Abstract
Dugongs (Dugong dugon) are listed as vulnerable to extinction due to rapid population reductions caused in part by loss of seagrass feeding meadows. Understanding dugong feeding behaviour in tropical Australia, where the majority of dugongs live, will assist conservation strategies. We examined whether feeding patterns in intertidal seagrass meadows in tropical north-eastern Australia were related to seagrass biomass, species composition and/or nitrogen content. The total biomass of each seagrass species removed by feeding dugongs was measured and compared to its relative availability. Nitrogen concentrations were also determined for each seagrass species present at the sites. Dugongs consumed seagrass species in proportion to their availability, with biomass being the primary determining factor. Species composition and/or nitrogen content influenced consumption to a lesser degree. Conservation plans focused on protecting high biomass intertidal seagrass meadows are likely to be most effective at ensuring the survival of dugong in tropical north-eastern Australia.
Highlights
Dugongs (Dugong dugon) are the last surviving species within the family Dugongidae (Grech, Sheppard & Marsh, 2011; Marsh & Lefevbre, 1994) and are listed as ‘vulnerable to extinction’ by the IUCN Red List of Threatened Species (IUCN, 2011)
We examine a sub-set of potential factors influencing the selection of seagrass species by dugongs feeding in intertidal seagrass meadows in tropical north Queensland, so as to improve our understanding of the relationship between dugong and their seagrass food
In the analysis of site-specific effects on the two predominant species, H. ovalis and H. uninervis, the relationship between above and below ground biomass was significantly different among sites (ANCOVA: H. ovalis: F4,102 = 21.54, p => 0.001; H. uninervis: F5,131 = 14.93, p => 0.001, see Supplemental Information 1)
Summary
Dugongs (Dugong dugon) are the last surviving species within the family Dugongidae (Grech, Sheppard & Marsh, 2011; Marsh & Lefevbre, 1994) and are listed as ‘vulnerable to extinction’ by the IUCN Red List of Threatened Species (IUCN, 2011). Dugong diet consists predominantly of seagrass and they are restricted in range to tropical and subtropical locations of the Indo-west Pacific where shallow seagrass meadows are common (Marsh et al, 1982; Marsh, O’shea & Reynolds III, 2011). Throughout most of this distribution they occur as small relatively isolated populations (Allen, Marsh & Hodgson, 2004), with the only substantial populations being found in northern Australian waters (Marsh, Grech & Hagihara, 2012; Marsh & Lefevbre, 1994; Marsh, O’shea & Reynolds III, 2011).
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