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In March 2017, the oldest female of a group of chimpanzees living in the Municipal Zoological Garden in Warsaw, died in her sleep at the age of 53, due to natural causes. The article reports reactions of the eight other individuals in the group, four males and four females, including the daughter and the granddaughter of the old female, the following day. The corpse generally elicited more interest in the females than in the adult males. The females touched the body gently and groomed it more often than the males, who tended simply to look at and sniff it. However, the most diverse reactions, ranging from gentle touching to jumping on and hitting the corpse, were seen in the youngest male. By contrast, the oldest male never approached the corpse. In general, the chimpanzees at the zoo reacted in a manner much milder than is often reported from the wild.

Research on prosocial behaviors in primates often relies on the two-choice paradigm. Motoric lateralization is a surprisingly big problem in this field of research research, as it may influence which lever will ultimately be chosen by the actor. The results of lateralization studies on primates do not form a clear picture of that phenomenon, which makes it difficult to address the problem during research. The authors discuss possible ways of managing this confounding variable.

The aim of this study was to verify whether chimpanzees (Pan troglodytes) demonstrate an auditory laterality during the orientation reaction, and which hemisphere is responsible for processing the emotional stimuli and which for the species-specific vocalizations. The study involved nine chimpanzees from the Warsaw Municipal Zoological Garden. They were tested individually in their bedrooms. Chimpanzees approached a tube filled with food, located in the centre of the cage. Randomly selected sounds were played from the speakers when the subject was focused on getting food. Individual reactions were observed and outcomes reported. The four types of sound used: thunderstorm, dog barking, chimpanzee vocalization and a zookeeper’s voice. To test whether chimpanzees demonstrate auditory laterality we used a single sample X test. The existence of auditory laterality has been confirmed. The sound of the storm caused the orientation reaction to the left, while chimpanzee vocalization - to the right. On this basis we can conclude that among chimpanzees, arousing stimuli are being processed by the right hemisphere, and species-specific vocalizations by the left. However, the set of stimuli was limited so the study did not unequivocally resolve this issue.