Freshwater semi-aquatic mammals include species from 1/3 of all mammalian orders, and represent some of the world’s most endangered mammals. In many cases, loss of just one species can remove an apex freshwater predator or keystone species. Habitat degradation and illegal/unregulated harvesting are some of the key factors in declines of freshwater semi-aquatic mammals on a global scale. Coupled with these factors is a warming climate and its impact on ecological function and resilience of freshwater systems. Despite their near global distribution, little is known about current research needs for conservation planning and adaptive management for many of these species. Data gaps leave these species and their ecological role in aquatic systems at risk. My research used a multi-tiered approach. Firstly, I identified all semi-aquatic (“freshwater/terrestrial”) species on the IUCN Red List of Threatened Species and aggregated findings to determine species status, population trends, and threats (n = 138 species). Using ISI Web of Science database, I performed a systematic review of each species to quantify peer-reviewed research over 20 years and the nature of that research (e.g., population monitoring, human-wildlife conflicts, phylogeny and genetics, physiology and anatomy). Finally, I identified areas where future research is warranted.
Results/Conclusions
Currently, 14.5% species of freshwater mammals are endangered, 13.8% vulnerable to extinction, 9.4% near threatened, and 15.9% data-deficient. Almost 1/2 of these populations are in decline, while only one species, the Eurasian beaver, has increasing populations. Of 44% classified as least concern, 25.8% have declining populations. Populations of other species are stable (17.4%), or unknown (33.3%). Within the literature, geographic isolation is inversely associated with the number of publications per species rather than species rarity. The greatest number of papers represent North American and Eurasian species, despite the larger representation of semi-aquatic mammals in Africa and South America. Areas of research are diverse, ranging from emerging diseases and conservation threats; however, for species with the lowest representation in the literature, papers tend toward morphological investigations and general habitat associations. For conservation to be effective, specific research needs must be targeted to the most vulnerable species and the ecological systems on which they depend. Semi-aquatic mammals depend on increasingly compromised aquatic habitats, which makes these mammals vulnerable to climate change and habitat loss, and adds urgency to their conservation.