the size of the colony. Make sure to account for the colony does not occupy the whole area inside the image.

6. You can become a volunteer research by going to www.penguinwatch.org and helping count penguin populations. This work has led to published research papers!