Mammalian predators can be particularly deadly to both the vigilant and careless penguin. Many different seals and sea lions make their days complete by preying on unsuspecting penguins. Orcas, or killer whales, have also been known to make meals out of penguins as well. However, adults not only have to worry about themselves but also their chicks. While they present almost no threat to the adults, some small mammals can easily raid nests and take away the progeny.

    This is a picture of a stoat. A fierce-looking creature, isn't it? Stoats are about as large as weasels, and they have field days with penguin nests, particularly those of the Yellow-eyed penguins.

    They operate like many nest predators in that they wait for the parent to be distracted or to simply neglect its parenting duties. As you can tell, their teeth are designed for meat predation, and that's exactly what a penguin chick provides for them: a nutritious, meat-filled meal. They may also feed on the eggs if it provides them with what they desire. They are usually solitary creatures and are dominant over the females of the species.

    Like stoats, other small mammals like rats, cats and dogs can invade penguin nesting areas and take away neglected chicks. Some of these small mammals are natural predators of penguins; some are not. Cats, dogs and rats are not. They have been introduced by human beings into the otherwise natural habitat of the penguins. Slowly, these small mammals will reduce the population of penguins unless their predation is curbed. (This is not, of course, a judgment call; it is, however, an observation of fact.)

    Seals are by and large krill feeders, but their diets also include fish, squid, young seals and other marine animals of similar size. However, for the seals that roam around penguin colonies, penguins are the primary diet and krill is thus received through secondary means. The chief predator of penguins in the seal family is the Leopard Seal. (Please close window when finished.) One such seal was found to have 18 Adelie penguins passing through it's digestive system. Obviously, the Adelie penguin isn't much of a meal for the Leopard seal, so several are taken in a feeding.

    Seals pose virtually no threat to penguins while on land - they're simply too slow and clumsy (not that penguins on land are agile and graceful either). However, when in the water, the seal is deadly. So much as a shadow or dark spot in the water is enough to make penguins madly dash out of the sea on to ice floes. When a penguin fails to escape, a Leopard seal grabs it by the head and thrashes it repeatedly about the surface of the water; typically this kills the bird in a short time by severing the spinal cord from the brain, inducing respiratory and cardiac failure. If massive skull compression doesn't kill the penguin first, the death is imaginably agonizing if penguins are capable of feeling this sort of pain. Massive bleeding and dismemberment follows. (One wonders if the repetitive thrashing isn't a form of "play" for the Leopard seal.) Remains of Leopard seal kills are easy to spot: anonymous penguin pelts or skeletons with heads still attached often wash up on shore.

    The predatory nature of the Leopard seal and the excessive cries that come from penguins when one is spotted has suggested to Roger Tory Peterson that there may be a specific Leopard seal "alarm call." Leopard seals may be found around Chinstrap colonies, near Deception Island as well. They pose other threats to King and Emperor penguins around South Georgia.

    Fur seals, as seen in this picture, prey upon the crested penguins particularly, since fur seal domains encompass the Australian and New Zealand waters. Fur seals also have been noted to prey upon African penguins as well.

    Hooker's sea lions prey upon the Yellow-eyed and Gentoo penguins.

A seal thrashes a penguin (with petrels) - Art Wolfe
A Lepoard seal attacks a crested penguin
Another Leopard seal thrashes an Adelie penguin

    Orcas (Orcinus orca) belong to the Order Cetacea and the Family Delphinidae. They are whales; hence, they are mammals and exchange oxygen and carbon dioxide in the open air. Here you can see an orca preying upon fur seals. (You see, even the predators get preyed upon; it's all part of the so-called "food chain.")

    Orcas are a sexually dimorphic species of whale, and they demonstrate their dimorphism in their apparent size differences. The male orca can weigh up to 8 tons (16,000 pounds) and reach a length of 9.5 meters (31 feet). Whereas, the female only reaches 4 tons (8,000 pounds) and a length of 7 meters (23 feet). Both members of the species exhibit conical snouts, bulbous foreheads and highly mobile flippers. Additionally, the male may be identified by his characteristically long (1.5-2.0 meters) dorsal fin. Both subadult males and females demonstrate much smaller and more curved dorsal fins. Despite their obvious size differences, the male and female have very similar color patterns: black on the dorsal (top) surface and white on the ventral (belly) surface. However, geographic variances have been observed as well as all-black orcas and albinos.

    Orcas can be found in all the oceans, major seas and occasionally fresh water areas from the Arctic to the Antarctic Circles. When they are located, they are found in groups called "pods" which consist of 1 to 100 members, the average being 5-20 members. This pod is divided into two subgroups. One consists of the mature males and the other consists of subadult males and females. The groups travel together but may be separated by as much as four miles. Membership to the pod is long term. Pods typically develop repertoires of sonic calls and songs that remain unique to the group.

    Orcas are opportunistic feeders, meaning they eat whatever suits them. Diet varies according to the region of the world, the sex of the whale and even the age. Those animals esteemed enough to be consumed include small whales, sperm whales, pinnipeds, penguins, fish, rays, sea turtles, seals and cephalopods (octopus, squid). Reports of cannibalism have been few and far between, but otherwise noted.

    Reproduction in orcas is neither well documented nor understood. This may suggest that there is no set pattern to acquiring or maintaining a mate. Typically, North Atlantic orcas mate from October to November while North Pacific orcas mate in May to July Females become sexually active when they reach 15-16 feet and males become sexually active when they reach 19-20 feet in length. This usually takes a male 10-12 years of growing. The female has a 12-15 month gestation and gives birth to a 7-9 foot, 400 pound calf. She may become pregnant again in 3 to 8 years after the birth.

    Orcas have no predators, save man. When not pestered by man, mortality is low. A healthy orca can roam the oceans for 50 years. Orcas are generally inflicted by many of the ailments that inflict man, including periodontitis, fractures, parasites and vascular disease.