Whenever BF researchers go out into the field to investigate sighting reports, the witnesses they interview invariably describe the animal as being “apelike”. And many times in the reports we hear bits and pieces of what we think sound a lot like ape characteristics and behavior. But just how closely does reported BF behavior really compare to that of the great apes? Very early on in my own BF research I asked that question of myself, and I set out to find out everything I could on the subject of great ape behavior and how it compared to the reported behavior of BF. Here, in an appropriately sized nutshell, is some of what I learned.
In this article, we will discuss and compare the following areas of behavior:
1. Physical traits
9. Vocal communication
2. Ancestry 10. Tactile communication
3. Ecology 11. Olfactory communication
4. Social organization 12. Reproduction
5. Activity 13. Parent/offspring behavior
6. Postures & Locomotion
7. Manipulative skill
8. Visual communication
In a few of these areas we have
a pretty good bit of anecdotal evidence to make a meaningful
comparison; in other areas we know little if anything at all. I figured that if the areas in which we had information matched fairly well, maybe I could feel safe in making a few assumptions about the areas in which we had little or none. As to the apes, I will concentrate mainly on the three species of gorilla
(the Western lowland gorilla, Gorilla gorilla gorilla; the Eastern lowland gorilla, G. g. graueri; and the
Mountain gorilla G. g. beringei), and the two species of chimpanzee ( the three subgroups of Pan troglodytes, namely the Western masked chimpanzee, the white-faced, and the Eastern long-haired; and the bonobo or pygmy chimpanzee P. paniscus). In this analysis I rarely mention the orangutan because it is almost exclusively arboreal (tree-dwelling) in nature.
1. PHYSICAL TRAITS
Male gorillas range from 4 ½ ft to over 6 ft in standing height
and weigh from 300 to nearly 500 lbs. Female gorillas are roughly
30% smaller. Male chimpanzees range from 3 ¼ ft to almost
5 ½ ft and weigh up to 120 lbs. in the wild, females are roughly
25 % smaller.
For BF, the generally accepted average from sightings and footprint evidence is between 7 to 8 ft tall and anywhere from 750 to 1000 lbs for males, to 6 to 7 ft and up to 600 lbs. for females.
Gorilla coloration ranges from blue-black to brownish-gray with bald areas
black, with dominant males sporting silver hair on the back. Hair
length varies from 3 to 6 inches in mountainous areas to short and sparse
in the lowlands. Bald areas typically the nose, ears, chest, lips
,the palms of the hands and feet and small patches on the buttocks (callosities).
Chimpanzees range from all black to medium brown with bald areas black to yellow. Typical bald areas roughly the same as the gorilla. Hair up to 3 inches in cooler climates, shorter and sparser in warmer areas. All apes are as a rule solid-colored.
For BF, reported coloration ranges from solid dark brown/black to reddish-brown, with lighter colors only rarely reported. Length is generally reported as between 2 to 4 inches with occasional reports of patches of longer hair. Bald areas mostly black, and baldness is reported over most of the face, the palms of the hands and soles of the feet.
(A note on callosities: these are caused by the repeated act of sitting down, and this gradually wears the hair off the contact areas of the buttocks. This is present to some degree on all apes in the wild. Callosities are evident on the BF in the so-called “Redwoods” video; they do not appear on the animal in the Patterson film.)
In the apes they are generally humanlike except more robust due to the
wild omnivorous diet; adult males of both gorillas and chimps sport enlarged
For BF, we have no information on the teeth, except that large canines are occasionally reported.
Eyes: Forward-facing, Gorillas brown iris and brown sclera, chimps brown sclera with orange-brown iris. BF would differ from the known apes in having reports of white sclera, similar to humans, with brown or black iris.
Hands/Feet/Limbs: Gorilla and chimp hands and feet are similar; hands having four fingers and an opposable thumb, feet with four small toes and a big toe apart from and somewhat opposable to the others, for grasping with the feet. In these respects BF differs markedly in having a nonopposable thumb on its hand and humanlike non-grasping feet. In fact, it is even less adapted for climbing than humans are. Even the known fossil pre-human hominids all have opposable thumbs. There will be more on BF’s relationship with other fossil hominids in an upcoming article.
Gorillas are powerfully built, with broad shoulders and short, thick necks.
Long muscular arms hanging well below the knees, and short legs.
Large hands and feet with big fingers and toes. Older males tend
to be pot-bellied. Males also have prominent sagittal crest giving
the back of the head a conical shape; females are more round -headed.
Chimpanzees are much more slightly built, with somewhat shorter arms reaching
to the level of the knee. Chimps do not have sagittal crests.
BFs are reported to be powerfully built with broad shoulders and little or no neck apparent. Though not pot-bellied, they are heavy set and have wide hips. Both males and females are reported as having sagittal crests.
In terms of the evolutionary lineage,
all apes and humans are joined in the superfamily of Hominoidea,
with all the great apes traditionally placed in the family Pongidae and
humans in the family Hominidae. Recently it was discovered that the
African apes are much more closely related to humans than was first thought,
so now many scientists place the African apes alongside humans in the Hominidae
family and the orangs by themselves in Pongidae.
Strangely enough, there is no fossil evidence for any direct ancestors of either the gorilla or chimpanzee line. The current theory of mainstream science has it that the ancestral line of African apes and early hominids split apart about 6 million years ago, with orangs splitting off about 12 million years ago. BF ancestry is of course mere speculation and largely dependent on what we think BF actually is. If we subscribe to the popular Gigantopithecus theory and assume that the ancient Giganto was a biped, the best guess is that our BF is descended from a line that split into its own branch some 4 million years ago, long before the branch that developed into modern humans split from the main trunk. If this is the case, then BF is actually only very distantly related to modern humans, having gone on its own evolutionary path long before even the first Australopithecines walked the earth. If BF is not a Giganto, then it’s anyones guess.
Habitat/food: Gorilla and chimpanzee habitats are mostly equatorial African rainforests. Chimps are mostly frugivorous (fruit eaters) and spend fully half their time feeding in trees, though they can and do catch and eat small animals and monkeys. Gorillas are mostly folivores (leaf and foliage eaters) and spend almost all their time on the ground.
Some interesting things can be learned
by studying gorilla habitat. Gorilla populations are concentrated
in places where there is enough light reaching the ground level to promote
a dense undergrowth of leafy foliage. There are only two types of
area where this occurs enough to support such a large animal: along rivers
and other large waterways, and in harvested, regeneratingsecondary-growth
forest. It has been noted in several of my references that this secondary-growth
forest is much better able to support gorilla populations than old-growth
primeval forest. In lowland gorilla habitats, the animals do not
have to range far or vary their diets much. In the higher mountainous
regions, the available foliage is plentiful but of poorer quality than
the rainforest foliage and lacking in nutrients like vitamin B12, calcium
and potassium. Mountain gorillas make up for this by eating some
prey animals (mostly invertebrates) and mineral-rich soil.
Since the southeastern US is more temperate than these mountainous African areas, the available foliage here is probably of even poorer quality. Gorillas live mainly on foliage and the occasional insect or grub; chimps live on fruit, leaves, bark, stems, flowers, gum, seeds and nuts. Chimps will also eat eggs, young birds, monkeys, young antelope and bush pigs.
As for the BF, its size coupled with the much sparser and poorer quality food supply here probably forces it to maintain a diet similar to the chimp’s. It would be an opportunistic forager, spending nearly every waking moment searching for food. Even a wide range here could scarcely support a handful of these animals. I believe that the BF prefers fruit and foliage as its primary diet, but will supplement it with whatever is available if need be. I do not believe that BF is a particularly successful hunter of other animals, and it only does so as a last resort. If the reported finds of suspected prey animal carcasses are accurate, BF only eats other animals in an effort to make up for a serious vitamin or nutrient deficiency, as the mountain gorilla does. Regular carnivores do not (and simply can’t afford to) waste any edible part of a kill, and the amount of calories and physical effort required for a BF to catch and kill an adult deer is simply too much to make it a regular practice or a diet staple, if it is just going to eat a couple of organs and leave the rest.
Range/territory: Gorilla ranges vary widely depending on food supply and terrain, as do the chimps, and daily forays can stretch from about 100 yards to about 2 miles. Gorilla territories can range from 4 square km to 25 square km ( roughly 2 squ. miles to 9 sq. miles), in groups of from 2 to 20 animals. This works out to an average of one animal per every 0.45 squ. mile for the largest groups in the largest ranges. Chimp ranges are about the same but with larger groups, with population densities reported from 1 animal per 2 squ. km to 7 animals per squ. km.Interestingly, different species of ape and even different distinct groups of apes take great pains to avoid each other and as a rule avoid the others’ territories, with few exceptions. The BF also generally follows this rule when it comes to humans and human territory.
The BF’s population was once estimated at roughly 1 animal per 150 squ. miles in the Pacific NW, and I suspect the density is probably the same here, if not actually less. This means that a BF family or species group could theoretically range over very large areas, perhaps even multiple states. This is one of the problems with the theory attributing different numbers of toe digits to different species of BF, especially when different digit number tracks occur together within one particular area, even a fairly large area.
4. SOCIAL ORGANIZATION
There is significant difference
between the social organizations of the gorilla and chimpanzee. The
gorilla society consists of one dominant silverback male and a harem of
generally between 1 and 5 unrelated females and offspring. In this
society, juvenile males are eventually cast out and become rogues, seeking
to either start their own harems or dethrone the dominant male of a group.
Female gorillas leave their original family group upon reaching breeding
age and join another harem or start a new group with a rogue male.
Typical group sizes are from 2 to 20 animals. An interesting fact
to know is that inbreeding among gorillas is not uncommon. African
animal researcher Richard Estes reports that two family groups under lengthy
study were readily distinguishable by one group having wall-eyes and the
other having webbed hands and feet, both due to inbreeding. Chimpanzee
society is often downright confusing with a group numbering anywhere from
15 to 120 animals, and this group is normally split up into smaller family
These smaller units are multi-male, usually with one of the males dominant. These groups of males are usually related, with the females providing the fresh genetic pool by transferring to another group upon reaching breeding age. With regards to BF, the only researcher that has formally put forward a hypothesis on BF society is Dr. Grover Krantz, who obviously patterned it on gorilla society. He based his theory on material mostly obtained from the Blue Mountains in Oregon, where enough evidence was obtained to suggest the activity of a functional
BF societal unit. Most sightings seem to be of solitary males, and sightings of more than one animal at a time are extremely rare (but do occur). The evidence seems indeed to indicate a society closely resembling a cross between the small gorilla groups and that of the orangutan, which is solitary in nature. This is likely due to the tremendous ranges over which the BF have to forage for food.
All the known great apes, humans
included, are normally diurnal (active during the day). Gorillas
are most active during the first 4 hours of the day, in which most of the
movement and feeding occurs. Then the group usually rests, with activity
resuming from mid-afternoon until dark.
Gorillas normally build nests to sleep in, consisting of branches, leaves and other foliage fashioned into a crude sort of mattress roughly circular in shape. These nests are occasionally built in trees by smaller animals, but males and larger females nest on the ground. Chimpanzees keep pretty much the same schedule, and also build nests in trees using the same methods. BF is a marked contrast to the known apes in being normally nocturnal (active at night). The remains of BF nests are often reported in the NW, and the few photographed remarkably resemble gorilla nests.
All the great apes are quadrupeds and are knuckle-walkers. Humans are the only recognized bipedal primates. Apes run on all fours. Interestingly, all the great apes are more than capable bipeds when they want to be. The apes climb trees by grasping and pulling themselves up and by walking along the branches that support their weight, and hang from limbs with one or both hands or feet to reach food. Only gibbons move around in the trees primarily by brachiating (swinging). BF normally moves bipedally, although there are rare reports of moving on all fours. These are almost always smaller animals of less than 6 feet, and are probably juveniles. The rare reports of BFs in trees are almost always small animals as well. Another marked contrast between BF and the apes is that apes normally avoid entering the water. BFs in the water are often reported.
7. MANIPULATIVE SKILL
Gorillas have not been observed
making or using tools in the wild. Chimpanzees make and use grass
stem and stick probes to hunt for insects and other foods, and also use
rocks to crack nuts.
Both gorillas and chimps can peel fruit and throw stones and the like. BF may be more limited in its manual dexterity by not having an opposable thumb, and no reliable reports of any tool use by BF exist. Reports suggest it can perform any normal grasping chore and can throw objects, and it can perform any hand function that does not require an opposable thumb.
8. VISUAL COMMUNICATION
Apes and humans communicate visually through the use of facial expressions and body movements. Like humans, the apes employ a wide and complicated variety of facial expressions to indicate mood. Though the chimpanzee seems to have more subtlety and variety in its expressions, the facial expressions of gorillas and chimps are mostly the same. A few representative ones are described below.
Expressions of Anger:
Staring: The eyes are staring directly at the subject of its anger, with the head tilted slightly downward.
“Tense-mouth face”: Mouth open, lips drawn back showing the teeth and gums, with the animal usually screaming and performing a visual threat display.
Expressions of Fear or Alarm:
Uneasiness: Mouth is closed, lips drawn tight and slightly apart. Eyes are usually unsteady and darting about. This behavior is usually displayed toward human observers and not other apes. ( According to some researchers, this is the expression displayed by the animal in the Patterson film).
“Open-mouth grimace”: This is very similar to the tense-mouth face, except the lips are normally drawn farther back and the mouth is more open. Also the head is tilted back somewhat and the eyes are darting nervously.
All of these expressions vary in subtlety and intensity depending on the level of emotion. A very detailed discussion of ape expressions can be found in Richard Despard Estes’ Behavior Guide to African Mammals, which was a major source for this article.
With body language there is also a great deal of similarity between gorillas and chimps. Threat and dominance displays involve standing stiffly on all fours with hair bristling in order to appear larger. Social grooming is a common way of expressing social bonds. In the BF reports I have seen and heard, little is usually remembered in the way of facial expressions other than that the face is humanlike; when an expression is recorded, it is often described as a “scowl” or a serious expression. If a parallel is drawn with the apes, it is probably a sign of fear or alarm. Very little else in terms of body language is reported in most BF encounters.
9. VOCAL COMMUNICATION
All the great apes have limitations in their anatomies that limit the types of sounds they can make compared to the speech abilities of humans. Apes do have something humans do not and that is laryngeal sacs. These sacs serve as an amplification device for their vocalizations. Chimps have small sacs and gorillas have larger sacs. Interestingly, the orangutan has enormous sacs of up to 7litres (about 1.85 gallons). As we stated before the orang is solitary in nature and is often separated from other orangs by a considerable distance, so its calls would need the most amplication. If our solitary BF possesses the same ape traits, its laryngeal sacs would be massive in order to amplify its calls, which are often reported as being audible for miles around. I personally do not know of any BF descriptions which include anything that may be sacs, but being deflated and covered with hair may make them more unnoticeable.
Apes also communicate with sounds other than vocalizations. Gorillas are renowned for their chest-beating displays. They also break branches and strike the ground. All these behaviors are typical of male gorillas, especially dominant silverbacks, and are done in response to threats or intruders. Male chimpanzees only occasionally chest-beat, but they do strike trees with branches, also as a display. I do not know of any reports where the witness(es) saw a BF chest-beating, but sounds which closely resemble those made by chest-beating gorillas have been reported. There are numerous reports in the South of wood-knocking and ground-thumping BFs, but few in the NW. I believe that these sounds are made by male BFs in response to intruders into their territory. In these instances I believe the females usually whistle as a signal and warning to others, but otherwise remain silent.
The types of vocalizations made by both the gorilla and the chimp are quite similar, though again the chimp seems to have more subtle variation. Below is a summary table of some gorilla and chimpanzee vocalization types along with their meaning (this table patterned after tables in Estes’ Behavior Guide to African Mammals, pages 534 and 553).
Gorilla call Chimpanzee call Meaning
Wraagh same Being startled, under sudden stress
Hoot bark Bark Response to sight of non-group members
Hoot series Pant hoot Same as above, more stress
Owl hoot hoot Curiosity, questioning call
Pig grunt same Mild aggression or warning, assertionofauthority
Heard when a group is upset,usually by a human/
quarrelling between members
Roar no equivalent Under stress or threat
Growl no equivalent Mild aggression
In the South, BF vocalizations such as whistles, owl-like hoots, roars and screams have been widely reported. If we take these reports at face value and compare them to known ape sounds, a BF roaring would be a dominant male reacting to an intruder. Screaming would be any BF upset by a close encounter with humans, while screaming heard at a distance may be BFs quarrelling with one another. I could find no real ape equivalent to a BF whistle, but from my own studies of reports I believe these are group signals used primarily by females, perhaps to warn other females and to signal the male(s) that there is an intruder to be dealt with. The owl-type hoots may be used by any BF as a sort of probing call, perhaps in response to a presence it cannot identify.
10. TACTILE COMMUNICATION
Little tactile (touching) communication occurs in the apes other than the social grooming that establishes bonds between individuals. This grooming seems to be more important among chimps than among gorillas. The only other significant touching is the almost constant carrying and embracing of the young by their mothers. We have almost no information whatsoever for BF in this area, but the mother/offspring relationship is probably identical until the young can venture on its own. No one knows if BF engages in social grooming.
11. OLFACTORY COMMUNICATION
Male gorillas have numerous layers
of apocrine glands in their armpits that release a strong, pungent sweatlike
smell when the animals are fearful, alarmed or under stress. This
smell has also been observed from excited male chimps. BFs are renowned
for their often-reported strong odor, and a comparison with apes would
suggest that BF probably emits this odor as a sign of fear or alarm in
reaction to being in proximity to humans. Apes that enter the territory
of another rival group can be subject to attack, and I believe that
BF feels genuinely threatened when discovered by humans, especially if
it happens to be in human territory. Apes (gorillas especially) are
terrified of human hunters and will flee in absolute panic, often developing
Though BFs seem to react much more sedately, sightings are usually made by only one or two people at a distance. BFs may have a much more pronounced reaction if confronted at close range by a larger group of humans. The degree of cleanliness of the animal also probably contributes to the reported odors.
All apes are slow breeders. Few gorillas live beyond 35 years in the wild. Chimps live from 40 to 50 years in some instances. Female apes usually begin producing offspring in their early teens and males become productive at about 15 years of age, reaching their prime in their 20s. Unless an infant dies, female apes will produce roughly one offspring every 3 to 5 years. The gestation period for apes of 8 months is only slightly shorter than that of humans. There is no information on BF reproductive rates, but it probably follows the same pattern
13. PARENT/OFFSPRING BEHAVIOR
Infant apes are helpless at birth
just as humans are. They develop and mature much more quickly.
The period from birth to young adulthood only lasts about 10 years in the
apes. There are only a handful of reports of observed BF parent-child activity,
and most of these have other elements that make their authenticity questionable.
We have no consistent information of BF parental behavior but we can surmise
that it follows roughly the same pattern.
There you have it. We could
go into much more detail about gorilla and chimpanzee behaviors but it
wouldn’t be helpful to us at this point since so little is now known about
BF. In the future, I will be contributing more articles on BF of
a purely technical nature in accordance with the guidelines established
by the Georgia Swamp Ape Research Center for submitted papers. Knowledge
is power, and the more that we share our knowledge and the results of our
research with other researchers, the closer we will all be in attaining
Cryptozoological Director - United States
Please do not use this article without express written permission from the author.