Why Chimpanzee and Bonobo Mothers Carry Their Dead Infants: Insights from 83 Cases Across 15 Communities

Original publication: The Conversation, by Elodie Freymann. This summary distills a zoological investigation into why chimpanzee and bonobo mothers carry the corpses of their deceased infants, drawing on 83 observed cases across 15 communities. The behavior appears widespread and tightly linked to the infant's cause of death and age, offering a window into primate social bonds and responses to death.

• 83 cases across 15 communities show the behavior is widespread
• Carrying duration tends to be longer for infants who died of disease than for those killed violently
• The actions reflect strong mother–infant bonds and lingering care, not a full human concept of death
• Non-maternal carers and other species occasionally interact with deceased infants, suggesting an ancient biological pull toward the young

Introduction

In 2003, a chimpanzee mother in Bossou, Guinea, named Jire, carried the lifeless body of her one-year-old infant Jimato for roughly 68 days. As Jimato mummified, Jire swatted flies, placed the body on branches while she ate, and cradled it during her movements through the canopy and forest floor. This extraordinary display underscores a broader question: why do chimpanzee and bonobo mothers carry their dead infants for extended periods?

The article under analysis synthesizes data from 83 documented cases across 15 chimpanzee and bonobo communities. The authors find that corpse carrying is not a rare anomaly but a remarkably widespread behavior among these apes. The study then explores how the duration and manner of carrying relate to the infant's cause of death, age, and the strength of the mother–infant bond, situating the behavior within a larger framework of animal responses to death that extends beyond primates to other highly social species.

The Data Set and Key Patterns

The researchers compiled 83 cases from 15 communities, showing a pattern of significant prevalence rather than isolated incidents. They observe that mothers often engage with the deceased infant in ways they would not with living newborns. For instance, carrying by a single limb or allowing group members to approach the body are behaviors that hint at recognition of a fundamental change rather than a literal grasp of death as a human concept.

The strongest and most consistent pattern concerns the cause of death. Infants that died from disease were carried longer than those that died due to violence by other chimpanzees or social group members. A slowly progressing illness can blur the line between life and death, making it difficult for the mother to determine when normal maternal care should cease. In contrast, an infant who dies after a violent attack might be abandoned quickly as a survival strategy to escape danger and maintain social standing. This distinction highlights an adaptive element to corpse carrying that could be rooted in the practicalities of living in a risky social environment.

Infant age also influences how mothers respond. The bond between a primate mother and her newborn is regulated by hormones and daily interactions; thus, a sudden death does not immediately sever that bond. Across species, comparisons show that deep biological attachments influence how long a body is carried, suggesting a conserved mechanism tied to reproductive strategies and care for offspring, rather than a fully human conception of death.

Do Chimpanzee and Bonobo Mothers Truly Grasp Death?

One of the central questions the article raises is whether these mothers understand death as a final state. The observations suggest a nuanced reality. Mothers treat the bodies of deceased infants differently from living babies—carrying them casually by a limb, permitting others to inspect the body, and engaging in behaviors that are unlikely with living newborns. However, this does not imply a full human-like understanding of death. Instead, the authors propose that a potent residual impulse to care for their young, reinforced by hormonal and behavioral bonds, drives this phenomenon.

Additional observations indicate that the impulse to hold onto dead infants is not exclusive to mothers. In Gombe, Tanzania, non-maternal individuals were observed in nearly a quarter of infant corpse-carrying cases, while in Namibia, an unrelated male baboon carried a dead infant after its mother died. Among bonobos, other females have approached a mother’s dead infant to groom its body. Such patterns imply an ancient biological pull toward the young that transcends species and kinship, pointing to deep evolutionary roots for mourning-like behaviors in social animals.

Comparative Thanatology: A Broader Context

These findings contribute to the expanding field of comparative thanatology, which investigates how animals understand and react to death. The article notes that intense responses to death are not limited to primates. Elephants are known to visit bones and sometimes bury remains; dolphins push deceased calves to the surface; and orcas have been observed carrying their dead calves across vast distances. This cross-species evidence suggests that mourning-like behaviors may be a widespread feature of social living, offering insight into the evolutionary roots of human grief and ritual practices.

Implications for Human Cognition and Mourning

The authors reflect on the evolutionary trajectory of human mourning. They argue that loss of a child in early humans would have triggered hormonal and emotional withdrawal similar to what is observed in chimpanzee and bonobo mothers today. Yet the human capacity to ritualize death—funerals, wakes, burials—likely emerged after the line separating humans from our last common ancestor with the other great apes. The core takeaway is that while deep attachments to offspring appear to be a shared biological feature, the human experience of death involves additional cognitive constructs that likely evolved later in our lineage.

Concluding Reflections and Open Questions

While the evidence supports a robust and widely observed tendency among chimpanzee and bonobo mothers to carry their dead infants, it also raises important questions about the nature of animal cognition. Do they “know” their babies are dead in the human sense, or do they respond to a persistent hormonal and caregiving drive that persists after life ends? The article emphasizes that the patterns observed are best explained by a lingering instinct to protect and care for the young, rather than by an abstract understanding of death’s finality. This distinction provides meaningful clues about the origins of human mourning while highlighting the continuities and differences that separate us from our closest living relatives.