The Marine Mammal Research Group at Otago University is pleased to announce two new publications on the distribution and habitat preferences of bottlenose dolphins in Fiordland, NZ:
Bennington S, Rayment W, Currey R, Oldridge L, Henderson S, Guerra M, Brough T, Johnston D, Corne C, Johnson D, Slooten L, Dawson S (in press) Long-term stability in core habitat of an endangered population of bottlenose dolphins (Tursiops truncatus): Implications for spatial management. Aquatic Conservation Marine and Freshwater Ecosystems. https://doi.org/10.1002/aqc.3460 ABSTRACT: A small population of approximately 68 bottlenose dolphins, Tursiops truncatus, resident in Doubtful Sound, New Zealand, is subject to physiologically challenging conditions, and is exposed to anthropogenic pressure from tourism. • A voluntary Code of Management incorporating dolphin protection zones (DPZs), in which tour boat access is limited, was established in 2008. • Kernel density estimation (KDE) was used to quantify dolphin habitat use over a 13‐year period in order to describe seasonal variation in habitat use and consistency of habitat use over a decadal period, and to provide quantitative estimates of the extent of overlap between DPZs and core areas (50% volume contour) of habitat use. • Habitat use varied seasonally, with the inner fjord area used more frequently in warmer months, and with a shift in use to the outer fjord in colder months. Patterns in habitat use were highly consistent over the 13‐year duration of the study. • The spatial overlap between the area of core dolphin habitat and DPZs was low (<18%) overall, and some DPZs were rarely used during colder periods. • Consistency in habitat use through time vindicates spatial management, but low overlap between core habitat and current DPZs suggests that an expansion of the DPZ areas would confer greater protection. Bennington S, Rayment W, Dawson S (2020) Putting prey into the picture: improvements to species distribution models for bottlenose dolphins in Doubtful Sound, New Zealand. Marine Ecology Progress Series 653:191-204. https://doi.org/10.3354/meps13492 ABSTRACT: Species distribution models (SDMs) often rely on abiotic variables as proxies for biotic relationships. This means that important biotic relationships may be missed, creating ambiguity in our understanding of the drivers of habitat use. These problems are especially relevant for populations of predators, as their habitat use is likely to be strongly influenced by the distribution of their prey. We investigated habitat use of a population of a top predator, bottlenose dolphins Tursiops truncatus, in Doubtful Sound, New Zealand, using generalised additive models, and compared the results of models with and without biotic predictor variables. We found that although habitat use by bottlenose dolphins was significantly correlated with abiotic variables that likely describe foraging areas, introduction of biotic variables describing potential prey almost doubled the deviance explained, from 19.8 to 39.1%. Biotic variables were the most important of the predictors used, and indicated that the dolphins showed a preference for areas with a high abundance of a reef fish, girdled wrasse Notolabrus cinctus. For the dolphins of Doubtful Sound, these results show the importance of prey distribution in driving habitat use. On a broader scale, our results indicate that making an effort to include true biotic descriptors in SDMs can improve model performance, resulting in better understanding of the drivers of distribution of marine predators. Please email me at [email protected] if you would like to request pdfs.
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