The Kingdom of Rarities (7 page)

Golden-mantled tree kangaroo (
Dendrolagus pulcherrimus
)

Why the kangaroos reclaimed the treetops remains a mystery, but one reason might be that in the rain forest many of the most delectable leaves are above ground level. Tree kangaroos love to nibble epiphytic orchids, among other canopy-dwelling plants. New Guinea's tree roos feed both in the canopy and on the ground in the early morning, thus taking advantage of the absence of primates on this side of Wallace's Line to garner the fruiting displays of trees while also occupying the niche that a ground-feeding herbivore might hold elsewhere.

Flannery also noted when he was in PNG the devastating effect of subsistence hunting, especially for species that are naturally rare and have a very circumscribed range. He suggested that one can predict the extinction dates of rare birds and mammals on the basis of the arrival time of Christian missionaries. Before missionaries came, mountain clans respected strict taboos on hunting. Some places were off-limits, such as where spirits dwelled; some species benefited from taboos on hunting during the breeding season as well. These bans honored traditions but also ensured that hunted species with low reproductive rates could recover. When priests arrived, they urged converts to ignore taboos and other pagan beliefs; overhunting was one result.

The team kept their eyes out for more wildlife sightings. The absence of local hunters in the upper Fojas meant that the region might be ideal habitat for another species seldom observed: the long-beaked echidna, New Guinea's oddest and least studied mammal. On one of the last few nights of trail surveys, frog expert Steve Richards spotted an echidna that was slowly trundling down one of the survey paths. One of the local men put the rather helpless creature in a large bag and toted it back to camp for the others to see.

The long-beaked echidna is the largest of the four echidnas. Although more commonly known as spiny anteaters, echidnas have
only an ancient relationship to the anteaters of South America. Echidnas and their distant relative the duck-billed platypus defy the belief that mammals are unable to lay eggs. Egg laying reveals these primitive mammals' primordial relationship to lizards and birds and earns these species their own order of mammals, called the Monotremata. Had the island's hunters frequented these uplands before the Beehler expedition, however, echidnas would have vanished, their meat being highly prized.

The highlanders may be among the sharpest-eyed hunters in the world. Their skill evolved from necessity, as dietary protein is hard to find in this region. Their knowledge of local natural history is unparalleled and their concept of taxonomy decisive, if nothing else. The late Ian Craven handed local hunters an illustrated guide to the birds and mammals of the Arfak Mountains, west of the Fojas. They laughed and pointed excitedly at many of the species found in their area but stared blankly at other common residents. Ian was puzzled at first: he knew they had seen, and had a local name for, everything in the guide. As it turned out, the hunters' binary taxonomy of approval or silence had little to do with presence versus absence or common versus rare; rather, their classification hinged on the Kingdom of the Tasty and the Kingdom of the Inedible.

Life in the fog and the burgeoning quagmire: Bruce and his team could add another dimension to the isolation they felt. Sometimes the mist was so thick that the upper Fojas became their own world in the clouds. And then there were the incessant downpours. Bruce's field notes took the voice of an adolescent sent to summer camp for the first time, trying to convey his joy in the outdoors to his parents while simultaneously scaring the daylights out of them. “Camp grows ever more horrific with continual rain and mud. Wear high rubber boots all day every day. Forest is superb! Have added 12 new bird species to Foja list!”

Bruce's expedition was confirming the impression Jared Diamond had formed in 1979 on his first visit—this was indeed a lost
world. Every day brought a new natural history revelation, as if Bruce had pinpointed with his GPS the lat-long of paradise for a naturalist. The Fojas also offered a new perspective on seclusion. For exiles such as Alexander Selkirk, Robinson Crusoe, and even Napoléon Bonaparte, a remote location was viewed as punishment. But in the mountains of New Guinea, the tropical Andes, and the eastern Himalayas, geologic events have led to the separation of populations and adaptive radiations. These phenomena have bestowed upon the natural world a menagerie of rarities—birds and mammals and plants and butterflies and beetles so extraordinary, gifts over evolutionary time of natural isolation.

After two weeks, though, the expedition was drawing to a close. Food was running out, and the hard-won research permit was about to expire. Bruce's diary: “4 Dec. The bog turns into a lake again! A problem if helicopter comes when bog is a lake! Tons of rain falling and trails are appalling.” The weather was indeed getting worse, but the discoveries kept coming, right up until the last day of the expedition.

There remained a small problem—the ability of the helicopter to fetch them safely. Bruce's notes summed it up with his usual gusto: “7 Dec. Heli arrives at 4 PM (was supposed to arrive at dawn!). We take 45 minutes to get out with enveloping cloud stopping our escape. Three tries before we actually get out of the cloud and to the clear where we can see our way down the mountain—very frightening . . . Arrive at Kwerba at dusk. The others must spend night on the mountain while we luxuriate in warmth and washing in the stream with soap!”

Bruce's expedition could take pride in its place in the annals of scientific exploration. But the Foja expedition had missed the golden age of natural history. That period reached its apogee in England about the middle of the nineteenth century. Had Bruce's group steamed up the Thames in 1837, they would have known
triumph: handshakes all around from Darwin, Wallace, Huxley, and the officers of the Royal Society, perhaps even knighthood. Instead, the expedition's leader was met by his family and a faithful golden retriever. Bruce immediately returned to his desk at Conservation International. Proposals needed writing, spreadsheets checked, and the bureaucratic machinery jump-started after his hiatus.

Weeks after the expedition's return, Conservation International's public relations department issued a press release about the team's successes under this tantalizing headline: “Scientists Uncover Biodiversity Trove in a ‘Lost World' in Western New Guinea.”

“I was as close to the Garden of Eden as you're going to find on Earth,” Bruce remarked. And with that sound bite, for about a fortnight, Bruce Beehler may have been the world's most famous field biologist or, thanks to his dramatic phrasing, the most quoted. His reference to Eden echoed through the popular press. Requests for interviews poured in. Beehler obliged and offered more statements ripe with imagery: “There was not a single trail, no sign of civilization, no sign of even local communities ever having been there.”

Most reporters didn't care about Beehler's spectacular faunal finds; a new honeyeater meant little to them. It was his words that painted a serene vision, one that offered a different, uplifting message, as high and rare as the Fojas. In contrast to the daily stream of mayhem in Iraq and Afghanistan, they could report that an Eden still exists on Earth. Bruce avoided mentioning, though, that what passes for paradise to a biologist is typically a miserably wet place for most mortals. Better to stick with the sound bites.

What, in retrospect, can the Beehler expedition tell us about rarity and abundance? One of the first insights involves the distinction between geographic rarity and population rarity. Most of the endemic species of the Foja Mountains exhibit geographic rarity—tiny global distributions. In their natural habitats some of these species may be, like the golden-fronted bowerbird, easy to locate and observe but may nevertheless trick the biologist into treating
them as “common” when they are really just “obvious,” an important distinction. The real revelation for some species, such as the six-wired bird of paradise, is how narrow their elevation distribution is—just a vertical sliver of the mountainside—thus making them globally rare because of their restricted range. By contrast, the golden-mantled tree kangaroo is twice rare—it is both geographically rare (confined to a few mountain uplands in New Guinea's northern coastal ranges) and population rare: hard to find even in its favored habitat.

Birds of paradise of one species or another once inhabited all of the island's area below timberline. But their distinct distributions reveal a clear pattern of rarity. Ten species are rare because they are endemic, confined to tiny mountain uplands or offshore islands. Some, such as the black sicklebill and pale-billed sicklebill, are naturally rare or uncommon, with very low population densities. They are the largest members of the bird of paradise family (the Paradisaeidae), and these outliers tend to be widespread but nowhere common. Others, including the yellow-breasted bird of paradise, appear to prefer very specific habitats, being absent from some sites and found in others.

Although the main purpose of the Foja expedition was not to parse rarity but to discover new species and recover lost ones, it nevertheless confirmed that even in a place without a historical presence of humans, rarity is a common phenomenon. In this region, with its tiny human population confined to the lowlands, birds of paradise are not threatened by hunting. Thus, we can see their populations at what biologists call carrying capacity—densities one would likely see that reflect what the habitat can support. From Bruce's field notes it became clear that some, including the manucodes and the lesser bird of paradise, are naturally common within their range and easily encountered. Others, such as the pale-billed sicklebill, are uncommon and elusive. By contrast, the remarkable black sicklebill, which has been hunted out in many parts of New Guinea, turned out to be present in fair numbers in the
Foja uplands, where no hunting takes place. The big surprise was the absence of the superb bird of paradise, which is perhaps New Guinea's most common and widespread mountain-dwelling species. It is known in virtually every mountain range in New Guinea except for the Fojas.

The last observation is truly puzzling and requires further study. But the other sightings, or lack of them, show that even in perhaps the most remote spot in the tropics, the rules of rarity still apply. Many species—be they birds of paradise, tree kangaroos, frogs, butterflies, or palms—naturally occur at low population densities and hence are rare. Viewed the other way around, there may be something about the very nature of rain forests that prevents some species from becoming superabundant. The Fojas are rich in species, so perhaps the sheer number of species in the ecosystem leads to a novel mechanism at work—a kind of diffuse competition in which the interactions of many species keep others in a limited range or at a low density. We will revisit this potential structuring force in the Peruvian Amazon in the next chapter. For now, it is simply enough to note that ecological interactions in the New Guinean rain forests seem to keep many species scarce.

In further conversations with Bruce, I turned to a behavioral trait that intrigued me: the lack of shyness shown by the wildlife. Could it be a result of evolving in a region with no large terrestrial predators to stalk them or humans to hunt them? Bruce confirmed my guess of the relative dearth of predators in this upland forest. So, if large and midsized spotted cats never cross Wallace's Line and aerial predators are uncommon, then looking up or around is a distraction from dancing. Bruce concluded, “It makes the forests of New Guinea something of a peaceable kingdom, friendly to the birds of paradise and bowerbirds.” It may seem as if Bruce slipped back into sound bite mode again, but not entirely. Nature is replete with starvation, disease, intense parasitism, and death from typhoons or drought, even in the Fojas. His point was simply that here was a
place where fierce predators of these birds had less of an ecological and perhaps evolutionary influence.