1. Dugongs in East Malaysian waters: an international perspective
Helene Marsh
James Cook University Australia
Coordinator IUCN Dugong Action Plan

2. The modern sirenia (seacows)- dugongs and manatees

3. Biodiversity importance of Order Sirenia
Taxonomically unique
2 families
Trichechidae
Antillean manatee Trichechus manatus
Amazonian manatee Trichechus inunguis
West African manatee Trichechus senegalensis
Dugongidae
Dugong Dugong dugon
Steller’s sea cow Hydrodamalis gigas

4. Global conservation status of modern sirenia
Antillean manatee vulnerable
Amazonian manatee vulnerable
West African manatee vulnerable
Dugong vulnerable
Steller’s sea cow extinct

5. Distribution of extant sirenia

6. Conservation significance of dugongs
One of only four members of order Sirenia
Only member of family Dugongidae
Only strictly marine herbivorous mammal
Largest population size (>100,000) and range of extant Sirenians

7. Habitat partitioning: extant Sirenia
Dugong
strictly marine
coastal and estuarine
Antillean and West African manatees
coastal, estuarine and freshwater (may be dependent on access to freshwater)
Amazonian manatee
freshwater in Amazon River system
All restricted to tropics and sub-tropics

9. Dietary partitioning: modern Sirenia
Dugong
seagrass specialist, eats invertebrates at higher latitude ends of range
obligate bottom feeder
Manatees
generalist feeders on salt & freshwater vegetation
feed throughout water column
opportunistic omnivores
Steller’s sea cow
surface feeder on cold-water algae

10. Dugong digging up seagrass like a bulldozer
Conclusion: Seagrass conservation is essential to dugong conservation

11. Movements Dugong >60 animals satellite tracked most movements local
several animals made long-distance movements
longest movement ~800 km in few days

12. Dugong Movements Frequency Maximum movement 8 7 6 5 4 3 2 1 0-10
0-10
>640
>10-20
>20-40
>40-80
>80-160
>
>
Maximum movement

13. Preliminary information on genetics of female dugongs
Genetic types of female dugongs from Southeast Asia (Indonesia, Thailand, Philippines generally distinct from those from Australia) - overlap at Ashmore Reef between Australia and Timor
Two maternal lineages in Australian coastal waters - overlap in Torres Strait between Australia and Papua New Guinea
One Australian lineage also recorded from East Africa and the Arabian Gulf

14. Dugong Life history Lifespan < 70 yr Age first breeding 6-17yr
Gestation period mth
Calving interval > yr
Lactation ~ 1.5 yr
Adult survivorship >95%
Max rate of increase < 5%
Sustainable harvest ~2%

15. Conclusions Dugong conservation MUST address the issues of
Rate of change in dugong numbers is very sensitive to changes in adult survivorship
The impact of mortality (drowning in nets, boat strikes, hunting) on dugongs is serious
When dugongs don’t have enough to eat because of habitat loss, they delay breeding - this reduces the level of mortality that is sustainable
Dugong conservation MUST address the issues of
habitat conservation AND mortality reduction

16. Threats to dugongs- overview from 37 countries

17. Dugongs tangle in mesh nets and accidentally
drown in many countries

18. Habitat loss due to extreme weather events
1000 km2 of seagrass habitat
were lost in Hervey Bay Queensland
after two floods and a cyclone

19. Hunting and
poaching kill dugongs
in at least 26 countries

20. Propellors kill and maim
manatees and some dugongs

22. Evidence for dugong decline- 37 countries
Anecdotal evidence suggests that dugong numbers have declined in at least 17 countries and that dugongs are extinct in 3 more
No evidence of reduction in extent of range - reduction of area of occupancy within range
Situation particularly serious in East Africa, Indian region and parts of Southeast Asia
Quantitative evidence of decline available only for Queensland, Australia

23. Trends in dugong numbers Qld Shark Control Program• • 50 • 40 • • • • 30 • •
Total dugongs caught per year • • • • 20 • • • • • • 10 • • • • • • • • • • • • • • • • • • •
1960
1970
1980
1990
2000

24. Response to dugong decline in Queensland, Australia
Moratorium on hunting on urban coast
16 Dugong Protection Areas (6353 km2)
no gill-netting (red)
gill-netting with restrictions (yellow)
Restructuring of fishing industry - buyout of fishers

25. Suggested approaches to dugong conservation
Identify areas that still support significant numbers of dugongs
Consider with extensive local involvement how dugong mortality can be minimised and their habitat protected
If possible, protect dugongs in the context of comprehensive plans for coastal zone management using the dugong as a flagship species

26. Amanda’s slide

27. Situation in East Malaysia
Dugongs present in unknown numbers
Anecdotal evidence of decline
Threatened by:
habitat loss and disturbance from coastal development
fishing mortality (kelong, gill nets etc)
dynamite fishing
boat strikes
These threats need to be addressed in the context of the
best scientific information if the dugong is to be conserved