The prey is too big to swallow whole – and is suddenly snatched away by a second penguin. A third penguin joins the scuffle, while the first makes a last-ditch bid for its catch. A tug of war ensues, and the hapless squid is torn in two.
This underwater brawl was captured on a video camera taped to the back of the second penguin, revealing this unexpected foraging behaviour for the first time. “This is completely new behaviour, not just for gentoo penguins but for penguins in general,” says Jonathan Handley, a doctoral student at Nelson Mandela Metropolitan University in Port Elizabeth, South Africa.
Handley used high-definition video cameras waterproofed with custom-made Perspex casings, which functioned perfectly to depths of more than 200 metres.
“These images are unique in that they were captured underwater in a situation that would have been unobservable without this technology,” says Norman Ratcliffe, a seabird ecologist at the British Antarctic Survey in Cambridge, UK. “It is interesting that the interaction was over a squid: a large and difficult-to-capture prey item that is clearly worth fighting for.”
We already knew that penguins stole pebbles from each other’s nests and have records of seabirds fighting over food –behaviour known as kleptoparasitism.
The Falkland Islands are home to around 130,000 breeding pairs of gentoo penguins – the world’s largest population ofthis species. Handley studied them over three breeding seasons from 2011 with the assistance of Falklands Conservation, a local non-governmental organisation.
He says a large squid would be prize prey for a penguin, providing high-energy food for both a parent and chick, and reducing foraging time. “The majority of their prey is small and quickly consumed,” he says.
But he believes it is unlikely that gentoos specialise in becoming food thieves. They would probably only steal food that other penguins need to handle for a long time such as a huge squid, he says, allowing them the opportunity to steal it.
Handley says the theft of nesting material such as pebbles and plants – which provide eggs with thermal insulation and protection from rain and meltwater – has been observed when in short supply in penguin colonies belonging to thePygoscelis genus (better known as brush-tailed penguins), which includes gentoos.
So why do they do it? “Individuals able to acquire more resources, including both food and nesting material, will be able to provide better parental care for offspring, thus increasing the offspring’s chance to survive until fledging,” Handley says.
Journal reference: Polar Biology, DOI: 10.1007/s00300-015-1772-2