Did you know giant tortoises were common on all continents except the Antarctic? Galapagos giant tortoises are a relic of prehistoric times that have formed close bonds with their environment, and like many other tortoises, still play an indispensable role as seed dispersers. The effects of their disappearance are difficult to quantify on mainland. We require a natural laboratory like the Galapagos islands to evidence the ecological impact of their extinction.
Galapagos National Park (GNP), with the support of Galapagos Conservancy and SUNY-ESF, is currently carrying out a pilot project for the ecological restoration of the island Pinta through the introduction of thirty nine adult giant Galapagos tortoises. These will be the first tortoises to set foot on Pinta since Lonesome George (Geochelone abigdoni), the last specimen endemic to Pinta, was removed from the island almost four decades ago. The introduction of “ecological analogues”, or species with a high degree of genetic relatedness with those that once occupied an ecological niche, has rarely been attempted around the world (like for example, the reintroduction of wolves to Yellowstone Park to control herbivore Populations). This is the first time that it will be tried in the Galapagos islands in hopes to revert some of the negative impacts that humans have had directly or indirectly though the introduction of invasive species.
The Galapagos Islands used to be a world-renowned destiny for whalers, buccaneers, and sailors since the XVIII century, where they could easily catch dozens of tortoises at once to obtain fresh meat that would not spoil during their long journeys. By the end of the XIX century, the exploitation of tortoises intensified to such a degree that tortoise oil was used to light up the streets in Quito at night. Today, 10 of the 14 identified galapagos tortoises still have populations in the wild. In the case of Pinta, we know that the G. abigdoni populations were already so small 100 years ago that they could have already be considered “ecologically extinct” then. Records from the California Adademy of Science from 1906 state that they removed three male tortoises from Pinta. G. abigdoni was considered extinct in the wild since, until Lonesome George was discovered by chance and taken to captivity in 1972.
In 1959, the same year that GNP was established, fishermen introduced three goats to Pinta, and their numbers exploded to over 30,000 in less than 15 years. After arduous efforts from GNP, Pinta was finally declared goat-free in 2003. The eradication campaign eliminated over 40,000 goats on Pinta, which clearcut large part of the island’s vegetation, severely threatening the 176 native plant species and the ecological processes that have sustained local flora and fauna for millions of years. The presence of goats and the absence of tortoises was a fatal combination, as it heavily altered plant communities. For example, the native woody shrubs that goats would prefer not to eat (Castela galapageia and Cryptocarpus pyriformis) have become abnormally abundant. Furthermore, the absence of a large herbivore could result in the demise of other endemic species, especially those that are most shade intolerant. Due to the close interaction between tortoises and Pinta’s vegetation, several experts have advocated for the return of tortoises to Pinta to restore and balance the ecosystem.
Unfortunately, Lonesome George is the last known member of its species (G. abigdoni), and any solution that involves his descendants (to this day nonexistent and with each passing year his reproduction becomes less likely) would take decades to bring about while the island ecosystem continues to degrade without a tortoise population. The most genetically similar tortoises to G. abigdoni are those from Española island (Geochelone hoodensis). A recent study has shed light on the possibility that there may still be G. abigdoni descendants on Volcan Wolf, Isabela Island. Until these tests are finalized, GNP chose to introduce a small population of non-reproductive tortoises - thirty-nine hybrid tortoises that were kept in captivity by the GNP. Their behavior, movements, and impacts were monitored from May to July 2010 after their initial introduction and follow up studies will take place throughout the following years. These tortoises were chosen for their morphology and size. The GNP has the support of Dr. James Gibbs and Elizabeth Hunter from SUNY ESF, who are leading the monitoring project with three main goals:
- Monitor tortoise impacts on island vegetation
- Estimate what is the island’s tortoise carrying capacity with the present plant composition
- Develop a strategy for future releases
The return of tortoises to Pinta, besides an besides an event of great ecologic importance, also has great symbolic value for GNP. Not only are Galapagos tortoises the most emblematic creatures of the “bewitched islands”, but Pinta is the specific island where Lonesome George comes from, perhaps the best known galapago in the world. We hope this project helps us return Pinta to a more pristine state. Projects like these, which help us better understand the complexity of the systems in which we live in and our place within them, may demonstrate our capacity to be a a positive influence on the ecosystem.
Read more about this fascinating project on its official blog: http://retortoisepinta.blogspot.com
on 2012-11-18 16:55 by The HumanCoral Team
On June 24 the symbol of the Galapagos National Park and of conservation worldwide, Lonesome George, passed away. Lonesome George was thought to be the last remaining member of his species, Geochelone abigdoni. However, George might have not been so lonesome after all: scientist have just found 17 hybrid tortoises which can trace ancestry to G. abigdonion the island of Isabella. Five of them are juveniles, suggesting that there may be a live purebred specimen still running around. Yale and the Galapagos Conservancy hope to collect hybrids and any surviving members of both Pinta and Floreana Island species and begin a captive breeding program that would restore both species.