Shelter aggregations, social behaviour, and seasonal plasma corticosterone levels in captive and wild Duvaucel's geckos, Hoplodactylus duvaucelii : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Albany, New Zealand
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Date
2010
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Massey University
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Abstract
The development of effective conservation management strategies is reliant on a thorough
understanding of the basic biology and life history of the species of concern. New Zealand’s
endemic herpetofauna species have undergone severe range contractions since human arrival
due to habitat modifications and predation by introduced mammalian pests. Current
conservation management practice involves the eradication of such pests as well as the
restoration of habitat involving native species reintroductions. Albeit these conservation
attempts, detailed information on physiology, ecology and behaviour of most New Zealand’s
lizards is scarce, including the Duvaucel’s gecko (Hoplodactylus duvaucelii). In recent years,
several H. duvaucelii have been translocated to islands within their historical range as part of
restoration projects and in 2006/7 a captive breeding‐for‐release programme has been
established. This provided an excellent opportunity to explore some fundamental aspects of H.
duvaucelii’s basic physiology and behavioural ecology. I investigated seasonal plasma
corticosterone concentrations of captive and wild geckos in relation to several physiological and
ecological factors to enhance our understanding of natural fluctuations of seasonal hormone
patterns. Such information can aid in evaluating stress related changes in hormone patterns of
individuals and populations, which is particularly relevant for the captive management. I
compared plasma steroid hormone patterns of captive geckos from a breeding colony with their
wild source population over several seasons to assess whether captive lizards suffered from
chronic stress, which could compromise their wellbeing and the fitness of future offspring.
Further, I explored several aspects of H. duvaucelii’s social behaviour, including diurnal shelter
aggregations, scent communication and social interactions using experimental and exploratory
studies on captive and wild geckos. The hormone study provided evidence that H. duvaucelii are
suitable for captive breeding as they seem to have adapted well to captivity and did not show a
chronic elevation of stress hormone levels. Moreover, my research has shown that H. duvaucelii
are essentially social lizards that form shelter aggregations year‐round. Adults showed a high
tolerance of juveniles in their diurnal shelters and geckos were able to detect and discriminate
scents from conspecifics in several social contexts. These social traits as well as the year‐round
occurrence of male‐female pairs combined with H. duvaucelii’s life history traits suggest that
this species may possess a social system of high complexity. In conclusion, this dissertation
provides a foundation for future research and delivers the first insight into the social behaviour
and basic endocrinology of this New Zealand endemic lizard.
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Keywords
Geckos, New Zealand lizards, Hoplodactylus duvaucelii, Aggregation, Scent, Social behaviour, Corticosterone