Tue, April 2, 2019

Do gorillas grieve?

Fossey Fund scientists in Rwanda and Congo have been observing how gorillas react to the death of one of their own species. In a study published last month, the researchers describe behaviors that have many similarities to human mourning – whether the gorillas knew the deceased or not.

As part of long-term studies on gorilla behavior, the researchers observed and filmed mountain gorillas in the Volcanoes National Park, Rwanda, following the deaths of two members of their social groups.

The first death involved the legendary silverback Titus, who died in September 2009. Titus, a 35-year-old dominant male once studied by Dian Fossey, died from natural causes related to his advanced age. Here’s how the Fossey Fund reported it at the time.

At 9:30 a.m. Rano, and other group members – males Urwibutso, Turakora and Pato – were located about 100 meters away from Titus and they continued moving around the site of Titus. The group appeared to be very stressed. At 10:30 a.m., juvenile Ihumure was still together with Titus’ body. He was lying down one meter away from Titus and clearly distressed.  Eventually, he started to move slowly away from Titus, in order to look for food.

At 12:40 the other males arrived at Titus’ site, led by Rano. They all sat down few meters from Titus. The blackback Turakora approached Titus’ body, touching his back and smelling him. The other two blackbacks sat two meters away. Rano was also looking at Titus and for few minutes nobody displayed. They spent the rest of the morning and early afternoon very close to Titus’ location.

Silverback Titus

Tuck’s death was the second observed during the study. When she died in 2010 at age 38, she left behind a young son. Again, from the Fossey Fund archives:

Her juvenile son Segasira, who had shared a night nest with his mother, did not take a step away from the dead body until late morning. He lay on top of her and sat on her, grooming her and resting against her. He looked at his mother’s face intently and tried to move her head, searching for some reaction. Surprisingly, he also approached her nipple, suckling for a few seconds.

The three blackbacks (young adult males) of the group also stayed close to Tuck’s body, bent over and covering their faces in the cold rain. Her older son Urwibutso displayed many times, even kicking Tuck on the abdomen, apparently hoping to elicit a response from the old female.

Inspecting the corpse of Tuck

The team also studied the behavior of a group of Grauer’s gorillas who found the body of a recently deceased adult male in Kahuzi-Biega National Park, Democratic Republic of Congo. This time, the body belonged to a stranger, not a member of the group.

“It was really surprising to see how similar the behavioral responses were toward the bodies of long-term family group members and a presumably unknown gorilla,” said Dr. Amy Porter, who observed the group’s interaction with the body. 

The authors interpreted these behaviors as a combination of grief and curiosity.  “While we have no way of knowing for sure what the animals were thinking, in the case with the adult female Tuck, there is compelling evidence her young son was grieving”, says Porter.  “Similarly, with the dominant silverback Titus, the male Ihumure who shared a close social relationship with Titus after his mother transferred groups, remained near the corpse and even slept with it.  In the case with the extra-group silverback, I would suggest the responses were more of a reflection of curiosity.”

While the findings of the study help us better understand gorilla behavior, it also has implications for conservationists working to save the species.

Close inspection of bodies can present a serious risk for disease transmission.  Contacts between healthy individuals and infected bodies may be a major mode of transmission for diseases like Ebola, which killed thousands of gorillas in Central Africa.

The study was led by the Fossey Fund with collaborators from University of California Davis, Uppsala University, and the Congolese Institute for the Conservation of Nature. You can help us continue important research into gorilla behavior and conservation by clicking on the DONATE button at the top of the page.

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