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Name: Giant Tortoise
Family: Testudinidae
Scientific Name: Geochelone elephantopus
Length: Up to 150 cm (59 in)
Weight: Up to 250 kg (550 lbs)
Other Names: Galapagos Giant Tortoise

Category: Reptiles
Number of Species: 28
Endemic Species: 19

Twenty-eight species of reptiles have been recorded in Galapagos in recent times. Nineteen of these species are endemic to the archipelago, 11 of which are confined to single islands, and three species have been introduced.

Giant Tortoises, also know as Galapagos tortoises, are mainly found in the highlands of Islands like Santa Cruz, San Cristobal, Isabela and Española. However, giant tortoise are also often seen on lower elevations during the warm / wet season. Giant tortoises are endemic to Galapagos with 15 subspecies recorded around the archipelago. Their total population is estimated to a number of 15,000.

Identification:
Galapagos tortoises are unmistakable due to their large size and distinctive shape. The Galapagos tortoise exhibits two distinct carapace shapes: dome-shelled and saddle-backed, although intermediate forms do occur. In all subspecies the sexes are alike, although males are much larger than females, and have a concave plastron (ventral plate) and a noticeably longer and thicker tail.

Behavior:
Giant tortoises are usually only active from about 08:00 until 16:00. Mating may occur in almost any month of the year but reaches a peak during the warm / wet season, with eggs usually hatching between December and April. Sexual maturity of a Galapagos tortoise is attained at the age of about 20 - 25 years. During the breeding season male giant tortoises chase each other and posture by raising their heads as high as possible, the dominant individuals being those able to raise their heads the highest.

Important News:

• Chelonoidis elephantopus, a type of giant Galapagos tortoise that was thought to be extinct has been "found" in the genome of a similar species, Chelonoidis becki. Read more about the Galapagos Tortoise species not extinct.
• The island of Santa Cruz within the Galápagos Islands has not one but two distinct species of giant tortoise, a new genetic study finds. This is the new Galapagos Giant Tortoise species that was discovered recently. Read more about the new Galapagos Giant Tortoise species.

Life expectancy in the wild is thought to be over 100 years, making it one of the longest-lived species in the animal kingdom. Harriet, a female specimen kept in the Australia Zoo, was the oldest known Galápagos tortoise, having reached an estimated age of more than 170 years before her death in 2006. The Zoo claims that Harriet was probably 169 years old in 2004, although media outlets claimed the greater age of 175 at death based on a less reliable timeline.

All subspecies of Galápagos tortoises evolved from common ancestors that arrived from mainland South America by overwater dispersal. Genetic studies have shown that the Chaco tortoise of Argentina and Paraguay is their closest living relative. The minimal founding population was a pregnant female or a breeding pair. Survival on the 1000-km oceanic journey is accounted for because the tortoises are buoyant and they can breathe by extending their necks above the water, and are able to survive months without food or fresh water. Because they are poor swimmers, the journey was probably a passive one facilitated by the Humboldt Current, which diverts westwards towards the Galápagos Islands from the mainland. The ancestors of the genus Chelonoidis are believed to have similarly dispersed from Africa to South America during the Oligocene.

The closest living relative of the Galápagos giant tortoise is the Argentine tortoise (Chelonoidis chilensis), a much smaller species from South America. The divergence between C. chilensis and C. nigra probably occurred 6–12 million years ago, an evolutionary event preceding the volcanic formation of the oldest modern Galápagos Islands 5 million years ago. Mitochondrial DNA analysis indicates that the oldest existing islands (Española and San Cristóbal) were colonized first, and that these populations seeded the younger islands via dispersal in a "stepping stone" fashion via local currents. Restricted gene flow between isolated islands then resulted in the independent evolution of the populations into the divergent forms observed in the modern subspecies. The evolutionary relationships between the subspecies thus echo the volcanic history of the islands.

The largest species of Tortoise is in fact the Galapagos Tortoise, often reaching enormous size—they can weigh as much as 300 kg (660 lbs) and can grow to be 1.3 m (4 ft) long. The biggest Galapagos tortoises on record reached 880 pounds and over 6 feet long. The species is native to the Galapagos islands, and subspecies are found on seven of the islands in the archipelago. Humans have caused species numbers to dive, due to hunting, habitat loss and introduction of non-native species. But recovery programs have helped to bring numbers back. Even so, the species is still listed as vulnerable to extinction.

Con đực có thể nặng hơn 500 pounds (227 kg) và nữ trung bình khoảng 250 pounds (113 kg).Chúng có đôi chân dày, chắc chắn để giữ tất cả trọng lượng đó, nhưng họ vẫn dành nhiều thời gian nằm xuống để bảo tồn năng lượng.Mặc dù chúng là động vật khổng lồ, vỏ của chúng không rắn.Thay vào đó, chúng được tạo thành từ các cấu trúc tổ ong bao quanh các buồng không khí nhỏ.Điều này làm cho con rùa có thể mang trọng lượng của vỏ mà không gặp nhiều khó khăn.Vỏ bao gồm các xương sườn động vật, vì vậy một con rùa không thể "bước ra" vỏ của nó, giống như bạn có thể thấy trong phim hoạt hình.Phổi nằm trên đỉnh của thân rùa, dưới mái vòm trên cùng của vỏ.

Khi bị đe dọa, con rùa kéo mình vào vỏ của nó với một tiếng rít.Âm thanh rít lên chỉ là con rùa để không khí ra khỏi phổi.Nếu một cuộc chiến nổ ra giữa những người đàn ông, những con rùa đối mặt với nhau bằng những ánh mắt hung dữ, mở miệng và vươn đầu cao nhất có thể.Bất cứ ai đạt được chiến thắng cao nhất, ngay cả khi anh ta nhỏ hơn nhiều so với nam giới khác!Người thua cuộc kéo đầu anh ta với một tiếng rít ồn ào, và trận chiến kết thúc.Đối với chúng tôi, điều này có vẻ như họ chỉ cần đưa vào một chương trình;Nhưng đó là một vấn đề nghiêm trọng đối với những con rùa, đặc biệt là trong tự nhiên, nơi các trận đánh xảy ra trên bạn tình hoặc một món ăn cụ thể hoặc một loạt thực phẩm.

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