There are two subspecies that belong to the gentoo penguin family: Pygoscelis papua papua and Pygoscelis papua ellsworthii. A prominent tail, bright orange-red bill, and the blazing white patch on their eyes are the striking features of these species that makes them stand out from other members of the penguin family. The scientific name Pygoscelis papua, meaning "rump-tailed", is given to a gentoo penguin for its sweeping tail while it's waddling on the shore. Gentoos are black on the back and white on the front side, and the shape of their body is similar to a boat. This body structure allows them to swim at greater depths with a greater speed. Gentoo penguins are considered as the fastest underwater swimmers amongst all penguin species, thanks to their fat and webbed feet. The feet are orange in color with black, long claws on them. This unique physical feature allows them to move well on slippery ice as well as climb a rough terrain. Grooming is an important part of a gentoo penguin's routine, and they engage in grooming more often than other species. The process of grooming involves getting the oil from the oil gland near the tail and distributing it all over the feathers with the bill. They have to twist and turn their body to be able to spread the oil properly. Although gender distinction is difficult in this penguin species, males are usually larger than females. The average height that a gentoo penguin may grow up to is 20 to 36 inches, and they weigh around 5 kg. Baby gentoos are grayish in color with a white frontal side. The white crown covering the area from one eye to the other over the head is underdeveloped in them at this stage. Gentoo penguins are found in many islands of the Antarctic region. However, the main colony of gentoo penguins is on the Falkland islands. They typically live on islands, or other secluded areas to protect themselves from land predators. Other regions where they develop their colonies are Kerguelen islands and South Georgia. Certain smaller colonies of this species are found on the Macquarie island, Heard Island, South Shetland Islands, and the Antarctic Peninsula. Gentoo penguins are partial migratory animals. This is because at certain times, they leave their nesting location after the breeding season. Usually, the colonies nesting in the Antarctic Peninsula have the tendency to migrate, whereas the subantarctic population is known to be sedentary. Gentoo penguins feed on crustaceans, krill, squid, cephalopods, and small fish. Like all other penguin species, gentoo follows a total carnivorous diet, which comprises only marine animals. While krill becomes the important food on the southern part of the gentoo habitat, they feed on small fish in the northern locations. Moreover, fish makes up only 15% of their diet, whereas krill and crustaceans make up for major portion of their diet. Being a large-sized animal, this penguin can consume a fish that weighs more than 1 kg and which can be over 40 cm long. Nesting Gentoo penguins usually reside along the shoreline, which gives them easy access to food while being closer to their nesting place. They begin their search for an appropriate nesting location between June to November. After reaching a suitable nesting ground with the entire colony consisting of thousands of pairs, each gentoo pair starts building their nest. The nesting material includes stones, moss, tussock (grass) etc. It also requires plants, and once these material are in place, they fertilize the ground with their droppings. This enhances the growth of grass, and the moss spreads around. One of the characteristic features of gentoo nesting is the presence of small pebbles. The areas with small pebbles are selected, as they are the main building blocks of the nest that helps protect eggs during the breeding season. Breeding Although gentoos are active all round the year, they have their annual breeding season, which begins in March. Unlike other species, gentoos breed in snow and ice-free regions, but due to their widespread distribution, these habits may vary to a great extent. For instance, on the Antarctic Peninsula, as mentioned above, the main nesting material is pebbles, whereas in the subantarctic regions, preferences for the nesting material are twigs, seaweed, grass, etc. During the breeding season, gentoos prefer foraging along the shorelines and stay closer to the nesting area, within 18 miles of the colony. A male gentoo performs some displays for building a nest site and attracting a female. The female takes a survey of the nesting area, and the pebbles used in the construction become the deciding factor in selecting the male and his territory. Moreover, the male offers a stone to the female to please her and receive her favors. Further, the female lays two spherical and greenish-white eggs, each weighing approximately 125 grams (the weight of the first and second egg may vary depending on the nesting location). The first egg is laid 5 days post breeding, and the second one is laid after 3 days. After this, both parents share the responsibility of incubation, which lasts for about 31 to 39 days. After the incubation, the eggs are hatched, and interestingly both eggs hatch on the same day in spite of being laid on different days. Since the chicks are delicate and weak, they have to be in the nest for 75 long days until they are ready to fledge and go for their first visit to the ocean. Gentoos resort to loud trumpeting to communicate with their mate and young ones. They are well-known for producing a variety of sounds for several occasions. For example, when the male or female returns after feeding, it will point the beak up straight in the air and throw out loud squawks to make the partner aware about their arrival. When a predator is invading its territory, a gentoo will make a low hissing sound, or give out grunts, depending on the severity of the threat. The chicks are also very talented in producing various sounds, like high-pitched chirping when hungry, or a modified whistle call before reaching their first molt, after which they develop an adult voice for calling. Interestingly, the chicks are so intelligent that they can recognize and distinguish the call of their parents from several other gentoos nesting in their colony. Gentoos are the shyest of all penguin species, and do whatever it takes to avoid a fight. Although being a highly territorial animal, it will do nothing more than gaping at its fellow mates with its beak wide open, when enemies attack its territories. Apart from its enemies, a gentoo penguin is also not very comfortable with its own companions. When the colony begins to grow larger and crosses over around hundred pairs, the pairs start splitting up and forming a new, smaller colony. Although being a shy, asocial (in consideration to other creatures) animal, this penguin possesses the quality of being tolerant. It shares its nesting place with other sea birds and penguin families. In terms of commitment towards the family, gentoos deserve an appreciation for being monogamous creatures. Gentoos are one of the most territorial animals. For a major part of their life, they stay on the same location where they breed. If they have to move their colony, it is because of the excessive ice formation in winters. In such circumstances, these sea and land dwellers have to move to an ice-free location. Adult gentoos begin their annual molt away from the nesting location, after the chicks have fledged and finally departed from the nesting site. There are two stages of molting, namely the pre-molt and the actual molting stage.

• The pre-molt stage begins in January and lasts for up to 55 days. During this period, gentoos make long, foraging trips to the sea to meet their objective of gaining maximum weight at this point of the year.
• This phase is followed by actual molting, which lasts for 25 days. This proves to be an event that requires high energy, and the gentoos have to overgorge themselves to create fat reserves. During the molting period, they cannot take foraging trips to the sea; so they fast while losing 200 gm of weight per day.

Considering their uncommon nesting location, gentoo penguins do not really have any land-based predators. However, their potential threats are the sea animals, like leopard seals, sea lions, orca (killer whale), etc. Sea birds, like skuas, gulls, etc., might also prey on the chicks and steal the unattended eggs.