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Spotlight

A Jewel in the Subantarctic's Crown

Dr Simon Pollard

Approaching Anchorage Bay, on the north of Antipodes Island, I thought of the first time The Beatles visited the United States, when they were welcomed by thousands of fans at Kennedy Airport. What reminded me of the Beatles visit was the phalanx of seabirds filling the bay like a wild and welcoming crowd. Once ashore, a deafening cacophony assaulted my ears as thousands of erect-crested and rockhopper penguins, squawking and fighting, burst forth in a chorus of stuttered screams. Light-mantled sooty albatrosses cried out operatic arias. From the mammal section came the low, guttural bellow of disgruntled elephant seals. The whole choir of the Antipodes barked its discordant message.

Isolated and Unvisited

Perhaps the animals had a right to sound indignant at our arrival -- the 12 members of our expedition were among the few humans to set foot on Antipodes Islands since the late 1970s, when New Zealand's Department of Conservation last sent a group of scientists to check on its inhabitants. Not only is the island legally off-limits to visitors, it is also hard to reach. The Antipodes are the most remote of New Zealand's five subantarctic groups, which lie scattered like stepping stones to Antarctica. More than 800 kilometres southeast of the southern tip of New Zealand, the islands can only be reached by a three- or four-day boat trip.

Twelve square kilometres in area, the main island is the remnant of an extinct volcano that emerged from the seabed 1.5 million years ago. It was built up by a series of eruptions characterized by huge fountains spraying out molten rock. The sea wore away the slopes of the ancient volcano, resulting in a dramatic coastline of rugged, crumbling cliffs, some towering almost 300 metres above the surf.

The first people to discover the island were the sailors of H.M.S. Reliance, who sighted it in March 1800. The name Antipodes was chosen to reflect the island's position, which is almost opposite, or antipodal to, Greenwich, England. The British often called the mainland of New Zealand the Antipodes because it was the most remote part of the Empire.

Our visit to Antipodes was a rare opportunity to study the island's ecosystem in relation to other subantarctic islands and mainland New Zealand. For shelter, we lived in a three-room research hut built on Reef Point, just south of Anchorage Bay, during the last DoC expedition.

One of the disadvantages of life on the island quickly became apparent as we tried to move about -- the coastline is fringed with two-metre-high clumps of tussock grass. The plant tops weave into one another in many places, making it difficult to get around, and it often took 15 minutes of wading through waves of grass to traverse 50 metres. On the North Plains, 100 metres above sea level, the grassland vegetation is only 30 centimetres in height and much easier to walk over compared with the coastline's tussock.

I was invited by DoC to visit the Antipodes to survey the spiders living on the island, and I was especially interested to see whether jumping spiders (my favourite group) lived there. They are a hardy variety; some have even been found living at 7,000 metres on Mount Everest. In New Zealand's South Island, jumping spiders are common at high elevations, where they shelter in nests beneath rocks and crevices. Most jumping spiders are not web spinners; as they roam outside their nests, they depend on their excellent eyesight to detect prey, predators, and mates.

After a few minutes' search above Anchorage Bay, I found some dense silken nests clumped together under the rock out-crops. Closer examination revealed dozens of unblinking jumping spider eyes staring back at me. Although it is unusual to find mature jumping spiders clumped together, I suspect they were spending the colder months in their nests before emerging to feed and mate during the summer. I found a few other spider species, but jumping spiders were the most common.

Because cliffs ring most of the coast-line, the island's penguins congregate in dense colonies at the few suitable sites where they can climb out of the water to nest. We were the first expedition to visit the Antipodes when the erect-crested penguins were laying eggs; this allowed Peter Carey and Colin Miskelly, from the University of Canterbury's Zoology Department, to further unravel the breeding biology of this little-known bird. Taking time out from the penguin colonies' deafening noise, they also estimated the size of the island's elephant and fur seal populations and surveyed the many other nesting bird species.

The most incongruous residents of the island are its parakeets. As I watched these birds flying among the penguin colonies and on the North Plains, they seemed as out of place to me as penguins would be in a tropical rain forest. One species and one subspecies are endemic to Antipodes, and although it is surprising that both could survive on such a small island, they have adapted to distinct food niches, thus avoiding direct competition. The larger Antipodes Island parakeet, considered to be the original colonist, feeds mainly on leaves of tussock and sedge. Reischek's parakeet, a subspecies of the red-crowned parakeet, found on one other subantarctic island and on New Zealand's northern offshore islands, is mainly a seed-eater.

Elephant Seal Soap Opera

In a small cove, just below the hut, I spent a number of hours with a male southern elephant seal, his harem of seventeen females, and their pups. The male was enormous, measuring some six metres in length and weighing perhaps three tonnes. Compared to the female, the male's huge size is testimony to how sexual selection influences the evolution of male characteristics. Bigger males can out-compete smaller ones in contests over territories that will attract large numbers of females. Southern elephant seals breed at subantarctic latitudes and on the Antipodes they live on boulder beaches at the bottom of steep cliffs. Unlike the smaller fur seal, the males cannot use their front flippers to move on land, and instead they undulate over the rocks like a gigantic slug.

While I was looking for spiders, he was looking out for rival males and disgruntled females intent on leaving him -- a seal "soap opera" was a wonderful distraction from peering under rocks. The females were constantly bellowing at one another and snapping at one another's pups. The male, acting like a couch potato most of the time, would occasionally leap into action to ward off the advances of a satellite male that spent hours trying to sneak up on to the beach to mate. When the rival got too close, the resident bull would raise his head, bellow loudly and move towards his competitor. This would send the suitor scuttling back out to sea until he felt confident enough to try coming ashore again.

Plot twists drive all soap operas, and this one did not disappoint. I watched as the male left his harem to retrieve a female that suddenly tried to elope with the sneaky surfer. The male, his bellows reverberating out of his pouchy proboscis, great gobs of mucus erupting from his nostrils, rolled his blubbery body into the water. Transformed from a giant land slug into a sleek missile, he headed toward the couple at sea, and after beating up the opposition, he herded the female back to his beach, now and then holding her head under water. Within half an hour, however, she managed to escape and was reunited with her relatively diminutive male. Seething with resentment, the cuckolded male immediately mated with another member of his harem, before lolling around in the surf. He seemed unconcerned as I moved among his harem or approached him closely. I was pleased he didn't see me as a rival or, worse, a potential mate. In comparison to the competition I must have appeared a puny threat.

Soon after the Antipodes were discovered, hunters arrived on the islands and began killing thousands of elephant and fur seals for their skins and oil. In one year, a single ship carried off the skins of 60,000 fur seals, equivalent to about 60% of the entire fur seal population of New Zealand today. Within 30 years, the islands' seals had been nearly wiped out. Their low numbers today reflect the slaughter that took place almost 200 years ago.

In the latter part of the 1800s and into the early 1900s, the New Zealand government sent search parties to the Antipodes to look for shipwrecked sailors. A survivor's hut, still standing today, was built on Antipodes Island in 1886. Graffiti, scribbled on its walls from visitors long dead, looks deceptively fresh and only the dates betray the shelter's true age. To provide shipwreck victims with a food source, domestic animals and vegetation were introduced to the island.

Seabird Paradise

Fortunately for the island's fragile ecosystem, these attempts failed. Landing on the island must have been traumatic enough for cows and sheep, but the weather and difficult terrain proved too much for the animals to endure. The island also managed to escape the scourge of rats. Common castaways from ships, these aggressive rodents prey on the eggs and young of nesting seabirds, and have wiped out entire colonies on many remote islands. At some stage, mice made it ashore, but though they are fairly common, they seem to have had little impact on the survival of nesting birds.

The absence of introduced predators was especially evident on the North Plains, where I could see hundreds of white dots dispersed among the fawn-colored vegetation. These turned out to be wandering albatross chicks sitting on their nests waiting for their parents to return from the sea with food. Although the chicks were only six months old they already stood one metre high. With their three-metre wing span, the parent's agility and gracefulness in the air did not extend to arrivals or departures, with crash landings common, and frantic wing-flapping necessary for takeoff. In another six months, the chicks will leave the island to stay at sea for seven years, before returning to breed. Every year, some 4,000 pairs of adult albatrosses, which breed every two years, return to the island.

The seabirds seemed like fish out of water. Although masters of the air and sea, they are vulnerable and fragile on land, where they must come to breed. This vulnerability seems epitomised by records from the Whitney South Sea Expedition of the American Museum of Natural History which visited the Antipodes in 1926 and collected bird specimens for the museum. According to the Journal of R.H. Beck (a well-known ornithologist), he shot 51 birds before 8.00 am, "which is the most I ever shot before breakfast". While we may cringe at such an admission, the sealers and scientists of previous times saw their world through different eyes.

The sight of wandering albatross chicks dotted over the North plains made it difficult to for me to imagine how they could survive anywhere else. How could they sit there for a year and not get picked off by predators? In places where humans have introduced such predators as mustelids, rats and cats, a similar scene would be impossible. Before humans landed on New Zealand's mainland, coastal areas that resemble the Antipodes were filled with bird species now restricted to the Antipodes and a few other subantarctic islands.

The inhabitants of the Antipodes, however, continue to thrive because the cycle of life and death has, except for a brief period of human disturbance, essentially remained unchanged for hundreds of thousands of years. As I struggled across the tussock grass, I felt like I had travelled back to a time when humans had little impact on the destiny of other species. Few such places remain.

In the final verse of his poem "Unharvested", Robert Frost asks:

May something go always unharvested!
May much stay out of our stated plan,
Apples or something forgotten and left,
So smelling their sweetness would be no theft.

Dr Simon D Pollard is Curator of Invertebrate Zoology at Canterbury Museum.