Monitoring the impacts of invasive mammals on arboreal geckos' habitat use, cell foam retreat use, and the effectiveness of different monitoring techniques : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology, Massey University, Auckland, New Zealand
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Date
2012
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Massey University
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Abstract
Gecko ecology was studied in areas of pest control and no control in four
areas around Auckland. The density index of geckos was highest at Waiheke
(treatment, i.e. pest control) with an average of 137.5 geckos ha¯¹ compared with
Waiheke (control, i.e. no pest control): 56 g/ha¯¹, Tawharanui: 20.3 g/ha¯¹ and
Shakespear: 9.5 g/ha¯¹. The Waiheke sites were then studied further; gecko
condition was measured and males were found to have lower body conditions at the
non pest controlled sites, rats were also found to be more abundant at these sites and
large invertebrates less abundant. Habitat was also analysed and geckos were found
to be captured under cell foam retreats (CFRs) in areas with lower canopies, higher
forest density, a higher proportion of undergrowth cover and smaller canopy areas
and tree diameters. These parameters were then used to compare the detectability of
geckos with their densities and areas with the lowest densities were also found to
have the lowest detectability. The efficiency of CFRs was then compared with VES
nightspotting, Onduline artificial cover objects (ACOs) and tracking tunnels. CFRs
and VES were found to be similarly efficient with 1.66 geckos hour¯¹ for CFRs
compared with 1.10 geckos hour¯¹ for VES. ACOs and tracking tunnels did not
detect any geckos during this study. The humidity at the time of capture correlated
with the number of geckos captured per check, with less geckos captured as the
humidity increased.
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Keywords
Predators, Wildlife monitoring, Introduced mammals, Non-indigenous pests, New Zealand, Mokomoko, Arboreal geckos