The Giant Tortoise of the Galapagos Islands

Of all the wildlife species that can be encountered on a Galapagos cruise, the Giant Tortoise (Geochelone nigra) is perhaps the one most associated with this fascinating and remote archipelago. In fact, the region's name is derived from the Spanish word for saddle, referring to the shape of its ancient inhabitants' shells.

At one time these large, lumbering reptiles lived all over the world, but today they're only found in one other place, the Aldabra Atoll, in the Seychelles. For those fortunate enough to embark on a Galapagos cruise through this fascinating archipelago, the opportunity to meet this amazing reptile up close and personal is a privilege not to be missed.   

Origins

Scientists have discerned that the original tortoises came from the mainland of South America several million years ago, and established colonies on 10 different islands of the archipelago. Each colony constitutes a different sub-species and, in the ensuing millennia, three of these have become extinct due to factors ranging from volcanic activity to human impact.

Physical Appearance and Behaviour

It's clear from their name that these reptiles are larger than the average tortoise, but they vary in size and appearance, depending on where they live. They are herbivorous, feeding on vegetation including grass, leaves and fruit. They also drink huge amounts of water, which they are able to store in their bladder.

Those that have evolved on the larger islands are bigger and have a dome-shaped carapace (shell), which has adapted due to the high rainfall. Those from the small, drier islands are smaller in stature and have a carapace shaped more like a saddle. These species' shells also angle upwards, in order to allow their necks to protrude further to reach higher food sources.

Giant Tortoises can survive for long periods of time without food and water, which, although an ingenious natural adaptation for survival, ironically led to a dramatic demise in the species. In the 18th century, many were captured and stored alive in the hulls of ships by whalers, to be used as an on-going source of fresh meat.

The breeding season is generally around March and April, although they can mate at any time of the year. The female lays between 2-25 eggs, with the smaller species tending to lay far fewer. The incubation period is around 4-5 months. While many do not survive to reach sexual maturity (around 25 years), those that do can live to 150 years of age. 

Communication

Most of their communication is behavioural and they display dominance or aggression by facing off and stretching their necks as far as they can with their mouths hinged wide open. Whoever gets their head highest is generally considered the winner of any argument! Males also vocalise when mating, making a noise similar to a cow, but females are unable to make any sound at all. 

Where to See Them

While on some islands the species is now extinct (Fernandina, Floriana, Santa Fe and Pinta), with the establishment of the Charles Darwin Foundation and the archipelago's National Park, conservation efforts are now in place. The best place to encounter these noble animals on a Galapagos cruise is on the large island of Santa Cruz, at the Charles Darwin Research Station and in the highlands, where they roam wild.