An integrated approach for predicting the fate of reintroduced populations : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Conservation Biology at Massey University, Palmerston North, New Zealand
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Date
2017
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Massey University
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Abstract
I provide a comprehensive account of the fate of a reintroduced population of North Island
robins (Petroica longipes) at Tawharanui Regional Park, a predator-free peninsular site in
the Auckland Region. All factors affecting the success of reintroductions do so through
survival, reproduction, or dispersal. I use an integrated Bayesian approach to assess the
impact these factors have on population persistence. I estimated population growth by
combining vital rates (survival and reproduction) using 9 years of post-release monitoring
data. There was no change to estimates when informative priors that accounted for site-tosite
variation were included. I determined that despite low recruitment, the population will
persist under current circumstances. I then focused on what was causing low recruitment
by distinguishing juvenile survival from permanent natal dispersal. Habitat fragmentation
prevented juvenile dispersal out of the park, and juvenile survival was low with most
mortality occurring within four months of fledging. It is low juvenile survival that is
causing low recruitment, indicating the habitat quality is marginal. Despite this, current
habitat quality and connectivity is sufficient to maintain a population, but there may be
implications for management if connectivity is increased in the future. Finally, I assessed
whether it would be sensible to harvest this population as their location makes them a
convenient source for future reintroductions. I projected population dynamics 10 years into
the future and examined the implications of a one-off harvest on population persistence.
Whilst there was negligible chance that the population would go extinct, a harvest at any
level reduced the number of females in the population throughout the 10 years, with larger
harvests causing a greater reduction. My results can be used within a decision analysis
framework to facilitate the decision of whether Tawharanui would be a suitable source
population for future reintroductions.
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Keywords
North Island robin, Reintroduction, Wildlife reintroduction, Mathematical models, Auckland, New Zealand, Tawharanui Regional Park, Research Subject Categories::NATURAL SCIENCES::Biology::Other biology