The Cambodian Marine Mammal Conservation Project

The Irrawaddy dolphin is usually greyish to dark blue-grey or pale blue, while the underside is paler. It has a round forehead, no beak, and an upward mouthline that gives it a smiling appearance. Its neck is long and flexible with a distinct neck crease.

Its dorsal fin is small, triangular and with a blunt tip. Conversely, the pectoral fins are large and spatulate, with curved leading edges and rounded tips. Therefore, they are sometimes mistaken for a finless porpoise, which is smaller and has no dorsal fin.

An Irrawaddy dolphin can weigh 90-200 kgs and reach lengths of 180-275 cm.

Irrawaddy dolphins’ main diet is fish and squid. They hunt by using echolocation, which is also used for communication.

Females are sexually mature between 7-9 years of age and reproduce throughout the year. The gestation period is about 14 months. A female gives birth to a single calf every 2-3 years. The lifespan of Irrawaddy dolphins is around 30 years. The relatively late sexual maturity and long birthing cycles make these dolphins vulnerable to threats.

Irrawaddy dolphins usually travel in groups of 2 or 3 but can be as many as 25 in one group. They are shy of boats, are relatively slow moving and when alarmed they generally dive.

So far, we have found them to be socialising, foraging, travelling, and diving in the study area. As well as behaviours including spy hopping, breaching, tail slapping and fluke up. In other places, they have also been seen spitting water from their mouths, presumably to help them hunt by confusing schools of fish or for sexual courtship.

The dugong’s body is a large cylindrical shape that tapers at both ends. It has thick, smooth skin that is a pale cream color at birth but darkens to brownish to dark grey with age. It has two teats, one behind each flipper. Its brain weighs a maximum of 300 g, about 0.1% of the animal’s body weight.

With very small eyes, dugongs have limited vision. However, it has acute hearing within narrow sound thresholds. Its nostrils are located on top of the head and can be closed with valves. The lungs are very long and extend almost as far as the kidneys, which are also highly elongated to cope with the saltwater environment.

The main difference between males and females is the location of the genital aperture in relation to the umbilicus and the anus. And the male’s testes are not visible externally.

Dugongs swim by moving the two flippers and their broad tail in an up and down motion, and by use of their two flippers. They are slow-moving and have little protection against predators. Young dugongs hide behind their mothers when in danger. However, they have no natural predators in the Kep Archipelago other than humans, making them a keystone species and an important indicator species of ecosystem health.

Dugongs are often called “sea cows” because they graze on the seagrasses that grow on sandy sea floor in shallow, warm water. A dugong can graze up to 40kg of seagrass per day (Gilon, 2022).

Females reach sexual maturity around 6 years of age and may have their first calf between the ages of 6 and 17. Males reach sexual maturity between 6 and 12 years of age.

Because breeding occurs year-round, males are always waiting for a female in estrous. The average reproductive rate is very low, about 1 calf per 2.5-7 years depending on location. This may be partially due to the long gestation period of 13-14 months.

Human activity is the biggest threat to dugongs.

First of all, dugongs are threatened by seagrass habitat loss and degradation due to coastal development and water pollution. On the other hand, dugongs are also victims of bycatch and direct hunting. They have been hunted for food, oil, leather, traditional medicine, amulets, ornaments and jewelry despite the conservation status. (Marsh et. al., 2002).