This paper presents the necropsy findings in South American fur seal (Arctocephalus australis) pups from Uruguayan colonies. Animals ( ) were aged between 0 and 18 months old. From 0 to 6 months, 69.4% of the pups showed a poor body condition, while 68.8% of animals from 7 to 18 months had fair-to-good body condition. From 6 to 7 months of age, the stomach content included fishes, crustaceans, and foreign bodies. Starvation in the first months of life and traumatic lesions in pups older than 9 months were the most frequent causes of death. Uncinaria spp. was the only parasite found in the small intestine between 0 and 6 month-old pups. Parasites with indirect cycle (Contracaecum spp., Corynosoma sp., Tetrabothriidae) were present from 6 months of age as well as the first report of the nematode Strongyloides spp. in pinnipeds. Orthohalarachne spp. was found in the respiratory tract. Mycobacterium pinnipedii was isolated from 9 animals without gross pathological lesions. Other pathological conditions were found in lesser extent. This information contributes to the main causes of death of A. australis pups at different ages and could be useful to perform further health studies on this wild pinniped species. 1. Introduction Parasitological and pathological studies have been useful in the study of wild ranging pinnipeds populations generating knowledge towards their conservation. Systematic necropsies performed on stranded pinnipeds constitute a strategy in wildlife research, giving information about the direct causes, predisposing factors, or possible threats that determine the mortality of a population or susceptibility to certain diseases [1–10]. Parasitological approaches provide a clue on feeding habits for each species or age class depending on the preys it consumes. Overall, it is known that most parasitic species affecting pinnipeds are heteroxenic having fish as intermediate or paratenic hosts; in pups, lactogenic route constitutes an additional source of gastrointestinal parasites [11, 12]. Among pinnipeds, the South American fur seal (SAFS), Arctocephalus australis (Zimmermann, 1783) (Carnivora: Otariidae), is a species distributed in several countries of South America [13]. The largest breeding colony (estimated population: 300,000 animals [14]) is harboured in Uruguay, and it is distributed in different islands, sharing the same settlement with the South American sea lion (Otaria flavescens Shaw, 1800) [15]. Females give birth to one pup per season, and lactation typically ranges from 8 to 12 months, though it can occasionally extend further
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