What's in a database? Insights from a retrospective review of penguin necropsy records in Aotearoa New Zealand

Abstract

Wildlife necropsy databases often provide data for morbidity and mortality studies of free-ranging species, with implicit relevance for conservation goals, as well as domestic animal and human health. Retrospective reviews are a common way to derive insights from such opportunistic data, despite the methodological difficulties of performing these analyses, alongside findings being prone to bias. This study reviews morbidity and mortality data from Sphenisciformes of Aotearoa New Zealand, using records extracted and manually refined from submissions to the national Wildbase Pathology Register. The review corroborates the broader consensus that hoiho (yellow eyed penguin, Megadyptes antipodes) are most commonly diagnosed with infectious/inflammatory disease (43.1%, 422/978 diagnoses), kororā (blue penguin, Eudyptula minor) with traumatic injuries (42.9%, 156/364 diagnoses), and emaciation being a common finding across both species (33.9%, 393/1463 diagnoses). Further, there are marked spatiotemporal trends in submissions, driven primarily by the affected species and the submitting organisations, highlighting the biases within such databases that must be factored into the application of results. Typographical errors, redundancies from synonymous terms, and missing data are captured as barriers to performing manual reviews of free-text data. Overall, this study highlights strengths and limitations of storage and review of wildlife necropsy data while providing insight into threats faced by the penguins of Aotearoa.

Fig 1. Count of whole carcass, post-hatch Sphenisciformes accessions stored in the Wildbase Pathology Register to July 2020.

Total count of penguin accessions (y-axis) across years (x-axis) of the Wildbase Pathology Register of New Zealand. Species are represented by colours as per the figure key, with kororā (blue penguin, Eudyptula minor) and hoiho (yellow eyed penguin, Megadyptes antipodes) specifically represented as the most populous accessions. ‘NA’ on the x-axis represents records for which no year was recorded. 2020 shows relatively few accessions as the study period ends in July of this year.

Fig 2. Species distribution over all months summed across years, of whole carcass, post-hatch Sphenisciformes accessions stored in the Wildbase Pathology Register to July 2020.

Total number of penguin accessions (y-axis) entered in each month (x-axis) summed across all years of the Wildbase Pathology Register of New Zealand. Species are represented by colours as per the figure key with kororā (blue penguin, Eudyptula minor) and hoiho (yellow eyed penguin, Megdyptes antipodes) specifically represented as the most populous accessions. ‘NA’ on the x-axis represents records for which no month was recorded.

Fig 3. Map of whole carcass, post-hatch Sphenisciformes accessions stored in the Wildbase Pathology Register to July 2020 and projected population densities across Aotearoa New Zealand.

Made in ArcGISPro the map shows submissions of Sphenisciformes (yellow circles) centred over the cities which are most closely associated with the submissions as recorded in the Wildbase Pathology Register. Brown shading indicates relative human population densities of the official New Zealand territorial boundaries as per the figure legend. Population data is drawn from projected population data for 2023 [47] from the New Zealand government. Coastline and island polygons were obtained from Land Information New Zealand [42]. Territorial authority boundaries were sourced from Stats NZ [43]. Both datasets are licensed under Creative Commons Attribution 4.0 International.

Fig 4. Species distribution of all diagnoses encountered over 10 times in a review of whole carcass, post-hatch Sphenisciformes accessions stored in the Wildbase Pathology Register to July 2020.

Total number of accessions (x-axis) for which each diagnosis (x-axis) was assigned. Colour indicates if the bar represents hoiho (yellow eyed penguin, Megadyptes antipodes), kororā (blue penguin, Eudyptula minor), or other species as per the figure key. Individual findings which were assigned to fewer than ten accessions are not included.

Fig 5. DAMNITV grouping of diagnoses found in a review of whole carcass, post-hatch Sphenisciformes accessions stored in the Wildbase Pathology Register to July 2020.

Frequency of diagnoses (y-axis) grouped by category according to the DAMNITV mnemonic (x-axis). Letters in the mnemonic indicate broad categories of diagnoses as: D=Degenerative, A=Anomalous, I=Infectious and Inflammatory, M=Metabolic, N=Nutritional and Neoplastic, and T=Traumatic. Colour indicates if the bar is representative of hoiho (yellow eyed penguin, Megadyptes antipodes), kororā (blue penguin, Eudyptula minor), or other species as defined in the figure key.