Causes of death in Magellanic penguins Spheniscus magellanicus in southern Brazil.

Magellanic penguins Spheniscus magellanicus are seasonal migratory seabirds. During the migratory period, these penguins are observed mainly in the seas of Argentina, Uruguay, and Brazil. Studies on mortality events in the species are limited, particularly those comparing free-ranging and captive penguins. This study describes the causes of death and pathological findings in Magellanic penguins using necropsy records from a retrospective study (2011-2021). Records from 164 penguins were analyzed, comprising 95 in captivity, 68 free-ranging, and 1 of undetermined origin. Non-infectious diseases (n = 104) were predominant in free-ranging penguins and included starvation (n = 49), suspected drowning (n = 27), hypothermia secondary to oil pollution (n = 25), trauma (n = 2), and intestinal obstruction (n = 1). Infectious/inflammatory diseases (n = 23) were most frequent among captive populations, including cases of malaria (n = 9), aspergillosis (n = 7), other mycotic infections (n = 3), bacterial infection (n = 2), protozoal meningoencephalitis (n = 1), and granulomatous air sacculitis of unknown origin (n = 1). Juvenile penguins constituted most cases in both non-infectious and infectious categories. There were 37 cases of undetermined diagnoses. Gastrointestinal parasitosis, cutaneous lesions, and pulmonary edema were the main secondary pathologic findings. These results enhance our understanding of the diseases affecting the Magellanic penguins and provide valuable insights for the conservation and maintenance of free-ranging and captive penguins.