''Chelonoidis niger microphyes'', also known as the Volcán Darwin giant tortoise, Darwin Volcano giant tortoise or Tagus Cove giant tortoise, is a

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

of Galápagos tortoise endemic to the Galápagos archipelago in the

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...

ial eastern Pacific Ocean. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''microphyes'' (“small when full-grown”) is based on the mistaken assumption by describer Albert Günther that the holotype specimen (with a carapace length of only 57.2 cm) was of an adult male.

Taxonomy

This tortoise is a subspecies of ''Chelonoidis niger'', and is sometimes considered to be a distinct species of its own. The type locality is Tagus Cove, near the base of Darwin Volcano on Isabela Island.

Description

Male tortoises grow to about 135 cm and females to about 86 cm in length, with domed

carapace A carapace is a Dorsum (biology), 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 tor ...

Behaviour

The tortoises are mainly active in the early morning and late afternoon, resting in shade during the hottest part of the day and sleeping beneath shrubs at night. After heavy rain they wallow in muddy pools. Adults migrate seasonally from the

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

of the volcano to its lower slopes to graze on vegetation after wet season rains.

Feeding

The tortoises feed on grass, leaves, berries and

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.cacti A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...

in the dry season.

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.

Distribution and habitat

The tortoise's range is limited to an area of about 67 km² on the south-western slope of Darwin Volcano on the northern part of Isabela Island. There it inhabits deciduous and evergreen forests as well as dry grassland.

Conservation

The tortoise population is estimated to comprise some 500–1,000 mature individuals, a decline of 94% since 1840, and the subspecies is considered to be Endangered. The tortoises were historically overexploited for food and oil by sailors and settlers. Ongoing threats include predation of eggs and hatchlings and competition for food by introduced animals, including feral dogs, feral cats,

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' ( pack rats), ''Bandicota'' (bandicoot ...

mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

, domestic pigs and goats, as well as habitat degradation and volcanic eruptions.

References

{{Taxonbar, from= Q12745312 microphyes Subspecies Turtles of South America Endemic reptiles of the Galápagos Islands Reptiles of Ecuador Taxa named by Albert Günther Reptiles described in 1875