Deaths in yellow-eyed penguins (Megadyptes antipodes) on the Otago Peninsula during the summer of 1990.

About 150 rare, adult, yellow-eyed penguins died over a short period during the summer of 1989-1990 on the Otago Peninsula. These were from a total mainland population estimated at 240 breeding pairs. Penguin chicks and non-breeding birds were not affected, but there were indications of shortages in feed supply for birds that bred successfully. Thirteen dead penguins were examined. In ten birds, the cause of death was not established. Although it was commonly found that adult birds had little or no food in their gut, none were considered to have starved to death. No consistent pathological lesions were found, nor were any viruses, Chlamydia or significant bacteria recovered from selected tissues. Toxicology tests ruled out poisoning by copper, zinc, iron, lead, arsenic, selenium, cadmium, mercury, organophosphates, organochlorines, polychlorinated biphenyls, hexachlorobenzene or the toxins of Clostridium perfringens, Clostridium botulinum and dinoflagellates. The problem did not recur during the following summer.