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Giant Tortoises
The giant tortoise was one of the most devastated of all species in the Galapagos Islands. Only the rice rat was hit harder, with the majority of endemic rat species now extinct. Humans first exploited giant tortoises as a food source; a practice that continues today at a low rate. In later years, they were harvested for oil. Some introduced species (primarily rats, pigs, dogs, and the Solenopsis ant) prey on tortoises (particularly eggs and young tortoises); others (goats and burros) damage or destroy tortoise habitat.
With the establishment of the Galapagos National Park and the CDF in 1959, a systematic review of the status of the tortoise populations began. Only 11 of the 14 original populations remained and most of these were endangered if not already on the brink of extinction. The breeding and rearing program for giant tortoises began in response to the conditions of the tortoise population on Pinzón, where fewer than 200 old adults were found. All of the hatchlings had apparently been killed by introduced rats for perhaps more than a century. Without help, this population would eventually disappear. The only thing saving it was the longevity of the tortoise. The rearing program began in 1965, with the first transfer of tortoise eggs from Pinzón to the new tortoise center on Santa Cruz. In 1970, the first 20 tortoises were repatriated to Pinzón; they had reached an age and a size at which they were considered “rat proof.”
Video: Berry Blanton, BZ Productions
Within a few years, several other tortoise populations were included in the program. Other than the Pinta population, where only one tortoise remained (Lonesome George), the Española population, with only 2 males and 12 females, was the closest to extinction. The few tortoises found on Española were brought into captivity between 1963 and 1974, and the rearing center also became a breeding center. Eggs and hatchling tortoises were brought from natural nests in the wild from Santiago, Santa Cruz, Isabela (Cerro Azul, Sierra Negra, and Wolf volcanoes), and San Cristóbal. Problems in these populations included low population numbers; nest destruction by pigs, dogs, and the Solenopsis ant; habitat destruction by goats; and poaching by fishermen and residents.
Successful Partnership of Research and Management
Of all the bi-institutional programs of the CDF and the GNPS, the tortoise program best exemplifies the critical integration of research and management in achieving conservation goals. In the 1960s, the research was aimed at determining the status of the populations. The results of the fieldwork identified those populations that needed to be included in the program and at what level (breeding population in captivity, tortoise eggs and young brought into captivity, or simply nest protection or pig control in the field). In the 1970s, the field research was shifted to determining the behavior patterns and requirements for successful breeding, nesting, and rearing. These results were then incorporated into the management practices at the tortoise center. In the 1980s, experiments in the Breeding and Rearing Center focused on determining the best methodologies for incubation and rearing. The results were immediately incorporated into the daily and yearly programs.
Then in 1988, the CDF and the GNPS hosted the international workshop: The Herpetology of the Galapagos Islands. Over seventy scientists, administrators, naturalists, and resource managers met to debate and explore how to combine research and management to better conserve the herpetological fauna of Galapagos. A series of both general and specific conclusions and recommendations resulting from the workshop provided a framework for planning, prioritizing, and implementing research and management for the next decade and beyond.
By 1990, work in the center was focused on tortoises from Española, Pinzón, Santiago, and occasionally Santa Cruz. Bringing eggs and hatchlings in from the southern Isabela populations was put on hold while a second breeding and rearing center was built in Puerto Villamil, Isabela. The San Cristóbal program was initially terminated in the early 1980s when the local human population successfully eradicated the feral dogs, the primary cause for the population decline. In 2003, the GNPS established a breeding and rearing center on that island. Natural recruitment occurred on Volcán Wolf and that population was considered out of danger.
With improvements in methodologies resulting from the experiments in the 1980s, the tortoise program had even greater success in the 1990s. An annual total of 500 to 700 young tortoises (hatchlings to 3-year-olds) were routinely reared in the center; prior to 1991, the total averaged 332, with a range of 53 to 462 tortoises. Mortality of young tortoises in the center was reduced to an average of less than 3% per year; in the 1980s, it averaged 18%, with a range of 4.2% to 31.8%. The almost factory-like production of young tortoises allowed for the expansion of the program. Areas that received more attention during the 1990s included nutrition and general health of the tortoises, genetic analyses, and the expansion of the program in southern Isabela. Much of the work was accomplished with the help of consultants and visiting scientists.
Expansion to Isabela and San Cristóbal
In the early 1990s, a second tortoise center opened in Puerto Villamil, Isabela. This center was originally planned during the wildfire of 1985 but was not fully operational until the wildfire of 1994, which coincided with an increase in poaching of tortoises in Isabela. GNPS and CDF personnel took advantage of the focus on the wildfire of Isabela to inform the world of the threat from poaching. In addition, helicopters used in fire-fighting were also employed to evacuate tortoises, not from fire areas but from areas on Sierra Negra where they were threatened due to illegal hunting. The Isabela tortoise center is a breeding and rearing center, currently with tortoises from both Sierra Negra and Cerro Azul.
In 2003, the GNPS established a breeding and rearing center for giant tortoises on San Cristóbal with the tortoises enclosed in a large, natural area.
Lonesome George
The situation of Lonesome George, the last known survivor of the Pinta population, became of primary concern during the 1990s. Unlike the other tortoises in the center, George became severely overweight. At the end of the 1980s it became apparent that George had to go on a diet. Since that time, veterinarians and nutritionists have examined him periodically and personnel of the center have implemented their recommendations. George was put on public view in a new corral. To accompany him, two females were brought from Volcán Wolf (thought at the time to be the population most closely related to Pinta tortoises). Unfortunately, George seems either incapable or unwilling to reproduce.
Success of the Program
Overall, the tortoise program is a tremendous success. In 1990, the first nests of the repatriated tortoises on Española were found and the first live hatchlings in 1991. The old tortoises in the breeding center of Santa Cruz have grandtortoises! Although undocumented, reproduction by repatriates is certainly occurring on other islands. In March 2000, the 1000th tortoise was repatriated to Española. By early 2007, more than 4000 tortoises had been repatriated to their island of origin (see Table below).
Number of giant tortoises repatriated by population and decade, 1970 to 2007.
| POPULATION | 1970 | 1980 | 1990 | 2000 | TOTAL |
|---|---|---|---|---|---|
| Cerro Azul (Isabela) | 103 | 102 | 8 | 371 | 584 |
| Española | 79 | 208 | 696 | 499 | 1482 |
| Pinzón | 182 | 86 | 244 | 40 | 552 |
| San Cristóbal | 42 | 13 | 0 | 0 | 55 |
| Santa Cruz | 0 | 67 | 28 | 269 | 364 |
| Santiago | 115 | 90 | 282 | 129 | 616 |
| Sierra Negra (Isabela) | 0 | 51 | 52 | 253 | 356 |
| Volcán Wolf (Isabela) | 14 | 23 | 3 | 0 | 40 |
| TOTAL | 535 | 640 | 1313 | 1561 | 4049 |
Source: CDF files.
Evaluations of the populations on Pinzón and Española carried out in the 1990s indicate survival of 68-77% of repatriated tortoises on Pinzón and a minimum of 55% on Española. These are high survival rates for a repatriation program. Several factors play a role. Most importantly, the majority of the natural habitat is still intact, and secondly, the tortoises are reared in semi-natural conditions similar to their native island.
The Problem of Introduced Species
Key to the ultimate survival of the giant tortoises is the elimination of introduced mammals, both predators and competitors. On Española, the only introduced mammal, the goat, was eradicated in 1978. During the first decades of the program, the other populations were under constant threat from introduced mammals. To support the repatriation program, tortoise protection was carried out by park wardens in the nesting zones of Santa Cruz, Santiago, and southern Isabela. Pigs were regularly hunted during the nesting and hatching seasons. Tortoise nests were located and protected from pigs by constructing a temporary rock wall around them.
By the early 1990s, the tortoise population on Volcán Alcedo, one of the largest and healthiest populations in the archipelago, was in trouble. The small goat population, which grew from a few individuals that had crossed the Perry Isthmus more than 15 years previously, exploded. Prime tortoise habitat was disappearing at an alarming rate. Worry over the future of the tortoise population spurred a “tortoise summit,” held in England in April 1995. An international workshop of experts was then held in 1997 to plan the eradication of goats from northern Isabela. Project Isabela was the result. Completed in 2006, Project Isabela achieved the eradication of goats from Pinta, Santiago, and northern Isabela, pigs from Santiago, and donkeys from Santiago and northern Isabela. These successful eradications have had a positive impact on the tortoises and their habitat.
In 2007, an international workshop was held to examine the potential eradication of introduced rodents from the archipelago. The resulting plan is aimed primarily at the eradication of rats from Pinzón. With the eventual success of Project Pinzón, yet another tortoise population will be out of danger and will no longer need the protection of the rearing and repatriation program.
The Future for the Giant Tortoise
With the eradication of introduced mammals, many of the giant tortoise populations are nearing the point when the breeding and rearing center will no longer be required. Monitoring their populations and restoring their habitat will now be part of larger island restoration programs. On Española, restoration of the Opuntia cactus forests that were decimated by goats is beginning. On Santiago, restoration of the vegetation in the absence of goats, pigs, and donkeys will need to be monitored to ensure that the plant communities return to near pristine condition, allowing the tortoise population to complete its recovery on its own. When rats are finally eliminated from Pinzón, island restoration and a naturally reproducing tortoise population will become a reality. Work on southern Isabela, where introduced mammals still exist and where poaching of tortoises is more common than elsewhere in the islands, will continue. Current genetic analyses may also highlight small remnant populations that will need intensive management in the future.
On Pinta, where the return of the Pinta tortoise is questionable if not impossible, a plan for restoring the island, including the return of giant tortoises, known as Project Pinta, is underway. A group of scientists from Yale working on the genetics of Galapagos tortoises for more than a decade determined that the Española tortoise is genetically the closest to the Pinta tortoise. In 2008, the first tortoise hatchlings resulting from the Española breeding and rearing program will be released on Pinta. The re-establishment of a tortoise population on Pinta is the next step in the restoration of the island, now that it is free of introduced mammals.
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