Browsing by Author "Nelson, Nicola"

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Behavioural mechanisms affecting the success of translocations. An investigation using New Zealand’s rarest ratite, the rowi
(Te Herenga Waka—Victoria University of Wellington, 2014) Abbott, Rachael; Bell, Ben; Nelson, Nicola
Translocations are increasingly being used for conservation management of threatened species (Sarrazin & Legendre, 2000). Outcomes are influenced by a range of factors including effects of early rearing experience, conspecific familiarity, density of resident conspecifics, and habitat quality at the release site, all of which may impact on the behaviour of released individuals and subsequent survival and fitness (Law & Linklater, 2007; Linklater & Swaisgood, 2008; Sarrazin & Legendre, 2000). Conservation success, defined as the realisation of goals set out at the start of a project, can be improved by detecting factors causing suboptimal outcomes and identifying potential solutions (Buner et al., 2011; Green et al., 2005; Mihoub et al., 2011). I aimed to expand current knowledge on factors influencing translocation outcomes by investigating the conservation management of the rowi (Apteryx rowi), the rarest species of kiwi. Current rowi conservation practices provide an opportunity to investigate this type of translocation management model. I provide new evidence and knowledge of behavioural mechanisms driving translocation success, include an expansion of current home range cognitive mapping theory relevant to conservation translocations, and present the first study of rowi home range behaviour (defined as the pattern of space use which leads to the emergence of a stable home range). Rowi conservation management involves removing eggs from the wild, hatching chicks in captivity, rearing on a predator free island until they are large enough to no longer be at risk of predation by stoats (Mustela erminae), then translocation back into the single remaining mainland population at Ōkārito forest. Over three years, experimental releases (n=66) were undertaken into both the existing population of rowi at South Ōkārito, and into an adjacent but unoccupied area of their former range at North Ōkārito. After intensive post-release monitoring, the effects of various elements of the translocation process on post-release survival, dispersal, conspecific association, habitat selection and home range behaviour were examined. An investigation into the effects of season of release, conspecific density, sex, and release group size on survival during the 90 day critical period following release, found release season and release group size are the most likely factors to influence post-release survival, with highest survival in spring, and for large release groups of four or more birds per release site. Habitat quality throughout the Ōkārito forest was estimated using invertebrate biomass as a proxy. A Geographic Information Systems (GIS) layer showing relative estimated invertebrate biomass was created and used to provide values of habitat quality at release locations and within home ranges. An investigation of the influence of habitat quality on post-release dispersal, conspecific association and home range behaviour found maximum dispersal distance was affected by the release site (North or South Ōkārito), and the interaction of release site and the estimated invertebrate biomass at the release location. Mean home ranges (± SE) of translocated rowi (3.35 ± 0.37 km²), were larger and of lower habitat quality than those of wild rowi (1.06 ± 0.09 km²). No effects of release group size on dispersal distance or conspecific association rates post-release were found. The effects of early rearing experience are proposed as a key factor influencing translocated rowi behaviour. By monitoring the survival, dispersal, conspecific association and home range behaviour resulting from the translocation of rowi reared in a non-natural social situation, I highlight the potential impact of prior social experience and social memory on cognitive mapping and home range establishment. This innovative approach has the potential to be a valuable expansion to current home range cognitive mapping theory, and warrants further study. Translocation is a vital tool in conservation, and has undoubtedly been instrumental in improving the situation of rowi since the first application to rowi conservation in the 1990s. This study has demonstrated that further improvements in the effectiveness and efficiency of translocations for conservation can be gained through sound scientific analysis of factors affecting the mechanisms leading to translocation success. Ongoing monitoring, analysis and reassessment of translocation management practices are recommended to ensure optimal conservation outcomes.
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BIOL327: Biology: Population and Community Ecology
(Victoria University of Wellington, 2010) Nelson, Nicola
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Conservation of Brothers Island Tuatara (Sphenodon Guntheri)
(Te Herenga Waka—Victoria University of Wellington, 1998) Nelson, Nicola
Brothers Island tuatara (Sphenodon guntheri) is one of the rarest reptiles in the world. Between 1995 and 1998, I studied fundamental aspects of its life history and demography, monitored and assessed results of the first contemporary tuatara translocation, and analysed the long term viability of existing and proposed populations. North Brother Island supports the only self-sustaining population of Brothers Island tuatara. About 350 adults are restricted to this single island of 4ha in Cook Strait, New Zealand. High annual adult survival (0.93 for males and females) and longevity (61-71 years) have been estimated from analysis of ten years of capture-recapture data and a point sample 40 years ago. Viability analysis, using the computer program VORTEX, indicates this population has a high probability of long-term survival, but that sex ratio, harvesting and small population size are primary risk factors. Genetic and environmental stochasticity were unable to be included in these analyses due to lack of information on effects. In 1995, 68 tuatara were translocated from North Brother to Titi Island, Marlborough Sounds, New Zealand. During 26 months of monitoring, 51% of released tuatara were recaptured. Adult tuatara on Titi Island are in better condition, as indicated by weight/length comparisons, than adults on North Brother Island. Translocated juveniles have increased by up to 106% in weight. Evidence exists for breeding on Titi Island. The translocation is progressing successfully, but it will take decades to confirm establishment. This population has a high probability of survival, but would benefit in the short-term from supplementation in the next ten years. The New Zealand Department of Conservation proposes to establish a third wild population of Brothers Island tuatara on Matiu/Somes Island. Population viability analysis was carried out to test founder scenarios for this population. A population founded on 20 adults (10 females and 10 males) harvested from North Brother Island and 29 juveniles available from a head-start program, had a high probability of long term survival. In summary, the conservation status of Brothers Island tuatara is improving and programmes appear to be progressing successfully.