Penguins everywhere! Antarctic populations increasing

Adelie penguins crossing in front of the research icebreaker N.B. Palmer.
  Photo © John Diebold.

To prove that Antarctica still keeps many secrets and is full of surprises, an enormous penguin colony has been discovered by satellite imagery combined with ground and aerial drone surveys. 

Writing in Scientific Reports,¹ Borowicz et al. detected a previously unknown colony of more than 750,000 Adélie penguin-mating pairs on the Danger Islands. That island group is located in a rarely visited area near the tip of the Antarctic Peninsula across from South America. The Danger Islands are on the eastern side of the Antarctic Peninsula. Colonies on the western side have suffered a decrease in population over the past few decades. These decreases have been attributed to climate change. Historical aerial photos of the Danger Islands show that the population there has been stable over the years. The discovery of a robust population on the eastern side of the peninsula minimizes the overall impact of global warming on the population in the peninsula region.

Asking the larger question, how have the numbers of Adélie penguins fared over recent decades, Lynch and LaRue² reported another surprising result in 2014. They conducted a census of Adélie populations across all of Antarctica and found a greater than 50% increase in the population of mating pairs since the last estimates in 1993. Part of the increase was due to using improved satellite imagery and other survey methods. They found a total population of almost 3.8 million mating pairs. Borowicz et al. note that the Lynch and LaRue census missed much of the giant colony they found on the Danger Islands, so the number of mating pairs is likely even larger. Looking closer, Lynch and LaRue also found that populations decreased on the western side of the Antarctic Peninsula but that decrease was offset by a substantial increase in mating pairs on East Antarctica. They attribute these patterns to climate change. For one, Adélies depend on krill associated with sea ice. Sea ice has decreased off western Antarctic Peninsula due to warming temperature there but has increased in the Ross Sea and in East Antarctica, thus supporting population growth. I discussed the connections between sea ice and climate change in a blog in 2014. For another reason, climate change has caused coastal ice retreat in many regions around the continent. In East Antarctica, this has created ice-free ground for new colonies to be established and for existing colonies to expand. They propose eleven new colonies in their census. 

Penguins inspecting human, Sulzberger Bay, Marie Byrd Land.
Photo © B. Luyendyk

These studies are good news. Who doesn’t love penguins? I’ve encountered a few, from a legal distance, in my Antarctic visits. One memorable encounter occurred from an icebreaker off Cape Adare where a very large colony was established on a cliff face hundreds of feet tall. The black basalt rock was stained pink – penguin guano, pink from digesting krill, their main food. Even from a mile or so offshore, the stench was overwhelming!

1 Borowicz, A., McDowall, P., Youngflesh, C., Sayre-McCord, T., Clucas, G., Herman, R., Forrest, S., Rider, M., Schwaller, M., Hart, T. and Jenouvrier, S., 2018. Multi-modal survey of Adélie penguin mega-colonies reveals the Danger Islands as a seabird hotspot. Scientific reports, 8(1), p.3926.

2 Lynch, H.J. and LaRue, M.A., 2014. First global census of the Adélie Penguin. The Auk, 131(4), pp.457-466.