First documentation of humpback whale (Megaptera novaeangliae) post-mortem attendance of a stillborn

Cetaceans are some of the most charismatic marine species receiving regular widespread public attention. They display highly complex behaviour including post-mortem attentive behaviour sometimes referred to as grieving behaviour. Post-mortem attentive behaviour in cetaceans has been documented predominantly among odontocetes and remains largely absent from the literature on baleen whales, limiting current understanding of the cognitive and emotional dimensions of death-related responses in mysticete cetaceans. Here, we describe a case of prolonged post-mortem behaviour by a female humpback whale and her escort toward a deceased calf. The adult female remained in close proximity to the calf, engaging in repeated interactions and maintaining attendance over several hours and possibly days. Unlike reports in odontocetes, the female did not attempt to lift the calf to the surface. The observed behaviours were consistent with epimeletic and post-mortem attentive responses documented in socially complex mammals and indicating a strong maternal attachment to the calf. This case study highlights the need for continued systematic documentation of rare neonatal mortality events to better understand the cognitive, emotional, and evolutionary significance of post-mortem behaviour in large whales. Understanding how nonhuman animals respond to death provides insight into their emotional lives, social bonds, and cognitive capacities.