The biology and ecology of Sirenia are comprehensively reviewed by Marsh et al. (2011) and Reep and Bonde (2006), so the reader is directed to these for background on these species. The study of manatee health dates back to the 1800s, when animals were transported from Central and North America to Europe (Murie 1870). The life span of these individuals was short, and sparse health data were collected. More recently, dugongs (Dugong dugon) have been held with greater success under human care: in India in the 1950s (Jones 1967); an orphaned dugong in Cairns Oceanarium, Australia, in the 1960s (Oke 1967); and in a few other locations since the 1980s (Lanyon et al. 2006; Tsukinowa et al. 2008; Burgess et al. 2013). Veterinarians initially evaluated a limited suite of blood parameters (Medway, Black, and Rathburn 1982). More extensive efforts to assess the health of wild sirenian populations have been more recent (Bonde, Aguirre, and Powell 2004; Lanyon et al. 2010; Sulzner et al. 2012). Health assessments (HAs) have been performed in conjunction with tagging operations in the United States, with HAs performed to enhance the understanding of animals’ health during taggings, thus focusing on detection of adverse effects of capture and restraint, and any therapeutic interventions, when needed. Techniques for HA developed during these tagging operations have now been widely shared, adapted, and used for health investigations of sirenians throughout their habitats (Bonde et al. 2012; Sulzner et al. 2012; Walsh and de Wit 2014). More recently, as health concerns in wild manatees, such as toxicoses, diseases, and injuries, have been documented (see Chapter 43 ), HA emphasis is shifting, with the aim being to determine health status of individual animals, in order to better understand environmental factors influencing population health, vital signs, and changes in health status. In response to concerns about the health of dugongs, and an 858inability to determine cause of death in a significant proportion of recovered carcasses on the east coast of Australia, health assessment efforts on wild dugongs have been conducted annually there since 2008 (Lanyon et al. 2010, 2015; Lanyon, Sneath, and Long 2012).