"The Adélies dive very beautifully. We did not see this at first, before the sea-ice had gone out, because to enter the water they had only to drop a few inches, but later, when entering from the ice terraces, we constantly saw them making the most graceful dives.
At the place where they most often went in, a long terrace of ice about six feet in height ran for some hundreds of yards along the edge of the water, and here, just as on the sea-ice, crowds would stand near the brink. When they had succeeded in pushing one of their number over, all would crane their necks over the edge, and when they saw the pioneer safe in the water, the rest followed...
The reluctance shown by each individual of a party of intending bathers to be the first to enter the water may partly have been explained when, later on, we discovered that a large number of sea-leopards were gathered in the sea in the neighbourhood of the rookery to prey on the penguins. These formidable animals, of which I show some photographs, used to lurk beneath the overhanging ledges of the ice-foot, out of sight of the birds on the ice overhead. They lay quite still in the water, only their heads protruding, until a party of Adélies would descend into the water almost on top of them, when with a sudden dash and snap of their great formidable jaws, they would secure one of the birds.
It seemed to me then, that all the chivvying and preliminaries which they went through before entering the water, arose mainly from a desire on the part of each penguin to get one of its neighbours to go in first in order to prove whether the coast was clear or not, though all this manoeuvring was certainly taken very lightly, and quite in the nature of a game. This indeed was not surprising, for of all the animals of which I have had any experience, I think the Adélie penguin is the very bravest. The more we saw of them the fonder we became of them and the more we admired their indomitable courage. The appearance of a sea-leopard in their midst was the one thing that caused them any panic. With dozens of these enemies about they would gambol in the sea in the most light-hearted manner, but the appearance of one among them was the signal for a stampede, but even this was invariably gone through in an orderly manner with some show of reason, for, porpoising off in a clump, they at once spread themselves out, scattering in a fan-shaped formation as they sped away, instead of all following the same direction."
--- Antarctic Penguins / George Murray Levick
BBC - Earth - If you think penguins are cute and cuddly, you're wrong
"Reputation: Penguins only live in icy regions near the poles. Penguins form lifelong loving relationships with their partners and are the perfect caring parents.
Reality: Most penguin species live in temperate or tropical places. They frequently cheat on their partners and engage in homosexual acts. Penguin mothers kidnap each other's chicks...
Douglas Russell of the Natural History Museum in London, UK unearthed a paper called "Sexual Habits of the Adélie Penguin". It was labelled "not for publication".
The paper was the work of George Murray Levick, Scott's expedition scientist and the first person to witness an entire breeding season. He was shocked by what he saw: gangs of males engaging in homosexual sex, sexually abusing chicks, and mating with dead females. At the time, the material was judged too depraved for public consumption...
One confused penguin even kidnapped its own natural enemy, the chick of a penguin-eating bird called a skua...
Emperor penguins form long-distance relationships that endure the Antarctic winter, and this has made them the poster children of monogamy. The penguins themselves have different ideas, and regularly get "divorced". Similarly, 81% of king penguins choose a different mate every season.
Infidelity is also commonplace. Nearly a third of female Humboldt penguins cheat on their partners.
This cheating is sometimes driven by factors that, to us, seem shockingly mercenary.
Adélie penguins build nests out of stones, and a shortage of stones has pushed many females into "prostitution": they mate with other males in exchange for stones. Some duplicitous females have started going through the elaborate courtship ritual to get the stones, and then running off before the male can mate. Both sexes also steal stones from their rivals' nests."