Regional Studies in Marine Science 8 (2016) 459–465 Contents lists available at ScienceDirect Regional Studies in Marine Science journal homepage: www.elsevier.com/locate/rsma Reproductive parameters of the Taiwanese humpback dolphin (Sousa chinensis taiwanensis) Wei-Lun Chang a,b,1 , Leszek Karczmarski b,*,1 , Shiang-Lin Huang a,b , Glenn Gailey b , Lien-Siang Chou a,* a Institute of Ecology and Evolutionary Biology, National Taiwan University, Roosevelt Rd., Taipei 106, Taiwan b The Swire Institute of Marine Science, School of Biological Sciences, The University of Hong Kong, Pokfulam Rd., Hong Kong highlights • Births occur throughout the year but decrease in late summer through mid-winter. • Calving interval is ∼3.3 years; less than 3 calves survive annually to the age of 1-year. • Calf survival rate and survivorship decrease across the initial three years of life. • Low recruitment rate and long calving interval imply a slow population growth. • The population has a very limited capacity to resist anthropogenic stress. article info Article history: Received 3 May 2016 Received in revised form 31 July 2016 Accepted 3 August 2016 Available online 10 August 2016 Keywords: Taiwanese humpback dolphin Calving interval Calf survivorship Crude birth rate Annual recruitment rate Photo-identification abstract Reproductive parameters represent an integral component of species’ natural history and are essential for well-informed conservation management, but often difficult to access in marine mammals. In this study we estimated the reproductive parameters, including crude birth rate, calf survivorship, annual recruitment rate and calving interval of the Taiwanese humpback dolphin, Sousa chinensis taiwanensis, a critically endangered small population inhabiting inshore waters off the Taiwan west coast. With over 400 boat-surveys completed across five years, 21 mother–calf pairs were individually identified through photographic identification techniques. Births occurred in both warm and cold months, but seemingly decreased in late summer through mid-winter. The reproductive parameter estimates were 0.046 for the crude birth rate, 0.667 for the survival rate to the Age-1, 0.041 for the annual recruitment rate and 3.26 years for the calving interval. Generally, between one and three calves (mean = 2.75) survive annually to the age of 1-year. The low recruitment rate and relatively long calving interval imply a slow population growth and hence limited capacity to resist anthropogenic stress. As the annual recruitment may be lower than current mortality figures, we emphasize the need to re-assess the impact-mitigation baselines and population viability based on these latest reproductive parameter estimates. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Reproductive parameters, including calving interval, birth rate, calf survivorship, and annual recruitment rate, represent an integral component of species’ life history. These parameters become especially important when considering conservation measures for threatened or endangered animals, as reliable * Corresponding authors. E-mail addresses: leszek@hku.hk (L. Karczmarski), chouls@ntu.edu.tw (L.-S. Chou). 1 Wei-Lun Chang and Leszek Karczmarski contributed equally to this work. estimates of reproductive parameters are essential in assessing population viability and forecasting population trends, which in turn facilitates the classification of the population status (Currey et al., 2009; Huang et al., 2012; Huang and Karczmarski, 2014). For cetaceans, the reproductive parameters can be estimated through the examination of stranded or by-caught specimens (Perrin and Reilly, 1984; Rosas and Monteiro-Filho, 2002; Jefferson et al., 2012), or through a periodic sampling of wild populations with photographic identification (photo-ID) techniques (Wells and Scott, 1990; Herzing, 1997; Mann et al., 2000); the latter is particularly effective for relatively small populations with limited ranges (e.g. Wells, 2014). http://dx.doi.org/10.1016/j.rsma.2016.08.001 2352-4855/© 2016 Elsevier B.V. All rights reserved.