Adaptability and responses to threats in a highly successful rail, the pūkeko, Porphyrio melanotus melanotus

The success of a species is inherently linked to behavioural flexibility. This is especially true for species that colonise new regions as well as long isolated island species which subsequently encounter introduced predators. Aotearoa New Zealand is a classic example of the devastating effects invasive species and anthropogenic habitat disturbances can have; over 50 species have gone extinct since human arrival. However, not all native species have experienced such negative effects. The pūkeko (Porphyrio melanotus melanotus) is a widespread, common rail which self-introduced from Australia ~1000 years ago. There are many mechanisms that may have contributed to this success; inherent species adaptability potentially being one. This thesis aimed to explore the success of this species by analysing their responses to threats, as well as potential factors mediating these responses. This involved collecting morphological and hormonal data, as well as experimental and observational field studies. I found no hormonal sex differences in the population, as well as no correlation with a dominance ornament, which may reflect unusual selective pressures on both sexes. I analysed the responses of pūkeko to two distinct threats: territory intruders and severe habitat disturbance. This involved a study testing their responses to two potential predators: one mammalian (ferret) and one reptilian (snake). While pūkeko co-evolved alongside mammalian and snake predators in Australia, they are currently only exposed to mammalian predators in New Zealand. Results indicate that pūkeko correctly identify ferrets as potential threats, but not snakes, implying they may have lost their ability to recognise snakes. Furthermore, an opportunistic study was undertaken when a severe habitat disturbance occurred. Despite a significant population decline immediately following the habitat disturbance, as well as total reproductive failure, the population returned to pre-disturbance numbers after seven months. These findings support the hypothesis that pūkeko are, at least in part, such a successful species because of their apparent behavioural flexibility and ability to adapt to threats. This is further amplified by the assumed lack of adaptability in many endemic species; as their ranges shrink in response to these threats, pūkeko have taken advantage of this lack of competition and expanded their range.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Biological Sciences

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2021

Author dc:creator

• Sweeney, Aileen Patricia

Advisors dc:contributor.advisor

• Cain, Kristal
• Holwell, Greg

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/64507

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/64507