- By J W
February 23, 2015
It turned out that the huge tarantula on the floor of the cabin on Isla Santa Clara was actually a very special endemic species, found only on two islands in the world. It could have been more massive, as far as tarantulas go, but at about 2 inches long, it was huge enough for my taste, especially since I would be sleeping in its spot on the floor that night. I gently shooed it out the door of the cabin, but wondered how many more tarantulas were still hiding in the cracks, ready to come out at night when I unfurled my sleeping bag. Would it be any consolation that if I woke up with a huge tarantula on my face, at least I’d know it was endemic?
When a species is “endemic” to somewhere, it means it’s only found in that place and nowhere else on earth. This tarantula is endemic only to Isla Santa Clara and the westernmost tip of Isla Robinson Crusoe, both in the Juan Fernández Archipelago of Chile. For the folks that live on the Juan Fernández Islands “endemic” is a household word. The islands here are replete with endemic plants, endemic birds, endemic tarantulas, and endemic algae. The archipelago’s ratio of endemic plant species to land area is one of the highest in the world—making it a hotspot for global biodiversity and a high priority for prevention of extinctions. So the trick is to remember that even though that giant spider may seem common when it’s on the floor of the cabin, it’s actually super rare world-wide, and inherently vulnerable to extinction due to its tiny range.
Jessie and I visited Isla Santa Clara, the only unpopulated island in the Juan Fernández Archipelago, last week with Sara DeRodt of Island Conservation, and two park rangers and a biologist from the Chilean national park system (Corporacion Nacional Forestal; CONAF) and Ministry of Agriculture (Secretariat de Agriculture–SAG). The goal of our trip was to check on the breeding status of the island’s seabird colonies, while the park rangers conducted surveys of insect life and checked on endemic native plants and patches of invasive plants.
Sounds pretty easy right? Well….not so much. Beginning with the boat landing (an exciting process of jumping from a zodiac onto a rock with waves breaking over it), to unloading our supplies (hurling the bags off the boat, while avoiding waves and mewling Juan Fernández fur seal pups) to sleeping on the floor of the cabin (fear of tarantulas + ranger snores = little sleep), the trip was very…shall we say…exciting? Next time, I am definitely bringing my wetsuit.
Despite the difficulties of getting to the island, Santa Clara is a unique and beautiful island. Although it’s been hugely impacted by humans over centuries, it’s a testament to this area’s resiliency that it’s still home to some many special plants and animals who find their homes in between the rocks of volcanic scree cliffs and in the dry soil at the top of the island. Santa Clara is a steep, rocky island, crowned with a large plain dominated by introduced annual European grasses. Beautiful endemic shrubs – mainly Col trees with bright orange flowers – occasionally break up the smooth vista of grasses. While small populations of the native flora managed to survive generations of rabbits, humans, and grasses, regeneration has been slow (we’ll talk more about this later). To our east, we had a spectacular view looking over the fur seal rookery at the sheer peaks of Robinson Crusoe Island.
Hiking through the grasses, Jessie, Sara, and I searched for the burrows of Pink-footed Shearwaters, tucked away in the nooks and crannies of the plain. Like the best of us, they enjoy the company of neighbors and tend to nest in small colonies of burrows (think shearwater ‘burbs’). We were looking for special neighborhoods (subcolonies) that have been studied by researchers for over 10 years. For each burrow in our study, we wanted to understand how well the adults are able to raise chicks each year (in scientific jargon we’d call it how “productive” the Santa Clara population is). This entails sticking a long camera down the burrow, documenting the contents (empty, adult with egg, or chick), and extrapolating it to the other burrows in the neighborhood. For a population as small as the Pink-footed Shearwater’s (around 60,000 worldwide! …usually there are more ants in my office kitchen than there are Pink-foots in the world), it is critical to monitor whether they are able to create enough chicks to sustain their population in face of the many challenges they encounter (habitat degradation, predation from invasive mammals, getting killed by fishing nets, and more).
For the Santa Clara population of Pink-foots, while they were lucky enough to avoid the introductions of feral cats, coatimundis, rats, and mice that occurred on its neighbor Robinson Crusoe Island, the island was not spared from rabbits. In the past, introduced rabbits not only ate the native flora into the ground, they competed with the Pink-foots for burrow space and often excluded them from their own homes. This trip, however, we didn’t see any rabbits, because the island is now rabbit-free!
Often, the most effective and immediate fixes for island ecosystems is to eradicate invasive mammals, and happily, the national park with the help of Oikonos eradicated the rabbits from the island in 2003. Between 2003 and 2005, the breeding population of the Pink-footed Shearwaters on Santa Clara increased from around 2500 pairs to around 3500, as shearwaters were able to reclaim burrows that the rabbits had pushed them out of. Even more dramatic was that there were no longer rabbits eating all the native plants. Today, ten years after the eradication, there are sprouts of some of the rarest plants in the world coming up on the island. For the first time in hundreds of years, the plants are free to spread from their tiny refuges on the cliffs, to reclaim the inviting plateaus. However, the process of regeneration has been slow. Many of these species are slow-growing shrubs, not nearly as quick as the grasses their sprouts must compete with.
With many of the native plants on the archipelago in imminent danger of extinction, the refuge of Isla Santa Clara is a huge opportunity. On neighboring Robinson Crusoe Island, any plant restoration project requires fencing out cattle and rabbits, making large-scale restoration difficult. But on Santa Clara, no fencing is required. In recent years, Oikonos has worked on a pilot restoration project planting species endemic to Isla Santa Clara on the island, and with minimal maintenance, many have survived. As we checked the nests of Pink-footed Shearwaters (which contained fluffy new chicks!), we also enjoyed the recently planted Col trees and Pruinata shrubs that were thriving nearby. There is great potential to expand this restoration and bring back many of these plant species from the brink of extinction. The pilot restoration project on Isla Santa Clara has been successful but the scope has been limited to a few hundred plants. Now what is needed is to scale up the project so that the recovery of native plants is occurring island-wide. However, progress on this front has been slow as Oikonos scientists work with park management to determine the scale of the restoration effort and the balance between active restoration efforts and natural processes of recovery. Encouragingly, transplanted plants in both of the focal shearwater breeding colonies are already beginning to flower and produce seeds.
Our time on Isla Santa Clara was short—only one night, and I didn’t find any tarantulas in my sleeping bag. The Pink-footed Shearwater chicks were growing, as were the native plants. It was wonderful to see an island that is a true refuge for the native species of the archipelago. It was amazing to see what a difference removal of rabbits had made. Whether the process of plant recovery is slow or we help it along, it’s good to know there is a safe spot for endemic plants, seabirds, and tarantulas. At the end of our trip, we found ourselves again drenched, repeating the process of hurling bags over the waves onto the zodiac. We motored back to the town San Juan Bautista on Isla Robinson Crusoe, and, above the backs of petrels and albatrosses soaring over the waves, we could see a few green dots of the Col plants clinging to the harsh, isolated volcanic island that is their only home.