Land Iguanas in Galapagos
From Galapedia
| Land Iguanas in Galapagos | |
 Land Iguanas in Galapagos. | |
| Species: | Conolophus subcristatus, Conolophus pallidus |
|---|---|
| Habitat: | dry lowlands |
| Diet: | principally herbivores, supplemented with insects, centipedes, carrion. |
| Status: | Vulnerable |
Reminiscent of the age of dinosaurs, Land Iguanas are fascinating to behold. During his visit in 1835, Charles Darwin commented on the large numbers of Land Iguanas present on Santiago Island; sadly, this is no longer the case. They have been forced to extinction on this island by human activities and the presence of invasive species. Breeding programs and research supported by the Charles Darwin Foundation (CDF) is restoring Land Iguanas on many islands back to their natural levels.
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Unique to Galapagos
Two species of endemic Land Iguanas are found in Galapagos:
- Conolophus subcristatus is widespread, found in the drier parts of the western and central islands, including South Plaza, Santa Cruz, Isabela, Seymour and Baltra Islands. It has yellow to dark brown or black coloring, varying between islands.
- Conolophus pallidus is found only on Santa Fe Island. It is more yellow and has more pronounced spines on its back.
Adults can grow to more than a meter in length, weigh up to 13 kilograms and can live for 60 years. Body temperature regulation is important, achieved by basking in the sun or sheltering in the shade. Birds remove parasites and ticks whilst the reptile stands high on all four legs.
Land Iguanas live in the dry lowlands, and get water from the cacti that make up a large proportion of their diet. Adults are principally herbivores, supplementing this with insects, centipedes or carrion. They swallow cactus pads or fruits without removing spines; however they can be observed removing spines by scraping them with their claws.
Land Iguanas mature between eight and fifteen years of age. They congregate and mate during specific periods, which vary between islands. Females then migrate to suitable areas to nest. After digging a burrow about half a meter deep, the female lays two to twenty eggs.
Eggs take three to four months to hatch. Hatchlings are highly vulnerable to predators, including herons, egrets, owls and hawks. On South Plaza, where the territories of marine and land iguanas overlap, the two sometimes hybridize, resulting in a mixture of features from each species. It is likely that the hybrids are sterile.
Vulnerability
Between 5000 and 10000 land iguanas are found in Galapagos. Both C.subcristatus and C. pallidus are listed as Vulnerable on the IUCN Red List.
Today, the iguanas that Darwin wrote about on Santiago Island are extinct. Land Iguanas were lost from Baltra and vast areas of southern Isabela. On other islands, the populations are severely diminished.
Feral dogs have caused much destruction. Whilst dogs have been controlled, a significant threat to land iguana populations appears to be feral cats. Normally, hatchlings need to survive the first year of life, when food is often scarce and native predators are a danger. However, feral cats prey on individuals up to three to four years old.
Goats wipe out entire areas of vegetation that the iguanas depend on for food. Pigs find and eat the eggs in the buried nests. Whalers and settlers probably found iguanas as tasty as tortoises.
Land Iguanas on Baltra Island had vanished by 1954 after the island housed an American airbase during the Second World War. A possible combination of habitat destruction and feral animals (including cats) proved fatal to the iguana population.
CDRS research activities
The colony of land iguanas on Seymour was introduced from Baltra during the 1930's. These later served as the basis for a captive rearing program for Baltra land iguanas.
The success of repatriation was dependent on the eradication of feral cats from the island. The Galapagos National Park Service (GNPS) and CDF scientists carried out a three-year program to eradicate feral cats from Baltra Island. Reduction of the cat population resulted in immediate improvements in survival rates and reproductive success of repatriated land iguanas. The CDF and the GNPS carry out regular monitoring of this population.
Populations at Bahia Cartago, Isabela were devastated by feral dogs during the 1970's. The primary conservation action was immediate removal and protection of the adults. These were also bred in captivity and successfully repatriated to their original locations, at three sites - Bahia Cartago (Isabela), and Cerro Dragon (Santa Cruz), and Baltra Island.
Sadly, the successful eradication of goats, pigs and donkeys from Santiago came too late to save the land iguana populations there. In addition to the control of feral mammals, future activities for the restoration of Land Iguanas on other islands will include:
- continuing the current restoration programs
- investigating the magnitude of impacts caused by cats on northern Isabela
- evaluating a potential restoration program on southern Isabela where only a few scattered populations remain.
