One of my favourite pastimes as a zookeeper is eves dropping on the public’s conversations about the animals in front of them. I do enjoy a little chuckle to myself when passing folk stop at the binturong thinking they’re looking at the moon bears or when adults in particular mix up the orange and black stripy tigers with the lions but my favourite thing to listen out for is all the names’ people give the ring-tailed lemurs- I’ve heard them called racoons, meerkats and my personal favourite, llamas.
Now if I’ve got the time, I will always try to gently correct people so they can feel like they’ve learnt a little something. However, the number of times a day I hear people calling to their family “let’s go and see the gorillas” really tickles my pickle.
Despite the gigantic signs at either end of the house stating, ‘Chimpanzee Habitat’, the amount of passers-by who mistake the chimps for gorillas is high. And maybe I take it more personally than some as I have spent the best part of ten years working primarily with gorillas that to me, there is no comparing them, but I do appreciate for visitors seeing the chimps for the first time, they may appear quite similar which is why I thought I would dedicate this blog to the differences between the two greatest of the great apes: the gorilla and the chimpanzee.
Range
Both species live naturally across numerous African countries; chimps have the widest home range spanning more than 2.6 million kilometres across Senegal, the belt of the Congo River and through to western Tanzania and Uganda. Western Lowland Gorillas (the ones you will find in zoos) habituate the countries of Gabon, Congo, Cameroon, and Nigeria.
However, if you look at going Gorilla trekking on holiday, you will most likely travel up to 14,000ft up the slopes of dormant volcanoes in Uganda or Rwanda to see the Mountain Gorillas which are not kept in captivity due to their specialist diets and environment.
Lowland gorillas and chimps have been known to share certain homelands together relatively peacefully in Gabon. That being said, there have been two separate recorded incidents since 2019 in which gorillas and chimps have clashed, both times resulting in the chimps killing an infant gorilla.
Size
I don’t think anyone can truly understand and appreciate the immense size and power of a fully grown silverback gorilla until you are stood next to one. The largest of all the apes reaches around 6ft tall if fully upright with an even bigger arm span. They weigh in at around 200kg (30 stone) and have an exceptionally large head caused by a ridge of bone at the top of the skull used to reinforce the weight of the head muscle. Despite this large head, gorillas have a smaller brain and although considered an incredibly intelligent species, they could be easily outsmarted by a larger brained chimp.
Female gorillas are around half the size of the males’ reaching weights of up to 100kg.
If you are familiar with our chimps here at Wingham, you may have spotted our silver-coloured chimp. This is Lucas and he is NOT a silverback.
Chimpanzees are primarily all black however, just like us, some can go a little grey a little early and Lucas is a just a handsome silver fox. Chimps are much smaller than gorillas with adult males weighing only around 60kg and the females at 50kg. They also have large sticking out ears compared to the gorillas small backwards facing ears.
Chimps are slightly hairier as well, and their hair covers their body except the muzzle whereas male gorillas will have a bare broader chest.
Diet
Except for the odd insect, gorillas are completely herbivorous meaning they eat just vegetation and fruits whereas chimpanzees are omnivores, so as well as foliage and fruits, they will also feast on honey, soil, birds and their eggs and small mammals including other primates. The second infant gorilla killed by the troop of chimps I mentioned earlier was eaten by the chimps.
Chimps are accomplished hunters and although they don’t partake in it that often, their preferred prey is the red colobus monkey, but they will also eat bush babies, young baboons, and warthogs.
Social structure
Chimps live in troops of anything from 20 up to over 150 individuals but do spend most of their time moving in much smaller groups with a mixture of ages and genders. This is called a “fission-fusion society”. This means a group’s composition and size will change throughout the day and with the environment: when the chimps merge into a large group for example, sleeping all in one place, it is called fusion and when they split into smaller groups, it is known as fission.
These smaller groups serve a variety of purposes depending on the makeup, for example a group of lactating females may band together to create a nursery group for the young whereas an all-male group may form for hunting expeditions. Multiple males will live together in one group, and they are nearly always related as the boys tend to stay with their natal group and it is the females that leave at puberty. Males are dominant over the females but with a strict hierarchy between them.
You will notice chimps spend a lot of time grooming each other which creates a strong bond between group members with often the higher ranking being groomed by the lower. Gorillas do not groom each other.
Parallel to this, the social structure of the gorilla is completely different and is led by one dominant male, the silverback. Silverbacks get their name due to the iconic silver hair that runs from their shoulders all the way down their back. A silverback is the dominant male in a gorilla troop.
Other males in the group, usually the silverback’s offspring, will remain smaller with black backs until they leave the troop. Living with their father suppresses the hormones needed to grow larger and change hair colour. Troop size is much smaller compared to the chimps consisting of multiple adult females and their offspring.
It is usually the males that leave the group around 10 years old to form a bachelor group or if mature enough, to establish their own group with any emigrating females. The silverback is the lead decision maker in everything the troop does from choosing feeding and nesting sites to resolving conflict. If the silverback dies, the females will stick together for protection however any juveniles will be at risk from infanticide if a new male comes along.
Communication
Gorillas have over 20 different vocalisations ranging from the contented grumble to the dog-like alarm bark and many more grunts and screams in between.
Gorillas have over 20 different vocalisations ranging from the contented grumble to the dog-like alarm bark and many more grunts and screams in between. Fights between the group are not common and most conflicts are resolved by displays and threat intimidations rather than physical contact. And of course, there is the iconic, unique to gorillas, chest beat.
This involves a cupped hand hitting a bare chest and not clenched fists as everyone assumes. The cupped hand makes the hollow sound lounder and echo further. If you look further into Koko the Gorilla, you can find information on the hand reared female that was “taught” sign language to communicate with her keepers in USA, again indicating their high intelligence.
Chimpanzees have very expressive faces which they use a lot more to convey their message. One easily identified expression is the ‘fear grin’. This big smile with teeth together and bared indicates the chimp is frightened, similar to our nervous smile. Not to be confused with the same smile but with teeth open indicating she is playful.
To show aggression, a chimp will stand bipedally and sway, swinging their arms back and forth to exaggerate their size. Males have a dominance display which you may well have seen Lucas doing, where they will stamp their feet, slap their hands on the ground and push objects around or hurl them at other chimps to intimidate each other.
The most common vocalisation in the chimp world is the ‘pant-hoot’ used to keep groups together, signal social rankings and often when Georgia is hungry! Pant-hoots are made of four parts, starting with soft “hoos”, the introduction; that gets louder and louder, the build-up; and climax into screams and sometimes barks; these die down back to soft “hoos” during the let-down phase as the call ends.
Endangered Status
As both of these primate species are our closest living relatives, sharing around 95-99% of human DNA, it saddens me to say that they both now classed as endangered or critically endangered due to habitat loss, the bush meat trade and the illegal pet trade.
I hope that has cleared up any confusion about the two species and given you a nice insight further into the apes and please do feel free to correct others you may hear in the chimp house on your next visit talking about the gorillas in front of them 😉.
