March of the Fossil Penguins

Fossil penguin discoveries and research

Penguin Poop and Volcanic Ash: A Tale from Deception Island

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In celebration of World Penguin Day (April 25), let’s review a recent research paper on three exciting topics: penguins, poop, and volcanoes! A new paper by Dr. Stephen Roberts and colleagues reported a history of penguin colony collapses and revivals. Technically, there are no fossil penguins here: the populations studied only date back to 6,700 years ago. While ancient by human standards, this represents only 1/10,000th of the history of penguins as a group. And, the populations were studied not by looking at skeletons, but by looking at droppings!

The team studied guano (bird droppings) on Ardley Island. This small island sits near the tip of the Antarctic Peninsula and is a nesting site for many seabirds, including a thousands of Gentoo Penguins. As the penguins occupied the site, their droppings accumulated into guano layers. While guano may seem like merely an unfortunate byproduct of penguin digestion, it is serious business. Guano has long bee used as fertilizer, and been the subject of treaties, territorial disputes, and even wars. The Guano Islands Act of 1856 basically claimed all unoccupied guano-bearing islands in the oceans for the United States. Peru and Chile even fought a “Guano War” (also known as the Chincha Islands War) over disputed guano-rich islands.

Guano is also a useful substance for scientists, as the ratios of different isotopes can reveal how long ago a guano layer formed and what the animals that made it might have been eating. The amount of guano that forms per year also gives an estimate of how many penguins were “contributing”. In this study, scientists found evidence that penguin populations on Ardley Island had crashed precipitously several times in the past. The culprit? A volcano. Roughly 60 miles to the southwest lies Deception Island. The volcano that created this island has erupted periodically over the past few thousand years.

Deception_Island,_Antarctica_(24313628833)

Deception Island. Photo by Christopher Michel.

By looking at carbon isotope levels in plants, bone, and sediments from guano layers, the team was able to estimate the age of each layer and tie the penguin poop peaks and crashes into the timeline of local events. At least three times, the belching eruptions of the Deception Island volcano wiped out the penguin colony. Because no skeletons from the time of the volcanic eruptions remain intact, the fate of the penguins living in the area in the days of the eruptions is uncertain. Falling ash may have wiped out nesting adults and chicks, buried eggs, or spoiled food sources. It is also possible the effects did not wipe out the full grown penguins, but instead forced them to flee their breeding colony leaving an abandoned landscape of rocky shores.

Nevertheless, the penguins ultimately prevailed. After each eruption, the penguins slowly returned, typically taking 400-800 years to regain their original population levels. Today, thousands of penguins are happily inhabiting the island  (and building up that guano layer bit by bit).

Gentoopenguin_chicks_kinggeorgeisland

Gentoo Penguin chicks on present-day Ardley Island. Photo by Henrike Mühlichen

 

Reference:

Roberts, S. and Monien, P. and Foster, L. and Loftfield, J. and Hocking, E. and Schnetger, B. and Pearson, E. and Juggins, S. and Fretwell, P. and Ireland, L. and Ochyra, R. and Howarth, A. and Allen, C. and Moreton, S. and Davies, S. and Brumsack, H. and Bentley, M.J. and Hodgson, D. (2017) ‘Past penguin colony responses to explosive volcanism on the Antarctic Peninsula.’, Nature communications. .

 

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Written by Dan Ksepka

April 25, 2017 at 10:55 am

Posted in Uncategorized

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