The deadly Ebola virus - currently the cause of an epidemic that's claimed an estimated 1,400 human lives in West Africa - can also devastate great ape populations. Between 2003 and 2004, Ebola spread through gorilla groups living in Odzala-Kokoua National Park in the Republic of the Congo, causing what primatologists called a "demographic crash." Of roughly 380 gorillas living in the Lokoué forest area, only 40 survived.
But life is slowly returning to normal for the survivors, a new study in the Journal of Animal Ecology shows. Six years after the crash, despite high competition for the females who remain, gorillas are once again forming breeding groups.
"This means that there is a chance the population recovers," says Damien Caillaud, a primatologist at the Dian Fossey Gorilla Fund International who was not involved in the study, in an email to The Dodo. There's still a long road ahead for these primates, however, as female gorillas wait five years between births to reproduce again.
"In the best conditions, it will take at least 50 years for the population to fully recover," Caillaud says. "The only positive news is that it is highly unlikely that Ebola will strike again, because the gorilla density is now too low to allow Ebola to get transmitted between groups and affected an entire population."
Breeding gorillas live in troops made up of females, young blackback males and an adult male silverback. During the outbreak, however, blackbacks were more likely to live alone. It's not as if these young gorillas actively chose this lifestyle to escape the disease, says Céline Genton, a study author and conservation biologist at the University of Rennes in France. Instead, if a silverback gorilla perishes from Ebola (or other causes), his group disbands.
From a platform in a jungle clearing, Genton and her colleagues monitored the impact and aftermath of the Ebola outbreak, identifying specific gorillas by nostrils, wrinkles, scars and other body patterns. There was a surge in the formation of breeding groups among survivors, the researchers saw, after the disease had passed. This suggests "a certain resilience in the response to disruption," the authors write.