The Eastern gorilla (Gorilla beringei) is divided into the:
Eastern lowland gorilla (Gorilla beringei graueri)
Mountain gorilla (Gorilla beringei beringei)
The Western gorilla (Gorilla gorilla) is divided into the:
Western lowland gorilla (Gorilla gorilla gorilla)
Cross River gorilla (Gorilla gorilla diehli)
However, the number of species and subspecies is a subject to debate. “Our taxonomy is not definitive; taxonomy never is.” (Grubb et al. 2003). The majority of information on gorillas has come from a very small population of mountain gorillas studied for over 35 years at Karisoke Research Center, Rwanda (Robbins 2007). Because of the difficulty of habituating lowland gorillas, only a limited number of studies involving direct observations have been conducted and much remains unknown. The differences in social organization, group composition, and behaviour in the two species have been hypothesized to be a function of ecological variables like habitat, resource availability, diet, and foraging strategies (Watts 1996; Parnell 2002). Research in field as well as in captivity proves that we cannot assume that all knowledge of the behaviour and demography of mountain gorillas applies to all gorilla populations. (Harcourt and Steward 2007; Campbell et al. 2007; Robbins 2007). Given their large brain and body size, gorillas have a long maturation time and are long-lived, have long inter-birth intervals, and reproduce relatively few times in their lives (Campbell et all 2007). Almost all gorillas in all populations live in cohesive...