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There are 2 species - the Western and Eastern gorillas, and both species have silverback males. The larger of the two is the Eastern Gorilla. The maximum size of a male gorilla can be over 225 kg (500 lb) and 1.83 m (6 ft) in the wild, with much heavier weights recorded in captivity. (Although I can't find a decent reference to the recorded sizes either.)
1 Eastern lowland gorilla (Gorilla gorilla graueri) is slightly larger in size weighing up to 220 kg (484 lb) and darker in coloration than the western lowland gorilla. They live in the rainforests of central Africa.  Mountain gorilla (Gorilla gorilla beringei) is the largest and rarest of all three subspecies. Adult males may weigh over 227 kg (500 lb.) They are found at high elevations of the Virunga Volcano range that separates Zaire from Rwanda and Uganda.