The western Santa Cruz tortoise (''Chelonoidis niger porteri'') is a subspecies of

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

endemic Endemism is the state of a species being found 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 found else ...

Santa Cruz Island Santa Cruz Island ( Spanish: ''Isla Santa Cruz'', Chumash: ''Limuw'') is located off the southwestern coast of Ventura, California, United States. It is the largest island in California and largest of the eight islands in the Channel Islands ...

in the Galápagos. They are found only on the southwestern slopes of the island, with an estimated range of 141 sq. kilometers. There are approximately 3400 individuals in the wild, and have seen rising numbers in population, despite being critically endangered.

MtDNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...

evidence shows that there are actually three genetically distinct populations on Santa Cruz Island. They are characterised by a black, oval carapace (to 130 cm) that is domed, higher in the centre than in the front, and broad anteriorly. Their life expectancy is 175 years. In 2015, the small, eastern Cerro Fatal population of the island was described as a distinct subspecies, '' C. n. donfaustoi'', most closely related to ''chathamensis'' (and forming a clade with it plus ''abingdoni'' and ''hoodensis''), while the main southwestern ''porteri'' population was found to be closer to the Floreana and southern Isabela tortoises.

References

Chelonoidis Subspecies Taxa named by Walter Rothschild Endemic reptiles of the Galápagos Islands Reptiles described in 1903 {{turtle-stub