LAUSR

Long‐term studies of morbidity and mortality in free‐ranging primates are scarce, but may have important implications for the conservation of extant populations. Infants comprise a particularly important age group, as variation in survival rates may have a strong influence on population dynamics. Since 1968, the Mountain Gorilla Veterinary Project (MGVP, Inc.) and government partners have conducted a comprehensive health monitoring and disease investigation program on mountain gorillas (Gorilla beringei beringei) in Rwanda, Uganda, and the Democratic Republic of the Congo. In an effort to better understand diseases in this species, we reviewed reliable field reports (n = 37), gross post‐mortem (n = 66), and histopathology (n = 53) reports for 103 infants (less than 3.5 years) mountain gorillas in the Virunga Massif. Our aim was to conduct the first comprehensive analysis of causes of infant mortality and to correlate histological evidence with antemortem morbidity in infant mountain gorillas. Causes of morbidity and mortality were described, and compared by age, sex, and over time. Trauma was the most common cause of death in infants (56%), followed by respiratory infections and aspiration (13%). Gastrointestinal parasitism (33%), atypical lymphoid hyperplasia (suggestive of infectious disease) (31%), and hepatic capillariasis (25%) were the most significant causes of antemortem morbidity identified post‐mortem. Identifying the causes of mortality and morbidity in infants of this critically endangered species will help to inform policy aimed at their protection and guide ante‐ and post‐mortem health monitoring and clinical decision‐making in the future.