Western lowland gorillas show a high-degree of tolerance for non-relatives. Different family groups regularly interact, and non-relatives commonly eat and play together. Photo by Germán Illera
Feb. 7 (UPI) -- The western lowland gorilla is characterized by a dynamic social structure and peaceful familial relations, according to a new survey of the primate's behavior inside the African equatorial rainforest.
For five years, biologists from the University of Barcelona monitored three families of the western lowland gorilla, Gorilla gorilla gorilla, in the dense rainforest of the Republic of Congo. Previous studies of western lowland gorilla behavior mostly relied on observations of open clearings where families gather to eat plants rich in mineral salts.
Open clearings featuring shared resources are often places of peaceful coexistence, but the latest research, published in the journal Proceedings of the Royal Society B: Biological Sciences, showed western lowland gorillas continue to live harmoniously deep in the forest.
As the five-year survey revealed, individual gorillas frequently switched families without issue. Gorillas from different families regularly interacted, eating and playing together with no signs of aggression.
There is no record of infanticide among western lowland gorillas, which could be why young gorillas are so comfortable temporarily joining family groups with no close relatives.
"This social behavior may have played an important role in the evolutionary story of the species, easing the exchange of information and a better exploitation of trophic resources," according to a news release.
Among the highlands of the African Rift, eastern mountain gorilla families mostly keep to themselves. Interactions between non-relatives are often aggressive.
Scientists aren't sure why the two closely related species display such distinct social behavior.
The western lowland gorilla, eastern mountain gorilla and River Congo gorilla are all threatened by deforestation and poaching. The latest research suggests the western lowland gorilla's dynamic social structure makes the primate especially vulnerable to disease. Infections can quickly spread as individuals move freely from family group to family group.
The western lowland gorilla population was devastated by the Ebola virus outbreaks in the Congo between 2002 and 2004.
In addition to regularly observing the gorilla families, scientists conducted a genetic analysis of dozens of fecal samples. The results confirmed the frequency of familial exchange and non-aggressive socializing.
"Such extended sociality can promote the sharing of behavioral and cultural traits, but might also increase the susceptibility of western lowland gorillas to infectious diseases that have decimated their populations in recent times," scientists wrote in their paper.