Pup mortality in New Zealand sea lions (Phocarctos hookeri) at Enderby Island, Auckland Islands, 2013-18

A hypervirulent strain of Klebsiella pneumoniae, causing septicaemia and associated meningitis and polyarthritis, is identified as the leading cause of pup mortality in New Zealand sea lions (Phocarctos hookeri) at Enderby Island, accounting for approximately 60.2% of deaths annually between 2013 and 2018. This finding, derived from advanced diagnostic methods including histopathology, microbiology, and matrix-assisted laser desorption/ionisation-time of flight mass spectrometry, challenges previous underrepresentation of this pathogen due to its often cryptic presentation. The study highlights the significant threat posed by hypermucoviscous K. pneumoniae to pup survival, with additional mortality likely occurring post-dispersal beyond summer monitoring periods. Less common causes of death included starvation (14.8%), trauma/asphyxiation (9.9%), and other infections (7%). This research provides a foundation for evaluating risk factors and developing mitigation strategies to address this critical conservation issue.

Michael, S. A., Hayman, D. T. S., Gray, R., Zhang, J., Rogers, L., & Roe, W. D. (2019). Pup mortality in New Zealand sea lions (Phocarctos hookeri) at Enderby Island, Auckland Islands, 2013-18. Plos One, 14(11), e0225461. https://doi.org/10.1371/journal.pone.0225461