Various non-human species show behaviors that resemble mourning for lost companions. Elephant groups have been observed covering the bodies of their kin with branches and soil, lingering near the remains as if guarding them. Primates, especially chimpanzees, have been documented returning to sites where they left their dead and, in some cases, mothers carry their deceased infants for extended periods. A question that interests researchers is whether these animals can recognize the skeletons of members of their own species. In a recent study, scientists found that chimpanzees direct more attention to the skulls of their peers than to ordinary objects in their surroundings.
Researchers note that chimpanzees and elephants share several traits. Both are long-lived, possess large brains, and undergo extended development. They live in intricate social groups and show prolonged care for injured or dead members. Observations of behavioral responses, including close handling of corpses, sudden seizures, and repeated visits, reveal striking similarities between these two taxa, according to the researchers.
Until recently, the possibility that some species could grasp elements of death beyond basic exposure had not been given much attention. The idea that chimpanzees might identify remains of their own kind, or perhaps lack knowledge of anatomy, has circulated in scientific discussions. A team from Kyoto University in Japan, led by researcher André Gonçalves, examined chimpanzee responses to images of skulls that were specific to their species as well as more generic skull shapes. The results did not disappoint: chimpanzees once again showed surprising levels of interest in their fellows’ skulls.
Choice for faces
The researchers report that chimpanzee skulls retain features that resemble the faces of living individuals. This means that broad contours and the general arrangement of eyes, nose, and teeth likely trigger a network of brain regions that originally evolved to detect and interpret facial features. Such a connection helps explain why the skulls can elicit attention similar to real faces.
Photographers and observers noted a visual cue in the study: a chimpanzee inspecting an eye-tracking screen often fixated on elements that resemble facial features. A test image set included faces, skulls, and abstract shapes that mimicked chimpanzee skulls, allowing researchers to measure gaze duration and focus.
A test chimpanzee at an experimental facility participated in an eye-tracking session, illustrating how attention shifts when presented with face-like cues. The study, published in a reputable scientific journal, found that chimpanzees not only favor faces of their own kind but also show a distinct bias toward skulls that resemble those of their species. Teeth drew the strongest and longest attention, followed by facial contours, eye sockets, and nasal structures.
Researchers propose that chimpanzees may “know” when a skull resembles a member of their own species due to a phenomenon similar to pareidolia, a brain tendency to perceive familiar patterns in random images. This explains why people sometimes see faces in clouds or rocks. In this context, primate skulls appear to resemble faces enough to engage the brain’s face-detection system.
While the exact extent of wild chimpanzees’ awareness remains uncertain, scientists observed that they spend more time attending to skulls that resemble their peers than to non-biological objects in the same environment. The conclusion drawn is that chimpanzees may process these skulls as socially relevant remnants rather than as mere inorganic material. The researchers emphasize that the perception of a skull suggests a recognition of shared ancestry rather than a precise knowledge of anatomy.
Elephant experiments
These insights align with earlier field studies on African elephants. In 2006, Karen McComb and her colleagues at the University of Sussex demonstrated that elephants show notable interest in the skulls and teeth of their peers, more than in other natural stimuli. This sustained attention hints at a deep, long-term memory tied to social bonds and kinship.
The mechanisms behind these responses may differ between elephants and chimpanzees. The researchers suggest that elephants interact with skulls by drawing on past experiences. When organic matter decomposes, facial features such as ears and trunks may fade, whereas chimpanzee skulls preserve broader facial patterns that appear more recognizable to the brain. The comparison highlights how different species might rely on distinct cues when engaging with remains.
In the experimental series, the chimpanzee subjects began with ten adults and later continued with seven. One phase presented the animals with 180 images showing four species (cat, chimpanzee, dog, and rat) arranged around a screen, each image displayed for six seconds to measure gaze time. The findings clearly showed that chimpanzees preferred the faces and skulls of their peers, with stones shaped like chimpanzee skulls garnering less attention. They tended to view front and diagonal angles more than side profiles and fixated longest on teeth, followed by the nose and eye regions.
Experts suggest that the brain’s face-detection module is shaped by the structural features that recur in skulls. The skull’s contour, teeth, and eye sockets appear to map onto a recognition system that directs attention to species-specific facial cues. It is as if the species-specific facial pattern lingers in the neural circuitry, guiding perception even when the stimuli are inanimate.
Reference report: Royal Society Open Science [Citation: Royal Society Open Science].