Otter research in Asia: Trends, biases and future directions

Asia is home to five of the 13 species of otters found around the world. While studies on the otter have been increased considerably over the years, the focus and pattern of research in Asian Otter has not been analyzed properly. Here, we review the English literature published online on Asian otter species from 1990 to 2019 to portray trends and current state of research in otters to identify research gaps and suggest future research directions. A total of 244 original research papers were retrieved from online sources and categorized by research themes. Publications were analyzed using descriptive statistics, line graphs, Kendell's tau b coefficient, Kruskal-Wallis test, Wilcoxon rank sum test and a generalized linear model to detect trends in thematic and geographic focus. Our review documents a notable increase in the number of publications in Asian otter species after 2005. A persistent geographical bias was observed in the published studies where 32% of the total papers come from South Asia and 25% from South East Asia with lesser papers from Western Asia and no papers from Central Asia. Baseline surveys are the most common studies, followed by studies on ecology, genetics, conservation, trade and disease. Overall, our review shows that the status, distribution and trend of Asian otter population is still limited and more research is needed for less studied otter species, such as the hairy-nosed otter (Lutra sumatrana) and Pacific populations of the sea otter (Enhydra lutris). We also found that information on the potential impacts of climate change on otter species, and taxonomy as well as phylogenetic relationships among Asian otters is limited. We recommend that more studies be carried out in regions of Western Asia and Central Asia firstly on status and distribution and then on their ecology to improve our understanding of otter species in the face of increasing impacts on their habitats. (C) 2020 The Author(s). Published by Elsevier B.V.