Sirenews (ISSN 1017-3439) appears twice a year
in April and October and is
edited by Daryl P. Domning,
Department of Anatomy, Howard
University, Washington, D.C. 20059 USA
(fax: 1-202-265-7055). It is
supported by the U.S. Marine Mammal Commission
and Sea World, Inc.
NUMBER 25
APRIL 1996
IN THIS ISSUE: - MASSIVE MANATEE
DIEOFF IN FLORIDA (p. 6)
-
ON CULTIVATION GRAZING BY DUGONGS (p. 8)
-
WHEN SEACOWS WALKED ON FOUR LEGS (p. 10)
EDITORIAL: BAD NEWS OR GOOD?
Several significant
developments for Florida
manatees have occurred since
our last issue. One is the
publication of the workshop volume on manatee population biology edited by Tom
O'Shea, Bruce Ackerman, and Franklin Percival (see
Recent Literature, below).
The upshot of the two decades of painstaking work
summarized in this impressive
compilation is that Florida
manatees actually seem to have increased in numbers since protective
efforts were begun. At
the end of
the volume, O'Shea and Ackerman
conclude that "the
increases in numbers of manatees
counted in aggregation areas in winter reflected an increase in the Florida
population from the
1970's through the 1980's .... We are uncertain whether
such a trend continued in the
1990's." Furthermore, "Reproduction parameters revealed by
studies presented in these proceedings ... indicated the potential for
more rapid growth than previously recognized": as high as 7% per year at
Crystal River. "This higher potential for
population growth makes the probability of true population growth in
other areas during the 1970's and 1980's more plausible than previously
thought...."
These conclusions
were promptly underlined by the results of
two statewide aerial surveys conducted by the Florida Department of Environmental Protection
after cold fronts in January and
February 1996: total counts of
2,274 and 2,639 manatees, respectively. These numbers are
dramatically higher than the previous high count of 1,856, made in 1992;
and as minimum estimates
of actual manatee abundance, they show that the true population
size is
closer to 3,000 than to the figure of
2,000 routinely quoted in recent years.
Although survey coordinator
Bruce Ackerman noted in a press release that weather conditions nearly perfect
for
counting manatees accounted
in part for this result, the evidence
for a growing manatee
population seems to be mounting.
What are
we to make of this? Is the manatee population on the road to
recovery and removal from the
endangered species list? Have all the protective regulations had their desired effect, so that no further constraints on boaters or developers are
needed? If manatee numbers have grown along with human numbers in Florida,
does that not show that human
population growth is harmless
to wildlife, maybe
even beneficial? Was the
whole uproar over
the supposed plight of the manatee in fact just an environmentalist hoax
to begin with? Or (to put a more charitable face on it) is this a demonstration
of the self-correcting nature of science in the light of new data?
Before jumping to any of these conclusions, we
should read more of what O'Shea and
Ackerman had to say: "Possible increases in manatee population size since
the mid-1970's may be attributable to
intensified conservation. However, the threats to manatee
survival and habitat loss
have accelerated and
are expected to increase. A turning
point may soon
be reached, if it
has not already. This contention
is supported by the
possibility that upward trends in counts at power plants
in winter may have diminished in the late
1980's and early 1990's ...; by the
lack of a notable increase of
counts and a higher number of
deaths in southwestern Florida
...; by the high number of recovered carcasses in 1994 [plus a still higher
number in 1995 and a disastrous start to 1996 - see other news in this issue];
and by increased numbers of boats and the more complex technology of
high-speed boating.... Because of the lack
of accuracy and precision in estimates of population size, the size of
the Florida manatee population could decrease even while counts may seem to
increase or be stable.... Given that negative effects on manatee
populations will continue to
increase with burgeoning
human populations in Florida and that decreases in adult mortality can
result in growth and long-term
persistence of Florida
manatee populations ..., no prudent alternatives exist
to maintaining proactive,
vigorous management aimed at mortality reduction."
In short, the catch is
that even if the manatee population has grown under the protection it has
received, we are
rapidly approaching the
limits of the
protective measures now envisioned. The legally-mandated
Manatee Protection Plans are already in place in at least four of the 13
Florida counties considered critical for manatee protection, and further
tightening of regulation beyond
what is in these plans is likely to be strenuously opposed. Meanwhile,
the numbers of humans,
boats, and new
developments continue to grow without
limit. An aggressive manatee-protection campaign has bought the population valuable
time, but the onslaught of demography will soon throw the manatee and its allies
back on the defensive, facing
ever-grimmer odds. The population recruitment suggested by the latest synoptic
surveys may still prove to have been no more than reinforcements thrown into a
losing battle.
The shape
of this battle is already
evident to those who read the published
evidence more closely. O'Shea
and Ackerman cite "data ... that suggest substantial population
growth from internal recruitment
at the Crystal River and at
Blue Spring and
slower growth or stability on the Atlantic
Coast...." These
preliminary results show,
in other words,
that manatees have increased in precisely those areas where
they are most strictly protected,
but may have been unable to do
so where boating activity and boat-caused mortality are heaviest. What we see here, in fact, is an inadvertent experiment
to determine what level
of human harassment manatee populations can tolerate. The
results neatly demonstrate both their
ability to flourish, given reasonable protection, and (more
realistically) their likely inability to survive much longer, as the worst that
Florida is presently throwing at them worsens still further.
This was
not, however, the message that
was reaching the public in the wake of
the 1996 synoptic surveys. As manatee researchers anticipated
when the State of Florida
began these surveys several years ago, they are two-edged weapons. While
it is always useful to have minimum counts to plug into population models, the
danger is that these minimum counts
will be taken as
actual estimates of
population size, and
growth in these
numbers will be misinterpreted as actual growth in
population. They are in fact being misinterpreted this way in the Florida
press, by boating advocates and others, and some have
even begun to call for downlisting of the Florida manatee to a
less endangered status.
The issue of downlisting should, in principle,
be easy to dismiss. The revised Florida Manatee Recovery Plan (1996
version, due to be published in a few
weeks) states that "downlisting should be considered when
... the population
is growing or
stable, when mortality factors
are controlled at
acceptable levels or are decreasing,
and when critical habitats are secure and threats to
them are controlled or decreasing." Of these three criteria, it is
obvious that the latter two are not likely to be met in the
foreseeable future: human-caused mortality continues
to rise, and the threats of human population
growth and development pressures are
anything but "controlled or
decreasing." In practice,
however, only the
first criterion readily registers in the public consciousness, where
higher manatee counts necessarily mean a recovering population.
Sometimes, however,
one problem is solved by another; and
the misleading press coverage of the January and February
surveys was fortuitously swept from the headlines by the disastrous manatee
dieoff in March. For the moment, this antidote
of well-founded alarm seems to have taken effect, but spells
of complacency are bound to recur. When they do - and whenever any of us
has occasion to communicate with the public or the mass media on
these issues - we need to emphasize as strongly as possible the
following points:
1. The statewide synoptic surveys provide
only minimum counts, not estimates of
the total population; they
are extremely sensitive
to weather conditions
and cannot be compared statistically with each other
or with estimates
derived from other techniques.
2. While it
is possible that the total manatee population in Florida has
increased, it is more certain (and more significant) that increases have
occurred in precisely those areas where manatees are best
protected, while in areas of lesser protection there has been little or no increase (and none that is likely to be
sustained).
3. We can take no comfort in
any numerical increases that have been achieved, because the protective measures
that made them
possible are approaching
the limits of political acceptability, while the
threats to manatees
only increase and
can be expected to
wipe out the recent gains. For
this reason, no talk of
downlisting the Florida manatee
is even remotely justified.
4. The manatee
population is still small in
absolute terms, and always
vulnerable to unexpected
catastrophes like the March 1996 dieoff - especially when, as in this case,
the victims are predominately adults in their prime, which are
the animals most essential to survival of the population. When some 2% of that
population can be wiped out in one such event - over and
above all other sources of mortality - there
is ample cause for concern about the species' future.
Not all these points are easy to make in sound bites, but
this is the message we
urgently need to get out. - DPD
DEATH REPORTED
Jesse R. White, D.V.M.
Dr. Jesse White,
well-known marine mammal veterinarian, died on 23 January 1996 at his home in Dunnellon, Florida, at the
age of 61 years. A native of Oklahoma, he received his D.V.M. degree
from Texas A&M University at College Station in 1962. He served as
Staff Veterinarian at the
Miami Seaquarium, 1967-86, and Marine Mammal Veterinarian for the Florida Department of Natural Resources,
Homosassa, Florida, 1986-87. In 1984, he
founded the Florida Manatee Research and Education Foundation, an
organization for which he always served as
Director and President. He was an Adjunct Professor at the College of
Veterinary Medicine, University
of Florida, 1983-87, and Clinical Professor in the Department of Small Animal Medicine at the
same institution from 1987 until
his death. He
received several lifetime
achievement and conservation awards from professional associations, and was the
first veterinarian to serve
on the U.S. Marine Mammal
Commission's Committee of
Scientific Advisors. His publications focused on manatees and marine
mammal care and maintenance. He was particularly interested
in captive breeding of manatees, and it was during his tenure at the
Miami Seaquarium that
the first successful
and regular breeding
of captive Florida manatees began. (John
R. Twiss, Jr. and DPD)
SHOULD THE SIRENIA SPECIALIST
GROUP ESTABLISH A HOME PAGE
ON THE WORLD WIDE WEB?
A couple
of weeks ago,
I attended a
meeting of the
IUCN Species Survival Commission (SSC)
Steering Committee which was held in Australia. I was invited to
attend the meeting as
an observer along with other Specialist Group Chairs from
the region. The Australians enjoyed being the only delegates not suffering from jet lag, a
reverse of the usual situation.
The issue
of communication among and within Specialist Groups was discussed.
The SSC is planning
to set up a home page on the World Wide Web which will concentrate
on being a link among the home
pages established and maintained by various
Specialist Groups. This
initiative raises questions for the Sirenia Specialist Group:
_ How many members would have access to a Sirenia SSG home page on the
World Wide Web if one were established?
_ Is there anyone who is
prepared to establish and maintain such a page?
The page would have many advantages. Here are a few:
_ It would be a source of
up-to-date information on manatees and dugongs.
_ It would be an additional
method of distributing this newsletter.
_ It could enable Group
members to access the gray literature and
publications lists of other members, etc.
_ It could be an effective
method of distributing the Dugong and Manatee Action Plans when they are
finalized.
I do not see a Sirenia Specialist Group home page duplicating the role of
MARMAM.
Your reactions, please;
and is there a volunteer who is willing to establish and maintain the
page? - Helene Marsh
NIRS BREAKS THROUGH SIRENIAN
FOLIAGE
The conventional methods used for
analyzing nutrient contents
of seagrasses are laborious and expensive. This is essentially why most studies dealing
with sirenian and/or seagrass nutritional ecology have
limited numbers of replications. This may now be a thing of the past.
Near-infrared reflectance
spectroscopy (NIRS) has been in
use for the
analysis of agricultural and
food products since the late 1960's. This technique
makes use of a small segment of the electromagnetic
spectrum (just above the visible region, 700 nm to the edge of the
infrared region, 2500
nm), called near-infrared (NIR). The NIR
spectrum contains information on
the major building blocks of the biological world (CH, OH, and NH groups).
I applied this technique in my research
entitled "The ecology of seagrasses as food for dugongs and green
turtles" at James Cook University. It allowed
me to predict multiple
constituents of seagrass
relevant to a dugong's (and green turtle's) perspective, for a
large number of samples
(ca. 1,200, which
would have been
expensive and laborious
using conventional
methods). This technique
allowed me to
select the "best" (most typical)
calibration set (15-20% of the total),
based on the population's spectral variability, for which precise conventional nutritional/chemical analyses
were performed. These
calibration data were then used for the development of predictive
equations for each constituent using a
cross-validation technique. The
predicted values have a good agreement with the laboratory values. The
r˛ values for the different constituents were: 0.99 for nitrogen,
0.96 for organic matter, 0.94 for neutral detergent fiber, 0.91 for acid detergent fiber, 0.90
for lignin, 0.91 for water-soluble
carbohydrates, and 0.92 for in vitro
dry matter digestibility.
NIRS analysis
offers several advantages. It is rapid,
nondestructive, and
environmentally safe. One
of its most important features is that it can analyze samples
for multiple constituents. Even though this technique has existed for
more than 20 years, it
has never been employed in nutritional
ecology of wildlife. This technique will certainly simplify the task of
trying to understand why sirenians prefer certain species of
foliage. - Lem V. Aragones
COURSES ON ZOO ANIMAL BEHAVIOR
AND WELFARE
Edinburgh Zoo,
in conjunction with the University of Edinburgh, is again offering
a two-week summer school
course from 15 to 26 July
1996 on Zoo Animal Behaviour
and Welfare. It is designed for
all those involved in management and husbandry of captive animal populations, and
will update participants on the latest
scientific theory and
its practical
implementation. Registration deadline
is 31 May 1996.
A new two-module short
course on Assessment and Implementation of Animal Welfare Programmes
will also be
offered on 1-3 November and
6-8 December 1996.
(The first weekend module will
cover scientific assessment of animal welfare; the second, animal welfare in
practice.) Covering aspects of the new Royal College of Veterinary Surgeons'
Certificate in Animal Welfare, Ethics
and Law, this course will introduce the current scientific methods that are used to assess and understand
animal welfare and demonstrate how these can be practically implemented.
For information
on either course, contact Hamish Macandrew, UnivEd Technologies
Ltd., FREEPOST, 16 Buccleuch Place,
Edinburgh EH8 0LL, UK; tel.: 0131-650-3475;
fax: 0131-650-3474.
LOCAL NEWS
AUSTRALIA
Dugongs Take Years
to Recover From Seagrass
Loss. - Preen and
Marsh (1995) report dugong
deaths associated with the loss
of some 1000 km˛
of seagrass in Hervey
Bay, Queensland, Australia,
following a flood and two cyclones in 1992. Aerial surveys have been used to track the resultant changes in dugong numbers in the region.
The surveys suggest
that the decline
had ceased by 1993:
Date Population Estimate
1988 2206 ± s.e. 420
1992 1109 ± s.e. 383
1993 579-629 ± s.e. 126
1994 807 ± s.e. 151
However, calf counts
associated with the surveys suggest that the population
may take even longer to recover than originally
predicted.
Date % Calves
1988 22
1993 2.2
1994 1.5
These figures parallel changes in the pregnancy rate and proportion of reproductively active males in Torres
Strait dugongs coincident with
an extensive seagrass dieback in
that region in
the mid-1970's (Marsh 1995). Data from Australia
suggest that large-scale diebacks
of tropical seagrasses, often associated with extreme
weather events such as
floods or cyclones,
are relatively common (Poiner
and Peterken, 1995).
In addition to any direct mortality of
dugongs associated with such
diebacks, their impacts on the life
history of dugongs in the affected
area is likely to be serious and
long-lasting. The only data I know of concerning temporal changes in the pregnancy rates of
manatees are from Marmontel (1995), who provides
evidence that suggests an increase in Florida from 1976 to 1991.
Does anyone
else have any
data suggesting temporal changes
in the life history parameters of sirenians?
References
Marmontel, M.
1995. Age and reproduction in Florida
manatees. In: T.J.
O'Shea, B.B. Ackerman, and
H.F. Percival (eds.). Population biology of the Florida manatee. Information &
Technology Report (U.S. Dept. Interior, Natl. Biological Service) 1:
98-119.
Marsh, H. 1995. The life history, pattern of breeding, and population dynamics of the dugong. In: T.J.
O'Shea, B.B. Ackerman, and H.F.
Percival (eds.). Population
biology of the
Florida manatee. Information
& Technology Report
(U.S. Dept. Interior, Natl.
Biological Service) 1: 75-84.
Poiner, I.R., and C. Peterken. 1995. Seagrasses. In:
L.P. Zann and
P. Kailola (eds.). The
state of the marine environment report
for Australia. Technical Annexe: 1. The marine
environment. Canberra,
Australia, Dept. of Environment,
Sport and Territories.
Preen, A., and H. Marsh. 1995. Response of dugongs to
large-scale loss of
seagrass from Hervey Bay, Queensland, Australia. Wildlife Research 22: 507-519.
- Helene Marsh
CARIBBEAN REGION
Manatee Plans and Materials Being Developed. - The regional
management plan for the West Indian Manatee in
the Wider Caribbean was approved
at the Third Meeting of the Interim
Scientific and Technical Advisory Committee
to the Protocol Concerning Specially Protected Areas and
Wildlife (SPAW) in the Wider Caribbean Region (Kingston, Jamaica,
11-13 October 1995). The
plan will be
published in English, French, and Spanish.
The Caribbean
Environment Programme is also
supporting the preparation of manatee
recovery plans in Belize, Colombia,
Honduras, Mexico, Suriname,
Trinidad and Tobago, and Venezuela, and
the development of educational activities on manatee conservation in
Belize, Jamaica, Mexico,
and Suriname. It
is also producing
a number of educational materials for children
in English, Spanish, and French on
manatee conservation as part of a region-wide public awareness and
education campaign. A
number of these products (poster, coloring book,
and bumper stickers) are
available, as is a directory
of manatee experts and
institutions from the Wider
Caribbean including Brazil.
Address: Regional Coordination Unit for the Caribbean Environment Programme, 14-20 Port Royal Street, Kingston, Jamaica;
tel.: 1-809-922-9267/9268/9269; fax:
1-809-922-9292. - (Source: The
Pilot [UNEP], No. 13.)
FLORIDA
Major Manatee Dieoff in
Southwest Florida. - Beginning 5 March 1996, fresh manatee carcasses began turning up in southwest Florida between Englewood
and Marco Island. The animals were large adults, and the only gross
abnormality was a diffuse
bilateral pneumonia. By 10 March,
as many as four carcasses were
being reported per day.
By the 13th there were reports of
11 deaths in one day, and
the Florida Department of Environmental Protection's (DEP) Marine
Mammal Pathobiology Laboratory in St. Petersburg, which was handling
the necropsies, moved its
operation to a
field station on Sanibel Island
to process the carcasses
more efficiently. As of 4
April, the total number of
carcasses reported in the area since 5 March
amounted to 110, with
the total continuing to
mount as this
went to press. Even if a few of
these turn out to have died from causes
other than that of the majority,
this will still easily rank as by
far the largest single mass mortality of West Indian manatees in recorded history.
All of the carcasses
so far necropsied were in good
flesh; none had any indication of cold stress and all had pulmonary
lesions characterized as
diffuse, bilateral discoloration of purple and bright red
on the
serosal surface of the lungs. On a cut surface, the lungs
were congested and bled. In
the more severe cases, the
primary airways were filled with a
serosanguinous exudate that
was adherent and occluded the secondary airways. In the
less severe cases, the
airways were open, but
the pulmonary parenchyma
appeared the same in all cases
and there was a conspicuous absence
of inflammation. All other organs appeared grossly
normal. Death was rapid
and the result of pulmonary
failure.
The vast
majority of animals
were large (275 cm or more); the smallest were 191
cm and there were no
perinatal-sized animals
involved. At least
seven animals were pregnant. Tunicates were not observed in
any of the GI tracts.
Microbiological results indicated a diversity of bacteria that, in the absence of an inflammatory
response and of consistency between cases, were
considered secondary to the event.
Following the
guidelines of the Marine Mammal Protection Act, the
Florida DEP has requested technical advice from the Working Group for Unusual Marine Mammal
Mortality Events. In addition to State biologists,
Federal scientists from the U.S.
Fish and Wildlife Service,
National Biological
Service, National Marine Fisheries Service, and Armed Forces Institute of
Pathology are cooperating in the response to the dieoff, as well
as scientists from
the University of Florida, University of Miami, Miami
Seaquarium, Sea World, and Erasmus University in The Netherlands.
In 1995, Florida reported a total of 201 manatee deaths. This year, 200 have died in Florida's waterways in little more
than three months.
The same
area of southwest Florida was
the scene of another mass mortality
in 1982 in which some 37 manatees died. These deaths were
traced to ingestion of tunicates that contained red-tide organisms. That outbreak included cases of manatees behaving abnormally,
and some animals recovered; but in this case there have been no reports of sick
or strangely-acting manatees,
only deaths. Although
the 1996 incident
has coincided with a
red tide that has killed sea
birds and other marine animals, preliminary screening of manatee blood for red-tide
toxins has been negative. Neither have
any of the other analyses so
far produced any
conclusive evidence of a cause.
On 1 April,
researchers captured six manatees in the area of the
dieoff and extracted
blood from them
in an attempt to obtain a
control group of live
animals with which to
compare analytical findings from the
carcasses. For instance, if the
live animals have been exposed to the disease, they might
show unusual blood
cell counts or perhaps antibodies. Alternatively,
whatever is causing the disease
may be present in
the control group's blood but
for some reason absent from the blood of
the animals that have
died. Passive Integrated
Transponder (PIT) tags were also placed in the
captured animals, so if any of them turn up dead in the near future, they could provide insight
into the incubation period if an
infectious disease is to
blame, or possibly
give other clues about the cause of death. At this
time a viral infection is
considered a likely
culprit, but unusual bacteria
and natural or
man-made toxins have not
been ruled out.
(Source: Florida DEP)
Award and New Job for Pat Rose. - Patrick M. Rose, who has
headed the Florida Department of Environmental Protection's (DEP)
manatee program for the
past twelve years, was
recently the recipient of a 1995 special edition National Conservation Achievement
Award sponsored by the
National Wildlife Federation (NWF).
This award
recognizes contributions
made by dedicated public servants
in the cause of conservation.
Recipients are selected by the Awards Committee of the NWF Board of Directors.
Pat has
long been known
for his aggressive championing of boat speed zones and
other protective regulations on behalf
of the Florida manatee, and has borne the brunt of many hard-fought
intra-agency political battles,
as well as much bitter public criticism incurred in the course of
regulatory controversies. To
him belongs much of the credit for
the great success DEP has had to date
in enacting manatee protection.
Pat instituted
the Florida Audubon Society's manatee program, then
became the U.S. Fish and Wildlife
Service's first Manatee Coordinator,
before starting DEP's manatee
program. He is
also a noted manatee
photographer, and his still and motion pictures have
appeared in many publications and films.
In recent
weeks he has left DEP
to become the new
Director of Government Relations for
the Save the
Manatee Club, which has
opened a new satellite office
in Tallahassee in order
to become more
involved in advocacy
for stronger manatee protection. Pat's dedication and government experience will be major assets
to this effort, and his
many friends and
colleagues are happy that his talents will not be lost to
the cause of manatee
conservation. (Sources: DEP, Save the Manatee Club Newsletter)
Save the Manatee
Club Goes Online. -
Visit the Save the Manatee Club's new
web site! Facts about manatees, information about the Adopt-A-Manatee program (including an online adoption
application), and materials for
educators are all featured. Address: http://objectlinks.com/manatee.
GERMANY
More on Manatee Breeding in Nuremberg. - A letter to the U.S. Marine Mammal Commission from Dr. Peter