Hello and welcome to Face the FACS‘s chimpanzee study compilation! This document is a work-in-progress passion project. There are parts left blank, because I am either still searching for the information or have not gotten around to it yet.
Want to help?
Please email me if you have any information or references to add: facetheFACS@melindaozel.com
I’m currently looking for more information on – Central and Nigeria-Cameroon chimpanzee subspecies.
what's in the guide?
Table of Contents
intro to chimpanzee subspecies
WHY ARTISTS SHOULD CARE: If you are creating a chimpanzee character using multiple references, knowing which subspecies you are working with can help you achieve consistency and realism. (Of course, there is no problem with deviating from realism and intentionally taking your own creative license!)
WHY RESEARCHERS SHOULD CARE: Subspecies of chimpanzees display unique behaviors and physical characteristics; classifying this sub-information may yield clearer, better organized data regarding behavior and genetics.
What is a subspecies? (And why it can be difficult to wrap your head around.)
“Distinguishing between a species and a subspecies can be difficult: most people are aware of the definition of a species, but when it comes to defining a subspecies, it can be a bit hazy and subjective.
Technically, a species is a population or groups of populations that can potentially interbreed freely within and among themselves. This is a naturally-defined concept, something which exists by itself. Subspecies, on the other hand, are subgroups within a species that have different traits and are defined by scientists. Let’s examine this concept more closely.
. . .
A widely accepted definition for subspecies is that of Mayr and Ashlock (1991:43): ‘A subspecies is an aggregate of phenotypically similar populations of a species inhabiting a geographic subdivision of the range of that species and differing taxonomically from other populations of that species.’
. . .
As you can imagine, a subspecies is subordinate to a species. This means that while you can have a species of its own within its own genus, you can’t have a subspecies of its own. You can only define a subspecies in relation to a species — and you need at least two subspecies for the idea to make sense (else that single ‘subspecies’ would actually be the whole species). This is where things start to get even murkier.”
Read the rest of this article here.
QUICK NOTE ON BONOBOS
Bonobos are not chimpanzees. They are a different species altogether.
“The bonobo (/bəˈnoʊboʊ, ˈbɒnəboʊ/; Pan paniscus), also historically called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee,[3] is an endangered great ape and one of the two species making up the genus Pan; the other being the common chimpanzee (Pan troglodytes).[4] Although bonobos are not a subspecies of chimpanzee (Pan troglodytes), but rather a distinct species in their own right, both species are sometimes referred to collectively using the generalized term chimpanzees, or chimps. Taxonomically, the members of the chimpanzee/bonobo subtribe Panina (comprised entirely by the genus Pan) are collectively termed panins.[5][6]”
chimpanzee subspecies types
Four subspecies of chimpanzees have been recognized, with the possibility of a fifth.
- the 4:
- Central
- Eastern
- Western
- Nigeria-Cameroon
- the possible 5th:
- Southeastern
The content in the tabs below is in large thanks to the compiled research and information provided by the New England Primate Conservancy. I highly recommend checking out their site for more in-depth study.
chimpanzee subspecies chart
Central Chimpanzee
P. troglodytes troglodytesk
Image from New England Primate Conservancy.
LOCATIONS
- Cameroon
- Central African Republic
- Equatorial Guinea
- Gabon
- Republic of the Congo
- Democratic Republic of the Congo
PHYSICAL FEATURES
- largest of the 4 chimpanzee subtypes
- most significant gender differences
- longer arms
- less facial hair – small tortoise shells and share the goods
Eastern Chimpanzee
P. troglodytes schweinfurthii
Image from New England Primate Conservancy.
LOCATIONS
- Central African Republic, South Sudan
- Democratic Republic of the Congo
- Uganda
- Rwanda
- Burundi
- Tanzania
- Zambia
PHYSICAL FEATURES
- smallest of the chimpanzees
rounder heads - less pronounced brow ridges
- shorter limbs than other subspecies
- known as the “long-haired” chimpanzee
- smallest of the chimpanzees
LIFESTYLE & BEHAVIOR
- ranges from the Congo River/ Ubangi River in southeast Central African Republic and Democratic Republic of Congo (DRC) to Burundi, Rwanda, western Uganda and western Tanzania, with a small population in South Sudan
- majority of the population is found in DRC
- inhabits tropical forests and forests that extend into
Western Chimpanzee
P. troglodytes verus
Image from New England Primate Conservancy.
LOCATIONS
- Guinea
- Guinea-Bissau
- Mali, Senegal
- Sierra Leone
- Liberia
- Ivory Coast
- Ghana
PHYSICAL FEATURES
- thought to be the most genetically differentiated of the four subspecies,
- even leading researchers to speculate that they could be a separate species
LIFESTYLE & BEHAVIOR
- exhibit a number of unique behaviors
- make wooden spears to hunt other primates
- use caves as homes
- share food with each other
- use stones or branches to crack nuts
- are active during the night
- in places that can be extremely hot and dry, they have been observed immersing themselves in water to cool down
Nigeria-Cameroon
P. troglodytes ellioti (also known as P. t. vellerosus)
LOCATION
- Nigeria
- Cameroon
PHYSICAL FEATURES
- smaller teeth
- smaller ears
- smaller skulls
- smaller ears
- thicker fur
LIFESTYLE & BEHAVIOR
- use stone hammers to crack nuts and tools made from plants to extract bees
- most threatened and least distributed of all the common chimpanzee subspecies
Southeastern Chimpanzee
P. troglodytes marungensis
This is the fifth possible subspecies. The previous four subspecies are widely recognized; however, it remains controversial whether the Southeastern chimpanzee warrants its own category of subspecies.
LOCATIONS
- Burundi
- Rwanda
- Tanzania
- Uganda
chimpanzee facial landmarks
Click image to check out merchandise for this design 🙂
comparative primate facial landmarks
chimpanzee facial actions chart
chart 1
KEY
✓ = AU identified
✗ = AU not identified, but muscle present
a = AU not identified and muscle absent
AU | AU name | muscle(s) | human FACS | chimp FACS | NOTES |
1 | inner brow raiser | frontalis (medial) | ✓ | ✗ |
|
2 | outer brow raiser | frontalis (lateral) | ✓ | ✗ |
|
1+2 | inner brow raiser + brow raiser | frontalis (full) | ✓ | ✓ | full brow raise is not a single AU. It is the combination of AUs 1+2 (inner brow raiser + outer brow raiser). Thus far, separation of AUs 1 and 2 has only been recorded in humans. |
4 | brow lowerer | procerus, depressor and corrugator supercilii | ✓ | ✗ | procerus present and functions to pull down brows at glabella. ds and c unclear. brows are seen to lower (p or ds) but not knit (c) |
5 | upper lid raiser | orbicularis oculi | ✓ | ✗ | muscle present and au6 identified |
6 | cheek raiser | orbicularis oculi | ✓ | ✓ | muscle present and au6 identified |
7 | lid tightener | orbicularis oculi | ✓ | ✗ | difficult to identify this subtle action due to morphology and colouration of eye area and eye movements |
8 | lips toward each other | orbicularis oris | ✓ | ✗ | not readily identifiable due to less eversion and contrast of lip margins |
9 | nose wrinkler | lev. labii sup. alaeque nasi | ✓ | ✓ | muscle present and AU9 clearly identifiable, action may also recruit procerus |
10 | upper lip raiser | levator labii superioris | ✓ | ✓ | muscle present and AU10 clearly identifiable, capable of independent action |
11 | nasolabial furrow deepener | zygomaticus minor | ✓ | ✗ | possible incipient muscle, absence of cheek fat would make action difficult to detect if present |
12 | lip corner puller | zygomaticus major | ✓ | ✓ | muscle present and AU12 clearly identifiable, capable of independent action |
13 | sharp lip puller | levator anguli oris | ✓ | ✗ | muscle poorly developed, lack of cheek fat would make action difficult to detect if present |
14 | dimpler | buccinatorius | ✓ | ✗ | muscle present but AU14 not clearly identified, perhaps due to lack of cheek fat |
15 | lip corner depressor | depressor anguli oris | ✓ | ✗ | muscle present and capable of independent action but AU15 not yet seen independently |
16 | lower lip depressor | depressor labii inferioris | ✓ | ✓ | muscle present and AU16 clearly identifiable as independent action |
17 | chin raiser | mentalis | ✓ | ✓ | muscle small but distinct and independent action seen. absence of chin boss means cues to AU17 differ in the chimpanzee. |
18 | lip pucker | incisivii labii, orbicularis oris | ✓ | a | muscles not clearly identified. puckering of lips not clearly identified in chimpanzees |
20 | lip stretch | risorius | ✓ | ✗ | risorius not present. similar action seen likely to be due to platysma action (AU 21) (scroll for OZEL NOTE AU20) |
21 | neck tightener | platysma myoides | ✓ | ✗ | muscle present but AU21 may be more difficult to identify due to hair covering neck and jaw |
22 | lip funneler | orbicularis oris | ✓ | ✓ | muscle present and AU22 clearly identifiable, |
23 | lip tightener | orbicularis oris | ✓ | ✗ | not readily identifiable due to less eversion and contrast of lip margins |
24 | lip presser | orbicularis oris | ✓ | ✓ | muscle present and AU24 clearly identifiable |
25 | lips parted | depressor labii inferioris/levator labii superioris/orbicularis oris | ✓ | ✓ |
|
26 | jaw drop | nonmimetic muscle | ✓ | ✓ |
|
27 | mouth stretch | nonmimetic muscle | ✓ | ✓ |
|
28 | lips suck | orbicularis oris | ✓ | ✓ | muscle present andAU28 identifiable |
39 | nostril compressor | depressor septi nasi, nasalis | ✓ | ✗ | nasalis muscle present but not differentiated. AU38 and AU39 not seen in chimpanzees |
43 | eye closure | orbicularis oculi | ✓ | ✓ | present |
45 | blink | orbicularis oculi | ✓ | ✓ | present |
source for chart 1:
Caeiro, C.C., Waller, B.M., Zimmermann, E. et al. OrangFACS: A Muscle-Based Facial Movement Coding System for Orangutans (Pongo spp.). Int J Primatol34, 115–129 (2013). https://doi.org/10.1007/s10764-012-9652-x
**Yes, this study was on orangutans, but it hosted a cross-species comparison chart with information on chimpFACS.
chart 2
source for chart 2: Vick, Sarah-Jane & Waller, Bridget & Parr, Lisa & Pasqualini, Marcia & Bard, Kim. (2021). S-J Vick , B. M. Waller, L. A. Parr, M. Smith Pasqualini & K. A. Bard (2007) A Cross Species Comparison of Facial Morphology and Movement in Humans and Chimpanzees Using FACS . Journal of Nonverbal Behavior, 31: 1-20.
NOTES FROM CHART 1
OZEL NOTE AU7 – lid tightener: Though it has not been documented in official chimpFACS or chimpanzee studies, I’ve personally observed and documented the lid tightener action in chimpanzees. See action here.)
OZEL NOTE AU20 – lip stretcher: As indicated by chart 2 and the research of Rui Diogo, the risorius muscle has been found to be present in some chimpanzees. These conflicting findings parallel the risorius muscle’s inconsistent presence in humans. It is one of the most variable facial muscles and has been reported absent in human cadavers at drastically different rates, depending on the study.
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