A gregarious bird, but less so than some other penguin species (2), the gentoo can form breeding colonies ranging from thirty to thousands of pairs (5). Arriving at suitable nesting ground between June and November (the exact date depending on the location) (2), each pair of penguins will set about the task of constructing a nest from stones, tussock grass and moss (2). The penguins tear up plants to use as nest material and fertilise the ground with their droppings, resulting in grass growing well the subsequent year, hence their favourable reputation with sheep farmers (5).
Into these nests two white, spherical eggs are laid, which are incubated by both the male and female for 31 to 39 days (2). The penguin chicks fledge after 85 to 117 days, but continue to be fed by their parents for a further 5 to 50 days. Gentoo penguins, which reach sexual maturity at the age of two years (2), are not only faithful to certain nest sites, with most returning to the previous year's nest, but they are also loyal to breeding partners, with many forming long-lasting pair bonds (3).
Walking with a rather comedic, waddling gait on land, the gentoo penguin shows its true talents when in the water. With its stream-lined body and 'flippers' that provide effective propulsion through the water (6), the gentoo penguin dives deep into the ocean in pursuit of its prey, and is capable of reaching impressive depths of up to 170 metres (3). The exact diet of the gentoo penguin varies depending on location, but can include Atlantic krill, other crustaceans, fish, cephalopods and polychaetes (2).