Animals that establish new sites near the edge of the species' range may be vulnerable to disturbance as they are low in numbers and are not tied to the sites. Pinniped distributions world-wide are changing as many species are recolonizing areas of their former ranges and establishing new colonies. Little research is available on the impact that vessel presence may pose on pinnipeds at such sites. This study documents responses of New Zealand fur seals to vessels in the Bay of Plenty, New Zealand, at a recently established breeding colony. Fur seal behavior at the breeding location was recorded in the presence of vessels. GLMM and GAM analyses revealed that fur seal responses varied with month, time of day, duration of vessel exposure, and the distance to the vessel. Age and sex of the seals, and the number of seals present also influenced fur seal response. Fur seals at this site became disturbed when vessels approached to the 10-20 m distance category, and a precautionary minimum approach distance of 50 m has been suggested. This research provides direction for monitoring and minimizing impacts of vessels on fur seals, especially where new sites are being colonized.
Movement of species beyond their indigenous distribution can fundamentally alter the conservation status of the populations involved. If introductions are human-facilitated, introduced species could be considered pests. Characterizing the colonization history of introduced species can therefore be critical to formulating the objectives and nature of wildlife management strategies. The black swan (Cygnus atratus) is native to Australia but is considered a reintroduced species in New Zealand, where the endemic population was reported extinct during the 19th century. After the reintroduction of a small number of individuals from Australia, the New Zealand population expanded unexpectedly rapidly, which was attributed to simultaneous waves of migration fromAustralia. An alternative, but hitherto unformalized, hypothesis is that local extant populations remained and admixed with introduced individuals. To contribute to our understanding of the reintroduction history of the species, we investigated dispersal patterns and demographic histories of seven populations from Australia and New Zealand, using population genetic inferences from a microsatellite dataset. Our results on genetic structure, dispersal rates, and demographic histories provide mixed evidence on the origin of New Zealand black swans. The hypothesis that reintroduced individuals mixed with remaining local individuals and that the subsequent dramatic population expansion may have been due to genetic rescue of the inbred indigenous population cannot be discarded and needs further investigation. K E Y W O R D Sconservation, Cygnus atratus, kakianau, pest species, phylopatry
Recently, several research groups have published insights into the evolutionary history of black swans, especially the history of these species in New Zealand. These studies use different evidence bases, address different questions, and provide different perspectives on possible histories. Here, in response to Rawlence et al., we reiterate the aspects of our study and its findings. We conclude that all recent contributions have been valuable, and are not necessarily mutually exclusive in regard to their interpretation. Our paper on New Zealand extant black swans (Cygnus atratus; Montano et al., 2017) suggests that individuals of the species were still present on the island before the human-driven reintroduction that was documented to occur in the 19th century. As we point out the limitations of our inferential analysis, we highlight the multiple evolutionary scenarios that can lead to the signatures of an old coalescent time among extant C. atratus lineages in NZ. Remaining individuals of the species that migrated from Australia previously to the human reintroduction could have admixed with newly introduced individuals which would be detected as an old coalescent time for the current population.Our study does not indicate a specific time for the potential spontaneous immigration events from Australia to NZ as this information is not recoverable in our analyses. Most importantly, we simply address the admixture of populations of the same species and never call into question the extinct species of C. sumnerensis. Assessment of hybridization between C. sumnerensis and C. atratus is beyond the scope of our paper, and it is not addressable without adding genetic samples of C. sumnerensis to our analysis. In reply to Rawlence et al., the findings of Rawlence et al., 2017are not in contrast to ours as the two studies do not address the same question (i.e., extinction of C. sumnerensis from the current NZ black swans genetic pool and the potential population admixture of C. atratus between introduced individuals and local individuals already living in NZ, respectively). Rawlence et al., 2017 indeed report that fossils of NZ black swans after Maori colonization belong to C. atratus, the species that we consider in our paper, and they also suggest that spontaneous migration of C. atratus occurred from Australia to NZ previous to human-driven reintroduction. All these aspects support the hypothesis suggested by our paper about a population admixture of C. atratus between local and introduced individuals of black swans in NZ. Therefore, the status of current NZ C. atratus could fit the definition of xenonative or restored native defined in Crees & Turvey, 2015, depending on the results that will be achieved with further genetic investigation.In conclusion, besides specific limitations of our statistical analysis that are explicitly noted in our study, we recommend further investigation on the genetic origin of current NZ C. atratus populations as this aspect of our research is not conclusive but cannot be addressed by the a...
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