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Description
The Gentoo Penguin is one of three species in the genus Pygoscelis.
Mitochondrial and nuclear DNA evidence suggests the genus split
from other penguins around 38 million years ago, about 2 million
years after the ancestors of the genus Aptenodytes. In turn, the
Adelie Penguins split off from the other members of the genus
around 19 million years ago, and the Chinstrap and Gentoo finally
diverging around 14 million years ago.Males have a maximum weight
of about 8.5 kg (19 lb) just before molting, and a minimum weight
of about 4.9 kg (10.8 lb) just before mating. For females the
maximum weight is 8.2 kg (18 lb) just before moulting, but their
weight drops to as little as 4.5 kg (10 lb) when guarding the
chicks in the nest. Birds from the north are on average 700 g
(1.5 lb) heavier and 10 cm (4 in) taller than southern birds Gentoo
penguin reaches 75–80 cm. They are the fastest underwater
swimming penguins, reaching speeds of 36 km/h. Gentoo are adapted
to very harsh cold climates.
Habitat
Gentoos breed on many sub-Antarctic islands. The main colonies
are on the Falkland Islands, South Georgia and Kerguelen Islands;
smaller populations are found on Macquarie Island, Heard Islands,
South Shetland Islands and the Antarctic Peninsula. The total
breeding population is estimated to be over 300,000 pairs.
Breeding
Nests are usually made from a roughly circular pile of stones
and can be quite large, 20 cm high and 25 cm in diameter. The
stones are jealously guarded and their ownership can be the subject
of noisy disputes between individual penguins. They are also prized
by the females, even to the point that a male penguin can obtain
the favors of a female by offering her a nice stone. Two eggs
are laid, both weighing around 500 g. The parents share incubation,
changing duty daily. The eggs hatch after 34 to 36 days. The chicks
remain in the nests for about 30 days before forming creches.
The chicks molt into sub-adult plumage and go out to sea at about
80 to 100 days.
Diet
Gentoos live mainly on crustaceans such as krill, with fish making
up only about 15% of the diet. However, they are opportunistic
feeders, and around the Falklands are known to take roughly equal
proportions of fish, crustaceans and squid.
Threats
In the water, sea lions, leopard seals, and orca are all predators
of the Gentoo. On land there are no predators of full grown Gentoos.
Skua can steal their eggs; however, some other seabirds have managed
to snatch chicks.
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