Penguins On Thin Ice
by Howard Youth
Each year many thousands of tourists watch penguins swim in a narrow pool set into the Flamingo Hilton's 15-acre courtyard. From the 20th floor of this Las Vegas colossus, the black-backed birds look like mermaids doing laps in a puddle. Strange as it may seem, the Americans watching these show-birds far outnumber those who trek to see the penguins' millions of wild cousins. Weird, but understandable. After all, wild penguins live far outside our easy reach. To see most of the species, you incur great expense and endure long airplane flights and choppy boat rides, not to mention brave icy winds or searing sun.
Still, penguins are favorites. "Because their legs are set so low down on their bodies, penguins stand upright," writes penguin researcher Pauline Reilly in her book Penguins of the World, "and perhaps it is this similarity to ourselves that makes penguins so attractive to people." They remind us of awkward people in tuxedo plumage, waddling around, flapping their ungainly flipper-like wings. Images of penguins as clumsy, cuddly humanoids appear in cartoons and on air conditioner ads and ice cream trucks.
But in the wild, far from slot machines, newsstands, and aquariums, penguins lead very birdy lives, albeit in often outlandish circumstances. They defend territories, dive for food, feed their young, commute from nests to the sea, and avoid, as best they can, getting torn to shreds by predators. Real-life penguinsas scientists are only now beginning to learnare far more compelling than their cute cartoon facsimiles.
The adaptations that set penguins apart from most other birds enable them to thrive in harsh environments where few other creatures can survive. Antarctic penguins even lack the mites and lice that plague many of the world's birdsit's just too cold out there. Within this fascinating family, the world's 17 penguin species vary widely in size, habitat, and diet, but also in habits. Unfortunately, just as varied are the threats facing penguin populations.
From the Equator to the Bottom of the World
Depending upon which etymology you choose to believe, the word "penguin" derives either from the Latin word pinguis, meaning fat, or the Welsh words pen gwyn, meaning "white head." Both names probably first described a flightless bird that is not a penguin at allthe now-extinct great auk. The great auk, a relation to the flying puffins and other auks alive today, was harvested to extinction for its fat by 1844. Before then, the black-and-white seabird was familiar quarry for people living along North Atlantic coasts. Neither auks nor penguins had white heads, but fishermen weren't necessarily focused on such details, so most etymologists stick to the Welsh words as a probable origin for the name. European explorers probing mysterious southern waters stumbled upon true penguins as early as the late 1400s, when the first penguin reference was penned off Africa's southern coast during one of Vasco da Gama's voyages. Today, scientists refer to birds as penguins only if they belong to the family Spheniscidaethe only flightless aquatic birds. The family name comes from the Greek word for wedge, referring to the penguin's curved flipper-wings. (See "What's in a Name")
The oldest known penguin fossil dates back 50 to 55 million years, and 32 extinct penguin species have been identified, including some bruisers that probably weighed up to 300 poundsmore than a giant panda. Although no missing link has been found, scientists believe penguins descended from flying relatives. Genetic analysis reveals that penguins' closest relatives may be the highly aerial frigatebirds and the deep-diving loons, which certain penguin species resemble when they swim with their necks and backs exposed above water.
No penguins live north of the Equator, but one species lives on it. Native to the sun-baked Galapagos archipelago, the Galapagos penguin, a small black-and-white bird with a pale orange bill locked in what looks like a perpetual grin, leaves the hot shore by day to scour the cold Cromwell Current for fish. At the other extreme, the emperor penguin, a husky black-headed bird splashed with dollops of orange on its neck and a wash of yellow on its breast, breeds in the middle of Antarctic winter on ice, and never walks on land. Standing almost four feet tall and weighing up to 90 pounds, the emperor is the world's largest penguin, dwarfing the world's smallest, the pigeon-sized blue, or little, penguin of Australia and New Zealand (which despite its bluish gray back is the least colorful of the lot). Contrary to popular belief, more than half of the world's species of penguin never set foot on mainland Antarctica.
Whether living along the coasts of South America, southern Africa, Australia, New Zealand, or Antarctica, all penguins must leave the cold seas to molt and nest, and they must live near cold waters rich in their favored foodsfish, squid, and small shrimp-like crustaceans called krill.
Feast and Famine
Like the seals, sea lions, and whales with which they share the seas, penguins are supremely adapted for a marine existence. The land offers no sustenance to penguins. They thrive on the seas' bounty. Penguins of some species spend 75 percent of their lives at sea. Equipped with keen underwater vision, penguins hunt both day and night. Their sleek plumage, torpedo-shaped bodies, and flightless flipper-like wings, driven by well-developed breast muscles, make them excellent fishers. Tightly packed feathersup to 70 per square inchand blubber insulate the diving birds.
Penguins, for all their awkwardness on land, epitomize grace and power under water. They fly underwater with powerful wing strokes, diving, careening, grabbing prey, and avoiding a mixed bag of predators, including sharks, killer whales, sea lions, and leopard seals. Penguins dart through the sea at speeds up to 15 miles per hour. Penguins of many species also "porpoise," briefly shooting above, then below the surface in a rollercoaster-like motion.
Scientists do not fully understand the penguins' underwater feeding tactics. They do know that the birds often dive deeply for their prey, thanks in part to heavy, solid bones that help them sink as they dive. (Flying birds have more or less hollow bones that lighten their payloads.) Most penguins rarely dive deeper than 30 feet, but the heavy emperor penguin holds the record at over 130 feet, and may stay submerged as long as 18 minutes at a time. Penguins catch prey headfirst in their forceps-like bills, then swallow their food, which is grasped firmly within the mouth by rows of sticky bristles. In the black depths, deep-diving penguins probably spot the glow of their krill prey thanks to the small animals' bioluminescence.
Penguins' dark-above, light-below coloration serves to hide or advertise them underwater, depending upon which theory you like. Many scientists believe the penguin's pied coloration hides them from predators and prey. When seen from above, penguins' dark backs meld with the sea's depths; when seen from below, the birds' white bellies blend with the light-enriched waters above. Others theorize that a pied penguin's striking plumage distresses schooling fish, causing them to separate and become easier to capture.
Many penguins hunt alone, but others, especially those that feed upon fish, hunt in groups. For instance, Galapagos penguins hunt in groups of up to 200 individuals. Southern Africa's jackass and South America's Magellanic penguins often join predatory fish, other seabirds, or sometimes sea lions for feeding frenzies targeting small schooling fish.
Penguin Cities
When it comes to nesting, New Zealand's yellow-eyed penguins are usually lonersand they stand out as such among the otherwise gregarious penguin family. These brightly colored birds, with gaudy yellow eye bands and faded yellow crowns and throats, nest out of sight of one another amid dense vegetation on coastal and island slopes.
But elsewhere in the penguin world, nesting is a group activity and penguins rank among the most social of birds. Many species nest in huge colonies that blanket large stretches of terrain. The colonies cover acres of ground with stinking guano, blotting out most of the vegetation that once grew there. Yet penguins are a combative lot, protecting tiny territories whose boundaries are within pecking distance of their nests. In dense colonies, penguins returning from the sea must run a gauntlet of nips and jabs on the way to their nests. Those pairs nesting at the outer edges of the colony receive fewer pecks but pay the price by being more vulnerable to such loitering nest looters as the gull-like skuas and giant petrels.
Like teens at a prom, courting penguins often follow the rhythms of the group. Penguins generally return to the same colonies year after year, where they seek nest sites and mates. Males and females of a few species, notably the short-billed, tuxedo-plumaged Adélie of Antarctic ice floes, and the blue penguin, usually take the same mates and nest sites each season.
Males usually return to the colony first, followed shortly after by females. For the four subtropical and tropical speciesthe Galapagos, jackass, Magellanic, and Humboldt penguinsthis means returning to underground burrows, cracks, or caves that shelter nesting pairs from the scorching sun and land-based predators. These birds nest at any time of year, depending upon food availability. The fiordland penguin nests under tree roots in coastal rainforests off New Zealand.
Recognition is key for a pair's survival and the survival of their offspring. Pair bonds form quickly, and mates recognize each other by wing-flapping, neck raising, and other displays. Such exuberance is contagious. Often when one pair starts to greet, the excitement ripples through the colony, as if the birds are doing a strange form of the wave.
In the icy waters near Antarctica, Adélie, chinstrap, and gentoo penguins emerge and return to rocky open areas, where huge colonies cover the landscape. On such open colonies, nests consist of scraped depressions lined with small rocks, bones, or grasses. Pairs often fight over stones, precious nesting materials that are regularly stolen by neighbors. In areas where all three of these species mingle, varied behaviors probably reduce competition for nest sites and food. For instance, Adélies often place their pebble-lined nest depressions on higher ground than the less numerous gentoos. When feeding, Adélies tend to catch smaller krill, chinstraps larger ones, while gentoo eat krill that vary in size depending upon region.
The penguin giantsthe emperor and somewhat smaller king penguinsdon't build nests at all. Unlike other penguins, which usually lay two eggs, these birds lay a single egg that is incubated under skin folds between their legs. The eggs rest on the birds' legs, and can be shuffled along the ice or ground for short distances.
While most penguin species split parental duties equitably, male emperors take the penguin prize for parental sacrifice. Many species nest near productive waters during warm months, but not emperors. The males nurture their eggs on their feet on distant ice fields, in the dead of the Antarctic winter. Female emperors lay their single eggs in May, the beginning of Antarctic winter, immediately passing them off their feet to their mates for safekeeping. Females tromp off for distant shores to feed, only returning to relieve their mates after the eggs hatch, some nine weeks later. Blasted by fierce winds and subzero temperatures, incubating males don't defend nesting territories. Instead, they huddle together, all the while keeping their eggs on their feet and under their warming skin folds. Upon hatching, young emperors may receive a small meal of regurgitated "penguin milk," a curd-like substance, from their long-fasting fathers. Females return shortly after, their stomachs filled with fish and squid that they will regurgitate for their young. Relieved at last, males begin their long commute back to the sea to feed, and then return to again feed their young, which fledge at about five months old. Like war-weary soldiers passing fresh recruits, long lines of dirty, hungry parents plod to the sea, streaming past recently cleansed and fed penguins marching back to their young.
The business of returning to land, courting, mating, and incubating eggs forces penguins to fast for long periods each year. Fasting lengths vary depending upon species and the distance from nests to feeding waters.
Between nesting and commuting, the male emperor may go without food for up to six months. In contrast, other species undergo nesting fasts of a few days or weeks. Emperors also hold the distance record for flightless bird travel: Adults waddle or toboggansledding on their bellies, using the toes to push and wings to steerup to 125 miles between open fishing waters and their icy nesting grounds.
All penguins share the duties of brooding, or sheltering, their nestlings from weather and predators. After three or four weeks, young penguins begin to keep themselves warm. This allows both parents time to leave the nest and gather more food for their fast-growing progeny. With their parents gone for long stretches, young penguins of some species, including emperors, kings, Adélies, and gentoos, seek the protection and warmth of their peers, forming groups called creches. When parents return from feeding expeditions, they enter the gaggle of clamoring young to find and feed, via regurgitation, their offspring. Researchers have found that adults and young birds give individualized calls that help them find each other in a crowd. Depending upon the species, young penguins stay in creches for between seven weeks and nine months before taking to the sea. In general, young penguins wander widely, returning to nesting colonies to breed after two to eight years.
Waddling into the Future
Penguins face a multitude of threats to their survival. In 1996, a conference on penguin conservation was held in Cape Town, South Africa. Under the auspices of the World Conservation Union (IUCN) and other groups, penguin researchers from ten countries met and began work on the Penguin Conservation Assessment and Management Plan. They assessed the status of the world's penguins and began charting conservation strategies for their future. The workshop's report, published in 1998, states that "Of all the penguin species, only those in the Antarctic do not seem to be facing grave, documented declines or other problems that put them at serious risk." But even in the Antarctic, penguins face certain threats. Commercial fishing fleets deplete the penguins' food supplies, tourist groups disturb colonies, and the close proximity of international research stations to traditional colony sites brings pollution and disruptive helicopter flights.
In other areas, introduced cattle, sheep, and rabbits destroy nesting habitat, while exotic predators take a heavy toll on eggs, young, and even adult penguins. In New Zealand, for example, introduced weasels, dogs, cats, pigs, and rats threaten fiordland and yellow-eyed penguins. Yellow-eyed penguins are considered vulnerable to extinction, with a total population of up to 6,000 birds. On several islands off New Zealand, the introduced wekaa flightless rail that is itself threatened by exotic mammals on New Zealand's main islandspreys upon the eggs and young of fiordland and royal penguins, two vulnerable species with localized distributions.
Dependent upon rich upwellings carried by cold ocean currents, penguins, like many other seabirds, can be devastated by changes brought on by meteorological phenomena. For example, El Niño can devastate South America's Humboldt and Galapagos penguin populations, replacing productive cold currents with infusions of warm water that leave the birds and their chicks to starve. Whether or not this phenomenon is on the increase could play a strong role in these localized birds' long-term prospects.
The endangered Galapagos penguin is the world's rarest penguin and it became even more scarce following the 1982-1983 visit by El Niño, which cut its food supply and reduced its population from perhaps more than 10,000 to about 450 individuals. The population had not yet recovered when El Niño struck again in 1997 causing penguin and other seabird colonies to fail again. Even without the threat of ocean current fluctuations, these island-bound birds are disturbed by tourists and fishing boats, and threatened by introduced dogs, cats, and rats.
Off the coasts of South Africa and Namibia, the jackass penguin has suffered steady declinesup to 75 percent during the 20th centurydue to commercial over-fishing, coastal industrial development, oil spills, introduced cats, and competition with rebounding populations of Cape fur seals.
Meanwhile, the sizes of remote colonies of the Antarctic speciesamong the largest bird metropolises in the worldremain steady. Recent population estimates for these abundant birds include more than two million pairs of king penguins, 2.5 million pairs of Adélie penguins, 6.5 million pairs of chinstrap penguins, and 11.5 million pairs of macaroni penguins, birds whose gold crests resemble the long, curly "macaroni" hairstyle popular centuries ago. The emperor penguin population holds firm at between 135,000 and 175,000 pairs.
Scientists are concerned about the potential effects of global warming on Antarctic penguins and their icy domain, as well as how climate changes will affect the ocean currents that provide most penguin populations with their abundant food. Nesting in sensitive, often localized areas, and dependent upon fluctuating marine resources, penguins, like sea lions and other marine predators, may face serious troubles in the future.
Conservation measures are being stepped up to better protect some of the seriously declining species by eradicating exotic pests, protecting nesting islands, and minimizing the impact of tourism and fishing upon the birds. But much more needs to be learned about these birds and how best to conserve them.
Meanwhile, continent-bound North Americans can marvel at penguins in aquariums, or in Vegas. These waddling ambassadors unwittingly invite us to learn more in order to protect their wild brethren nesting on battered rocks, in lush forests, or on drifts that remain invisible to most of us.
Howard Youth, an avid birdwatcher himself, is a Contributing Editor to ZooGoer.
ZooGoer 29(1) 2000. Copyright 2000 Friends of the National Zoo. All rights reserved.
