A new study led by Dr Peter Fretwell of British Antarctic Survey is the first to use satellite imagery to suggest that emperor penguins (Aptenodytes forsteri) can and do move between, and establish new, colonies.
Emperor penguins (Aptenodytes forsteri): adults and chicks. Image credit: Michael Van Woert / NOAA NESDIS / ORA.
Scientists have long thought that emperor penguins were philopatric, which means they would return to the same location to nest each year.
But the new study shows that emperor penguins may not be faithful to previous nesting locations.
“Our research showing that colonies seem to appear and disappear throughout the years challenges behaviors we thought we understood about emperor penguins. If we assume that these birds come back to the same locations every year, without fail, these new colonies we see on satellite images wouldn’t make any sense,” explained Dr Michelle LaRue from the University of Minnesota, who is the first author of a paper published in the journal Ecography.
“These birds didn’t just appear out of thin air – they had to have come from somewhere else.”
“This suggests that emperor penguins move among colonies. That means we need to revisit how we interpret population changes and the causes of those changes.”
Dr Fretwel, Dr LaRue and their colleagues found six instances in just three years in which emperor penguins did not return to the same location to breed.
The team also reports on one newly-discovered colony on the Antarctic Peninsula that may represent the relocation of emperor penguins from the Dion Islands, recently confirmed as having been abandoned.
Emperor penguins are a well-studied species and have recently been elevated to celebrity status with movies like the documentary ‘March of the Penguins.’
The ‘March of the Penguins’ colony, Pointe Géologie, has been studied for more than 60 years.
Scientists observe the colony every year and look for birds that have been banded by researchers to return to the colony.
In recent decades scientists have been concerned about how receding sea ice may affect the emperor penguins that breed on it.
Over five years in the late 1970s, the Southern Ocean warmed and at the same time the penguin colony at Pointe Géologie, declined by half (6,000 breeding pairs to 3,000 breeding pairs). The decline was thought to be due to decreased survival rates.
In other words, researchers thought that the warming temperatures were negatively impacting the survival of the species.
Satellite imagery has changed all that because now researchers can see the entire coastline and all the sea ice.
The satellite images show that Pointe Géologie is not isolated at all. Plenty of colonies are within easy travel distance for an emperor penguin.
“It’s possible that birds have moved away from Pointe Géologie to these other spots and that means that maybe those banded birds didn’t die. If we want to accurately conserve the species, we really need to know the basics. We’ve just learned something unexpected, and we should rethink how we interpret colony fluctuations,” Dr LaRue said.
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Michelle LaRue et al. Emigration in emperor penguins: Implications for interpretation of long-term studies. Ecography, published online June 05, 2014; doi: 10.1111/ecog.00990
