Gorillas Overview &Amp;Amp; Taxonomy

Gorillas are found in 10 equatorial African countries, in a broad diversity of habitats ranging from coastal lowland forests to high-altitude, Afromontane rain forests (odkaz na MAPs). There are two species of gorilla, separated from one another by the inner Congo Basin. Each species has two subspecies according to Colin Groves, 2001 (Caldecott and Ferriss 2005; Harcourt and Stewart 2007):

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 groups consisting of adults of both sexes and their offspring. These groups are usually lead and protected by a mature male who has a silvery mantle down his back and therefore known as silverback; immature males are called blackbacks and are subordinate to the resident silverback and rarely mate (Robbins 1995; Strier 2000). Median group size does not differ significantly between gorilla subspecies (odkaz na FIG below) (Harcourt and Steward 2007; Godwin 1994).

Fig ? Gorila group sizes. Median (Med) and maximum (Max) group size for different gorilla populations (represented by a dot on the graph), and medians for three subspecies (bar), western (West), eastern lowland (East), and mountain. Only weaned individuals are considered because infants can be missed in censuses. For each population only data from one census are shown. From Gorilla Society, page 114

The great apes are the largest of all primates, and gorillas are the largest of the apes. They are also, along with orangutans, among the most sexually dimorphic primates (see Tab-below). Male gorillas are not only far larger than females (for weight comparison see section 1.2.1), but develop distinctive secondary sexual characteristics