Scientists based the research on 20 years of data covering multiple groups of gorillas in Volcanoes National Park, in Rwanda. The scientists found that even when two females had been apart for many years, a newly arrived gorilla would still try to join a female she had formed a previous connection with.

When female gorillas leave one social group and join another, they tend to seek out groups with other females that they've lived with in the past, showing the power of long-term relationships.