NUMBER 16
OCTOBER 1991
IN THIS ISSUE:
- UPDATE ON GULF WAR OIL SPILL
(p. 12)
- COMPUTER ANALYSIS CLARIFIES
ANCESTRY OF THE
DUGONG (p. 16)
- MANATEE EXPLOITATION IN BRAZIL:
A REPLY (p. 5)
SIRENIA SPECIALIST GROUP MEMBERS
The Sirenia
Specialist Group has
been reorganized; an updated
list of the
current members follows.
The previous distinction between
Executive and Corresponding Members has
been eliminated. Telex and Fax numbers are given where known.
Dr. Paul K.
Anderson, Dept. of Biological Sciences, Univ.
of Calgary, Calgary,
Alberta T2N 1N4,
CANADA (FAX: 1/403/2899311)
Dr. Eduardo Rafael Asanza Cruz, Dept.
de Biologia, Universidad Catolica del Ecuador, 2184 Quito, ECUADOR
Dr. Daryl P.
Domning, Dept. of Anatomy,
Howard University, Washington, D.C. 20059, USA (FAX: 1/202/2657055)
Dr. William
J. Freeland, Principal Wildlife Research Officer,
Conservation Commission of the Northern Territory, P.O. Box
496, Palmerston, N.T. 0831, AUSTRALIA
Dr. Jerry Freeman,
Dept. of Biology, Interamerican University, San German 00753, PUERTO RICO
Dr. Hans de Iongh,
Ecologist, Centre for
Environmental Studies, Leiden
University, Garenmarkt 1a, P.O.
Box 9518, 2300 RA Leiden,
THE NETHERLANDS (TELEX:
39427 burul; FAX:
31/71/277496)
Dr. Toshio
Kasuya, Leader, Small Cetacean Section,
Far Seas Fisheries
Research Laboratory, 5-7-1 Orido,
Shimizu-shi, Shizuoka-ken
424, JAPAN (TELEX:
03965689 farsea j; FAX:
81/543/359642)
Ms. Janet Lanyon, Dept. of Ecology & Evolutionary
Biology, Monash University, Clayton,
Victoria 3168, AUSTRALIA
Dr. Helene
Marsh, Zoology Department, James
Cook University, Townsville, Qld.
4811, AUSTRALIA (TELEX:
7009 aa; FAX: 61/77/796371) (CHAIRPERSON)
Dr. Edgardo Mondolfi, UNEP, P.O. Box 30552, Nairobi,
KENYA
Dr. Thomas
J. O'Shea, Sirenia
Project Leader, U.S.
Fish & Wildlife
Service, 412 N.E. 16th Ave.,
Gainesville, Fla. 32601, USA
Dr. Daniel K.
Odell, Sea World of Florida, 7007 Sea World Drive, Orlando, Fla. 32821, USA (FAX: 1/407/3455397)
Mr. Demei Otobed,
Chief Conservationist, Palau
National Museum, Koror, Palau 96940,
REPUBLIC OF PALAU
Mr. James A. Powell,
Jr., P.O. Box 303, Buea,
CAMEROON (FAX: 237/322331 [ask for connection])
Mr. Tony
Preen, Zoology Department,
James Cook University, Townsville, Qld. 4811, AUSTRALIA
Dr. R. I. T.
Prince, Wildlife Research
Centre, Department of Conservation & Land Management, P.O. Box 51, Wanneroo, W.A. 6065, AUSTRALIA (TELEX: aa94616; FAX: 61/9/3061641)
Dr. Hector Quintero,
Dept. of Biology, Interamerican University, San German 00753, PUERTO RICO
Dr. Galen B.
Rathbun, U.S. Fish & Wildlife Service, P.O. Box 70, San Simeon, Cal. 93452, USA (FAX: 1/805/9273308)
Dr. John E.
Reynolds III, Dept. of Biology, Eckerd College, P.O. Box 12560, St. Petersburg, Fla. 33733,
USA
Mr. Patrick M.
Rose, Marine Mammal
Coordinator, Florida Marine Research Institute, Dept. of Natural
Resources, 100 8th Ave. S.E., St.
Petersburg, Fla. 33701, USA (FAX:
1/813/8230166)
Mr. Ismu Sutanto Suwelo,
Directorate General of Forests,
Centre for Forestry Official Education & Training,
Jalan Gunung Batu, P.O. Box 42, Bogor 16001, INDONESIA
Mr. Tas'an,
Gelanggan, Samudra, Jaya Ancol, Jalan Lodan Timur, Jakarta, INDONESIA
Biol. Manuel
Vasquez Phillips, Sanchez Ascona 313,
Col. del Valle, 03100 Mexico D.F., MEXICO
SIRENEWS
FAX NUMBER: PLEASE CHANGE YOUR
RECORDS!!!
We remind our
readers that material faxed to Sirenews should
be directed to Dr. D. Domning, Dept. of Anatomy, at the
following number only: 1/202/2657055. Please do not use any of the other
numbers formerly given in these pages, as this may
result in charges to your editor
for receipt (!) of the material.
SIRENIA WORKSHOP IN AUGUST 1993
The response from sirenian biologists to the
prospect of a Sirenia Workshop
as part of the
International Theriological
Congress to be held in Australia in 1993
has been enthusiastic, and Barry
Fox of the ITC organizing
committee has agreed
to timetable it. Unfortunately
for us, the venue for the conference has
been changed to the University of New South Wales in Sydney (well
south of the nearest dugongs)
because the University of Queensland
does not have a 900-seat lecture theatre
for the plenary sessions.
At the
Conservation Biology meeting
in Brisbane in September, I participated in an excursion to look at
dugongs and turtles in nearby Moreton
Bay (see Tony Preen's report in this issue).
We used the Sea World Boat, and the weather was kind. We had dugongs in clear water all around the
boat. Sea World would be happy to allow their boat to be used for a
similar excursion associated with
ITC, and I am trying to organize
this. The boat will take 40 and the cost was A$40 per head
including bus fares to the wharf (bring
your own lunch, drinks provided). -
Helene Marsh
RIVER COWS AND SEA PIGS?
A PROPOSAL
FOR REVISION OF SIRENIAN POPULAR NAMES
In discussions
with both biologists and the public I
find myself repeatedly having
to explain that a dugong is
not a manatee. My
explanation naturally starts with a few details of anatomy,
and progresses to differences in
ecology, presumed
differences in physiology,
and the still controversial
period over which dugongid and
trichechid evolutionary lines have been
evolutionarily separated. I point out
that formal classification places the
dugong and the manatees in a relationship similar to that existing between canids and felids.
The question
I'd like to
raise is whether
my fellow sirenologists would look favorably on popular names
that better reflect both
classification and major niche
differences among living and
recently extinct sirenians. My proposal is as follows:
1) Manatees are grazers and browsers. As manatees
may be obligated to
drink fresh water, and as the
two species which enter
salt water may
therefore be only secondarily
marine, manatees should be referred to as river cows.
Although T. manatus does
enter the marine environment and
root out
rhizomes, it is the atypical member of
the extant manatees, departing from
the riverine "mode" of
the other contemporary trichechids (T. inunguis is exclusively riverine, and T. senegalensis is
primarily riverine in habitat).
2) Hydrodamalis
gigas is obviously a seacow, being
both marine and a grazer on marine algae. No name change needed.
3) The dugong
should be referred to as the seapig.
Like the seacow it is strictly marine, but many months of watching
dugongs feed on a
variety of seagrasses,
having observed dugongs deliberately foraging on two species
of macroinvertebrates, and reflection on the unique aspects of dugong anatomy, all incline me toward regarding the dugong as a
somewhat omnivorous rooter into
the bottom (at the very least a
rhizome specialist). The dugong's
"pigness" is recognized by indigenous peoples who know it
well, as indicated
by the Sinhalese
and Tamil names "cudalpandi" and
"kadalpani", both of which
translate literally as sea pig.
I suspect even the Malay word "dugong" is similarly translatable. - Paul
K. Anderson
[EDITOR'S NOTE:
Comments on the above proposal are
welcome! As for myself, I think
of Hydrodamalis as more of a browser (= leaf-eater) than a grazer, and of the dugong as more like terrestrial
grazers (= broad-snouted, relatively unselective croppers
of "grassy" meadows) as well as being a rooter (though
some extinct dugongids probably did a lot
more rooting than dugongs do today). But
what's in a name:
could any single name, let alone
one borrowed from some mammalian landlubber, ever do justice to the natural
history of a sirenian? If a dugong is not a
manatee, still less is it a cow
or a pig. Maybe we should be
content to use "dugong" and
"manatee" and let the
journalists draw the terrestrial parallels!]
LOCAL NEWS
AUSTRALIA
Indigenous Hunting of Dugongs
in Queensland. - The current liberalization of
community attitudes to indigenous peoples in Queensland is long overdue, but may have
unfortunate consequences for
dugongs. Dugongs are currently
protected by the Fisheries Act, from
which people who are resident
on Trust
Territories (formerly
reserves) are exempt.
Other people may apply
for permits to take dugongs, but these are rarely granted (once in the last five years). This has meant no legal hunting throughout
most of the populous coastal areas of Queensland. The Act is now being interpreted differently.
Aborigines and Islanders living in Trust
Territories are being told they
can hunt anywhere in the State. This means that any hunting party is legal as
long as it is led by an Aborigine or Islander who is
officially resident on a Trust Territory. As Aborigines and Islanders move
around a lot, this change has effectively opened up the whole of the Queensland
coast to
traditional hunting, a
development which I view
as serious, in view of the large-scale movement of
Aborigines and Islanders to
coastal areas with limited
dugong habitat. -
Helene Marsh
Home Range
and Movements of
Dugongs in Subtropical Australia. - Thirteen
dugongs in Moreton
Bay, southeast Queensland, were tracked using satellite
transmitters. Six were tracked in
winter, four in spring and
three in
summer. Home ranges, based
on 95% of fixes and calculated
using the kernel estimator, averaged 64 sq. km and ranged from 28 to 123 sq. km.
Because the dugongs were only tracked
for an average of 50 days (range
20-88), these values probably
underestimate the dugongs' annual range.
Females
maintained larger home ranges than males.
There was no difference in the
range size between age classes or season of tracking. The dugongs did not have distinct core areas
in their ranges, but they did have areas of concentrated use.
On average, 50% of locations occurred in
15% of the home range area. There was extensive overlap between home
ranges, averaging 55% for full ranges and 25% for "core areas."
Most
locations (79%) occurred on seagrass banks. Most of the remainder came from low
tide refuges (channels between banks, or
deep water in the Bay). During winter,
dugongs undertake regular migrations
between the feeding areas on the
seagrass banks in Moreton Bay and a warm-water refuge in the
oceanic waters seaward of the Bay. By
travelling 15-25 km from their feeding areas, the dugongs can
move from water
temperatures of 16-17
C to temperatures of 20-21
C. The dugongs synchronize these
movements with the tidal currents. None of the dugongs undertook
large movements or left the study area. The maximum rate of
travel recorded was 4.7 km/h (14.3 km in 3 h). The dugongs were more active during the day than at
night. -
Tony Preen
BRAZIL
Manatee Exploitation in
Brazil: A Reply. - In regard to the
report by Monica Borobia excerpted in Sirenews
No. 15,
I would like to provide
some clarifications that
I consider very important.
First of all,
the former government agencies IBDF and SUDEPE today form
a single unit,
responsible for enforcement
of protective regulations for all
flora and fauna in Brazil. This agency
is IBAMA - Instituto Brasileiro
do Meio Ambiente e dos Recursos
Naturais Renova'veis [Brazilian
Institute of the Environment and Renewable Natural Resources] - which
maintains offices throughout the country in an attempt to
minimize the impact of hunting and commercial capture on species
in general, by means of laws and
regulations that seek to protect them.
The Amazonian
manatee is officially protected by law,
as a species in
danger of extinction, since 1967
(Fauna Protection Law, no.
5.197, 3 Jan.
1967; Portaria 3.481, 31 May
1973; Portaria N-11, 21 Feb. 1986).
Nevertheless, it should not be overlooked
that illegal hunting of manatees still
occurs in Brazil, and although
the number of captures is being reduced with every passing
year, it has not yet reached
zero. It is worth emphasizing that this hunting is neither encouraged
in any
way nor overlooked by government agencies, since there
exists an agency (IBAMA)
charged with enforcing
and executing the protective laws and punishing those who
break them.
However, the
Amazonian region and its great extent should be taken into
consideration. Many difficulties
and unforeseen circumstances can
arise in the course of
enforcing a Fauna Protection Law in such a vast and
inaccessible region. Each and every
capture of manatees
and other protected
species is considered
illegal, but it is not always possible
to enforce the law, due to the conditions that exist in the region.
Seeking to
better protect manatees, officers
of IBAMA, during the low-water
season, inspect areas near large lakes where the animals are concentrated for
the duration of the dry season, and
where they eventually become very vulnerable to hunters. This inspection is in order to prevent possible large-scale
massacres of the manatees.
Whenever lawbreakers are
met with, their equipment is confiscated, fines are imposed, and the data
are recorded and compiled in the Anua'rio
Estati'stico of IBGE. This registration of the
information does not in any way represent approval of the hunting on the part of the government agencies, but rather a recognition of the
real situation, without omission of
data.
In regard
to the published
issues of IBGE's
Anua'rio
Estati'stico which were quoted in Sirenews No. 15, we
are trying to contact the office of IBGE in Brasilia to find out the source of
these figures and to ask that this type of information
be identified as pertaining
to illegal captures
of animals threatened with
extinction, in order
to avoid further misunderstandings in relation to the
figures presented.
It is
worth emphasizing here once more
that we consider correct the attitude of IBGE in publishing the data
on captures of manatees, since if the hunting is taking place, even if
it is illegal, this should be made public. We believe it would be worse
for such data to be omitted, in the attempt to present a false image
of what is really happening today in regard to
manatee hunting in this country.
On the
other hand, regarding T. manatus, it is worth remembering that
the Manatee Study and Conservation
Center of IBAMA is
doing very interesting work in preserving the manatee and
raising consciousness among the populations of fishermen on the
Brazilian coast. They
are providing talks,
educational campaigns,
posters, videos, and
teaching materials to the
schools, and thereby obtaining very promising
results. Planned for 1992
is a similar
project of manatee
protection and
consciousness-raising in Amazonia, to be
developed by us here at the Aquatic Mammals Laboratory of INPA, in cooperation with the group
working with T. manatus. -
Ioni Colares [translated from
the Portuguese]
Manatees Found in
Maranhao, Northeastern Brazil. - A
recent marine mammal survey
along the Ceara'
and Maranhao coasts, northeastern Brazil,
revealed the presence and hunting of
West Indian manatees (T.
manatus) in areas
not previously
investigated. On 21 April 1991, I interviewed a former manatee hunter at the
locality of Rasgado, Prefecture
of Alcantara, Maranhao. He
informed me that he hunted and caught at least eight manatees, as
recently as September 1990, at
which time he was advised by officials
of the Department of Environment, Prefecture of Alcantara, that this activity
was illegal. Skeletal remains of these
specimens, caught in two
distinct areas (Rasgado
and Jenipauba) in Alcantara,
were retrieved. These included
two mandibles, one partial skull,
four ribs and other damaged bones, reportedly from the last manatees he killed
in September 1990.
Since D.
P. Domning's collection of an
indeterminate rib fragment in
1978, from an animal killed circa
1975-76 in the lower Mearim River, my findings are the first confirmed evidence
of manatee occurrence in Maranhao.
Further investigation should be
carried out in the future to determine whether T. manatus also occurs in
other parts of the state and to evaluate how illegal hunting is affecting the species in
the region.
This survey
was sponsored by World Wildlife Fund-US through a grant
to Salvatore Siciliano. The
Prefecture of Alcantara, through its
Department of Environment,
provided logistical support. A
paper containing details of the survey
is being prepared for Marine
Mammal Science. - Salvatore Siciliano
CAMEROON
Status and Distribution of Manatees in Cameroon.
- During June, July, and August
of 1989, a preliminary survey of manatees (T. senegalensis) in Cameroon
was conducted under the supervision of
James Powell, with support from
the World Wildlife Fund and
Wildlife Conservation International. The
objective was to determine the distribution and status of
this species in Cameroon by
conducting land and boat surveys
of specific watersheds in conjunction with
standard village interviews. The
study was intended to
complement the biological
research activities of Korup
National Park. For this reason, priority was
given to locating manatee populations in the Korup
vicinity. After this inventory was complete, other regions in Cameroon were surveyed to
determine the relative importance of Korup manatees to other manatee populations in the country.
Information on manatee
distribution and status was obtained for four regions: (1) Korup region (Rio del Ray estuary,
Ndian and Akpa-Yafe rivers); (2) Mamfe region (Cross, Manyu, and Munaya
rivers); (3) Edea region (Sanaga and Nyong rivers); and (4) Kribi region
(Lokoundje, Kienke, and Lobe rivers). These all lie on the Atlantic coast with
the exception of the Mamfe region.
Manatees inhabit
estuarine and riverine
habitats in the first three of these four regions. Manatee occurrence, based on the
frequency of reported sightings, appears to
be high in certain
areas of Korup,
such as the
Ndian River and
its tributaries. Ndian fishermen
see manatees regularly and
can observe up to
five manatees a day during the
rainy season. Manatees are seen
in the Akpa-Yafe River as far upstream as Korup National Park,
where a waterfall is located.
Fishermen in the Akpa-Yafe report
seeing at least one manatee a day
during the rainy season. The Akpasang is a small river directly off
of the Akpa-Yafe where
an average of two manatees are seen
each week during the
rainy season. To a
lesser extent, manatees
are distributed throughout the
Rio del Ray estuary, and are usually
seen during the
dry season when the upstream
rivers become shallower and less suitable for manatees. Rio del Ray fishermen see the
animal a few times a year;
usually no more than
one animal is sighted per observation.
The area of highest manatee density in the Mamfe
region is at the confluence of the Cross and Munaya
rivers. They are seen several times a
year at this place, and sometimes as
many as 3-5 are spotted during one sighting.
Manatees are distributed up the Munaya as far as the village of Tabo.
They are rarely seen in the Manyu or the
Awa River (which flows into the Cross River at
the Nigerian-Cameroonian border). Neither the Munaya nor the Manyu is
entirely suitable for manatees because they are shallow and rocky in several
areas. In addition, rapids are frequent,
particularly in the Munaya where a series of rapids occurs near Korup National
Park.
In the Edea
region, the highest concentration of manatees is where the Sanaga River meets
the Atlantic Ocean. Manatees occur in
the Sanaga up to the hydroelectric dam in Edea, but are
not observed as frequently in
Edea as in areas downstream. They are
seen in both the Dihende and the Dipombe
rivers, but rarely in the Nyong. There are also two lakes in
this region where manatees can be found:
Lake Ossa (which is connected to the Sanaga River) and Lake
Tissongo. We were unable to
visit Lake Tissongo
to confirm reports of
manatee presence. The
Sanaga River hydroelectric dam,
which regulates the amount of water
flowing into the Sanaga
River, may have an adverse effect
on local manatee populations.
A large area of potential manatee
habitat upstream of the dam may
no longer be available to manatees since the dam's construction. More important is its impact on manatees
downstream. The dam can potentially affect manatee habitat
by amplifying tidal changes
downstream and hence altering
food availability and habitat suitability.
Most of the
major rivers in the Kribi region are interrupted by waterfalls
and rapids where bands of harder rock cut across the river bed. While in Kribi, we
obtained no positive reports of manatees inhabiting the Lokoundje, Kienke,
or Lobe rivers. The Ntem River, which flows between Cameroon and
Equatorial Guinea, may contain excellent
habitat for manatees, particularly near the Campo Reserve.
Unfortunately, we were not able
to census this area.
The
vegetation varied throughout each region, but most areas contained a
diverse array of overhanging trees
and emergent vegetation. Due
to poor water
quality, submerged aquatic vegetation was difficult to
observe. Natant vegetation was found
predominantly in the Edea region.
Most villages
do not use manatee meat, so heavy exploitation is unusual. In Edea,
permits are issued to high-level
ministry officials that allow
them to take a manatee
for a special occasion. Two manatees were killed for such an occasion
in 1987. Nigerian exploitation of
manatees appears to be heavy
in the southern Korup
region. Due to Korup's proximity
to Nigeria, Nigerians regularly
fish in Rio del Ray near Korup National Park.
This three-month study enabled us to assess the
possibility of a manatee conservation project in Cameroon.
One promising strategy would be
to extend the borders of Korup National Park in order to safeguard an aquatic sanctuary for manatees.
What is needed now
is a qualitative
estimate of manatee
status, movements, and behavior in Cameroon. In addition,
in order to assess the manatee population trend, monitoring both the
manatees and the degree of hunting pressure is necessary. -
Melissa M. Grigione
FLORIDA
Florida
Manatee Mortality Update. - The
mortality total for the year as of the end of September has reached 131, which
is one more than the total by September
of 1990 with the exception of cold
stress deaths (46), and greater than the September
1989 total of 125.
Of the 131 manatees recovered in 1991,
43 were killed by
watercraft, 6 by floodgates or canal locks,
4 by other human-related causes, and 1 by cold
stress. Perinatal deaths amounted to
40, other natural causes
accounted for 6, and 30 deaths were from undetermined causes. Finally, an abandoned calf died at Sea World after valiant attempts to save
its life
over the last three months.
The total
watercraft mortality is up slightly from 40 as
of September 1990 and 41 as of September 1989. Perinatal deaths are also up from 37 (1990)
and 32 (1989). Floodgate/canal lock deaths are
up markedly from 1 (1990) and 3
(1989).
Dr. Bruce Ackerman evaluated the mortality data
and came up with the following conclusions. During the decade of the 80's (1980-89), the average annual increase in mortality was
6.8% per year from all causes and 12.9% due to watercraft impacts. One may
infer from these
data that the
threat from watercraft
is increasing faster than the overall threat to manatees. (Source: Florida Dept. of Natural Resources)
INDONESIA
Fifteen
Dugongs Sighted near Ambon, Indonesia.
- Within the framework of the Dugong
Management and Conservation Project in the
Maluku Province of eastern Indonesia,
an aerial survey was carried out
covering dugong populations in coastal waters of East Ambon and the nearby islands of Haruku, Saparua,
and Nusalaut. The project is a cooperative one between the
Environmental Study Centre of the
Pattimura University (UNPATTI), Ambon, Indonesia; the Foundation
AID Environment; and the State
University of Leiden, The
Netherlands. It aims at improved
conservation and management of dugong
stocks in the province.
No aerial census of dugong populations in
coastal waters of Ambon and its
surroundings has so far been
reported. The main objective of the survey was to make a first estimate
of the numbers of
dugongs surviving in the coastal waters
of these densely populated
islands.
The flight was carried out on 19 December 1990
with a Piper Aztec lower-decker rented
from the Summer
Institute of Linguistics, starting at 9:11 AM during low tide and comprising one and a half hours of effective survey
time. The position of the
wings was clearly a disadvantage for a more
quantitative survey, but the
view was sufficient
to obtain confirmed observations from more than one observer. Five observers joined the flight, two UNPATTI
staff and three Dutch staff and students. The survey was carried out at 400 m
distance from the shoreline, at a height of 135 m and a speed of 180
km/hr, covering a strip of 200 m
on both sides of the plane. There was
little cloud cover, low wind
velocity, and no glare. All dugongs were recorded by more than one observer.
A total of 15 dugongs was sighted, of which none was near the east coast of Ambon, 9 were near the coast of Haruku, 5 near the
coast of Saparua, and 1 near
Nusalaut. Of these, one was a cow
with a neonate calf. All dugongs
observed were within 500 m of the shoreline.
The number
of dugongs observed
is very encouraging, considering the
limited scope of the survey and the
fact that Ambon and
surrounding islands belong
to the most
densely inhabited part of the province. The project will continue
to implement aerial surveys in
order to compile more specific data on
dugong population size and distribution.
- Hans H. de Iongh and Bob Wenno
IVORY COAST
Road Threatens Coastal Manatee Habitat in Ivory
Coast. - A major road is being built
directly through one of the last intact blocks
of tropical rainforest in the Ivory
Coast, and also threatens coastal
ecosystems, particularly mangrove
forests around lagoons, that support West African manatees. The
road, which runs along the
Atlantic coast between Sassandra and
Grand Lahou, was being funded by
the African Development Bank, which agreed in March 1990, at the request of the World Bank, to delay
construction until money
to minimize the habitat destruction could be found. However,
an economist employed by the New York-based Environmental Defense Fund (EDF)
subsequently found road building
fully underway before any protection measures had been taken.
Sirenews will welcome further information on this project and the status of manatees in the affected
area. (Source: EDF Letter 22(2), April 1991)
JAMAICA
Status of Captive Manatees at Alligator Hole
River. - In June 1991,
Antonio A. Mignucci Giannoni, acting with UNEP funding under the auspices of
the Jamaican Natural Resources Conservation Department (NRCD), led a team to the Alligator Hole River nature
reserve in southern Jamaica, where four
Antillean manatees were introduced into a
semi-captive environment in the early
1980's (see Sirenews No. 12).
The team's objective was to determine the status and gender of the impounded
manatees.
They were
able to account for three of the animals,
but did not locate the
fourth, which had not been seen by the
reserve wardens in the two
previous months. Two of the others appeared externally healthy, but the third had suffered a deep cut to its
peduncle as a result of having once been tethered to the shore by its tail
(as were all the manatees), and
was only observed to swim slowly
with its front flippers. All the
animals are now allowed
to swim at liberty in the river,
but are extremely shy and could
not be approached closely or captured by the team. The data
available to the team led them to
conclude that at least two, and possibly all three, of these
manatees are female.
The team stated
that "no justification exists, not
even for education, to hold four,
possibly reproducing female
manatees (actually 4 to 8% of the total Jamaican population) apart [from] the
rest of the Jamaican manatee gene
pool." They recommended that a thorough environmental impact statement be drafted
to assess the effects of the
manatees on the river system; that a dedicated local biologist be found, hired
by NRCD, and trained to monitor the manatees;
that the manatees should meanwhile be left to roam the river
undisturbed; and that no more
manatees should be impounded
in the river, especially since
"it is not clear whether
the river can sustain indefinitely the small
manatee population now impounded there."
Sirenews endorses the team's
recommendations, and hopes that NRCD will implement them.
MOZAMBIQUE
Dugong
Study Planned in Mozambique. - A graduate student and I are beginning a study of dugongs and
dolphins in Mozambique. The work
will examine dolphin
and dugong occurrence
and distribution in Maputo Bay in
relation to increasing gillnet use and environmental degradation through
massive population increase and
demographic changes. The work will
encompass four broad facets:
1. Monitor
and document the gillnet
fisheries of the Bay area, through direct observations at landing points
and markets and interviews with
fishermen.
2. Assess
the occurrence of marine mammals
(dolphins and dugongs) in Maputo Bay
through boat surveys and searching beaches surrounding the bay for carcasses,
etc.
3. Document any fisheries interaction, through
interviews and observations at
markets, etc., and
the examination of carcasses found.
4. Determine which factors, other than
fisheries, influence marine mammal distribution
and abundance (an
assessment of organic pollution
and hydrographic features of the Bay).
- Vic Cockcroft (Centre
for Dolphin Studies, Port
Elizabeth Museum, Humewood, South
Africa)
PALAU
Dugongs in
Palau Resurveyed. - Dugongs
have been exterminated from several isolated archipelagoes through direct human exploitation. In the Micronesian region, dugongs now occur
only in Palau, and Palauan waters support what is
probably the most isolated dugong
population in the world. The closest dugongs are found in Irian Jaya to the south and the
Philippines to the west. In
both these areas, dugongs are believed to be
under threat from human exploitation. Thus it is very unlikely that the
Palauan population is being supplemented by
recruitment from these areas.
Last August, the Nature Conservancy sponsored a visit to Palau by Galen Rathbun, Tom O'Shea, Tony Preen, and myself. The objective of our visit was two-fold: (1) to repeat the aerial surveys for dugongs that had been carried out in 1977,