The intricate dynamics of friendship have long been a subject of interest among scientists, and now, a study on mountain gorillas has shed light on the complex pros and cons of these relationships. The research, conducted by the Dian Fossey Gorilla Fund and the universities of Exeter and Zurich, analyzed over 20 years of data on 164 wild mountain gorillas to examine how their social lives affected their health.

The study’s findings revealed that friendly females in small groups did not get ill often but had fewer offspring, while those in large groups got ill more frequently but had higher birth rates. In contrast, males with strong social bonds tended to get ill more often but were less likely to be injured in fights. The researchers propose that the stress of defending females and offspring may have contributed to the reduced immune function in males.

The study’s lead author, Dr Robin Morrison, highlighted the importance of considering both the benefits and costs of social relationships, stating, “Having a lot of strong social relationships is often really good – but sometimes it isn’t.” The research focused on the strength of each gorilla’s key social bonds, its integration in the group, and wider context such as group size, stability, and conflict with other groups.

The findings emphasize the forces that affect the evolution of social behavior. Dr Sam Ellis from the University of Exeter explained, “With these forces pushing in different directions, the ‘optimal’ social type will depend on an individual’s sex, age, offspring, and wider social group.” The study shows that the social environment is a strong predictor of health and lifespan in humans and other social mammals, but it is not a straightforward case of more and stronger social ties always being better.

The research was based on long-term observations of mountain gorillas in Volcanoes National Park, Rwanda. Dr Tara Stoinski, CEO and Chief Scientific Officer of the Dian Fossey Gorilla Fund, noted that this paper highlights the value of long-term studies in furthering our understanding of the evolution of sociality and how the benefits or costs of sociality can vary considerably across different environments.

The study was funded by the Swiss National Science Foundation and the Dian Fossey Gorilla Fund. The research is published in the journal Proceedings of the National Academy of Sciences, with the title “Group traits moderate the relationship between individual social traits and fitness in gorillas.”

The lives of Sumatran orangutans living in zoos have been found to significantly alter how they interact with their environment, according to a recent study comparing wild and zoo-housed individuals. Researchers analyzed over 12,000 instances of daily exploratory object manipulation (EOM), revealing that orangutans in zoos engage in more frequent, diverse, and complex exploration than their wild counterparts.

“Our study shows that orangutans in zoos not only explore more but also explore differently,” said Isabelle Laumer, first author of the study. “What’s especially fascinating is that even when exploring the same kinds of objects, zoo-housed orangutans showed a richer repertoire of actions and were more likely to use tools or manipulate multiple objects at the same time.”

The study compared EOM behaviors in wild and zoo-housed orangutans across a wide age range. Data were collected from 33 wild individuals aged between six months and 76 years, as well as from 24 individuals in four zoos in Germany and Switzerland, with ages ranging from seven months to 49 years.

The results showed that zoo-housed orangutans explored objects more frequently than their wild counterparts, while there was no difference in exploration duration when individuals did explore. In contrast, wild orangutans primarily explored naturally occurring objects like plants, bark, and sticks, whereas zoo-housed orangutans engaged with a wider variety of enrichment items designed to encourage manipulation and cognitive engagement.

Importantly, the age at which orangutans first engaged in specific types of exploration was consistent across both settings, suggesting an innate developmental sequence. However, zoo orangutans continued to explore into adulthood, while wild individuals’ EOM declined sharply around weaning age (about 8 years old), likely due to the demands of survival in the wild.

In human infants, object exploration enables learning about physical properties such as texture and weight while stimulating cognitive and motor development – a pattern observed in many non-human animals as well. The heightened exploration may enhance cognitive flexibility and problem-solving skills in zoo-housed orangutans, as they interact with varied enrichment items and have more time and energy to devote to learning through exploration.

“These findings underscore how profoundly the environment influences animal behavior and cognitive development,” said Caroline Schuppli, senior author of the study. “And it also offers unique opportunities – by comparing wild and zoo-housed animals, we can better understand the full extent of a species’ cognitive potential.”

Rewritten Article:

In a groundbreaking study, wild chimpanzees have been observed eating and sharing fruit that contains alcohol. Researchers from the University of Exeter set up motion-activated cameras in Guinea-Bissau’s Cantanhez National Park to capture footage of these fascinating creatures.

For the first time, scientists have confirmed that chimps are consuming fermented African breadfruit, which contains ethanol (alcohol). This raises intriguing questions about whether and why our closest relatives deliberately seek out alcohol.

In humans, drinking alcohol leads to a release of dopamine and endorphins, resulting in feelings of happiness and relaxation. Sharing alcohol through traditions like feasting helps form and strengthen social bonds. Could wild chimpanzees be getting similar benefits from eating fermented fruits?

The researchers used cameras to film chimps sharing fermented breadfruits on 10 separate occasions. The fruit was tested for alcohol content, with the highest level found being equivalent to 0.61% ABV (Alcohol By Volume). While this is relatively low, the scientists suggest it may be just the tip of the iceberg, as 60-85% of chimps’ diet consists of fruit, which could lead to significant consumption.

The researchers emphasize that chimps are unlikely to get “drunk,” as this would clearly not improve their survival chances. However, recent discoveries about a molecular adaptation that increased ethanol metabolism in the common ancestor of African apes suggest eating fermented fruits may have ancient origins in species including humans and chimps.

Dr Kimberley Hockings from the University of Exeter notes, “Chimps don’t share food all the time, so this behavior with fermented fruit might be important. We need to find out more about whether they deliberately seek out ethanolic fruits and how they metabolize it.” If so, it suggests the human tradition of feasting may have its origins deep in our evolutionary history.

Anna Bowland’s work was funded by the Primate Society of Great Britain, providing a fascinating glimpse into the behavior and biology of our closest relatives.