How Big Do Galápagos Tortoises Get? Size and Weight Explained

Typical size of adult Galápagos tortoises

The Galápagos giant tortoise is the heaviest living tortoise and the largest cold-blooded land animal alive today. Figures for the whole species are only a rough guide, because each island population has its own typical size and shell shape.

Shell length is usually measured along the curve or as a straight line from front to back, and the two methods give different numbers. That is one reason published figures disagree.

Record Galápagos tortoises

The largest reliably recorded individuals have weighed more than 400 kg (880 lb), and lengths of up to about 1.87 m (6.1 ft) have been reported. Guinness World Records lists a captive male named Goliath, raised in Florida, as the heaviest tortoise at 417 kg (919 lb). Animals in zoos are often heavier than wild ones because food is always available.

Early visitors were astonished. In 1535 the Bishop of Panama, who discovered the islands by accident, described tortoises big enough to carry a man. Three centuries later Charles Darwin noted that some needed six or eight men to lift them. Those accounts helped make the animals famous, and also made them a prized source of meat for sailors.

Why some islands have bigger tortoises

The biggest tortoises come from large islands with humid highlands, such as Santa Cruz and the volcanoes of southern Isabela. There, abundant grass and low plants allow tortoises with domed shells and short necks to grow very heavy. Larger bodies also cope better with the cool, misty conditions at higher elevations.

Saddleback tortoises from small, dry islands such as Española and Pinzón are much smaller. Food is scarcer, and these tortoises reach upward to browse cactus and shrubs rather than grazing on the ground. A smaller, lighter body needs less food and water, while the raised shell and long neck give extra reach. The page Why do Galápagos tortoises have saddlebacks? explains this in detail.

Within each population, males are much bigger than females. They also have longer tails and a concave lower shell that helps them balance during mating.

How fast do Galápagos tortoises grow?

Galápagos tortoises grow slowly but for a long time. A hatchling that weighs about as much as a chicken egg may need several decades to approach full size, and many keep adding weight slowly through much of their long life. Captive tortoises reach maturity at about 20 to 25 years, while wild tortoises probably take longer.

Growth depends heavily on food and climate. Young tortoises raised in breeding centers are kept for about four to five years, until they are large enough to resist rats and other introduced predators, before being released. In dry years wild tortoises grow very little, and growth rings on the shell are worn away with age, so they cannot be used to tell age reliably.

Weight also changes through the year. A tortoise that has just drunk deeply can store a large amount of water in its bladder, and animals lose condition during long dry seasons. A single weighing therefore gives only a snapshot of an animal’s size.

Island gigantism or old giants?

Many island animals become unusually large or small over time, an effect called island gigantism or dwarfism. Galápagos tortoises seem to be an exception. Fossils show that giant tortoises once lived on mainland South America too, so the ancestors were probably already large when they reached the islands.

Size may even have helped them arrive. Big tortoises float well, can keep their heads above water and survive months without food or fresh water. That makes them better at surviving a long ocean drift than small ones. Once on the islands, the lack of large predators allowed them to stay giant.

How they compare with other giant tortoises

The only other surviving island giants are the Aldabra giant tortoises of the Indian Ocean. The two overlap in size, but Galápagos tortoises on average are slightly larger, and individuals over 185 kg (400 lb) are more common. Most other tortoises are far smaller: the largest mainland species, the African spurred tortoise, typically weighs under about 100 kg (220 lb).

Giant tortoises also tend to be among the longest-lived animals. For lifespans across turtles and tortoises, see How long do turtles live?