In Côn Đảo, there exists only a small dugong population—also known as sea cows (Dugong dugon)—with an estimated 10 individuals. Globally, the dugong population is estimated at around 100,000, of which Australia accounts for approximately 85,000 individuals, where they are monitored via satellite tracking. The highest population densities are found in Australia and Papua New Guinea, followed by the Philippines and a few other regions.
The dugong is listed as Critically Endangered, facing a high risk of extinction. In Vietnam, dugongs are found primarily in the waters of Côn Đảo and Phú Quốc.
According to Côn Đảo National Park, dugongs typically travel in small groups of two to three. Although there is no exact census, ongoing monitoring suggests that the population around Côn Đảo numbers only about 10 individuals.
Samples of seagrass and sediment have been analyzed by the Nha Trang Institute of Oceanography. To date, nine seagrass species have been identified in Côn Đảo, mainly distributed around Lò Vôi, with smaller meadows at Đá Trắng, Họng Đầm, and Đầm Quốc. Dugongs show a strong preference for long-stemmed paddle-leaf seagrass, followed by small paddle-leaf seagrass. In a draft report, researcher Nick noted: “Typhoon Linda in 1997 devastated many of the park’s ecosystems, reducing seagrass cover by more than 30%. A mid-2000 survey showed that overall seagrass coverage had not yet recovered to pre-storm levels.”
As the only marine mammal that feeds exclusively on seagrass, the dugong is commonly called the sea cow. Among the ocean’s “gentle giants,” a newborn calf measures about 1.1 meters in length. Adults typically reach 2.4–2.7 meters and can weigh up to 400 kilograms. Dugongs are voracious grazers, consuming an average of 25 kilograms of seagrass per day.
Their snout is uniquely structured and highly flexible, enabling them to uproot seagrass from sandy substrates. The tooth pads play a crucial role in grazing and transferring food into the mouth. The digestive system resembles that of large terrestrial herbivores (such as elephants, horses, and cattle). The large intestine alone can reach up to 30 meters, about twice the length of the small intestine. The thick, paddle-like foreflippers act as supports while feeding, allowing the bulky body to glide slowly over the seabed, leaving behind distinctive grazing trails 10–15 meters long, sometimes straight, sometimes zigzagging.
Dugongs cannot remain submerged for long periods and must surface every 1–2 minutes to breathe for a few seconds. They generally move slowly at around 5 km/h, though they can reach short bursts of up to 20 km/h. Dugongs often rest in waters 2–10 meters deep, and their daily movements are influenced by tides, weather conditions, food availability, and external disturbances.
Sea cows have a remarkably long lifespan, often exceeding 70 years—much longer than terrestrial cattle. Males and females can be distinguished by the position of the genital opening. In males, the pelvic bones are located within the genital slit positioned midway between the anus and the navel; the testes are internal, and the penis protrudes only when aroused. In females, the genital opening lies closer to the anus. Both sexes reach sexual maturity between 7 and 19 years of age, at which point they measure at least 2.5 meters in length.
Pregnancy lasts 12–13 months, and females give birth to a single calf. Reproduction usually occurs when seagrass and seaweed are most abundant, providing fresh, nutrient-rich food essential for calves. Young dugongs begin grazing after a few weeks and are weaned at around 18 months. Females typically give birth only once every 3–7 years. This slow reproductive rate is a major reason scientists consider dugongs to be extremely vulnerable to extinction.
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