According to http://www.sirenian.org/sirenians.html Sirenians are special animals:
“While there are about 78 species of cetaceans (whales & dolphins) and about 235 species of primates (monkeys, apes, chimps), there are only 4 species of Sirenians living on earth today, three manatees and one dugong. A fifth species, Steller's sea cow, was hunted to extinction by explorers in the 1700s….”
The website writers explain that the remaining three species are “…primary consumers of sea grass and freshwater vegetation.” “…they are the ONLY marine mammal herbivores alive today.”
These docile, unique-appearing sea creatures are in danger of extinction. Causes include global warming related to waning habitat, human intervention, (boating) and the length and frequency of gestation. Wikipedia explains:
“Despite the longevity of the dugong, which may live for 50 years or more, females give birth only a few times during their life, and invest considerable parental care in their young. The time between births is unclear, with estimates ranging from 2.4 to 7 years.”
Wikipedia says, the Sirenians may have existed as early as the Eocene Epoch (50 to 55 MYA), but their main fossil record includes the Miocene Epoch (5 to 23 MYA).
The following chart of animal facts can be found at http://www.gbrmpa.gov.au/about-the-reef/animals/dugong
|Life span (maximum longevity -
most dugong die at a younger age)
|Age before breeding (females)||6-17 years|
|Age before breeding (males)||4-16 years|
|Gestation period||13-15 months|
|Number of young||1|
|Lactation length||14-18 months|
|Time between breeding||3-7 years|
|Maximum possible rate of increase
(e.g. low natural mortality and no human-induced mortality)
|5% per year|
|Estimated natural mortality rate||5% per year|
The World Wildlife Fund has many Sirenian gifts available with proceeds of course, supporting conservation and research.
http://www.sirenian.org/caryn.html has a reference list of reading material to assist your knowledge of these interesting but waning ocean creatures.
The Amazon book site list on Sirenians is long with some books available for as little as $0.10.
For the 'littler' visitors to this site, please enjoy this youtube on the Dugong and Manatee:
NOTE: According to my research, unlike the reference to the contrary in this video, the Dugong and Manatee are two different species.
As always...Nature prevails.