Expedition to Ross Island, Antarctica, to study Feeding Chases : 2006-01-08
In a few days, Dr Lloyd Spencer Davis will be leading another expedition to Antarctica: this time to conduct research on the feeding behaviour of Adelie Penguin chicks. He will be accompanied by his son, Daniel Davis, and scientist/filmmaker David Lickley from Science North, Canada.
Chicks of Adelie Penguins form creches at about three weeks of age when both their parents are typically away from the nest simultaneously to search for food to bring back to their chicks. In this species of penguin (and others of the genus Pygoscelis), when a parent arrives back at the creche with a belly full of food, it calls out to its chicks (usually they have a brood of two chicks), which typically run to the parent – and this is where it gets strange: the parent will then turn and run away, leading the chicks on what is known as a feeding chase. Such feeding chases take the chicks away from the protection afforded by the creche and expose them to predation from the likes of skuas.
Why would a parent do that? There are two competing theories or hypotheses as we call them: one suggests that in times of food shortage, such behaviour facilitates favouring the largest chick and ensures that at least it has a chance of surviving; the other suggests just the opposite – that feeding chases act to distribute food more equitably between the chicks.
The only real way to test between the predicted outcomes of the two hypotheses is to do so when there are food shortages, but even the most lenient of ethics committees would not countenance deliberately depriving chicks of food. However, Nature has stepped in and provided the experiment: a large ice berg, called B15, broke off the Ross Ice Shelf in 2000 and became grounded near the penguin breeding colonies on Ross Island. This so altered the ice patterns around the colonies that it meant that parents could not bring back nearly as much food to their chicks.
Having studied feeding chases on Ross Island before the berg arrived and with the berg there, now that it has started to drift northwards, Lloyd Spencer Davis and co. are returning to see whether the outcomes of feeding chases alter as the effect of the berg recedes.