Species Fact Profile: Galapagos Tortoise (Chelonoides nigra)

                                                            Galapagos Tortoise

Chelonoides nigra (Quoy & Gaimard, 1824)

Range: Galapagos Islands (Approx. 1000 kilometers west of Ecuador)

Habitat: Savannah, Woodland, Scrub Forest

Diet: Grasses, Forbs, Leaves, Fruits

Social Grouping: Herds

Reproduction:  Breed between January and August. Nesting can occur year-round, but usually between June and December.  Female lays eggs in drier lowlands so that eggs will be warmer during incubation.  Average of 10 (up to 16) billiard-ball-sized eggs laid in a nest hole dug with her back legs.  Females typically nest in the same location year after year.  1-4 clutches may be laid per season. Incubation period dependent on weather/temperature, but can range from 3-8 months.  Temperature plays a role in determining the sex of the embryos.   Young are independent at birth.

Lifespan: 150-200 Years

      Conservation Status: IUCN Vulnerable (some subspecies Extinct in the Wild).  CITES Appendix I.  USFWS Endangered

• Largest living tortoise species (rivaled by the Aldabra tortoise).  Body length up to 1.1 meters, generally weigh 150-200 kilograms, but can weigh over 400 kilograms.  Males typically larger than females
•       Skin is dark grey or brown to olive green, shell is black (sometimes covered with lichens that give in a mottled appearance).  In some subspecies the shell is dome-shaped, in some the front part of the carapace is bent upwards (saddle-backed), and in some it is intermediate in shape.  The feet are elephant-like with short toes and no webbing (although the tortoises can swim)
•       Skin is dark grey or brown to olive green, shell is black (sometimes covered with lichens that give in a mottled appearance).  In some subspecies the shell is dome-shaped, in some the front part of the carapace is bent upwards (saddle-backed), and in some it is intermediate in shape.  The feet are elephant-like with short toes and no webbing (although the tortoises can swim)
•       Among the plants in their diet are stinging nettles and manzanillo fruit, which is capable of burning human skin.
•       Have a mutualistic relationship with finches and mockingbirds, which clear the tortoises of ticks and other parasites.  Some tortoises exploit this relationship by letting the bird crawl under them, then dropping down and crushing them.  The tortoise will then step back and eat the bird
•       Capable of drinking large amount of water in one sitting, storing it in the bladder or pericardium.  On arid islands, they may lick dew off of rocks
•       Travel back and forth between the warmer but more arid lowlands (during the cooler hours of the day) and the cooler highlands, where there is more vegetation to eat, during warmer hours.  The regular use of set pathways has created “tortoise highways” built into the landscape.  Often travel back and forth in small groups.  
•       Over a dozen subspecies of Galapagos tortoise were once present on the islands, with many islands having unique tortoises that were adapted to the conditions of that island (such as some islands having longer necks and “saddle-backed” shells to help them browse on leaves more easily).  During Charles Darwin’s visit to the islands in 1835, he was told by the Governor that it was possible to determine which island a tortoise came from by looking only at the shell.
•       Today, five of the fifteen or so subspecies are extinct.  The most recently deceased was C. n. abingdonii, which was represented for many years by a single male individual, “Lonesome George.”  This tortoise died in June 2012
•       Morphology of the shells and comparisons to mainland tortoises helped inform Charles Darwin’s Theory of Evolution; Darwin also brought four live tortoises back to England with him.  Besides observing them, Darwin derived amusement from riding tortoises on the Islands; this practice was allowed at many zoos historically, and at some still is
•       These tortoises were originally considered to be the same species as the Aldabra tortoise, the only other surviving giant tortoise species.  It was believed that the tortoises of the Galapagos had been transported there from the Seychelles by sailors (similar to how sailors would stock many islands with goats, pigs, or wild cattle as a future food source).  Recognized as a separate species in 1834
•       Populations were greatly reduced by pirates, whalers, sealers, and sailors, who killed larger numbers of tortoises for their meat.  Tortoises can go for long periods of time without food or water, which allowed sailors to bring live tortoises on board so that they could be killed weeks or months later as a source of fresh meat.  Hundreds of thousands of tortoises were collected, especially adult females preparing to nest, as these were the tortoises most likely to be found along the coast, where they were more easily collected
•       Tortoises were also hunted for oil which could be extracted from their bodies
•       The Galapagos have been plagued with several invasive species which have negatively impacted the tortoises.  Cats, rats, and pigs destroy nests and eat hatchlings.  Goats compete with tortoises for food (in the process also stripping away vegetation and exposing tortoise nests to invasive predators).
•       Conservation initiatives include protection (all uninhabited parts of the Galapagos Islands were declared to be a national park in 1959), strict legal protection, removal of invasive species, and captive-breeding for release back into the wild (carried out in centers on the islands, under the direction of the Charles Darwin Foundation)