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Rise and fall of Ross Sea emperor penguin colony populations: 2000 to 2012

Emperor penguins photo by Jerry Kooyman
TitleRise and fall of Ross Sea emperor penguin colony populations: 2000 to 2012
Publication TypeJournal Article
Year of Publication2017
AuthorsKooyman G.L, Ponganis P.J
JournalAntarctic Science
Date Published2017/06
Type of ArticleArticle
ISBN Number0954-1020
Accession NumberWOS:000404282500002
Keywordsantarctica; Aptenodytes forsteri; Cape Colbeck; Cape Roget; climate; colonies; environmental-change; island; location; pointe-geologie; trends; western ross sea

There are seven emperor penguin (Aptenodytes forsteri) colonies distributed throughout the traditional boundaries of the Ross Sea from Cape Roget to Cape Colbeck. This coastline is c. 10% of the entire coast of Antarctica. From 2000 to 2012, there has been a nearly continuous record of population size of most, and sometimes all, of these colonies. Data were obtained by analysing aerial photographs. We found large annual variations in populations of individual colonies, and conclude that a trend from a single emperor penguin colony may not be a good environmental sentinel. There are at least four possibilities for census count fluctuations: i) this species is not bound to a nesting site like other penguins, and birds move within the colony and possibly to other colonies, ii) harsh environmental conditions cause a die-off of chicks in the colony or of adults elsewhere, iii) the adults skip a year of breeding if pre-breeding foraging is inadequate and iv) if sea ice conditions are unsatisfactory at autumn arrival of the adults, they skip breeding or go elsewhere. Such variability indicates that birds at all Ross Sea colonies should be counted annually if there is to be any possibility of understanding the causes of population changes.

Short TitleAntarct. Sci.

What do all these variations in inter-colony counts mean? We propose that there is a message in the apparent instability among the colonies if the general natural history of the species is considered.

First, emperor penguins do not have a nest site so there is no investment in property as there is with other penguins.

Second, there is no shared investment with a mate, and mate fidelity is the lowest of all penguins.

Third, the birds may elect not to breed annually, and considering the long fast of the male of 120 days, this is not a surprise.

These factors, the frequent fluctuations in individual colony annual counts and recent genetic analyses suggest that assessment of emperor penguin population trends in the Ross Sea requires counts at all seven colonies and not at single individual colonies.

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