Postmortem attentive behavior in leopard seals: insights into mother–pup interactions

Abstract Maternal behavior in mammals is critical for offspring survival and provides insight into the evolutionary pressures shaping reproductive strategies. Postmortem attentive behavior (PAB) is a rare form of epimeletic behavior in which individuals show attachment, distress, or curiosity toward deceased conspecifics, most often between mothers and offspring. While PAB has been documented in terrestrial mammals and cetaceans, it has been rarely documented in pinnipeds. Here, we describe multiple instances of maternal PAB in the Antarctic apex predator, the leopard seal ( Hydrurga leptonyx ), at two sites in Patagonia, Chile. We document PAB in two adult females, including repeated observations of one individual across three years. One female displayed PAB for up to 20 days—the longest documented case in pinnipeds and among the longest for any mammal. Behaviors included carrying and mouthing the pup, maintaining close proximity, and displaying territoriality over the carcass. We also conducted a necropsy on one pup, yielding the first detailed anatomical assessment of this species at an early life stage. Our findings suggest death due to emaciation, likely from inadequate nursing. As no pups have been observed surviving to weaning in Chile, potential drivers of high preweaning mortality may include habitat instability, genetic load, or insufficient maternal investment. This study offers novel insight into leopard seal reproductive biology, highlighting the need for continued monitoring of this Antarctic seal.