biologe

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Tag: facial expressions

Western lowland gorilla: locomotion, eating and facial expressions

We humans are nothing else than a species of great Apes and thus belong to the clade of the primates. Gorillas and chimpanzees represent our closest recent relatives.

 

Relationship to Homo sapiens

 

In earlier times, it was even stated that the two chimpanzee species and the two gorilla species altogether were the sister-clade of the Homo sapiens. This is not the standard of knowledge any more. Due to molecular evidence and other characters, it could be reconstructed that chimpanzees alone represent the sistergroup of modern humans. Gorillas are sister-taxon of the clade consisting of cimpanzees and Homo sapiens.

 

Knuckle-walking

 

The consequence of this systematic scenario is interesting, as the conspicuous mode of locomotion that can be found in gorillas and chimpanzees, the so called knucklewalking, might have also existed in very „primitive“ and extinct human species.

 

Two gorilla species

 

Another newer finding is that the four subspecies of gorillas (western lowland gorilla, Cross River gorilla, eastern lowland gorilla and mountain gorilla) represent two species, the western gorilla (Gorilla gorilla) and the eastern gorilla (Gorilla beringei). Visible in my film footage are specimens of the western gorilla, more exactly western lowland gorillas (Gorilla gorilla gorilla) from the Zoologischer Garten Berlin.

 

Preferred habitats

 

Gorillas live preferably on the ground, but are also good tree climbers. An exception is the mountain gorilla, which seems to avoid tree climbing. Gorillas even do not avoid water, but only access  water bodies, in which they can stand.

 

Social structure

 

The social structure of gorilla groups can be simplyfied as consisting of one dominant male (silverback), his females and subadult specimens. In case several adult males remain in a group, only the dominant silverback is reproductive. The normal case is that adult males leave their groups, remain for a while alone and try to find access to a new group. Interestingly, in gorillas also females leave their groups after adolescence . As a result, females of a group are usually not closer related with each other.

 

Diet

 

Gorillas represent the biggest great apes, but usually are vegetarians, preferring fruits, seeds and leaves as food. To gain enough nutrients, they need to invest a major time of their daily activities with eating. It is still unknown, which role carnivorous food plays for these apes. Some were observed during „termite fishing“. It might be that insects and smaller vertebrate might enrich their diet. In order to grasp smaller food particles, gorillas possess a quite well developed hand motor-skills, as visible in my footage.

Western lowland gorilla filmed in Berlin Zoologischer Garten, copyrights Stefan F. Wirth, Please like my videos also on youtube, in case you like them.

 

Facial expressions

 

As all gorillas, also the western lowland gorilla is characterized by very well developed facial expression abilities. it’s a character, which they share with chimpanzees and humans due to a common evolutionary event in the early ancestor line of the great apes. A differentiated facial expression, comparable with the one of humans, requires a suitable innervation, skull muscle origins and specific numbers and shapes of facial muscles.

 

Culture and the use of selfmade tools

 

It was earlier thought that cultural abilities and the use of selfmade tools would be unique for humans. The modern primatology could proof that this is not true. Both characters evolved obviously in the ancestor line of the great apes. Especially chimpanzees and gorillas are known for using tools, for example in order to perform termite-fishing. The transfer of a specific knowledge or abilities via teaching to the offspring is named culture. Also gorillas are able to do so.

 

Berlin, July/November 2018, Copyrights Stefan F. Wirth

Hamadryas Baboon Behaviors

They belong to the same phylogenetic clade of Primates than Homo sapiens. Hamadryas baboons (Papio hamadryas) miss our ability for a complex facial expression (unlike chimpanzees for example, our sister-group), but we can nevertheless read about their moods, when we look into their faces. When we watch boboons, then many of their behaviors and interactions look familiar to us.

The phylogenetic tree of the Primates (Apes), to which we humans belong, clearly prooves that we derived from old world monkeys due to evolution. Hamadryas baboons live in East Africa and there are well adapted in surviving in a dry environment. They are omnivorous feeders and prefer plants and seeds, but can also hunt smaller mammals or reptiles. This species of baboos is characterized by a specific sexual dimorphism, which represents an apomorphy for P. hamadryas.

Hamadryas baboons and aspects of their social behaviors. Copyrights: Stefan F. Wirth

 

Males have almost the double size of females, and their fur is silver-white and covered by a conspicuous mantle. The social system is rather complex. But it begins with a very simple society structure, which is called the „one-male unit“, which can be named synonymically a „harem“. Such a unit consists of one dominant male, several females and their infants. Several one-male units can cooperate with each other.

That way a more complicated social hierarchy within the populations is formed. I had primatology courses in Berlin, when I was a student and always had a special fascination for these baboons. That’s why I decided to record this footage in the Berlin Zoologischer Garten.

May 2016/ November 2018. Copyrights Stefan F. Wirth.