Comparative Analysis of Pathological Findings and Causes of Mortality in Marine and Terrestrial Mammals in Rehabilitation Centres: A Necropsy-Based Study

Wildlife rehabilitation centres provide temporary care for injured, diseased, orphaned, or displaced wild animals and can contribute to wildlife conservation by providing information on animal health and mortality. Post-mortem examination is an important tool for identifying pathological conditions and causes of death that may not be apparent during clinical examination. This study aimed to compare pathological findings and causes of mortality in pinnipeds and terrestrial mammals from two wildlife rehabilitation centres based on post-mortem gross examinations, while considering potential anthropogenic and environmental factors. Data were collected during traineeships at Zeehondencentrum Pieterburen–Seal Centre Pieterburen in the Netherlands and Alturas Wildlife Sanctuary in Costa Rica. Necropsy reports, photographs, and admission and outcome data were analysed for seven pinnipeds and six terrestrial mammals and compared with relevant scientific literature. Euthanasia was the most frequent outcome in both groups. Among the pinnipeds, other identified causes of mortality included peritonitis, septicaemia with multiple organ failure, and parasitic pneumonia. Among terrestrial mammals, trauma and one husbandry-related death caused by choking during feeding were recorded. Anthropogenic trauma, particularly domestic animal attacks and vehicle collisions, occurred among the terrestrial mammals, while no direct anthropogenic trauma was identified among the examined pinnipeds. Infectious and inflammatory conditions were observed in both groups, although they were identified as direct causes of mortality only among the pinnipeds. Overall, the observed mortality patterns differed between the two groups. However, these differences cannot be attributed specifically to marine or terrestrial environments due to differences in species, age, geographical location, admission circumstances, season, and centre-specific practices. The study provides a descriptive comparison of mortality and pathological findings and highlights the value of systematic post-mortem examination in wildlife rehabilitation. The small sample and lack of histopathological and microbiological testing further limit interpretation.