biologe

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Tag: sunny day

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

Common cranes and greylag geese 2018 on migration stop in Linum (Germany)

Migration stop Linum for cranes and geese, inflight of the cranes towards their night quarters

 

The area around the village Linum (Fehrbellin, Brandenburg, Germany) is famous as a bird refuge, in summer for storks (Ciconia ciconia), whereas in autumn cranes (Grus grus) and greylag geese (Anser anser) use the numerous wetlands as night quarters during their migration stop towards the Southern hemisphere. Many cornfields around offer enough nutrients, which the birds need in order to successsfully perform their long ways southwards. Besides these most conspicuous birds, also other species, such as common starlings (Sturnus vulgaris), stay for a while in that ecologically complex bird refuge.

The common crane uses diferent routes with different destinations, depending from where the groups started. Birds from Central Europe and Scandinavia (meanwhile often also from the Baltic region: Finland and Belarus) take the Western European route towards France and Spain, and more rarely North Africa. Details of that route can differ and are still topic of scientific evaluations. This is why organisations, such as NABU, ask people to forward observations about flying cranes to them.

The crane formations differ from those in greylag geese. G. grus flies in wedge-shaped arrangements, unequal angels or diagonal rows, all in order to reduce the air resistance and nevertheless having a close contact between bird specimens.

Climatic changes obviously influence the migration behaviors, for example of cranes. In that context, it was observed that they tend to return earlier back to their summer quarters in the North due to a warmer climate.

My footage was recorded on 13 and 14 October 2018. This week-end was considered unusually warm for the season autumn. With about 26°C during day time, these days must be formally named summer days.

In October, cranes usually begin between 17:00 and 17:30 with their impressive flights back to their night quarters at the waterside around ponds and lakes. Due to the intense sunlight and warmth on these days, in which I visited Linum, the spectacle differed a bit from the impressions, which I had during my visits in former years.

Cranes and geese covered the sky in greater numbers at the same time. I formerly didn’t observe so many geese in the air during the in-flights of the cranes. While cranes strictly were flying towards the watery areas of Linum, geese flew in all directions. Additionally may be due to the high temperature even in the evening, some crane groups seemed to feel comfortable feeding on cornfields close to the main street still after 18:00.

Berlin/ Linum October 2018
Copyrights Stefan F. Wirth