Galapagos tortoise or Galapagos Giant tortoise scientifically referred to as Chelonoidis nigra is known to be the 13th heaviest surviving reptile and the largest species existing on earth. The term Galapagos has been derived from the Spanish word ‘galapago’, meaning tortoise. Their enormous size and overwhelming requirements prevents them from being a good choice of pets.
Galapagos Tortoise Scientific Classification
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The Galapagos tortoise is known to have 15 subspecies of which only 11 are alive at present, including:
Size: The young animals are about 6 centimeters in size when they come out of their nest whereas the adult is 122 centimeters long.
Weight: An adult male tortoise can weigh between 250-300 kilograms whereas their female counterparts weigh around 110-180 kilograms. Heavier versions also existed though they have now become extinct.
Color: They have a dull brown shell with round or pentagonal markings.
Shell or Carapace: This species is characterized by a large saddle shaped or dome shaped shell, the plates of which are fused with its ribs in a protective framework forming an integral part of their skeleton. The carapace shape of the females is wider and elongated than males.
Teeth: This species has strong jaws but are devoid of any teeth.
Legs: They have large, thick scaly legs.
The Galapagos tortoise is found in the dry and hot regions of the Galapagos Islands, located at a distance of about 1000 km to the western part of the mainland of Ecuador.
They dwell in muddy wallows and puddles in preferably sunny areas. Some of them may be found resting under large overhanging rocks. In the hot and dry season they tend to move to the cooler highlands whereas during the rainy season they go back to the lowlands.
The tortoises being herbivores, mainly feed on green vegetation with their diet mainly comprising of lichens, grasses, leaves, berries and cacti.
- They are known to lead a lazy life, spending about 16 hours a day in sleeping.
- They enjoy warming their bodies by basking in the sun.
- Their level of activity depends on the temperature and availability of food.
- In the cooler seasons they are active at midday while during the summers they are mainly active early in the morning and late afternoon.
- The tortoise withdraws itself into its shell by emitting a hissing sound on being threatened.
- The smaller saddle backed tortoises live mostly in isolation, whereas the dome shaped individuals, being friendlier, are found to be moving around in herds.
- The subspecies living in regions of sparse vegetation have shells curled up like a saddle, helping them to stretch their neck and obtain food from larger bushes and trees, while the dome shaped shells are seen on those with greener habitats.
- Their shells do not have a solid form but comprise of honeycomb structures having small air chambers, helping them to bear its weight easily.
- Having a slow metabolism, their food is stored in their body whereas water gets stored in the bladder and pericardium (root of the neck), enabling them to remain without food or water for upto a year.
- They have low hearing capacity, mostly depending on their sense of smell and vibration to find food and avoid any danger.
- The smaller subspecies often have longer legs to help them get their food from high branches.
The adults do not have any natural predators, while the Galapagos Hawk is the only natural predator of the baby tortoises. Several mammals such as cats, dogs, black rats and feral pigs have also posed a major threat to young ones.
Mating and reproduction
Their mating season is throughout the year, with the most favorable time being from February to June. The males become territorial and compete with each other for the female. During the fight they glare ferociously at each other with the one able to stretch its head to the greatest height being the winner.Head biting is another common trait during their fights, mostly observed in the saddle back sub species. The males emit a harsh bellowing sound or grunt while mating and rams the shell of the female with that of his own.
Egg laying and hatching
During the period of egg laying (July to November) the female travels up to several kilometers to find dry areas for nesting. They use their hind legs to dig around 30cm deep cylindrical holes to lay 16 spherical hard shelled eggs, resembling a billiard ball, weighing between 82 and 157 grams. They leave the eggs to be incubated after sealing the nest hole firmly. Nests receiving low temperatures lead to males while females are born out of nests getting a higher temperature. The young tortoise comes out after a span of four to eight months, weighing 50 grams. Sexual maturity is attained between 20 years and 30 years of age.
Giant tortoises are known to live for the longest span among all vertebrates with their average life span being 100 years. Tortoises raised in captivity survive for at least 170 years.
The IUCN has declared this species to be” Vulnerable”. They have been threatened in their natural habitat since their pastures have been shared by the introduction of non-native animals like goats, pigs and rats. Their numbers reduced drastically from 250,000 in the 16th century to about 3,000 during the 1970s. Modern conservation measures helped the numbers to increase to over 19,000 in the beginning of the 21st century. As of now there may be only 15000 of them left.
Interesting facts about the Galapagos Tortoise
- The tortoise was named by the Spanish explorers who discovered the Galapagos Islands in the 16th century.
- This species played an important role in Charles Darwin’s ‘Theory of Evolution’.
- Lonesome George was the last survivor of the abingdonii subspecies, which became extinct with his death on 24th June, 2012.
- Harriet, kept in the Australia Zoo, owned by Steven Irwin, was more than 170 years of age, being considered the oldest Galapagos tortoise and the third oldest tortoise in the world after Tu’i Malila (radiated tortoise) and Adwaita (Aldabra Giant tortoise).
- They move at a speed of 0.3 mph, but the males are known to travel much faster during mating seasons.
- They keep growing even when they are 40 to 50 years of age.
- The tortoises living in arid regions are known to lick large stones and boulders to get the morning dew thereby leading to depressions in the rocks.
- Though the history of their evolution is not known, they are said to be the nearest kin of the Chaco tortoise of Paraguay and Argentina.
- More than 100,000 tortoises have been killed by pirates and merchants for their meat.
- The character of Galapagus in Ben 10 has been inspired from this species.