Galápagos Tortoises

Jacinto Gordillo Breeding Laboratory
Parque Nacional Galápagos - Ecuador

The word "Galápagos" is Spanish for 'saddle.'   The islands were named after the distinctive tortoise shell.

Galápagos tortoises are the largest in the world.   Of the original fourteen species only ten remain.  They can live up to 120 years.   Tortoise male/female (determination), is based on the incubation temperatures for 90-120 days:   26-28 degrees centigrade for males and 28-29.5 degrees centigrade for females

Giant Tortoises can weigh more than 55 pounds and live for more than 100 years.

Male vs Female ... In all species, mares are much larger than the females – in some species, nearly twice as large.   Another distinguishing feature is that all males have a concave undershell, which facilitates mating while the male mounts the females (helps the males from falling off).

Mating occurs at any time of the year, but peaks between January and August.   When two mature males complete for a female, they have a ‘height fight.’   They stretch up on their legs and extended their necks.   The tallest wins the female - the shorter one retreats.   A tall tortoise can reach 1.5 meters.

To attract females ... the male tortoises show off by bellowing loudly and bobbing their heads.   Males have concave base to their shell and mount the females from behind.   Mating may last for several hours, during which the males periodically ‘roar’ hoarsely.

Nesting .... Females walk server kilometers to reach dry, sandy nesting sites where they dig nests using only their hind legs.   Two of sixteen hard-shelled eggs (the size of tennis balls) are laid into one foot deep nest holes.

The young tortoises emerge from the nest 120-140 days later and may weigh only 80 grams and measure 2.5 inches.   The temperature in the nest plays a key role in the sex of the hatchling - If the nest temperature is low, more makes will hatch; if it is thigh, more females will hatch.

When the young tortoises emerge from their shells, they must dig their way to the surface, which can take up to one month.  The tortoises grow slowly until they reach their full size at about 40 years old.   Tortoises reach sexual maturity at 20 – 25 years old.   The oldest know tortoise was 175 years old.

Once the tortoises spread across the islands of the archipelago, they further evolved on their isolated islands into the difference races we were today – some with domed carapaces (shells) and other with saddleback carapacers. The word “Galapagos is Spanish for ‘saddle.’  The islands were named after this distinctive tortoise shell.

Shell Shape … The Galapagos tortoise comes in three main shapes; Saddled black, Domed shaped and Intermediate.

Saddleback Tortoise are found in the hotter, drier parts of the islands with sparse vegetation.  They tend to be more aggressive.   They have raised, saddle-like shells and long limbs and necks.   During dominance contests, they will stretch out the necks and front legs to give extra height.   These contests are normally restricted to just posturing with little actual fighting.  They also use this extra height to reach food height in bushes.

Dome-shaped Tortoises are found mostly on the cooler, wetter islands in areas with lush ground vegetation and lots of water and shade.   Domed-shaped tortoises have a more rounded shell, with shorter neck and limbs.   It does not need extra height as it normal just trundles through dense undergrowth trampling and easting the grass.   The front and of its shell is closed allowing it to retreat into an almost full protected casing.

Intermediate Tortoises have shells that do not look like either saddlebacks or dome-backs.   For instance, thy Sierra Negra volcano population, that inhabits southern Isabela Island, is notable for their flat, ‘tabletop’ shells.

Diet … All Galapagos tortoises are herbivores, (plant eaters).  Their diet consists mostly of cactus, fruits, vines, grasses and other vegetation.  Tortoises can store food and water very efficiently and for very long periods of time, and have been known to go without food or water for up to one year.

Speed … The tortoises are slow-moving reptiles with an average long distance walking speed of 0.3km/h.   If however they have a purpose, such as moving to water or nesting grounds, they can move with surprising speed and determination – covering 8 miles in 2 to 3 days.   They spend up to 16 hours a day napping.