Penguin populations in flux
By Summit Voice
FRISCO — Just six months after scientists documented breeding emperor penguins moving from sea ice to ice-shelf habitat, a new study reinforces the idea that Antarctica’s iconic birds may be more mobile than thought. It’s too early to say for sure, but that could be good news in terms in terms of global warming, which is likely to change the face of the frozen continent in the decades ahead.
The fundamental questions hinge on how dependent the birds are on their icy habitat. Some studies have shown that emperor penguins may suffer as sea ice shrinks, while other researchers recently doubled their estimate for total population numbers. Overall, penguin populations around Antarctica are in a state of flux. Read all our emperor penguin stories here.
The new study led by the University of Minnesota suggests that the penguins may be behaving in ways that allow them to adapt to their changing environment better than we expected. Specifically, the scientists found that the birds may be willing to move quite a distance to new nesting grounds. In three years of research, the scientists found six instances in which emperor penguins did not return to the same location to breed. They also report on one newly discovered colony on the Antarctic Peninsula that may represent the relocation of penguins.
The study will also be published in an upcoming issue of Ecography, a professional journal publishing research in spatial ecology, macroecology and biogeography.
“Our research showing that colonies seem to appear and disappear throughout the years challenges behaviors we thought we understood about emperor penguins,” said University of Minnesota College of Science and Engineering researcher and the study’s lead author, Michelle LaRue .
The new data from the long-studied Pointe Géologie emperor penguin colony may require rethinking the species population dynamics, LaRue said.
“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. 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,” she explained.
Researchers observe the colony every year and look, in particular, for birds that have been banded by researchers to return to the colony. In recent decades researchers 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.
High-resolution satellite imagery has changed all that because now researchers can see the entire coastline and all the sea ice. Because emperor penguins are the only species out on the sea ice, they can look at images and identify their presence through the telltale sign—their guano stain. Before satellite images, researchers thought Pointe Géologie was isolated and there was nowhere else for the penguins to go. 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,” LaRue said. “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.”