By Wacho Tapia, Director of the Giant Tortoise Restoration Initiative
The process of ecological restoration is normally observed only over the long term. In the case of Santa Fe Island, this process began in 1979, when the Galapagos National Park eradicated the goats, introduced to the island sometime prior to 1905, thus initiating the recovery of the island’s flora. However, the absence of giant tortoises for more than a century and a half meant that the recovery of ecological processes was not normal, or perhaps better said — historically accurate. Therefore, we began a project to repopulate Santa Fe with giant tortoises as part of the Giant Tortoise Restoration Initiative.
Since June 2015, 393 tortoises of the species from Española Island (Chelonoidis hoodensis) have been released on Santa Fe. This species is genetically similar to the original Santa Fe tortoise that went extinct in past centuries due to exploitation, and provides an ecological analog to repopulate the island. With the increase in tortoise numbers and distribution, the amount of field work requires ever more hours each day compared to our pre-tortoise monitoring trips. To be as close as possible to the tortoise search area, we camped in the interior of the island — in spite of not being able to bathe for eight days straight. This small change resulted in our having three to four additional work hours each day and allowed us to cover approximately 30% of the island in our effort to locate tortoises.
From our tortoise monitoring in 2015 and 2016, we learned that some tortoises repatriated to Santa Fe are moving long distances, which is different from repatriated tortoises on other islands where they tend to stay closer to their release point. Therefore, we expanded the search area based on the outlying tortoise observations from 2016 — but even this expanded search area turned out to be too small. Thanks to radio-telemetry equipment installed on 30 of tortoises released in 2015, we located two tortoise groups that had moved even farther away: one at the south end of the island approximately 300 feet from the coast, and the other on the northwest corner of the island at the base of one of the highest hills, nearly two miles from the release site.
All of the tortoises we encountered are in full growth mode and in excellent physical condition. The eight-year-old tortoises released in 2015, which had a maximum curved carapace length of 13 inches and weighed up to 8.4 pounds, now range between 17-18 inches in length and weigh up to 21 pounds. In addition, the shells of these larger tortoises are beginning to show the saddle-backed shape — an important adaptation to arid islands. It appears that the extensive cactus forests of Santa Fe provide a permanent and ample food source, even in times of drought. This is reflected in the rapid growth and excellent condition of all of the tortoises encountered.
But what most caught our attention was that in the two years since the first release, we have not found a single dead tortoise. To date, the survival rate appears to be close to or actually 100% — in comparison to long-term studies on Española Island where repatriate survival is just over 50%. Of course this survival rate will probably change as the years go by.
Having been doing research and monitoring in Galapagos for almost 25 years, I have had the privilege to visit and know all the islands of the Archipelago. I have witnessed countless events that few people on the planet have seen. On this trip, I saw a large number of nesting Galapagos hawks, one at a distance of only six feet (as per the rules of the Galapagos National Park). But never before have I been attacked when over 30 feet from a nest. A group of four hawks (presumably the parents and two other adult hawks) flew at me in full force to protect the nest and the single nestling within. If I had not been wearing a cap and a bandana for protection against the sun, I’m sure that their very strong and sharp claws would have caused serious injury. Without a doubt, the unique nature of Galapagos never ceases to amaze and excite me.
It has been four years since we began the process of monitoring Santa Fe, the first two years in preparation for the tortoise release. We have learned a lot about ecological processes occurring there. However, the road to ecological restoration is long. We will continue to release new groups of juvenile tortoises every one to two years — continuing to monitor their impact to aid us in making a final cut-off point for further releases. As they expand their range, we will continue to be more creative and ambitious in our effort to properly document changes in the ecosystem. This work will generate the scientific knowledge needed to inform conservation management decision-making, not only for Santa Fe but also for other islands.
I dream of the day when we will see giant tortoises spread across Santa Fe, when tourists will even be able to see them at the visitor site alongside the Santa Fe land iguana.
All photos © Wacho Tapia/Galapagos Conservancy.
Read more about the tortoises of Santa Fe Island.