(DRAFT) - Taxonomy
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
TAXONOMY
NAME - DUGONG
OTHER COMMON NAMES - DUGONG; COW, SEA; MESEKIU;AUURIYA;BABLOO; CHIGAMBI; DANGAL; DUHONG; DUJUNG; DUGUNG; DUYONG; MAGNO, GEBER; DUYUNG, IKAN; KADALPUDRU; LAMBOHARANA;URA and MUDA; ROUDJONG; RUYUNG; TROZONA;YUNGAN
ELEMENT CODE -
CATEGORY - Mammals
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - MAMMALIA,
ORDER AND SUBORDER - SIRENIA,
FAMILY AND SUBFAMILY - DUGONGIDAE,
GENUS AND SUBGENUS - DUGONG,
SPECIES AND SSP - DUGON,
SCIENTIFIC NAME - DUGONG DUGON
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Dugong
Dugong dugon (Muller, 1776)
KINGDOM: Animal GROUP: Mammal
PHYLUM: Chordata CLASS: Mammalia
ORDER: Sirenia FAMILY: Dugongidae
A dugong is roughly the size and shape of a large dolphin, but
with a less streamlined head and no dorsal fin. The muzzle is large
and fleshy; the eyes are small; the external ears consist only of tiny
openings; and the nostrils lie close together at the anterodorsal tip
of the snout. A pair of short upper incisor tusks is present, but
these normally do not erupt except in adult males. The cheek teeth
are simple and peglike. The neck is very short; the pectoral flippers
are short and rounded, without nails; the two mammae are located in
the axillae; hind limbs are completely absent; and the tail fin is
horizontally flattened and in the form of flukes like those of
cetaceans. The body is gray to bronze in color, somewhat lighter
ventrally, and sometimes with large unpigmented areas; the thick,
smooth skin is often extensively scarred in older animals. Dugongs
can exceed 3 meters in total length and 400 kg in weight, but most are
smaller.
Taxonomy - 1 (DRAFT) - Taxonomy
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
Dugongs were divided into several species and subspecies in older
literature, but today only a single taxon, Dugong dugon (Muller, 1776)
(31), is recognized. The only commonly-used generic synonym of Dugong
Lacepede, 1799 (23), is Halicore Illiger, 1811 (22). Specific or
subspecific epithets often used in combination with Dugong or Halicore
include australis Retzius, 1794 (36), dugung (or dugong) Erxleben,
1777 (14), hemprichii Ehrenberg, 1828 (13), indicus Desmarest, 1822
(12), and tabernaculi Ruppell, 1834 (38), among others. Scientific
names used previously include: Dugong dugon, D. australis,
D. hemprichii, D. indicus, Halicore dugong, H. dugung, H. australis,
H. hemprichii, H. indicus, H. tabernaculi, H. cetecea, H. lottum,
H. malyana, H. brevirostris, Manatus dugung, M. indicus, Trichecus
dugon, Trichechus dugong, T. Australis, T. dugung and generic names
such as Dugongidus, Platystomus, and Amblychilus (45). Other common
names for the dugong include: Sea cow (and equivalents in other
European languages); auuriya, avilliah, avolia, arus el-bahr, babi
laut, babloo, bagar al-bahr, baqara seit, baqarat al-bahr, ca-cui,
carin-belo, chigambi, dangal, duhong, dujong, dujung, dugung, dungal,
duyong, duyung, geber magno, gel magno, gueld, ikan duyung,
kadalpanni, kadalpudru, kadel pandi, lamboharana, mesekiu (Palau
Island/Micronesia language), muda ura, naga al-bahr, naqat al-bahr,
n'guva, perampuan laut, roudjong, rouyond, ruyung, trozona,
trozon-tsoy, youngon, and yungan (45).
No type specimens have ever been designated. Photographs of
dugongs and their skulls may be found in Husar, 1975 (21) and
Nishiwaki, 1985 (33). Most large museums in the United States have at
least some skeletal or other material of dugongs; good collections are
in the U.S. National Museum of Natual History (Wash., D.C.) and the
American Museum of Natural History (New York).
It is possible that untrained observers, or observers of animals
at sea, might confuse dugongs with small cetaceans such as Orcaella
or, especially, Neophocaena, which lacks a dorsal fin (32), however
both these cetaceans are smaller than dugongs especially in length and
girth.
Taxonomy - 2 (DRAFT) - Status
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
Marine Mammal
Commercial/consumption
Non-consumptive recreational
Ceremonial/Cultural
Medicinal
Aphrodisiac
Ornamental
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The dugong (Dugong dugon) has been designated an Endangered
species pursuant to the Endangered Species Act of 1973 (50 CFR 17.11;
P.L. 93-205, 87 Stat. 884; 16 U.S.C. 1531-1540), as amended. The
species has this status wherever found including the U.S. Pacific
Island Trust Territories.
This species is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation, or foreign law; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
The dugong is protected by the Marine Mammal Protection Act of
1972 (50 CFR 18; PL 92-522; 86 Stat. 1027; 16 U.S.C. 1361, 1362,
1371-1384, 1401-1407), as ammended.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
DOD -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public land under their control. Also responsible for
management/recovery on Department of Defense lands.
Status - 1 (DRAFT) - Status
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
STATE: Palau, Federated States of Micronesia
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: (PA) Trust Territory Conserv. Office;
(MC) Dept. of Resour. and Develop.
STATE STATUTE: (PA) The Trust Territory Endangered Species Act
1975, local laws stemming from a Palau District
Order.
(MC) Title 45; Fish, shellfish, and Game;
Chapt. 5; Endangered Species Act of Trust Terr.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The species is listed by CITES in Appendix I. It is listed as
vulnerable by IUCN, 1981.
ECONOMIC STATUSES:
The Dugong is hunted for food throughout its range, including
Palau. This exploitation is believed to be the principal cause of its
decline. There is a great deal of folklore concerning dugongs, and
where they are traditionally hunted this hunting has great cultural
significance and is often accompanied by elaborate rituals. Many
parts of the dugong, including meat, fat, oil, bones, tusks, and
"tears", are thought to have medicinal and/or aphrodisiac properties,
and these (particularly the latter) very likely motivate some taking
of dugongs in some areas. These practices apply throughout more or
less the entire range of the dugong, though of course local customs
vary. In Palau, the wearing of the atlas vertebra as a bracelet is an
old custom that apparently continues today. The dugong has potential
recreation non-consumptive value to tourists in the Pacific Trust
territories.
70/07/30:35 FR 12222/12225 - Proposed rule, amended list
70/12/02:35 FR 18319/18322 - Final rule, no Crit. Hab.
74/01/04:39 FR 01158/01185 - List, numerous rules and regulations
76/09/30:41 FR 43340/43358 - Updated list
76/10/27:41 FR 47180/47198 - Republished list, w/ corrections
77/02/22:42 FR 10465/10488 - Rule on CITES, species list
77/07/14:42 FR 36420/36431 - Updated list
78/03/06:43 FR 09168/09172 - Survey of U.S. species, CITES
78/05/03:43 FR 19176/19191 - Survey of U.S. species, CITES
78/12/11:43 FR 58030/58048 - Updated list
79/05/21:44 FR 29566/29577 - Notice of status review
80/04/03:45 FR 22848/22849 - Final rule on amendments to CITES
Status - 2 (DRAFT) - Status
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
80/05/20:45 FR 33768/33781 - Updated list
81/09/04:46 FR 44660/44674 - Final rule on amended CITES list
83/07/27:48 FR 34182/34196 - Updated list
85/07/22:50 FR 29901/20090 - Notice of Review
Status - 3 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
COASTAL
OCEANIC
LAND USE -
Bays and Estuaries
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Estuarine, intertidal FL6
Estuarine, intertidal FL5
Estuarine, intertidal FL4
Estuarine, intertidal FL3
Estuarine, intertidal FL2
Estuarine, intertidal BB2
Estuarine, intertidal AB2
Estuarine, intertidal AB1
Estuarine, subtidal OW0
Estuarine, subtidal AB2
1AB
Marine, intertidal RF1
Marine, intertidal FL6
Marine, intertidal FL3
Marine, intertidal FL2
Marine, intertidal BB2
Marine, intertidal AB2
Marine, intertidal AB1
Marine, subtidal RF1
Marine, subtidal OW0
Marine, subtidal AB2
Marine, subtidal AB1
COMMENTS ON HABITAT ASSOCIATIONS -
The dugong is characteristically associated with the seagrass
ecosystems of the Indopacific region (18). It feeds on virtually all
species of seagrasses, and is seldom found far from seagrass beds.
Such beds may grow on either sandy or muddy bottoms. Dugongs seem to
prefer to feed in water 1-2 m deep, and off points in preference to
the coves between the points (02).
Dugongs inhabit tropical marine waters of normal salinity and pH,
both clear and turbid. They may also be found in brackish, and
occasionally in hypersaline, coastal waters. They prefer calm waters
and will seek shelter behind reefs, headlands, or other features
offering protection from rough water. This may be partly because
protected waters favor growth of seagrasses, but also because
surfacing and breathing are more energetically costly in rough water
(07). Dugongs are usually found in water less than ten fathoms deep,
and in temperatures between 18 and 33 degrees Celsius (02,21,33).
Parturition takes place in water 1 m or less deep, or even
entirely out of water, on or among sandbars or on sandy flats,
frequently on a rising tide (to avoid stranding) and sometimes in
hypersaline areas.
Habitat Associations - 1 (DRAFT) - Food Habits
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
HERBIVORE
LIFESTAGE FOOD FOOD PART
General Vascular Plants-Submerged Nonwoody
General Roots/Tubers/Rhizomes-Herbaceous
General Poaceae
General Algae
General Parasitic/Epiphytic Plants
General Crustaceans
General Molluscs
General Coelenterata
General Fish
Food Habits - 1 (DRAFT) - Environment Associations
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Coastal Wetlands: Mangrove swamps
G Coastal Features: Reefs
Environment Associations - 1 (DRAFT) - Life History
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
The staple, and almost exclusive, diet of the dugong is composed
of tropical seagrasses (families Hydrocharitaceae and
Potamogetonaceae). All species of seagrasses in the dugong's range
are consumed, usually in rough proportion to their local availability
(07,09,30). Genera of seagrasses reportedly fed on by dugongs include
Amphibolis, Cymodocea, Enhalus, Halodule, Halophila, Posidonia,
Syringodium, Thalassia, Thalassodendron, and Zostera (06,09). Younger
plants are generally preferred to dense, older stands, which are
presumably less palatable, digestible, and/or nutritious (09). Both
leaves and rhizomes are eaten (the rhizomes having a higher starch
content and calorific value), except that in the case of Enhalus
(which has the largest and most fibrous rhizomes) only the leaves seem
to be consumed (30). Likewise, in the case of Amphibolis growing on
hard sand, only the leaves and not the tough stalks or deeply buried
roots are eaten (06). Even newborn animals may eat seagrasses,
including rhizomes (30). Dugongs leave feeding tracks where they have
stripped seagrasses from the bottom (07).
When seagrasses are unavailable, dugongs will resort to eating
marine algae such as Sargassum. This was observed following a cyclone
which damaged seagrass beds in Australia (39). However, dugongs do
not appear to chew algae adequately and may not be able to use them
efficiently as a food source (30). Dugongs which have fed extensively
on algae and which are found around island margins and nearby reefs
(possibly post-reproductive individuals) are lean and poor-tasting and
therefore not sought after by sophisticated dugong hunters, who prefer
seagrass-fed dugongs found farther offshore (29).
Various epiphytic algae have also been recorded in stomach
contents of dugongs; these are probably ingested incidentally while
feeding on seagrasses. Some marine invertebrates and fish have
likewise been found in dugong stomachs (09,43). Some of these were
also no doubt ingested accidentally, but the possibility cannot be
excluded that dugongs may eat some animals (such as clams and
holothurians) deliberately, as they have been reported to do in
captivity (02).
In subtropical areas such as Shark Bay, Australia, there are
seasonal variations in seagrass availability which may have a
significant impact on the energy budget of dugongs: the winter diet
(mostly Amphibolis) is higher in fiber and lower in carbohydrate - and
therefore furnishes less enery - than the summer diet (mostly
Halodule) (06). In tropical areas, however, seasonal variations are
presumably less important than variations in food availability due to
locality, weather, tides, and other factors.
HOME RANGE/TERRITORY:
Dugongs do not appear to defend territories. However, they may
possess established home ranges, and it has been suggested that this
is more true of mature individuals, whereas younger animals may wander
about more freely (02,16). No information is available on home range
size or on seasonal variation in range size or territorial behavior.
Dugongs are social, normally feeding and travelling in groups, or even
Life History - 1 (DRAFT) - Life History
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
in herds of several hundred; however, solitary animals are also often
observed (02,03,07,20,21,26,33,37,41,42). Individuals or groups may
possibly establish ranges within areas occupied on a seasonal basis by
the herd as a whole (02). It is unclear whether there is any seasonal
variation in gregariousness (07). The most constant social bond, and
the only one clearly domonstrated, is that between a cow and her calf
(03. Sexual partitioning of the habitat has been suggested (21) but
not verified.
PERIODICITY:
When not harassed or hunted, dugongs tend to alternate around the
clock between feeding and resting, and do not seem to have a regular
day/night cycle. Where they forage intertidally, the tidal patterns
impose rhythms on their activity. Where they are regularly hunted, as
at Palau, they typically do not feed during the day but come inshore
to feed at night. This restriction of inshore feeding to the hours of
darkness as a result of human disturbance may greatly reduce the
carrying capacity of an area (02,03,07,11).
MIGRATION PATTERNS:
Dugongs in at least some areas undertake extensive longshore
seasonal movements; some individuals may be migratory while others
remain as residents in a given area (18,26). Distinct seasonal
migrations can even occur within a single large bay (06). Local
increases in dugong abundance are also reported during monsoons and
rainy seasons (15,20,41), perhaps because dugongs take shelter inshore
from bad weather and are more conspicuous then. On a daily basis,
they often travel several km among various feeding and resting areas,
sometimes following established and predictable routes (02,07,11).
After feeding in one area for 1-4 weeks, they may move, individually
or as a group, to a similar area several km away (03).
COVER/SHELTER REQUIREMENTS:
Dugongs will take shelter in the lee of islands, reefs, or
headlands when wind and seas are high - apparently because surfacing
and breathing are more difficult and energetically costly in rough
water (02,03,07,16). However, they avoid confined bays and narrow
inlets (03). Ordinary resting areas generally lack seagrasses, give
ready access to water 10 m or more in depth, and have reference points
such as reefs, reef embayments, or derelict ships (02). Disturbance
by humans may force dugongs into unprotected waters where energy
expenditure and danger from predators are high (02,07). Thermal
refugia may be important in cooler areas at the margin of the
geographical range (02).
REPRODUCTIVE SITE REQUIREMENTS:
No particular site requirements for display or breeding are
known, though copulation may occur in sheltered bays (07,21).
Parturition takes place in water 1 m or less deep, or even entirely
out of water, on or among sandbars or on sandy flats, frequently on a
rising tide (to avoid stranding) and sometimes in hypersaline areas.
These features of a calving site seem to provide protection against
sharks and other predators (02,24,29).
Life History - 2 (DRAFT) - Life History
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
REPRODUCTIVE CHARACTERISTICS:
Sexual maturity is reached at a minimum of 9-10 years in both
sexes, but this is very variable and in some animals may not occur for
over 15 years. Gestation lasts 1 year or slightly more; lactation can
last at least 1.5 years. The usual litter size is one. Estimates of
the calving interval are from 3 to 7 years for various populations.
Ovaries tend to be active (and calves tend to be born) in the latter
half of the year, but there is no sharply defined breeding season. At
a given time, both fertile and infertile adult males may be found in
one population, and females also undergo sterile cycles. They do not
seem to come into estrus soon after giving birth, but the conception
can occur during lactation. Ovarian activity may be reduced in some
old females, but one pregnant female 42 years old was observed (27,28,
29). Sexual dimorphism in form and behavior is minimal. Simple
courtship or display, possibly including agonistic behavior, seems to
occur, and males may use their tusks to roll females onto their backs
(07). Several males will pursue one female in attempts to mate, and
mating seems to be promiscuous; but it is not known how often or for
how long a female is in estrus.
PARENTAL CARE:
Although precocial, newborn calves may require and receive some
maternal assistance in learning to surface and breathe properly
immediately after birth. Thereafter, the calf accompanies the mother
closely for at least a year. This prolonged association may be
important for communicating traditional knowledge of the habitat to
the calf, as well as for socialization. The calf may begin to graze
within 2-3 months after birth, but suckling probably continues
throughout the period of cow-calf association. Parents of both sexes
reportedly will try to protect calves from shark attack and will
continue to seek a calf in the area where it has been netted (02,42).
Males tend to be on the outside of a herd (26); this may be an
anti-predator tactic.
POPULATION BIOLOGY:
Dugongs are long-lived (50-60 years) mammals with low fecundity
and a large investment in each offspring. The minimum
pre-reproductive period is 9-10 years; calving intervals are 3-7
years; usual litter size is one; secondary and tertiary sex ratios are
1:1. Human-caused mortality is doubtless the main limiting factor in
most parts of the species' range, but mortality schedules are not
known for any dugong population. Both juvenile and adult female
mortality rates must be kept low for population survival: judging
from a simple population model, even the most optimistic schedule of
reproduction and juvenile mortality requires an adult survivorship of
about 90% per year for population stability (29).
SPECIES INTERRELATIONSHIPS:
Dugongs are dependent on seagrasses (Hydrocharitaceae and
Potamogetonaceae), their principal food, as described above under FOOD
HABITS above. The only organisms known to be significantly dependent
on dugongs are their internal parasites, the nematode Paradujardinia
Life History - 3 (DRAFT) - Life History
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
halicoris (40) and the trematodes Opisthotrema dujonis, O. australe,
Cochleotrema indicum, Pulmonicola pulmonalis, Lankatrematoides
gardneri, Folitrema jecoris, Rhabdiopoeus taylori, Taprobanella
bicaudata, Faredifex clavata, and Haerator caperatus (10). Most of
these genera are monotypic and occur only in the dugong. An
unidentified fish, possibly a commensal, has been observed in the
prepuce of a male dugong (19).
OTHER LIFE HISTORY DESCRIPTORS:
Dugongs are curious and will sometimes approach boats or swimmers
(02). They will also raise their heads out of water to scan the
surroundings - especially larger individuals which may be acting as
lookouts for a group (07). They have adequate vision and acute
hearing (02,21). They readily become entangled in nets and quickly
drown (17). If pursued in the course of capture attempts, they may
succumb to capture myopathy (25).
Life History - 4 (DRAFT) - Management Practices
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Controlling/Restricting Boating Activities
Beneficial Restricting Poaching
Beneficial Controlling/Restricting Noncommercial Harvest
Beneficial Regulating commercial harvest levels
Adverse Subsistence Hunting/Fishing/Trapping
Existing Subsistence Hunting/Fishing/Trapping
Adverse Incidental Capturing/Killing
Existing Incidental Capturing/Killing
Adverse Artillery/Explosions
Existing Artillery/Explosions
Adverse Poaching
Existing Poaching
Adverse Commercial Exploitation
Existing Commercial Exploitation
Adverse Inherent Reproductive Characteristics
Existing Inherent Reproductive Characteristics
Adverse Oil Spills
Existing Oil Spills
Adverse Gas/Oil Development
Existing Gas/Oil Development
Adverse Siltation
Existing Siltation
Adverse Environmental Contamination/Pollution
Existing Environmental Contamination/Pollution
COMMENTS ON MANAGEMENT PRACTICES -
Since prehistoric times, dugongs have been hunted by man
throughout their range for their meat, fat, hide, bones, tusks, oil,
and other products (01,34,41). Dugong "tears" (secretions from the
eye produced when the animal is out of water) are aloes sought,
especially for aphrodisiacs (01,35). Dugongs are long-lived (50-60
years) mammals with low fecundity and a large investment in each
offspring. The minimum pre-reproductive period is 9-10 years; calving
intervals are 3-7 years; usual litter size is one; secondary and
tertiary sex ratios are 1:1.
More localized causes of significant mortality have included
entanglement in fishing nets (e.g., in Sri Lanka, India, Australia,
Kenya, and Djibouti; 08,17,37,41) and shark nets set to protect
swimmers (in Australia; 16,17), and oil spills (e.g., in the Arabian
Gulf; 44). In the late 19th and early 20th centuries there was an
extensive commercial fishery in Queensland, Australia based chiefly on
dugong oil, which was sold for medicinal purposes (42).
Current threats to the species include continuation of
traditional hunting (usually by harpoon); hunting with modern
equipment such as outboard motors (which are used to chase dugongs to
the point of exhaustion and easy capture) (03), and explosives (which
have been used in Palau since World War II) (11), fishing with large
nets (especially synthetic-fiber nets), protection of bathing beaches
Management Practices - 1 (DRAFT) - Management Practices
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
by shark nets.
Future threats include increased boat or amphibious aircraft
traffic (03), petroleum exploration, or other industrial activity in
dugong habitat, more oil spills, vandalism or other harassment by
sport divers (03), and destruction of seagrass beds by any means
(e.g., dredging, sand mining, sewage or toxic waste disposal, silt
runoff from agricultural or mining activities on land, changes in
freshwater runoff, harvesting of seagrasses, etc.) (18).
UNAPPROVED PLAN:
Currently, there is no recovery plan available for the Dugong.
A report, "Status of the Dugong," by R. Brownell et al., lists some
recovery measures (11).
The naturally low recruitment rate of the Dugong renders
populations of this species highly vulnerable when exposed to
increased rates of mortality. As a consequence of man's hunting,
dugong populations throughout their range have diminished to relict
numbers, and some have become extinct. The population at Palau has
followed this pattern, and now fewer than 100 animals survive, a
number too small to sustain an overall mortality rate of more than 10
animals per year, including those taken by hunters. No recovery plan
for the Dugong has been written, but a report, "Status of the Dugong,"
5 May 1981, by Robert Brownell et al., outlines measures necessary for
the Dugong's protection and recovery:
1) schedule regular surveys of dugongs;
2) establish a program of specieal patrols to better evaluate
the extent of poaching (i.e., both commercial and non-
commercial take) and to exercise greater control;
3) institute an educational program designed to emphasize the
traditional value of the dugong and involve Palauans in
efforts to conserve and strengthen the dugong population;
4) regard the dugong as a wildlife resource to be shared with
the developing tourist industry, by means of planned and
carefully controlled boat "dugong safaris"; and
5) design and execute a study of dugongs on a long term basis
at Malakal Harbor to provide autecological data on dugongs
and to call attention to their importance, status, and
vulnerability.
Though dugongs are seldom struck by motor boats, injuries and
deaths do occur occasionally; boat operators should be made aware of
this problem. Present conservation of Dugongs includes (1) law
enforcement to discourage poaching and (2) aerial surveys conducted
every few years by NMFS.
Management Practices - 2 (DRAFT) - References
Species DUGONG
Species Id ESIS051011
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Allen, J., et al. 1976. Some observations on the biology of the
dugong (Dugong dugon) from the waters of South Sulawesi. Aquat.
Mamm. 4(2):33-48.
02 Anderson, P. 1979. Dugong behavior: On being a marine mammalian
grazer. Biologist 61(4):113-144.
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