Specimen of the Week 300 : Dugong skeleton
By Dean W Veall, on 14 July 2017
Hello Specimen of the Week fans, Dean Veall here. Over the last month here at the Grant Museum we have been interested in one particular group of marine mammals, cetaceans, in the run up to our Whale Weekender event where we invited members of the public to help us rebuild and clean our 8 metre long northern bottle-nose whale skeleton. This week I’ve chosen another marine mammal, a medium sized one though. Today it is the…
Dugongs (Dugong dugon) are one of four living species of the Order Sirenia; the other three species that make up this group are manatees. Unlike their sea cow relatives which reside in estuaries and freshwater, dugongs are found exclusively in coastal marine habitats. Adult dugongs usually grow to up to 3 metres in length and weigh over 1000kg. Our specimen is 2.7 m long which would suggest it was an adult. The closest living relative to the dugong are elephants.
Just like manatees, dugongs are often referred to as sea cows due their slow movement (not sure I believe this is a fair comparison as I’ve seen land cows move at speed and even jump over the moon*) as well as being large herbivores. Dugongs are the only truly herbivorous marine mammal, feeding almost exclusively on sea grass. One thing land cows and sea cows have in common is their propensity to be gaseous which makes them super buoyant. To compensate for this buoyancy their bones have become heavy and dense. Semi-nomadic, dugongs will travel long distances in search of food and are found in the Eastern hemisphere in the warm coastal waters from the western Pacific Ocean to the eastern coast of Africa.
Stellar’s sea cow (Hydrodamalis gigas)
The largest member of the dugong family, the Stellar’s sea cow, weighing 8-10 metric tonnes, was discovered in 1741 in the Bering Sea and within 27 years was declared extinct. This is just one of the many, many species that have gone extinct due to direct and indirect human action such as hunting and climate change. To illustrate this mass extinction event (when the rate of species extinction is higher than the background rate of extinction) scientists are increasingly using emotive language in an attempt to wake us up to the effects we, as a species, are having on the natural world. Just this week an article in the USA’s Proceedings of the National Academy of Sciences, scientists referred to as “biological annihilation” of wildlife which revealed billions of populations of animals had been lost in recent decades. For a long lived and slow breeding animal like a dugong, there is much to worry about. This animal is classified as vulnerable and even though is protected in the majority of its range it is susceptible to habitat degradation and fishing related activities. The last major worldwide study, made in 2002, concluded that the dugong was declining and possibly extinct in a third of its range, with unknown status in another half.
Dean Veall is Learning and Access Officer at the Grant Museum of Zoology.