Ingestion of foreign materials by odontocetes along the Catalan coast: causes and consequences

Ingestion of abnormal materials by cetaceans has been reported worldwide, but few studies have investigated the causes of foreign material ingestion. We retrospectively analysed necropsies performed between 2012 and 2019 on 88 cetaceans stranded along the coast of Catalonia, Spain, and evaluated the association of abnormal ingested materials with 2 risk factors, namely disease of the central nervous system (CNS) and maternal separation. Abnormal materials were found in the digestive tract in 19 of 88 (21.6%) cetaceans; of these, 13 (60%) had lesions in the CNS, such as morbilliviral encephalitis, neurobrucellosis or encephalomalacia, and 3 were diagnosed as having experienced maternal separation. In a logistic regression model, CNS lesions and maternal separation were identified as risk factors for ingestion of foreign material, but with wide confidence intervals, probably due to the small sample size. In contrast, abnormal ingestion was not identified in any of the 25 (28%) cetaceans whose cause of death was attributed to interaction with humans. Abnormal ingestion should be interpreted with caution, and efforts should be made at necropsy to exclude CNS diseases through pathologic and microbiologic investigations. If disease of the CNS is a significant risk factor for ingestion of marine debris by small odontocetes, results of monitoring programmes may be biased by the prevalence of CNS disease in a specific area or population.