I started my journey into the wet, blue and green world of the Sirenia from the Preface, in which the authors provide a brief and concise overview of the only herbivorous, fully aquatic mammals. The breadth of the information is based on the synthesis and review of numerous scientific publications, from genetics to behavioural studies and to the authors' own discoveries in the field. The title of the book is general and thus one would expect purely scientific information rich in facts and diagrams. However, starting with the Introduction the authors stimulate the reader, describing the dugong as ‘like a manatee that goes to the gym’ in explaining the body shape differences between manatees and dugongs. Quotations from H. Melville and D. Attenborough on the taxonomy and appearances of these mammals further enrich the book, which I recommend not only to professionals but to a wider audience.
The next chapter follows the route of Georg Wilhelm Steller on MV St Peters and the discovery of Steller's sea cow in the 1740s. Human acquaintance with this species was very short—it was extirpated just 27 years after its discovery, by ruthless hunting. The facts are enriched with illustrations and excerpts from Steller's notes on the animal's biology and on techniques used by hunters.
The chapter on the evolutionary history of the Sirenia introduces the numerous species that branched from its ancestors more than 50 million years ago. Interestingly, new fossil records show that this order of mammals had a much wider range and greater adaptability than previously assumed, and molecular analyses puts them in the same assemblage as golden moles and elephant shrews.
Chapter 4 is dedicated to feeding ecology and its importance to the conservation and survival of the four modern species of the Sirenia. The authors discuss the theory of optimal foraging and explore the impacts of dugongs and manatees on the productivity and structure of plant communities. The diagrammatic presentation of the skulls of the species nicely supports the differences in feeding habits. The following two chapters provide a wealth of information on the life history, behaviour and habitat of the Sirenians, and range from individual biology to peculiarities of social behaviour such as the ‘muzzle to muzzle kiss’ that is possibly used for information exchange, through chemoreception.
From the preface to the last chapter one can hear a silent ‘Sirenian trill’ echoing the challenges to ensure the survival of these mammals. The sound gets louder and culminates in the chapter reviewing established and potential threats to Sirenians, ranging from hunting to the ‘cold water syndrome’ affecting manatees in Florida. The authors point to one of the main weak links in the chain of conservation actions—the human factor—in which easier management activities are prioritized instead of applying the best available solutions simply because such actions could require more effort. The thread of conservation concerns continues into the analysis and discussion of the Red List categorizations of the Sirenia. Once again some of the notions cause further reflection—in this case on the generalized global assessment of the probability of the extinction of species and failures to highlight the urgency of an action at the critical point in time.
This journey around the world through the life of manatees and dugongs, participants in and users of marine and coastal ecosystems alongside humans and other species, ends with a framework for conservation of the Sirenians. This framework includes tools and actions such as targeted education, long-term commitments, and partnerships—all well known and tried but not necessarily easy to implement.
In summary, this book is a synthesis and communication tool for the ongoing work of hundreds of people, from field researchers in Florida or students in Australia to villagers in Senegal. The aim is to provide a creative and practical way to sustain a healthy environment for these unique aquatic mammals, and for us all.
