Temporal changes in habitat use by dugongs in a spatially restricted coral reef environment

Abstract

Context. The dynamic habitat use by dugongs (Dugong dugon) in small coral reef lagoon systems spatially limited by tides is not well understood and has hampered adaptive management. Aims. We investigated how dugongs locally used a high conservation value coral-reef lagoon system during different seasons and tides to support local management. Methods. We conducted local-scale aerial surveys to document the seasonal and tidal changes in the distribution and number of dugongs over seagrass and non-seagrass coral reef habitats in a small lagoon in New Caledonia. The surveys were conducted fortnightly over 18 months in different seasons and at different tides. Temperature loggers and existing local footage of dugong herding behaviour were used to study the habitat use and behaviour of the animals in the area. Key results. More dugongs were sighted in Cap Goulvain during the cool season than during the warm season. As tides restricted access to the intertidal seagrass meadows and during the cool season, more dugongs were sighted outside the lagoon on the fore reef shelf outside the lagoon. Dugongs were resting in large aggregations during their use of this non-seagrass habitat. Conclusions. Our study emphasises the importance of non-seagrass habitats for dugongs in spatially restricted coral reef environments as well as the importance of considering outer lagoon habitats as key dugong management areas. This study also adds evidence of behavioural thermoregulation in dugongs. Implications. The development of dynamic management strategies is essential, especially where different habitats should be protected at different times of the year.