[MARMAM] New publications Australian humpback dolphins

Guido Parra Vergara guido.parra at flinders.edu.au
Thu Jan 14 14:16:15 PST 2016

Dear colleagues

On behalf of myself and my co-authors, I am pleased to announce three new articles on the biology and conservation of Australian humpback dolphins (Sousa sahulensis):

*         Parra GJ, Cagnazzi D (2016) Chapter Seven - Conservation Status of the Australian Humpback Dolphin (Sousa sahulensis) Using the IUCN Red List Criteria. In: Advances in Marine Biology (eds. Thomas AJ, Barbara EC), pp. 157-192. Academic Press. Available at: http://dx.doi.org/10.1016/bs.amb.2015.07.006

Australian humpback dolphins (Sousa sahulensis) were recently described as a new species endemic to northern Australia and potentially southern New Guinea. We assessed the species conservation status against IUCN Red List Criteria using available information on their biology, ecology and threatening processes. Knowledge of population sizes and trends across the species range is lacking. Recent genetic studies indicate Australian humpback dolphins live in small and relatively isolated populations with limited gene flow among them. The available abundance estimates range from 14 to 207 individuals and no population studied to date is estimated to contain more than 104 mature individuals. The Potential Biological Removal method indicates populations are vulnerable to even low rates of anthropogenic mortality. Habitat degradation and loss is ongoing and expected to increase across the species range in Australia, and a continuing decline in the number of mature individuals is anticipated. Considering the available evidence and following a precautionary approach, we considered this species as Vulnerable under IUCN criterion C2a(i) because the total number of mature individuals is plausibly fewer than 10,000, an inferred continuing decline due to cumulative impacts, and each of the populations studied to date is estimated to contain fewer than 1000 mature individuals. Ongoing research efforts and recently developed research strategies and priorities will provide valuable information towards the future conservation and management of Australian humpback dolphins.

*         Hanf DM, Hunt T, Parra GJ (2016) Chapter Eight - Humpback Dolphins of Western Australia: A Review of Current Knowledge and Recommendations for Future Management. In: Advances in Marine Biology (eds. Thomas AJ, Barbara EC), pp. 193-218. Academic Press. Available at: http://dx.doi.org/10.1016/bs.amb.2015.07.004

Among the many cetacean species that occupy Australian coastal waters, Australian humpback dolphins, Sousa sahulensis, are one of the most vulnerable to extirpation due to human activities. This review summarises the existing knowledge, presently occurring and planned research projects, and current conservation measures for humpback dolphins in Western Australia (WA). Rapid and wide-scale coastal development along the northern WA coastline has occurred despite a lack of baseline data for inshore dolphins and, therefore, without a precautionary approach to their conservation. The distribution, abundance, habitat use, and population structure of humpback dolphins remain poorly understood. Less than 1% of their inferred distribution has so far been studied to understand local population demography. The sparse data available suggest that WA humpback dolphins occur as localised populations in low numbers within a range of inshore habitats, including both clear and turbid coastal waters. Marine protected areas cover a third of their inferred distribution in WA, but the efficacy of these reserves in protecting local cetacean populations is unknown. There is a pressing need for coordination and collaboration among scientists, government agencies, industry bodies, Traditional Owners, and local community groups to fill in the gaps of information on humpback dolphins in WA. The recently developed strategies and sampling guidelines developed by state and federal governments should serve as a best practise standard for collection of data aimed at assessing the conservation status of humpback dolphins in WA and Australia.

*         Brown AM, Bejder L, Parra GJ, et al. (2016) Chapter Ten - Sexual Dimorphism and Geographic Variation in Dorsal Fin Features of Australian Humpback Dolphins, Sousa sahulensis. In: Advances in Marine Biology (eds. Thomas AJ, Barbara EC), pp. 273-314. Academic Press. Available at: http://dx.doi.org/10.1016/bs.amb.2015.08.002

Determining the sex of free-ranging cetaceans can be challenging. Sexual dimorphism among external features may allow inferences on sex, but such patterns may be difficult to detect and are often confounded by age and geographic variation. Dorsal fin images of 107 female and 54 male Australian humpback dolphins, Sousa sahulensis, from Western Australia (WA) and Queensland (QLD) were used to investigate sex, age and geographic differences in colouration, height/length quotient and number of notches. Adult males exhibited more dorsal fin notches (p < 0.001) and a significantly greater loss of pigmentation on the upper half of their dorsal fins (p < 0.001) than did adult females. These differences likely reflect that males experience a higher frequency and/or intensity of intraspecific aggression than females. In QLD, heavily spotted dorsal fins were more frequent among females than males (p < 0.001). Logistic regression analyses revealed that dorsal fin spotting and loss of pigmentation on the upper half of the dorsal fin provided the best model parameters for predicting the sex of sampled adults, with 97% accuracy. This technique offers a rapid, non-invasive method for predicting sex in Australian humpback dolphins, which could potentially be applied to populations throughout their range. In contrast to adults, presumed immature animals showed little or no loss of pigmentation or spotting; however, the rate of development of these features remains unknown. There were pronounced differences between QLD and WA in the intensity of spotting on dorsal fins and the extent of pigmentation loss around the posterior insertion and trailing edge of the dorsal fin. While based on a limited sample size, these geographic differences may have conservation implications in terms of population subdivision and should be investigated further.

Articles available at links above or email: guido.parra at flinders.edu.au<mailto:guido.parra at flinders.edu.au>

All the best,

Guido J. Parra, PhD
Senior Lecturer | School of Biological Sciences Flinders University
* Staff: http://www.flinders.edu.au/people/guido.parra
Research leader | Cetacean Ecology, Behaviour and Evolution Lab (CEBEL)
* Lab: www.cebel.org.au<http://www.cebel.org.au/>

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