Abstract
Emerging wildlife diseases threaten recovery of endangered species, especially in small, insular populations where intensive management alters behaviour and contact frequencies, reshaping opportunities for transmission. Introduced species add risk when novel pathogens reach native fauna via direct contact, shared resources, or environmental contamination. The critically endangered kākāpō (Strigops habroptilus) has experienced a prolonged outbreak of exudative cloacitis, for which no initiating pathogen, transmission pathway, or reservoir host has been identified. The condition first appeared on Whenua Hou/Codfish Island c. two years after the introduction of Campbell Island teal (Anasnesiotis), suggesting a plausible interspecific reservoir and pathway into the kākāpō system. This thesis examined how socio-behavioural connectivity, management-related pathways, and pathogenic spillover may influence the occurrence and distribution of cloacitis among kākāpō on Whenua Hou.
First, nocturnal sociality on Whenua Hou was quantified using multi-year GPS telemetry to derive proximity-based association networks. Social network analyses showed that free-living kākāpō exhibit temporal plasticity of associations, with modular structure collapsing into mixed associations of larger groups during the austral summer when pre-breeding activity persists irrespective of mast-driven breeding. Outside this period, associations were generally infrequent and weak and showed no demographic assortment by sex, age class, or kinship. These findings provide the first quantitative description of kākāpō social organisation and a foundation for understanding disease transmission.
Second, transmission of cloacitis among kākāpō contact networks was tested against a management-related infection pathway. Overlaying infection data onto annual GPS-derived networks and supplementary-feeder visitation networks revealed no evidence for spread via nocturnal foraging interactions, indicating cloacitis is unlikely to transmit through direct social behaviour. By contrast, higher association rates and case clustering at feeders during breeding periods implicate aspects of provisioning that may contribute to disease spread where birds aggregate.
Third, the behaviour and activity of Campbell Island teal were described in their endemic range on Motu Ihupuku/Campbell Island as a potential proxy for their behaviour on Whenua Hou. Using trail cameras and visual surveys, spatial distribution, diel activity, and tidal foraging were quantified to characterise habitat use in their natural environment. These data established a behavioural baseline for the translocated Whenua Hou population and provided parameters for subsequent spatial overlap and spillover analyses.
Fourth, the potential for the Whenua Hou teal population to function as a reservoir host or environmental amplifier of cloacitis was tested. A weighted spatial framework integrating teal-related factors estimated exposure to kākāpō, which was compared with infection records. Cloacitis incidence showed no relationship with teal-associated risk, and infected birds exhibited lower estimated exposure consistent with reduced activity during infection. These findings indicate teal are unlikely to contribute to the occurrence or transmission of cloacitis on Whenua Hou.
Overall, the outbreak in kākāpō is unlikely to result from transmission during nocturnal associations or from spillover involving Campbell Island teal. Instead, infection risk appears concentrated in management-modified environments that increase contact among individuals and with contaminated surfaces. Integrating social network analyses, spatial risk modelling, and management data can reduce anthropogenic disease risk while supporting the recovery of Aotearoa’s endangered avifauna.