''Chelonoidis niger vandenburghi'', also known as the Volcán Alcedo giant tortoise, the Alcedo Volcano giant tortoise or the Alcedo giant tortoise, is a

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

Galápagos tortoise The Galápagos tortoise or Galápagos giant tortoise (''Chelonoidis niger'') is a very large species of tortoise in the genus ''Chelonoidis'' (which also contains three smaller species from mainland South America). The species comprises 15 subsp ...

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the Galápagos archipelago in the equatorial eastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''vandenburghi'' honours American

herpetologist Herpetology (from Ancient Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is a branch of zoology concerned with the study of amphibians (including frogs, salamanders, and caecilians (Gymnophiona)) and reptiles (in ...

John Van Denburgh John Van Denburgh (August 23, 1872 – October 24, 1924) was an American herpetologist from California (who also used the name Van Denburgh in publications, hence this name is used below). Biography Van Denburgh was born in San Francisco and enr ...

Taxonomy

This tortoise is a subspecies of ''Chelonoidis niger'', and is sometimes considered to be a distinct species itself.

Description

Male tortoises grow to about and females to about in length, with domed

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

Behaviour

The tortoises spend most of the day feeding, resting, or congregating in muddy pools. They sleep in the open at night. Adults migrate seasonally, travelling along the rim of the volcano's

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

and descending to the lower slopes to graze on new vegetation after wet season rains.

Feeding

The tortoises feed on grass, leaves, forbs, sedges, fruit and

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

s, obtaining water from their diet and pools of rainwater.

Breeding

Male tortoises compete with each other by extending their necks, gaping, biting and pushing. They utter loud guttural noises while mating. Females start nesting in May and June at the end of the wet season, laying clutches of 6–26 eggs in soft soil. Juvenile tortoises tend to stay at lower, warmer, elevations for the first 10–15 years of their lives

Distribution and habitat

The tortoise's range is limited to an area of on the

Alcedo Volcano Alcedo Volcano is one of the six coalescing shield volcanoes that make up Isabela Island in the Galapagos. The remote location of the volcano has meant that even the most recent eruption in 1993 was not recorded until two years later. It is als ...

on the central part of Isabela Island. There it inhabits deciduous and evergreen forests as well as humid

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

Conservation

The tortoise population is estimated to comprise some 6,300 individuals, a decline of 84% since 1840, and the subspecies is considered to be Vulnerable. The tortoise population formerly suffered through predation and trampling of eggs and hatchlings, as well as habitat degradation, by introduced animals including pigs, donkeys and goats. Volcanic eruptions have also affected the tortoises and their habitat, with a major eruption of Alcedo 100,000 years ago thought to be the cause of the subspecies' low

genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. It is d ...

References

{{Taxonbar, from= Q12745316 vandenburghi Subspecies Turtles of South America Endemic reptiles of the Galápagos Islands Reptiles of Ecuador Reptiles described in 1930