They look almost human and have similar traits but as well as differing from humans, gorillas also separate into species and subspecies between themselves.
Gorillas at a Glance
They’re agile, social and certainly strong; gorillas are primates which belong to the family of great apes officially known as Hominidae which includes orangutans, chimpanzees, gorillas and of course humans. They are ground-dwelling animals which live in “troops” usually led by an alpha male (silverback); they move around using their knuckles and have varying eating habits depending on the species.
At first glance; a gorilla is a gorilla to most people and this was the same thought of the scientific community until the late 1800’s to the early 1900’s. Just like many species in the animal kingdom they are split into groups based on very subtle differences.
It’s important to note that all gorilla species are listed as endangered, some more than others but conservation efforts are ongoing to try and preserve these awe-inspiring beasts.
They’re generally passive, gentle creatures in the wild but that does not mean they will stand to any threats or disturbances of their troop. If you do happen to come across them whilst on a trekking vacation or safari, calmly remove yourself from their vicinity without causing panic and hopefully they ignore you.
A species of animal is defined by characteristics and traits that the group shares that are passed down genetically through reproduction. The variations you find between gorillas are a reflection of their genetics; adaptations obtained through natural selection which help them to better live in different ecosystems and environments.
The differences may not always be physical but behavioral, as some species may tend to be more mobile, territorial or have variations in the diet as a result of the available food sources in different habitats.
The classification of life into branching categories is a practice called taxonomy. This simplified “phylogenic tree” shows us and helps us track the path of evolution that living beings have taken and how similar species are related despite their differences.
Taxonomists carry out their work by investigating the physical structure, genetics, behaviors and geographic locations of animal species and comparing to their closest relatives, any slight adaptation can determine a new species.
There are two main species of gorilla which are further split into two subspecies within each. These would branch off from the Genus “Gorilla” that you can see on the phylogenic tree diagram.
Western Gorillas (Genus: Gorilla, Species: gorilla)
Western Gorillas are the most populous and recognizable species of gorilla which are found in Central Africa in places such as Angola, Cameroon, Central African Republic, Republic of the Congo, the Democratic Republic of the Congo, Equatorial Guinea, and Gabon.
They love to live in densely forested areas, swamps and montane forests which provide plenty of food, shelter, water, nesting locations and most importantly to them; a lack of humans.
Western Lowland Gorilla (Genus: Gorilla, Species: gorilla, Subspecies: gorilla)
The full scientific name of this subspecies (g. gorilla or Gorilla gorilla gorilla) may sound redundant and ridiculous but as this was the only known species of gorilla until recent history it stands to reason that it’s named this way, similar to the scientific name of the black rat: Rattus rattus.
Western Lowland Gorillas make up a huge proportion of the western gorilla species with an estimated population count in the hundreds of thousands which is vastly more than their counterparts and is the only subspecies you will find in a zoo.
The territory of the troop can cover a huge area that can range between 8 and 45km2 which they travel as they forage for food and look for nesting sites. There can be multiple troops that share the same territory with no aggression shown.
Their diet is varied and highly seasonal consisting of fruits, pith, roots, shoots, fruit, nuts, bark, wild vegetables, and pulp. Even though they are predominantly herbivorous, they are omnivores and have the flexibility in their diet to consume insects and other invertebrates too.
Cross River gorilla (Genus: Gorilla, Species: gorilla, Subspecies: diehli)
g. diehli is the second subspecies of western gorilla and are very seldom encountered by humans due to their very small population of an estimated population of 250 adults. Their population has been noticed to be in rapid decline since 1995 as a result of human activity such as unsustainable hunting and environmental destruction with fears of young gorillas being sold in an illegal pet trade.
It is thought that this subspecies evolved as a response to the ice age; with food being much scarcer. They differ from their western lowland counterparts through their geographic dispersal and behavior.
Eastern Gorillas (Genus: Gorilla, Species: beringei)
Eastern gorillas are found in small locations in central Africa dependent on the subspecies. They tend to have an herbivorous diet consisting mostly of plants and foliage as seasonal fruits are not as prevalent in their habitats.
They are typically stocky in build with black fur as opposed to western gorillas whose fur color can range between browns, greys, reds and black.
Mountain Gorilla (Genus: Gorilla, Species: beringei, subspecies: beringei)
b. beringei are a subspecies of the eastern gorilla with two known separate populations, one population you will find around the Virunga Mountains which border Rwanda, DMC and Uganda whilst the other population is found in Bwindi National Park located in Uganda.
These gorillas have very low population counts with an estimated population of 880 individuals based on an IUCN survey taken in 2016 as with other gorilla (sub)species, the threat of illegal hunting and restricted habitat due to human activity is all too real and hard to prevent.
One major difference between this subspecies and others is the structure of their digestive tract, with intestines that are much more capable of digestive tough foliage. This difference can be reflected in their physical appearance as they have a much more rounded abdomen when compared to their close relatives.
Mountain gorilla fur tends to be black in color and is, in fact, the darkest of all gorillas. The fur is also somewhat thicker than other groups as they live in higher altitudes with lower temperatures. They are very stocky and muscular and also have an elongated skull structure which also sets them apart from other species.
Eastern Lowland Gorilla (Genus: Gorilla, Species: beringei Subspecies: graueri)
They are the largest gorilla species on average weighing in between 450–551lb. G. b. graueri are also known as Grauer’s gorilla named after the Austrian zoologist Rudolf Grauer who first established and identified this subspecies.
They are found in the eastern mountainous forests of the DRC with other smaller populations imported to various national parks for conservation purposes. It has been approximated that there are only 3600 individuals in the wild as of 2016 but it’s hard to keep track due to the unfortunate human conflict that persists in the region.
These apes also mostly feed on foliage and have a limited availability of fruit in their diet even though just like other gorillas, invertebrates are also eaten to supplement their diet.
Some scientists would recognize a third subspecies of the eastern gorilla group which would contain the population of mountain gorilla that inhabits Bwindi national park. They are often called Bwindi gorillas by those who recognize them to be a separate subspecies.
The debate is evidence-based and needs more evidence to fully suffice but there are records of genetic, morphological and behavioral differences between Bwindi gorillas and the rest of the mountain gorilla population.