How much seagrass does a dugong need? Metabolic rate of live wild dugongs, Dugong dugon , determined through indirect calorimetry (oxygen consumption)

Abstract

Deterioration of seagrass beds worldwide has raised concern about the future of dugongs because almost all aspects of their life history depend on availability of seagrass. Understanding their energy metabolism and consequently how much seagrass they need will inform protective conservation strategies for dugongs. This study determined resting metabolic rate (RMR) in five wild‐caught adult dugongs by measuring oxygen consumption (O 2 ). Measurement conditions met assumptions for RMR, except that dugongs were not postabsorptive, thus a postprandial (pp) allometric equation for herbivorous mammals of similar size was used to predict an expected RMR pp for dugongs of known mass. O 2 was measured for 30 min in a metabolic tank after brief habituation. Dugongs' RMR pp was approximately half that predicted for their body mass but was higher than for manatees. Based on dugongs' RMR pp and considering plant caloric and water content, the daily minimum intake of fresh weight seagrass was 40–65 kg Halophila ovalis , or 20–40 kg Halodule spp. Greater seagrass intake would be required for growing and reproducing dugongs. Slow growth and protracted reproductive rates of dugongs are likely related to limitations in seagrass energy and nutrients. To ensure viability of this vulnerable species, it is critically important to conserve extensive healthy seagrass beds.

Bibliographic Information