Diet of Dugongs: Are They Omnivores?

Preen, Anthony

doi:10.2307/1382325

Cited by 73 publications

(46 citation statements)

References 29 publications

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“…This finding is corroborated by previous research, which has demonstrated that dugongs selectively feed within coastal seagrass habitat (Preen 1995a,b, Marsh et al 2002, 2003, Sheppard et al 2007, Rajamani 2009). In a localized study in northern Sabah, Rajamani (2009) noted high concentrations of seagrass communities in waters within the intertidal zone and dugong feeding trails less than 1 km from shore.…”

Section: Discussionsupporting

confidence: 88%

Modeling habitat and bycatch risk for dugongs in Sabah, Malaysia

Briscoe¹,

Hiatt²,

Lewison³

et al. 2014

Endang. Species. Res.

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Bycatch of marine megafauna in fishing gear is a problem with global implications. Bycatch rates can be difficult to quantify, especially in countries where there are limited data on the abundance and distribution of coastal marine mammals, the distribution and intensity of fishing effort, and coincident interactions, and limited bycatch mitigation strategies. The dugong Dugong dugon is an IUCN-listed Vulnerable species found from the eastern coast of Africa to the western Pacific. As foragers of seagrass, they are highly susceptible to bycatch in small-scale fisheries. To address the knowledge gaps surrounding marine mammal bycatch, we used existing survey and fishing effort data to spatially characterize the risk of bycatch for this species. Using Sabah, Malaysia, as a case study, we employed presence-only modeling techniques to identify habitat associations of dugongs using a maximum entropy distribution model (MaxEnt) based on published sightings data and several geophysical parameters: coastal distance, depth, insolation, and topographic openness. Model outputs showed distance from the coast as the highest-contributing variable to the probability of dugong presence. Results were combined with previously published fishing effort maps of this area to develop a predictive bycatch risk surface. Our analyses identified several areas of high risk where dugong surveys were conducted, but also identified high-risk areas in previously unsurveyed locations. Such methods can be used to direct field activities and data collection efforts and provide a robust template for how existing sightings and fishing effort data can be used to facilitate conservation action in data-limited regions.

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Section: Discussionsupporting

confidence: 88%

Modeling habitat and bycatch risk for dugongs in Sabah, Malaysia

Briscoe¹,

Hiatt²,

Lewison³

et al. 2014

Endang. Species. Res.

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“…Moreover, sirenians are almost exclusively consumers of angiosperms and eat algae in significant amounts only when angiosperms are scarce (e.g., after storms, Spain and Heinsohn, 1973; or in the range of the extinct Steller's sea cow [Hydrodamalis], Domning, 1978); so far as is known, this has always been true. Sirenians also eat animals on occasion (e.g., Powell, 1978;Preen, 1995), but never, apparently, as a major part of the diet. We, therefore, seem justified in considering tropical marine sirenians as obligate seagrass consumers for all practical purposes, and as the only potential consumers of seagrass rhizomes.…”

mentioning

confidence: 99%

Use of tusks in feeding by dugongid sirenians: Observations and tests of hypotheses

Domning

Beatty

2007

The Anatomical Record

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Most living and fossil sea cows of the subfamily Dugonginae (Dugongidae, Sirenia, Mammalia) are characterized by large upper incisor tusks, which are thought to play an important role (at least primitively) in feeding on seagrass rhizomes. Testing this hypothesis is difficult, because the only extant tusked sirenian (Dugong dugon) is morphologically and perhaps behaviorally aberrant. The tests attempted here involve examination of stomach contents of wild Recent dugongs, experiments using plastic replicas of diverse tusks to harvest seagrasses, gross anatomical observations on tusks and skulls, measurements of tusk tip geometry, and observations of microwear on tusks. We conclude that (a) male D. dugon (with erupted tusks) do not consume more rhizomes than females (without erupted tusks); (b) the tusks do not play a significant role in feeding in the modern dugong; (c) larger, more bladelike tusks are more effective at harvesting rhizomes, but the effect of shape was not experimentally separated from the effect of exposed tusk length; (d) some fossil dugongines show apparent cranial adaptations for downward and backward cutting motions of their large, bladelike tusks; (e) geometry of wear surfaces is consistent with use of at least the more bladelike tusks as cutting instruments; (f) preliminary observations of microwear in D. dugon do not indicate more than occasional use of the tusks in purposeful harvesting of rhizomes, and then only opportunistically by large adult males. The hypothesis of such tusk use by extinct dugongines (in contrast to the living species) is so far corroborated, but available data and tests do not suffice to establish this conclusively. Anat Rec, 290:523-538, 2007Rec, 290:523-538, . 2007 Wiley-Liss, Inc.Key words: Sirenia, Dugongidae; Dugong dugon; tusk; feeding; seagrass rhizomes; stomach contents; dental microwear A quantitatively significant but poorly understood aspect of mammalian history is the long relationship between herbivorous marine mammals and the plants they have eaten. This history extends over the 50 million years of the fossil record of these mammals (mainly those in the Order Sirenia: dugongs and manatees), and chiefly involves the tropical-to-temperate, cosmopolitan marine angiosperms or seagrasses (Hydrocharitaceae and Potamogetonaceae), which today constitute one of the Earth's most productive ecosystems, as has presumably been true throughout the Cenozoic (Ivany et al., 1990). The greatly diminished diversity of modern sirenians, however, is a major obstacle to exploring how feeding adaptations, niche partitioning, and other

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“…Seagrass chemical composition is known to change with season (Preen 1995). In this study, stomach contents were collected over a 3 yr period, from September 1997 to September 1999.…”

Section: Discussionmentioning

confidence: 99%

Near infrared spectroscopy as a rapid and inexpensive means of dietary analysis for the marine herbivore, dugong Dugong dugon

André¹,

Lawler²

2003

Mar. Ecol. Prog. Ser.

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The objective of this study was to evaluate the potential of near infrared reflectance spectroscopy (NIRS) to estimate the botanical composition of seagrass mixtures in the stomach contents of dugongs more rapidly and cost-effectively than by conventional means. NIRS estimation of dietary composition is achieved by developing calibration equations that relate NIR spectra of samples to laboratoryderived values for botanical composition. Once calibration equations have been developed, these characteristics can be estimated for further samples from their spectra alone. We developed calibration equations using samples from the stomachs of 26 dugongs (from a total data set of 128 dugongs) and validated them against a further set of 14 stomach samples. Nine dietary components were identified, 5 of which made up less than 5% of the total diet. Acceptable calibrations were obtained for the major components of dugong diets: seagrass rhizomes (pooled across all species) and the leaves of the seagrasses Thalassia hemprichii, Syringodium isoetifolium and Cymodocea species. We did not attain satisfactory calibrations for minor (<10%) dietary components. NIRS is a valid method for obtaining rapid information on the main components of the dugong diet. With larger calibration sets and fresh samples it should also be able to provide information on minor dietary components. NIRS is applicable to dietary studies of marine herbivores and should thus be of value to marine ecologists generally.

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Diet of Dugongs: Are They Omnivores?

Cited by 73 publications

References 29 publications

Modeling habitat and bycatch risk for dugongs in Sabah, Malaysia

Modeling habitat and bycatch risk for dugongs in Sabah, Malaysia

Use of tusks in feeding by dugongid sirenians: Observations and tests of hypotheses

Near infrared spectroscopy as a rapid and inexpensive means of dietary analysis for the marine herbivore, dugong Dugong dugon

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