The Indonesian island of Sulawesi is widely considered a mammal conservation hotspot, mainly due to the high number of threatened endemic species with limited geographical ranges that are found there, and also due to the biogeographical importance of Sulawesi as the largest island in the Wallacea region. To date, there has been no comprehensive review to evaluate the status of what we know about mammals in Sulawesi. The overarching goal of our review is to contribute towards identifying knowledge gaps in the biology and ecology of mammals in Sulawesi. Our specific aims were to: 1) identify taxonomic and geographic bias in published research; 2) identify biases within existing ecological knowledge; and 3) identify key research priorities for the future. Our review covers a total of 280 articles (published between 1921 and 2017) on 144 species of mammal from Sulawesi. Through our review we found: 1) a strong taxonomic bias, with the majority of studies being conducted on primates (59% of published articles); 2) a geographic bias, where significantly fewer studies took place in the provinces of West Sulawesi and Gorontalo; and 3) a bias in research topics, with most studies (50% of published research) focusing on taxonomy and behaviour. As an outcome of this review, we provide specific recommendations for future researchers, including: 1) a checklist of understudied species, with particular emphasis on understudied species of conservation concern; 2) a checklist of understudied research topics, with an emphasis on the need to conduct detailed auto-ecological studies; and 3) suggestions on how to adjust research methods on population and habitat studies.
