The endangered yellow-eyed penguin is endemic to New Zealand. The South Island population is monitored closely and fluctuates between 400-600 breeding pairs. The Otago Peninsula, on the south-east coast of the South Island, is with 181 breeding pairs (2012-13) an important population stronghold for the species.
Since 21 January 57 yellow-eyed penguins have been found dead. Most birds were in excellent condition and experienced breeders. Dead birds had generally empty stomachs and often traces of vomit around their beak. In some cases blackish faeces stains were apparent.
Post mortems and histological examinations showed no evidence of an infectious disease or trauma. Avian malaria has been ruled out though some virology testing is still being undertaken. Currently, acute poisoning possibly via biotoxins is being considered the most likely cause of death.
The event is so far localised to the Otago Peninsula, down-current from Dunedin city’s sewage outlet. Several weeks of warm and unusually calm weather may have resulted in the development of a harmful algae bloom (HAB). However, no other seabirds are known to have been affected.
Since yellow-eyed penguins are almost exclusively bottom foragers we suspect any toxins associated with this event may have been ingested at the seafloor. Three freshly dead birds have been tested for a range of biotoxins, usually associated with HAB (e.g. domoic acid, brevetoxin, see below); but results all came back negative.
We are keen to hear of any ideas as to what could have caused such rapid and unexpected deaths. Apart from biotoxins – can you think of any other toxic agents (probably of anthropogenic origin) that could be responsible and thus would be worthwhile testing for?
List of biotoxins tested for so far: domoic acid, epi domoic acid, gymnodimine, azaspiracid, okadaic acid, DTX-2, DTX-1, PTX-2, PTX-2 seco acid, yessotoxin, hydroxy yessotoxin, homo yessotoxin, 45 hydroxy homo yessotoxin, YSP toxin 1, Brevetoxin B2, S-deoxy-Brevetoxin B2