Dear MARMAM subscribers,

 

We are pleased to announce the publication of two papers on southern Australian bottlenose dolphins:

 

Diaz-Aguirre F., Parra G., Passadore C. & Möller L. 2018. Kinship influences social bonds among male southern Australian bottlenose dolphins (Tursiops cf. australis). Behavioural Ecology and Sociobiology 72: 190. https://doi.org/10.1007/s00265-018-2621-4

full-text view-only: https://rdcu.be/bcFwc

 

Passadore C., Möller L., Diaz-Aguirre F. & Parra G. 2018. Modelling dolphin distribution to inform future spatial conservation decisions in a marine protected area. Scientific Reports 8 (1), 15659. https://doi.org/10.1038/s41598-018-34095-2

 

Abstracts:

Kinship influences social bonds among male southern Australian bottlenose dolphins (Tursiops cf. australis).

Male mammals employ a wide variety of mating strategies in order to increase their reproductive success, which in turn influence their social behavior. In some populations of bottlenose dolphins (Tursiops spp.), males cooperate in small groups or alliances to gain access to females for mating. However, the occurrence of these male cooperative groups has been predicted to occur only under certain social and ecological conditions, driven by factors such as differences in population density, operational sex ratio, and sexual size dimorphism. Here, we used generalized affiliation indices, social network techniques, and maternally and bi-parentally inherited genetic markers to investigate the affiliation patterns and genetic relatedness among male southern Australian bottlenose dolphins (Tursiops cf. australis) in a small embayment in South Australia. Photo-identification data and biopsy samples were collected in Coffin Bay from 2013 to 2015 through systematic boat-based surveys. We found that highly sighted male dolphins formed 12 social clusters composed of two to five individuals. Genetic analyses revealed that general male affiliation patterns were significantly correlated with mtDNA haplotype sharing. In addition, preferred affiliates showed significantly higher levels of genetic relatedness compared to casual and avoided male pairs. Our results corroborate theoretical expectations for the formation of social bonds in small delphinids and suggest that a high density of dolphins, with an expected skewed operational sex ratio and no apparent sexual size dimorphism, is likely to have favored the formation of strong male affiliations. In addition, the availability of genetic relatives within the population may have favored male affiliations based on kinship relationships.

 

Modelling dolphin distribution to inform future spatial conservation decisions in a marine protected area.

As marine predators experience increasing anthropogenic pressures, there is an urgent need to understand their distribution and their drivers to inform spatial conservation planning. We used an ensemble modelling approach to investigate the spatio-temporal distribution of southern Australian bottlenose dolphins (Tursiops cf. australis) in relation to a variety of ecogeographical and anthropogenic variables in Coffin Bay, Thorny Passage Marine Park, South Australia. Further, we evaluated the overlap between current spatial management measures and important dolphin habitat. Dolphins showed no distinct seasonal shifts in distribution patterns. Models of the entire study area indicate that zones of high probability of dolphin occurrence were located mainly within the inner area of Coffin Bay. In the inner area, zones with high probability of dolphin occurrence were associated with shallow waters (2–4 m and 7–10 m) and located within 1,000 m from land and 2,500 m from oyster farms. The multi-modal response curve of depth in the models likely shows how the different dolphin communities in Coffin Bay occupy different embayments characterized by distinct depth patterns. The majority of areas of high (>0.6) probability of dolphin occurrence are outside sanctuary zones where multiple human activities are allowed. The inner area of Coffin Bay is an important area of year-round habitat suitability for dolphins. Our results can inform future spatial conservation decisions and improve protection of important dolphin habitat.

Regards,