Southern Exposure
by David Challinor
Educational cruises to remote parts of the world are enjoying a bonanza, as elaborate brochures flood the mailboxes of potential customers. An aging and prosperous population accounts for this booming industry: They realize that the globe's "unspoiled" places may remain so for only a few decades more.
During the first half of January, I was the lecturer on an educational cruise from Buenos Aires around the tip of South America to Puerto Montt in southern Chile. My lectures introduced the flora, fauna, and geology of the area, alerting the passengers to what they might see. It was an exciting experience for me and my fellow passengers because most of what we saw was new.
We cruised south along the coast where the pelagic (ocean-going) bird life was soon evident in the flocks of giant petrels that followed the ship. These large, albatross-like birds are brown with ivory-colored bills topped with a tube, an identifying characteristic of this family. Farther south the albatrosses appeared: black-browed, gray-headed, and even the spectacular wandering albatross, the largest of them all.
Two days out of Buenos Aires the ship docked at Puerto Madryn at the base of Peninsula Valds, a large peninsula that juts into the Atlantic about half way down Argentina's coast. Southern right whales, a species that has been intensively studied, winter in the lagoons on either side of the peninsula. Although we arrived too late in the season to view whales, we did see both local gull species, the brown-headed and the kelp, which resembles the familiar great black-backed.
A small population of kelp gulls lives around San Jos lagoon on the north side of the Valds peninsula where they have developed an extraordinary habit. When right whales sleep on the surface of the lagoon, they sometimes get badly sunburned. As in humans, their skin peels from their backs in large sheets. The shed skin, or more properly the slough, is eaten by gulls of both species. However, some kelp gulls, only in this lagoon, dive on the surfacing whales and use their bills to gouge live skin from the whales' backs. This drives the whales to distraction and they submerge desperately to avoid the birds. Many whales have actually swum around the peninsula to the lagoon on the south side where the gulls have yet to learn this habit.
It takes 90 minutes by bus over gravel roads from the port to reach the end of the peninsula, but rich rewards awaited natural history enthusiasts. Among these were small herds of guanacos, the native camel from which llamas and alpacas were domesticated. These mammals range the length of the Andes, extending to the pampas of Patagonia where the landscape is rolling with sparse, shrubby vegetation. In the rain shadow of the Andes little rain falls and guanacos compete with sheep for the scattered forage. The lesser or Darwin's rhea can also be seen easily from the road and a special treat was the sighting of the elegant-crested tinamou scurrying along the road's verge. This bantam-sized bird is characteristic of the area.
The whales had already left for their summer feeding grounds at the Antarctic convergence, where the cold water from the ice shelves meets the warmer South Atlantic water. However, female southern elephant seals had hauled out to molt during one of the only two times each year they come ashore at Valds. The other haul-out took place some months earlier when they returned to give birth and then to breed. The large two-ton males migrate separately from the cows and had not yet returned. These extraordinary animals dive almost continuously, not only at their feeding grounds, but on their way to and fro. Satellite recorders show that the males travel farther vertically than they do horizontally over the ocean floor. They dive as deep as 2,000 feet or more, where they feed on fish not generally harvested by commercial fishers. How they find their prey is still unknown.
Tourists are not allowed on the beach for both their own protection and that of the seals, but from the beach overlook we saw the local red shoveler ducks and three species of oystercatcher: the black, the Magellanic, and the American, the latter a migrant from North America. A dozen neotropical cormorants sunned themselves on the rocks and appeared drab compared to their congeners, which we would see later in the Beagle Channel: the striking black and white imperial shag and the smaller red-faced rock shag.
Meeting the Penguins
While cruising along the south shore of San Jos lagoon, we stopped at a bird sanctuary consisting of a three-acre domed islet known as Isla de los Pajaros--Island of the Birds--which was about 200 yards offshore. Landing is forbidden but with binoculars we saw Chilean flamingos along the beach as well as our first glimpse of Magellanic penguins, the most common penguin in Argentina. In fact, the range of this genus (Spheniscus) extends from the Cape of Good Hope in South Africa to Argentina, around the tip of the continent up the coast to Peru, and out to the Galapagos.
Punto Tombo, about 100 miles south of the Valds peninsula, is Argentina's largest Magellanic penguin colony with about 225,000 breeding pairs. The birds' burrows fill the landward side of a long, high ridge of sand dunes that parallel the coast. The sandy soil must have just the right consistency for the birds to dig their nest burrows; soil quality is so crucial for nesting success that the penguins must climb over the dunes and walk a mile to reach the ocean.
Among the penguins' marine predators are orcas (killer whales) and during the week before our visit to Valds six of them were patrolling the shore close to the beaches. Our guide had the unforgettable experience of watching 30- to 40-foot-long whales hurtle themselves up on the beach to grab young sea lions and penguins. Valds is one of the few places in the world where this orca behavior has been observed, but the whales are not always successful in catching their prey. In fact, sometimes a whale surfs so far up on the beach that, pushed by a large wave, it becomes stranded.
Patagonian foxes also hunt penguins, particularly young ones. These amazingly tame foxes seem to ignore people's actions--when you watch them as they lie on the ground, they simply stare back. They are opportunistic feeders, also preying upon small rodents such as tuco-tucos and on carrion. Tuco-tucos, named for their distress call, are burrowing rodents that fill a niche similar to that of pocket gophers in North America.
The only large predators in Patagonia are pumas, whose range there is now restricted to the mountainous national parks, where their principal prey are guanacos. Pumas have probably the longest north-south range of any terrestrial mammal--from northern British Columbia to Tierra del Fuego.
A Wealth of Waterfowl
Although the Fuegian terrestrial mammal fauna is depauperate, bird life, especially waterfowl, is rich and varied. Two swans are fairly common: the black-necked and the Coscoroba. Coscoroba swans, all white with pink bills and legs, feed in mixed flocks on shallow water with their larger relatives, but they are not nearly as numerous as black-necked swans and seldom comprised more than five percent of the mixed swan groups I saw.
Geese, on the other hand, are ubiquitous and those that are primarily grazers have multiplied exponentially as a result of the conversion of so much forest land to pasture. This situation parallels the explosion of non-migratory Canada geese in North America, which was in large part the result of the rapid increase in the surface area of turf on lawns and golf courses. In Tierra del Fuego the most common goose is the upland or Magellan, which is generally confined to inland pastures where it assembles in large flocks to graze competitively with sheep. These geese have been hunted vigorously by sheep farmers, but with minimal effect on their numbers. Two other geese in the same genus (Chloephaga), the ashy-headed and the ruddy-headed, are also grazers but are not as common as the Magellan goose. The fourth species in the genus is the kelp goose, which does not eat grass but jumps agilely from rock to rock along the shore feeding on marine algae.
Among the ducks of the area, the most extraordinary one is the pato vapor or flightless steamer duck. This large duck, the size of a large mallard, can travel at high speed on the water's surface by using its short wings and powerful legs. Like the kelp goose, it sticks close to the shoreline, although its close relative, the smaller flying steamer duck, is often found on inland lakes. A common local waterfowl is the crested duck, which is seldom hunted because of its strong fishy flavor.
Sea Life and Sea Food
Although whales and porpoises are relatively plentiful, seeing them is mostly a matter of luck. Sea lions and fur seals, however, abound and are easy to see. The local sea lion is more than twice the size of the California one we associate with Fisherman's Wharf in San Francisco or with zoo exhibits. The southern genus ranges from southern Brazil, around the southern tip of the continent, north to Peru and even out to the Galapagos, 600 miles offshore. Sea lions generally haul out on sandy beaches and for millennia were a major food source for local Indians.
Fur seals are smaller than southern sea lions and frequent rocky coasts. Both sea lions and fur seals have circumpolar distributions in the Southern Hemisphere and when whaling declined due to overharvesting in the 19th century, sealers harvested untold millions for oil and fur. Both sea lions and fur seals have recovered from this slaughter, although not to their former numbers because, like their relatives in the Northern Hemisphere, they possibly face increased competition for food from commercial fisheries.
One reason why marine bird and mammal life is so varied and abundant in the temperate Southern Hemisphere is that this part of the globe is mostly ocean and thus teems with fish, so many in fact that in every port we visited, large trawlers and refrigerator ships were common. With the demise of the North Atlantic fish industry, fishing nations have moved their fleets south. At Puerto Madryn in Argentina the shore is littered with abandoned fishing boats whose owners can no longer compete with large offshore trawlers that remain at sea for weeks at a time.
Already the booming frozen-fish industry has probably reached its peak; in 1994 the Food and Agriculture Organization (FAO) in Rome identified Argentine hake, the most valuable commercial fish, as a "heavily fished species." The designation was made even though the catch increased rapidly between 1993 and 1994 thanks to large trawlers. By 1995 the hake catch dropped and is still dropping. The local shrimp industry collapsed a decade ago and the squid season has been shortened to preserve stock. Squid are an important prey for albatross.
It is hard to control worldwide offshore commercial fishing in the commons of the ocean. The harvesters have no investment in crop production--their only cost is in building and operating the harvesting machinery. It is no wonder then that commercially valuable species such as hake and cod will continue to be caught in maximum numbers as long as it is economical to do so. Little consideration is given to future generations of organisms, including our grandchildren, who are entitled to share the sea's bounty.
On the way up the Chilean coast to Puerto Montt there is a 300-mile stretch where the fjords are discontinuous and the ship had to enter the open ocean. During the day and a half at sea we encountered a head-on Force 9 gale, which reduced our speed by a third. Happily the next--and last--day of our trip, when we cruised up the Gulf of Corcovado to our destination, was calm and clear with the snow-capped Andes dominating the eastern shore. For most of the 200 passengers the breathtaking scenery erased memories of the previous day's stormy passage, and we reveled in seeing the perfect snow-covered cone of Osorno volcano, which Darwin and the Beagle crew watched erupting when they were anchored off Chilo Island in the 1830s.
But long before Darwin, the human history of this area began at least 12,500 years ago, at Monte Verde, 40 miles north of Puerto Montt. This is the oldest dated human settlement found in the New World. At Puerto Montt, we indulged in the heady experience of observing a place where humans have lived for more than 12 millennia. It was a fitting end to a marvelous journey.
Land of Clashing Plates
About 200 million years ago Africa and South America broke apart. They are still moving away from the mid-Atlantic ridge--each one at about three centimeters per year, or a total of six centimeters per year from each other. Meanwhile, South America's west coast has been crashing into the Nazca plate, which is still being forced under the continent. This action, called subduction, is elevating the Andes along the line of plate contact. About eight million years ago, the rising mountains blocked the Amazon, which is now believed to have originally flowed into the Pacific from its sources in the ancient sandstone highlands of Guiana and eastern Brazil. The huge lake, created by the blockage, eventually broke through the old rock and emptied into the Atlantic.
At South America's southern tip, however, the Antarctic plate is meeting the continental plate, causing the narrow end of the latter to bend to the east. The Beagle Channel and the western part of the Straits of Magellan are thus oriented east-west and represent ancient glacial valleys created during the great ice ages that started about 100,000 years ago. During the ice ages, so much of the world's water was locked up in the polar ice caps that the sea level was lowered several tens of yards. During this period the glaciers carved out today's channels and fjords.
--David Challinor
David Challinor is Senior Scientist Emeritus at the Smithsonian Institution.
(ZooGoer 26(3) 1997. Copyright 1997 Friends of the National Zoo. All rights reserved.)
