Semi-aquatic Mammals: Ecology and Biology

Freshwater semi-aquatic mammals represent some of the world’s rarest species living within some of its most threatened habitats. Better known species, including the platypus, North American and Eurasian beavers, the common hippopotamus, and various species of otters, are immediately identifiable as mammals that bridge the divide between an aquatic and terrestrial lifestyle. Semi-aquatic Mammals: Ecology and Biology weaves the evolutionary and ecological stories of these species into those of dozens of other less familiar species that are equally fascinating. With so many populations of these species in decline or of unknown status, it was time to compile what is known about these freshwater specialists to help us understand why these mammals are so special, and to help us discover what we still need to learn to ensure their ongoing survival.

There are more than 140 species of mammals that have an obligatory dependence on freshwater habitats. Therein lies the problem, freshwater and riparian habitats are disappearing at much faster rates than other habitats. Despite the rarity of intact aquatic ecosystems, freshwater semi-aquatic mammals are found on all continents, except for Antarctica and some of the larger oceanic islands, and represent all three major groupings of mammals. In spite of this extensive geographic and evolutionary range, so little is known about these remarkable species as a group. For example, much of what we know about the water opossum of Central and South America is accessible mainly through academic papers and the occasional mention in field guides. Even less is known about the threatened aquatic genet of central Africa and the endangered otter civet found only in select freshwater habitats of Southeast Asia. Semi-aquatic Mammals: Ecology and Biology presents a journey through time from the prehistoric relatives and extinct lineages of freshwater mammals to their current status and the management actions that aim to ensure species persistence in the face of ongoing challenges.

Along the way, this book combines extensive research into the physiology, morphology, and reproductive biology that allows these species to succeed in the thermodynamically and physically challenging environment of water, while meeting the demands of moving efficiently and safely on land. Not only are these mammals effective predators, they are targeted prey species in both terrestrial and aquatic habitats. Specialized physical adaptations, such as modified feet, fur, and tails, combined with equally intriguing behavioural adaptions allow some species to change entire ecosystems. Beavers build extensive systems of dams and channels that create aquatic networks rich in biodiversity and hydrological complexity. As the common hippopotamus moves from ponds to upland grasslands their channels create linkages for other species. Original illustrations by Dr. Meaghan Brierley bring these species and habitats to life throughout the book.


While compiling the research and then in writing this book, I found myself surrounded by a world of individual researchers whose work collectively formed a story of some of the most tenacious and equally fragile species of mammals on Earth. A small research note brought to life a prehistoric otter previously unknown to science, while another discussed the mechanism of oxygen exchange in modern otters with increased foraging depth. Together a story began to form that convinced me that if these species succeed despite current challenges, so will so many other species. At the same time, it also became apparent that despite the rarity of many of these mammals, the introduction of some semi-aquatic mammals beyond their natural ranges has created devastating challenges to ecosystems and other species around the world. Coypu, muskrats, American mink, and North American beavers are formidable competitors, and in the case of the American mink, noteworthy predators of other semi-aquatic mammals. In some areas, control efforts have been very successful, while other areas provide a cautionary tale of how difficult it can be to counter the mistakes of the past. I included specific chapters on conservation and management approaches to help set a path forward.

What gave me the greatest hope while writing the book is the successful recovery of species of beavers and river otters following their near-devastating population declines from overhunting in both North America and Eurasia. Less successful—but equally persistent and gradually improving—efforts to save populations of European mink and Russian desmans also provide hope. The International Union for Conservation of Nature (IUCN) tracks the status of all wild species, and provides guidance for population recovery. The work of species specialists, who often volunteer their time and expertise to the IUCN, was invaluable when presenting the conservation status for each species. Once again, as I wrote the book, the work of countless researchers and conservationists highlighted the precarious nature of these species and the habitats on which they depend. My hope is that Semi-aquatic Mammals: Ecology and Biology brings together the passion and commitment of those whose research and conservation efforts provide essential insights into these species. In so doing, this book can give voice to these remarkable mammals who reveal a path to ecological success against all odds.

Order Semi-aquatic Mammals: Ecology and Biology – published on October 13, 2020 – at the following link:

Glynnis A. Hood is a Professor of Environmental Science at the University of Alberta’s Augustana Campus. She is the author of Semi-aquatic Mammals: Ecology and Biology and The Beaver Manifesto.

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