By guest author and GC Adjunct Scientist Dr. James Gibbs of the State University of New York’s College of Environmental Science and Forestry (SUNY-ESF).
As we begin our fieldwork on Santa Fe Island, Wacho Tapia, director of the Giant Tortoise Restoration Initiative, says: “Do you know what today is?” I scratch my head and say dubiously, “Tuesday?” “Yes, but more importantly it’s the first anniversary of the release of Española tortoises on Santa Fe!” I’m slightly embarrassed to have missed the significance of the date, yet delighted to be here, one year later. We’re here to understand how these tortoises, new to Santa Fe, are doing, where they’ve wandered, and what they’re eating. We’re also looking at food habits of the endemic land iguanas and how much overlap there might be with the tortoise diet.
Perhaps our most important strategy is the old-fashioned tortoise search. Wilson Villamar — a long-term ranger with the Galapagos National Park Directorate (GNPD), full of energy, wit, and dedication — pretty much “runs the show,” while we strive to keep up. He has an eye for tortoises. He dodges in and out of pockets of habitat quietly assimilating tortoise signs (tracks, droppings, beds, etc.) until he converges on a tortoise, often tucked into a lava cranny or deep under a bush. By the time we catch up, he’s already found 2-3 tortoises. We sit down on the nearest rocks to “process” each tortoise, but before we finish, Wilson arrives with 4-5 more.
The search goes on for hours, day after day. We linger in spots with good soil, abundant cactus, and signs of tortoises, while moving quickly through rocky areas with little cover. We crash through brush, over hot open plains, often startled by iguanas exploding from their lairs. We navigate cliffs of jumbled lava to reach new search areas. Over the week, we cover most of the island, while avoiding — as much as possible — falling, heat exhaustion, and blisters. By the end, we find 165 of the original 201 tortoises released. They appear fit, fat, and active. Back in camp, we run the statistics, which suggest that all of the tortoises released last year are still alive.
While the rest of us search throughout the island, Wacho wanders through the main release area with a large antenna extended overhead, its cable attached to a beeping black box. He’s searching for the 30 tortoises specially marked with radio-tags. Over several days he encounters all save one; its radio died mysteriously, although we eventually find it by chance. Most tortoises have remained close to the release site, but we find few far afield.
Wacho also measures vegetation around large areas of cactus, some enclosed with tortoise-proof fences in 2014 and some not. Over the next ten years, we will be looking at the impact of these large reptiles (both giant tortoises and land iguanas) on the vegetation of Santa Fe. With just two years of data, it appears that cactus reproduction may be dependent on land iguanas and now tortoises for dispersal of seeds. But we will not be able to say anything definitive for several more years.
Throughout the week, we also collect tortoise and iguana “poop,” for Carlos Cano, an Ecuadorian MSc student at a university in Costa Rica. His research will determine dietary overlap between the newly released tortoises and the endemic land iguanas. Carlos is a delight — strong, cheerful, and a tireless worker. We identify each dropping (plump cylinders = tortoises, svelte cylinder = iguanas), measure the length, and pop them into labeled bags for careful analysis back on Santa Cruz. Most are mummified by the sun, making them easy to handle. The more recently deposited ones, some less than an hour old and still glistening… well, let’s just say the scientific outcomes warrant the effort!
On our wanderings, I find a goat skull, its bony prongs that once anchored the horns still evident. It crumbles in my hand – increasingly rare evidence of the goat herd that once covered the island, destroying the vegetation until they were eliminated in the early 1970s. Even now, when I poke into dark, deep caves, I find the floor carpeted with thousands of goat droppings, full of bits of the island’s vegetation from 50 and more years ago — reminders of the scourge of the past and the good work of the GNPD to rid Santa Fe and more recently other islands of goats. The island and its vegetation continue to recover, especially now, with its native herbivore community back at work.
As the sun wanes at the end of each day, we limp back to camp, change into shorts, and climb down the cliff to plunge into the cold water. The young sea lions join in our fun – delighting us with their company. Apparently, we pink, two-legged creatures, who stagger on the slippery rocks to then recuperate in the sea after a hot day of dust and tortoises, provide a pleasant distraction from their daily tedium of playing in the surf, chasing dazzling fish, and avoiding shark bites.
When we retire to camp for dinner, our radio crackles to life, bringing us snippets of news from outside. Soon the native rice rats appear, grey-brown, fuzzy, and beguilingly cute, but with powerful teeth. They skitter in and out of pots, hunt for morsels, and chase one another, at times even mating right there in our kitchen, as we sip our tea — the after-dinner entertainment on Santa Fe. On our final evening Wacho says, “Exitoso.” Our trip has been a success. We accomplished a lot in just a week. The tortoises are doing well and all appear to have survived their first year on a new island. So far, so good — the outcomes of this expedition and the probable 100% survival of the first cohort of 201 tortoises delight us all.
Dr. James Gibbs is Professor of Vertebrate Conservation Biology and Associate Chair of the Department of Environmental and Forest Biology at the State University of New York (SUNY-ESF). He has partnered with Galapagos Conservancy for many years in efforts to restore giant tortoise populations in Galapagos through the Giant Tortoise Restoration Initiative, and is a frequent guest contributor to the GC blog. Photo credits, from top: land iguana & tortoise © Carlos Cano; tortoise measuring © Adrián Martín; tortoise w/radio tag © Carlos Cano; photo of Carlos © Adrián Martin; rice rat and camp photos © Ellen Smith.