Dugongs are marine mammals that, together with the three species of manatee, belong to the order Sirenia. However, while manatees can live in freshwater, dugongs only occur in the ocean making them the only herbivorous marine mammal in the world. They are often referred to as ‘sea cows’ and amazingly are closely related to elephants. Dugongs occur mainly in sheltered bays, lagoons and around islands browsing on shallow seagrass beds. This species plays a significant ecological role by converting marine plants into nutrients, thereby filling a niche of immense importance for other marine life.
Dugongs are currently listed globally as vulnerable to extinction on the IUCN’s Red List of Threatened Species. They are extremely sensitive to anthropogenic threats. One of the most pressing threats to dugongs currently, is the loss and degradation of their coastal zone habitat (especially seagrass beds). Dugongs require very specific habitats for survival and many of these habitats have been destroyed, polluted or encroached upon by coastal development. Dugongs also face pressure from directed artisanal fishing and are often incidentally caught as by-catch in fishing nets. Gill netting in particular has been identified as the most significant threat to dugongs in the Western Indian Ocean. Currently no bycatch mitigation measures are enforced in Mozambique.
Mozambique’s first marine park, the Bazaruto Archipelago National Park (BANP) and its surrounding areas support the largest biologically viable population of dugongs (estimated to stand at 100-150 individuals) in Africa and the second largest in the Western Indian Ocean. The BANP is a crucial habitat for Mozambique’s declining dugong population (which country-wide is estimated to be only 250 individuals). Conservationists agree that the BANP needs to be a ‘safe haven for the remaining sea cows of Mozambique’.
MMF staff have been collecting information on the distribution of dugongs south of the BANP for the last few years. In particular the Inhambane estuary seems to boast a small viable population of dugongs with as many as 14 individuals, including mother-calf pairs seen at one time. Researchers are now working to establish if connectivity exists between these southern areas and the greater Bazaruto area up north.
It is thought to be unlikely that the Mozambican dugong population can survive, let alone recover to its historical abundance, unless drastic and immediate conservation efforts are put into place. Rigorous management is needed to ensure that existing individuals are protected and undisturbed, allowing their numbers to rejuvenate.
The Endangered Wildlife Trust (EWT) seeks to secure core dugong herds and habitat by mitigating major threats and strengthening existing structures in collaboration with various institutions and government authorities within the BANP. In collaboration with other organizations, the EWT have implemented the ‘Dugong Emergency Protection Project’ and MMF is working to support this project and the Mozambican government by helping to determine the population structure of dugongs along southern Mozambique coast, the extent of their range, the most critical and populated habitats, and their most severe anthropogenic threats.
Janneman Conradie, MMF’s director of conservation will support this project through aerial surveillance with Bantam microlight aircraft and MMF biologists will assist with both in and above water monitoring and coastal survey work.
Quick facts – Dugongs (Dugong dugon)
- Class: Mammal
- Diet: herbivorous. seagrass
- Lifespan: 70+ years
- Age of first breeding: 6-17 years
- Litter size: 1 calf every 2.5 – 7 years depending on food supply ( max 12 calves in its lifetime )
- If food supply is damaged by cyclones/habitat destruction/pollution, dugongs postpone breeding and/move on
- Calving intervals: ≥ 2.5 years
- Gestation: 13-15 months
- Lactation: 18 months
- Adult: 2.4 – 3 meters, max 4 meters
- Weight Adult: 230 – 500kg
- Depths: 40 meters, normally graze in less than 10 meters
- Communication: chirps, whistles and barks