Behavioral responses of wild chimpanzees toward a juvenile that suddenly lost its animacy due to a fall accident

Abstract

Detailed observations of animal reactions to a collapsed individual in wild are rare but essential to debates about the perception of death by nonhuman animals, including chimpanzees. A male juvenile chimpanzee named Volta, a member of the M group in the Mahale Mountains National Park, fell from a tall tree and was temporarily incapacitated, suffering a severe concussion and nasal bone fracture. However, Volta showed signs of gradual recovery. We compared the behavior of other chimpanzees towards Volta with the previous reports on the behavior towards collapsed or recently dead group members. We found that behaviors towards Volta were similar to those observed towards collapsed or dead members. These included other-regarding behaviors and aggressive behaviors, and notably, licking of Volta's blood, which has not been previously reported. Adult males tended to be in close proximity to Volta for longer periods than adult females. The social situation with adult males including alpha male, surrounding Volta likely influenced the behavior of other individuals. Exploring the state of recovery of the injured individual, by closely approaching, directing various behaviors, and observing the reactions of the victim, and demonstrate tolerance and consideration towards the victim.

Figure 1

Volta at 12:41 p.m., just after confirmation of the accidental fall; blood on the face has not dried.

Figure 2

At 12:44 p.m., Orion licking Volta’s face while holding a dead leaf with blood on it. Figaro, Omaly, and Nkombo were sitting on the tree about 5 m away from Volta and watching him. The crash site is on the right of the photo, approximately 2 m away from Volta.

Figure 3

Teddy (right) grooming Volta in a sitting position. Christmas (left) looking at blood on a dead leaf. Orion (upper left) sitting 3 m away from Volta and holding a dead leaf with blood on it in his mouth.

Figure 4

Teddy (right), suddenly bristling with hair, grabbed Volta’s right leg and began a charging display.

Figure 5.

Volta vomiting out stomach contents from his mouth.

Figure 6

Changes in the number of individuals in close proximity to Volta from the time of the fall accident (12:41 p.m.) to the end of the observation (17:35 p.m.) in 1-min intervals. The blue and white backgrounds represent changes in social context, with Period 1 up to Teddy’s arrival, Period 2 up to Teddy’s departure, Period 3 up to Orion’s departure, and Period 4 up to the end of observation.