The mating behavior of dugongs varies slightly with location. For example, in a mating herd in Moreton Bay, off the coast of Queensland, males take part in aggressive competitions for females in oestrous. In comparison, dugongs in South Cove in Western Australia display a mating behavior similar to lekking. A lek refers to a traditional area where male dugongs gather during mating season to participate in competitive activities and displays that attract females. As these lekking areas lack resources necessary to females, they are drawn to the area only to view the males' displays. Male dugongs defend their territories, and they change their behavioral displays to attract females. After attracting females, male dugongs proceed through several phases in order to copulate. The “following phase” occurs when groups of males follow a single female, attempting to mate with her. The “fighting phase” occurs after, consisting of splashing, tail thrashing, rolls and body lunges. This can be violent, as witnessed by scars observed on the body of females and on competing males from their protruding tusks. The “mounting phase” occurs when a single male mounts a female from underneath, while more males continue to vie for that position. Hence, the female is mounted several times with the competing males, almost guaranteeing conception. Dugongs are thus polyandrous.

Mating System: polyandrous

Female dugongs reach sexual maturity at 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 oestrous. The reproductive rate of dugongs is very low, and they only produce one calf every 2.5 to 7 years depending on location. This may be due to the long gestation period, which is between 13 and 14 months. At birth, calves are about 30 kg in weight, 1.2 m in length, and very vulnerable to predators. Calves nurse for 18 months or longer, during which time they do not stray far from their mother, often riding on their mother's back. Despite the fact that dugong calves can eat seagrasses almost immediately after birth, the suckling period allows them to grow at a much faster rate. Calves mature between 6 and 9 years of age for both genders.n. Once mature, they leave their mothers and seek out potential mates.

Breeding interval: Females dugongs breed every 2.5 to 7 years.

Breeding season: Dugongs mate year round.

Average number of offspring: 1.

Range gestation period: 13 to 15 months.

Average birth mass: 30 kg.

Range weaning age: 14 to 18 months.

Average time to independence: 7 years.

Range age at sexual or reproductive maturity (female): 6 to 17 years.

Range age at sexual or reproductive maturity (male): 6 to 12 years.

Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 27500 g.

Average number of offspring: 1.

Females dugongs invest considerable time and energy in raising calves and are the primary caregivers of their young. Mothers and calfs form a bond which is strengthened throughout the long suckling period of the calf, which is up to 18 months, as well as physical touches that occur during swimming and nursing. Each female spends about 6 years with their calf. During the first 1.5 years, mothers nurse their calf and demonstrate how to feed on seagrasses. The next 4.5 years, or until the calf reaches maturity, are spent feeding together and bonding. In their early years, calves do not travel far from their mother as they are easy prey for sharks, killer whales and crocodiles.

Parental Investment: precocial ; female parental care ; pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning