July 12, 2002
The Charles Darwin Research Station is probably best known for its breeding program for the various populations of giant tortoises. The project began in 1965 with the population of tortoises from Pinzón, and within 35 years CDRS repatriated more than 2,500 tortoises to 8 different populations.
At one time, the tortoises were extraordinarily abundant in the archipelago, but exploitation of the tortoise adults by humans and of the eggs and hatchlings by non-native mammals drove many of the populations to the brink of extinction. Had the Charles Darwin Foundation not intervened, the tortoises probably would not have been able to keep up with the introduced pressures.
The methodology used today to repatriate tortoises is the result of years of trial and error. Eggs are carefully removed from the wild and labeled with a code, which associates the eggs with information such as the time and location of collection. Scientists control the sex ratio of the hatchlings via incubator temperature and the hatchlings' carapaces are labeled as their eggs were. The tortoises are kept and cared for at the Breeding Center for 3-5 years (until they are large enough that predation is unlikely) and are then released onto the island from which they originated. Because of the repatriation project, success stories such as that of Española exist; 2000 marked the repatriation of the 1000th tortoise to Española, where only 14 individuals could be found a mere 30 years previous.
The Breeding Center at Santa Cruz has been so successful that a second was established at Isabella in Puerto Villamil in 1995 specifically to deal with the tortoise races on Isabella. Two races are currently being kept at the new Breeding Center, and nineteen tortoises were released in May 2002.
Repatriation of large terrestrial reptiles by CDRS is not restricted to tortoises, however. Researchers have also been successful in repatriating land iguanas in the Galápagos. There are two species of land iguanas found in the Galápagos archipelago: Conolophus subcristatus (native to six islands) and Conolophus pallidus (native to only Santa Fe). C. subcristatus is found on North Seymour, but is not a native of the island. William Randolph Hearst, curious as to why the iguanas were present on Baltra only a few hundred yards away and not on North Seymour, experimentally transplanted seventy iguanas from Baltra onto North Seymour in the 1930s. While such a thing (purposely introducing a non-native animal to a Galápagos island) would most certainly be frowned on today, it could be considered fortunate that Hearst tried his experiment - when a military base was built on Baltra during World War II, the Baltra population died out.
Land iguanas from North Seymour Island have since been repatriated to Baltra Island through a program developed by the Charles Darwin Research Station. The project started in 1991, when a number of captive-bred iguanas were introduced to Baltra. Six years later a census revealed that there were 97 iguanas on Baltra, of which 13 had been born and survived on Baltra. Today a more successful method of iguana repatriation to Baltra is in use in which eggs laid on North Seymour are brought the Breeding Center on Santa Cruz and individuals are eventually released on Baltra.
Iguanas have also been released onto Isabella and Santa Cruz islands, where the populations were suffering due to human-related stresses, the main pressures being the effects of introduced species. Only about 60 individuals survived on Santa Cruz after the introduction of dogs, and under similar stresses, some populations on Isabella were too far gone to be saved, though thirty from Cartago Bay were rescued. Of the iguanas from Santa Cruz, 38 were transferred to the small islet of Venecia. Proper nesting soil was also transferred to the islet. The artificial breeding ground created on Venecia has proven to be the most successful method for breeding the land iguanas: the 22 individuals taken from Santa Cruz and not placed on Venecia have been returned, and larger juveniles are repatriated from Venecia to Santa Cruz every other year.
There are not any amphibians native to the Galápagos; their semi-permeable skin prevents them from making trans-oceanic migrations on their own. However, frogs have been heard and seen in Puerto Villamil on Isabella for at least 20 years, but these frogs had not been identified or established on the island until 1998. Scinax quinquefasciata is a small frog, common on the Ecuadorian coast, and it is suspected that they hitchhiked to Isabella aboard a cargo ship.
The frogs are unwelcome mostly because they are insectivores, and the fear is that they will compete with insectivorous finches for food. They have become established at two ponds on Isabella: el Cantero and Las Diablas. Twelve thousand frogs have been collected from Las Diablas in recent years. Only five hundred were collected from el Cantero in 2001, but in 2002, a new population was discovered at el Cantero. Researchers are experimenting with pumping sea water into the two ponds to raise the salinity, which would discourage population growth of the frogs. Unfortunately, the frogs are finding refuge in the pools formed by rainwater in an introduced plant (kikuyo, Pennisetum clandestinum). The frogs have also been invading the houses and streets of Puerto Villamil after heavy rainfall. Control and observation of the frogs is ongoing as of June 2002.
Researchers at CDRS have concerns about the invertebrate species, native and otherwise, found in the Galápagos as well. As of July 2001, there were 318 known introduced insect species, and that number was rapidly growing at that time.
An example of an introduced insect to the Galápagos is the cottony cushion scale (Icerya purchasi), which is not only a problem for the agricultural community, but also for the conservational community. It is a pest on close to thirty native plants and sixteen endemic plants, as well as citric and other cultivated plants. As with other infestations of I. purchasi in other parts of the world, insecticides are ineffective against the pest in the Galápagos. While biological control of the scale has proven to be effective other places using an Australian ladybird beetle (Rodolia cardinalis), it was uncertain whether it was a proper option for the Galápagos archipelago, since it would be a purposeful introduction of a non-native species to the islands.
Entomologists at CDRS conducted several experiments to determine the effectiveness of the ladybird beetle on the cottony cushion scale as a pest on the native non-agricultural plants of the Galápagos. Also, it needed to be shown that R. cardinalis would not preferentially feed on native scale insects of the islands. The Australian beetle passed the tests, and was released in January of 2002.
Interestingly, the search for scale insects in the Galápagos to test against I. purchasi turned up two new species and a third species (Margarodes similus) that had not been seen since 1924, which also happens to be the closest relative to the cottony cushion scale. It would be a concern that the ladybird beetle would turn to M. similes, but the scale is an underground type with a hard shell that the beetle cannot penetrate.
The introduction of R. cardinalis is going to be monitored for about two years by scientists from the Darwin Research Station with help from the farming community and naturalist guides.
There is an instance of native biological control of an introduced hymenoptera species. The introduced wasp Polistes versicolor is a predator of the larvae of butterflies and moths, which are also a food source for some of the Galápagos finches. A native lepidopteran fights back, though: the larvae of the native moth Taygete sphecopila bore into the nests of the wasps, causing the destruction of the nest and of the larvae within.
But the terrestrial conservation concerns of the Research Station are not exclusively animal, but vegetable as well. As of yet, it is somewhat uncertain how many of the 560 native plant species of the Galápagos are actually endemic species and subspecies. One of the projects of CDRS is to identify and describe the plant species of the archipelago and to reestablish native plant biodiversity of the islands. Introduced animal species have destroyed much of the original flora of the islands, and introduced plant species also have a negative impact on the native plants, beating them out for space, sunlight, and nutrients.
There are about 475 introduced plant species known to exist in the Galápagos, and CDRS monitors the spread of non-native plants wherever possible. A system of priorities regarding invasive plant species has been established in the Galápagos and is based off of systems used in New Zealand and Australia. The most pressing concern is the prevention of invasions by more plant species, followed by control and eradication of the species already present in the archipelago. As of 1999, the methods used for eradication of introduced species was limited to removal by hand and the use of herbicides.
Another aspect of the control of introduced species has to do with a program of sustainable agriculture. The theory behind the program is that the better that the farmers in the Galápagos can keep up with the demand within the islands, the less necessary it will be to import agricultural products from the mainland, which is the major source of pest introductions. CDRS also works with the farmers to use the land and eliminate pests as effectively as possible. Other aspects of the program include credit for farmers who build water reservoirs on their land and advice for farmers on how to store and market their produce.
A quarantine system was developed by CDRS to prevent the introduction of new plant species and other species that might come along with the plants (e.g. disease and insects). The initial step is an inspection of all items coming into the archipelago at their respective departure points and to create guidelines for what sorts of things were permitted into the Galápagos. While quarantine is a tedious process, it is assumingly doing a lot of good for the islands since such things as insect eggs, fruit fly larva, a type of aggressive weedy grass, crabs, mollusks, and a rabbit, have been intercepted and prevented from invading the islands.
CDRS is also involved in the eradication of introduced animal species from the archipelago. The most interesting method for eliminating introduced animals is in use on Isabella, where trained hunters use advanced technology to take out the unwanted goats, pigs, and other intruders. The hunters are specialized to eradicate the goats as humanely as possible using their helicopters, Global Positioning System equipment, radiotelemetry, rifles, and telemetric sights.
The activities of the Charles Darwin Research Station with respect to terrestrial ecology are primarily concerned with the issue of introduced species, both directly and indirectly. Whether its repatriating iguanas and tortoises or eradicating goats and pigs, the Station is working to restore and replenish the ecological wonder that is the Galápagos archipelago.
About Us. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/about/main.html.
Advances in the fight against introduced plants. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/Ourwork/terrest/t11.html.
Alternatives for the control of the introduced wasp. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/Ourwork/terrest/t13.html.
Australian Ladybug released in Galápagos to control Invasive Insect. 25 January 2002. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/news/news01250201.html.
Biological Control of the Cottony Cushion Scale, Icerya purchasi, in Galápagos. 8 December 2001. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/news/news12080102.html.
The Charles Darwin Research Station. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/about/station.html.
Charles Darwin Research Station News. May 2002. Galápagos Conservation Trust. 9 July 2002. http://www.gct.org/newsmay.html.
Galápagos breeding and repatriation program sends its 1000th tortoise home to Española Island. March 2000. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/news/news04240001.html.
Galápagos Land Iguanas and Their Protection. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/terrest/iguana.html.
Gardener, M.R., A. Tye, and S.R. Wilkinson. Control of Introduced Plants in the Galápagos Islands. 21 July 1999. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/articles/qu0021079908.html.
Introduced frogs on Isabella Island. 11 September 2001. Charles Darwin Foundation. 10 July 2002. http://www.darwinfoundation.org/news/news09110103.html.
The Isabella project: Ambitious work of ecological restoration. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/Ourwork/terrest/t9.html.
Land Iguanas: A Natural History. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/terrest/iguana2.html.
Land Iguanas: How are they after they return home? Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/Ourwork/terrest/t7.html.
Märquez, C. Repatriation of Terrestrial Tortoise Populations in the Galápagos Islands. 21 July 1999. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/articles/qu0021079902.html.
More than 2000 tortoises have been returned home. April 2000. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/articles/ar00040046.html.
Project of sustainable agriculture. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/Ourwork/terrest/t16.html.
Quarantine: Better to prevent than lament. Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/Ourwork/terrest/t15.html.
The Scale insect pest: Is biological control the answer? Charles Darwin Foundation. 6 July 2002. http://www.darwinfoundation.org/Ourwork/terrest/t12.html.
Update on the Observation and Control of Frogs in Puerto Villamil. 5 June 2002. Charles Darwin Foundation. 10 July 2002. http://www.darwinfoundation.org/news/news06050202.html.