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 r² 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 km² 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 Mühling, Director, Tiergarten Nürnberg, supplements the information reported in Sirenews No. 22. He reports that between 1981 and 1995, 14 manatees in two generations were born at his zoo, including two births of twins. The founding stock came from Guyana.

The manatee pool is 1.6 m deep with a surface area of some 50 m² (not including an island). The manatees often rest in the shallow areas, while ducks in the enclosure rest in turn on the manatees' exposed backs.

No behavioral problems have been observed, even with up to ten manatees in the pool at once. As of June 1995, only four animals were still held, the others having been transferred to the Arnheim Zoo, Tierpark Berlin, Singapore Zoo, and Seapalace in Japan. Plans are now underway to enlarge the manatee pool and make more room for continued breeding.

INDONESIA

Cultivation Grazing by Dugongs in the Moluccas. - From 1990 to 1995 we studied the interactions between seagrasses and dugongs in the Moluccas, East Indonesia. This project was a collaboration between the Pattimura University at Ambon, LIPI Jakarta/Ambon and The Centre for Environmental Science of Leyden University, The Netherlands. We found convincing evidence that dugongs practice "cultivation grazing."

Preen (1993) postulated that seasonal nutritional stress in subtropical areas, and a response to this stress by "cultivation grazing," would be major factors in the observed difference in dugong herd size between tropical and subtropical areas.

An impact of environmental stress on herd size has also been observed for terrestrial herbivores. Increased densities of African elephants caused by restriction in available habitat led to an increase in group size (Laws, 1975). According to Preen (1993, 1995), "cultivation" grazing occurs when herds of dugongs forage intensively in an area, effecting a high level of seagrass removal over a large area. "'Cultivation' grazing allows dugongs to improve the quality of their diet by one or more of the following: (1) maintaining the meadow at a younger, actively growing stage, so the seagrasses contain less fiber; (2) converting the meadow to a lower seral stage composed of preferred and nutritionally superior seagrasses; and (3) concentrating the regrowth vegetation into areas that can be efficiently cropped. The nutritional benefits of these modifications to the seagrass meadows would maximize the fitness of individual dugongs." McNaughton (1979) postulated that the fitness benefits gained by individual animals through increased foraging efficiency could lead to the development of herding behavior in ungulates. According to Preen (1993, 1995), due to their mode of feeding, these benefits could only be achieved if the dugongs fed in large herds.

Preen (1993, 1995) also stated that in tropical areas, the benefits of cultivation grazing may not be necessary, or relevant, in which case there may be no pressure to feed in large herds.

The conclusions of Preen (1993, 1995) are contradicted by the findings of our study, since we observed concentrated feeding plots inside both intertidal and subtidal seagrass meadows in the Lease Islands, caused by cultivation grazing practice by small herds of dugongs (2-6 animals). These small herds could sufficiently disturb the seagrass bed, through a dense grazing pattern, to maintain monospecific meadows (Halodule uninervis and Halophila ovalis) of low standing crop.

The principal effect of cultivation grazing in an intertidal multispecies meadow in our study area (Nang) was the creation of monospecific Halodule uninervis pioneer meadows surrounded by multispecies associations. This pattern of grazing, similar to patterns described for Moreton Bay by Preen (1993, 1995), leads to the spatial containment of less favored species, like (in our study) Thalassia hemprichii and Cymodocea rotundata.

The principal effect of cultivation grazing in a subtidal monospecific Halodule meadow in our study (Haruku) was a higher in vitro digestibility inside the grazing plots, compared with the undisturbed meadow. This phenomenon has not been described by Preen (1993, 1995) for Moreton Bay. Cultivation grazing in monospecific meadows results in patches with lower standing crop, but with a higher in vitro digestibility, indicating a feeding strategy along a productivity gradient as described by Van der Koppel et al. (1995).

During our study we have identified at least five permanent feeding plots with concentrated, regular patterns of recropping by dugongs. We concluded that dugongs in these plots grazed in facultative feeding assemblages with loose social interaction rather than in fixed herds with strong social bonds. Cultivation grazing benefits all individual dugongs through an increased rate of digestibility and energy intake, but lowers the amount per bite and overall biomass in the grazing plots.

With a computer model we calculated the maximum sustained population size for Haruku Strait as 11 dugongs. With a maximum sustained number of 90 dugongs and the estimated minimum population of 22-37 dugongs for the study area, the quantity of the available seagrass in combination with mortality from accidental capture by man may be major factors determining population size, but seagrass quality seems to determine herd size and dispersion.

A "cultivation" effect similar to that observed for small groups of dugongs in the present study has been observed for small herds of manatees in Florida (Lefebvre and Powell, 1990). Florida manatees, with muzzles less specialized for bottom feeding, do not produce feeding trails in the manner of dugongs. Instead, when they feed on seagrasses, they crop circular patches (mean 27 m²). Interestingly, there is some evidence that they return to the same patches in subsequent years.

Our study confirms that the practice of recropping permanent grazing plots through cultivation grazing is moreover part of a permanent evolutionary pattern of adaptations of the dugong as a species in response to its low-quality forage, rather than a temporary response to seasonal nutritional stress as postulated by Preen (1993, 1995).

References

Laws, R.M. 1975. Elephants and their habitats. Oxford, Clarendon Press: 1-376.

McNaughton, S.J. 1979. Grazing as an optimization process: grass-ungulate relationship in the Serengeti. Amer. Nat. 113(5): 691-703.

Preen, A. 1993. Interactions between dugongs and seagrasses in a subtropical environment. Ph.D. thesis, Dept. of Zoology, James Cook Univ., Australia: 1-265.

Preen, A. 1995. Impacts of dugong foraging on seagrass habitats: observational and experimental evidence for cultivation grazing. Marine Ecology Progress Series 124: 201-213.

Van der Koppel, J., J. Huisman, R. Van der Wal, and M. Olff. 1995. Patterns of herbivory along a gradient of primary productivity: an empirical and theoretical investigation. Ecology (in press).

- Hans De Iongh (Centre for Environmental Science, Leiden University, The Netherlands)

[EDITOR'S NOTE: I strongly suspect that production of feeding trails is a function of seagrass and substrate type and density, not of degree of muzzle specialization. If seagrasses are sparse, delicate, and easy to uproot, a sirenian can maintain headway while removing most of the biomass, thereby producing a trail during a single dive. If the foliage is thicker and/or the rhizomes are harder to dig out, only a small patch can be cleared during a single feeding bout (dive), and there is no reason for patches cleared on successive dives to be linearly aligned, so a large circular feeding scar results. If manatees were observed feeding on (e.g.) sparse Halophila beds, they might be found to make trails too!]

PREEN RESPONDS: It is very pleasing that cultivation grazing has been documented from a tropical area, and that the process seems identical to that in subtropical Moreton Bay, where I did my study. The only substantive differences appear to be the size of the dugong herds and the size of the cultivation patches. In Moreton Bay the median herd size was 140, and cultivated areas were up to 75 ha within 11,054 ha of seagrass. In Hans De Iongh's study, the herds were 2-6 dugongs and the study area (Nang Bay) was 6 ha.

Hans has misunderstood the nature of cultivation grazing in Moreton Bay. It is not "a temporary response to seasonal nutritional stress." Rather, I speculated that seasonal stress may necessitate cultivation grazing (and omnivory; Preen, 1995, Jour. Mamm. 76:163-171) by dugongs when they live at the extremities of their range. However, this is not to suggest that cultivation grazing (or omnivory) are seasonal in Moreton Bay, as they are not, or to imply that cultivation grazing could not occur in more tropical areas. Indeed, in the Gulf of Carpentaria, in northern Australia (15.5° S), I have subsequently found that large herds of dugongs persistently feed in the same locations for extended periods, and that they appear to return to these areas, perhaps on an annual cycle.

Interestingly, in this area that is overwhelmingly dominated by an abundance of dense Syringodium isoetifolium, the dugongs feed more in the manner described for manatees. Rather than forming feeding trails, they tend to form small oval feeding patches (ca. 30 x 50 cm) from which they remove only the leaves. These patches grow and coalesce, and eventually very large areas are substantially denuded. It is only after most of the shoots have been removed that they start removing substantial amounts of rhizomes. The extent to which this grazing favors species like Halophila ovalis and Halodule uninervis depends on the extent to which the rhizomes of Syringodium are removed. Mere cropping of the leaves results in a rapid and vigorous shooting by the Syringodium. - Tony Preen

JAMAICA

The World's Most Primitive Seacow. - With support from the National Geographic Society, I have been working in Jamaica for the last three years, collecting fossils of Prorastomus, the oldest and most primitive sirenian known. A site in the hills south of Montego Bay, originally discovered by Roger Portell of the Florida Museum of Natural History, is yielding abundant postcranial bones of this Early to Middle Eocene animal, which was previously known almost entirely from a single skull found at another Jamaican site in the 1850's. Assisting Portell and myself in the field are Steve Donovan of the University of the West Indies, Kingston, Jamaica, and Kevin Schindler of the Lowell Observatory, Flagstaff, Arizona. The new material may represent a new species distinct from the type species P. sirenoides.

In addition to numerous ribs (which are typically sirenian in their bulk and density) and vertebrae, we have found a scapula, two humeri, an ulna, several pelvic bones, three femora, a tibia, a metapodial, a phalanx, and several skull elements and teeth. Much of the material collected remains to be prepared, and probably includes still other parts of the skeleton.

The appendicular bones of these pig-sized, 50-million-year-old seacows resemble those of land mammals far more than do bones of Protosiren, the next most primitive seacow known. Since even Protosiren retained well-developed hind limbs and was obviously amphibious, it seems that prorastomids were even more capable of terrestrial locomotion, although their aquatic adaptations (retracted nasal opening, dense ribs) indicate that most of their time was spent in the water. They still possessed two or more sacral vertebrae that were connected to the pelvis, but these vertebrae were not fused to each other, indicating a degree of spinal flexibility comparable to that of early whales like Rodhocetus. Prorastomids also seem to lack an enlarged tail like that of later sirenians, so they may have used the hind limbs to swim, like the primitive whale Ambulocetus.

Further fieldwork is planned, and as collecting and preparation proceed, we expect to rapidly learn more about the anatomy and lifestyle of this true "missing link" between land mammals and sirenians. - DPD

MEXICO

Manatee Rescue in Chiapas. - One of the most important areas for manatees in Mexico is the Usumacinta River and its basin, with streams and many lakes, in the states of Chiapas and Tabasco. The number of manatees in this area has not been estimated, but it appears they are fairly common.

During the first months of 1995, the southeastern states of Mexico suffered an extensive drought; the water levels of many streams and lakes decreased to critical levels. On 29 May we received news of a group of manatees isolated in an almost dry lake named San Juan (17°46'44" N, 91°55'45" W), located in the municipality of Catazajá in Chiapas. Manatees have been sighted in this lake for more than 10 years.

In March and April, the people from villages nearby took grass to the water to feed the manatees, because they realized that the water level in the lake was dropping fast, and the manatees had nothing to eat. By late May, authorities of Chiapas decided to rescue the manatees.

The rescue work lasted from 31 May to 4 June. Seventeen manatees were captured and moved. From the second day of capture we collected data on morphology and sex, and also took five samples of blood and eight of skin for genetic analysis.

The animals were corralled with a 100-m-long fishing net and then caught by hand by slipping a rope around their peduncles while the net was contracted slowly. They showed an extraordinary ability to escape from the net by lifting the lower edge with their noses. During transport, which lasted about 30 min, all animals showed passive behavior until they were successfully released.

The authorities decided to free the rescued manatees in the Catazajá Lake, which has a maximum area of 16,000 ha in the rainy season, and where the local fishermen estimate a population of 50-80 manatees.

Of the 17 captured manatees, five were adults and the rest were juveniles, including at least one calf. The sexed animals were seven females and four males.

The Chiapas state authorities are now planning to initiate an educational and research program in the region with the aid of the Quintana Roo Research Center, where a research program on the Antillean manatee was started in 1987.

A video of this rescue is available (8 minutes long, VHS). For information, fax: 983-20447 in Chetumal, Mexico. - Benjamín Morales Vela and David Olivera Gómez (El Colegio de la Frontera Sur [ECOSUR], Apdo. Postal 424, C.P. 77000, Chetumal, Q. Roo, Mexico)

NEW CALEDONIA

New Dugong Studies. - Jean-Philippe Das has been conducting studies of dugongs in New Caledonia, and in October 1995 he produced a wide-ranging 97-page privately-printed report entitled Etude des dugongs en Province-Nord: Compte-rendu. It covers the distribution, ecology, and status of dugongs in the province, giving data from aerial and interview surveys, catch data, and ethnobiological information. In 1994 he produced another report, Etude des dugongs en Province-Sud. He can be contacted at: 18 Rue Rameau, 91160 Longjumeau, France (tel./fax: 33-90-49-55-28) or at CEMMEN - Conservation et Etude des Mammifères Marins en Nouvelle-Calédonie, BP 13098, 98800 Nouméa, New Caledonia (tel./fax: 687-44-22-34).

PHILIPPINES

Symposium on Cetaceans and Dugongs. - A Symposium and Workshop on the Biology and Conservation of Small Cetaceans and Dugongs of Southeast Asia was held in Dumaguete, Negros Oriental, on 26-30 June 1995 and hosted by the Silliman University Marine Laboratory. The one-day Symposium was attended by over 120 participants from 10 countries.

The group agreed that its work should include the dugong, since it faces many of the same threats as small cetaceans and because in several nations dugongs and small cetaceans are studied by many of the same researchers.

The Workshop agreed to establish a small cetacean interest group in Southeast Asia, with a regional newsletter appearing at least three times a year (to be published by the Ocean Park Conservation Foundation). The proceedings of the Workshop are being edited by Dr. W. F. Perrin and will be published as a UNEP East Asian Technical Series Report. - (source: The Pilot [UNEP], No. 13.)

WASHINGTON, D.C.

U.S. Postage Stamp to Feature Manatee. - For the first time, a manatee is to appear on a United States postage stamp. Part of a sheet of 15 multicolored stamps featuring 15 different endangered species, the 32-cent stamp depicting a Florida manatee is scheduled for its first day of issue on 2 October 1996 in San Diego, California.

The U.S. is late in joining the club of nations that have put sirenians on their stamps: at least 31 other countries have already done so. The first were apparently Niger and Cameroon in 1962. Still conspicuously absent from the list is Australia. How about it down there?? It's a cheap and easy way for a government to help raise consciousness about sirenians among children and other collectors the world over. - DPD

Publication of Sirenian Bibliography Still Approaching! - After further delays caused by the past winter's government furloughs and shutdowns (what else can go wrong?), Domning's Bibliography and Index of the Sirenia and Desmostylia is now expected to appear this summer as Number 80 in the series Smithsonian Contributions to Paleobiology. It will consist of a single sewn, paperbound volume (about 8" x 10" format) of over 610 pages. It is an exhaustive, annotated and indexed compilation of 500 years of scientific and popular literature on the biology, paleobiology, and ethnobiology of sirenians and desmostylians. Since the Smithsonian does not retail its series publications to the general public, arrangements have been made for the Save the Manatee Club to obtain a limited supply of copies for sale to individuals. The retail price has been tentatively set at around US$25.00 per copy. If you wish to acquire a copy for personal use, please contact the Save the Manatee Club, 500 N. Maitland Ave., Maitland, Florida 32751, USA (phone: 1-800-432-5646), as soon as possible to reserve a copy and obtain up-to-date information on price and handling costs. To repeat, copies are not available for shipment at this time, but will be ready sometime in the next months. - DPD

ABSTRACTS

The following abstracts are of papers and posters presented at the Eleventh Biennial Conference on the Biology of Marine Mammals, held at Orlando, Florida, 14-18 December 1995.

RECENT LITERATURE

Anderson, P.K., and R.M.R. Barclay. 1995. Acoustic signals of solitary dugongs: physical characteristics and behavioral correlates. Jour. Mamm. 76(4): 1226-1237.

Bizzarini, F. 1994. Osservazioni sull'Halitherium schinzi Kaup, 1838 (Sirenia, Mammalia) conservato presso il Museo Civico di Storia Naturale di Venezia. Boll. Mus. Civ. Stor. Nat. Venezia 43: 163-171. [In Italian; Engl. summ.]

Brownell, R.L., Jr., K. Ralls, and W.E. Perrin. 1995. Marine mammal biodiversity: three diverse orders encompass 119 species. Oceanus 38(2): 30-33.

Cashman, M.E., T.L. Ness, W.B. Roess, W.G. Bradley, and J.E. Reynolds III. 1996. Isolation and characterization of a cDNA encoding interleukin 2 from the Florida manatee, Trichechus manatus latirostris. Mar. Mamm. Sci. 12(1): 89-98.

De Iongh, H.H., B.J. Wenno, B. Bierhuizen, and B. Van Orden. 1995. Aerial survey of the dugong (Dugong dugon Müller, 1776) in coastal waters of the Lease Islands, East Indonesia. Mar. Freshwater Res. 46(4): 759-761.

Domning, D.P., S.K. Donovan, H.L. Dixon, R.W. Portell, and K. Schindler. 1995. The world's most primitive seacow: a new sirenian site in western Jamaica. [Abstract] Geol. Soc. Amer. Abstrs. With Progs. 27(6): A386.

Domning, D.P., and H. Furusawa. 1995. Summary of taxa and distribution of Sirenia in the North Pacific Ocean. The Island Arc 3(4): 506-512.

Duignan, P.J., C. House, M.T. Walsh, T. Campbell, G.D. Bossart, N. Duffy, P.J. Fernandes, B.K. Rima, S. Wright, and J.R. Geraci. 1995. Morbillivirus infection in manatees. Mar. Mamm. Sci. 11(4): 441-451.

Gingerich, P.D., M. Arif, M.A. Bhatti, H.A. Raza, and S.M. Raza. 1995. Protosiren and Babiacetus (Mammalia, Sirenia and Cetacea) from the Middle Eocene Drazinda Formation, Sulaiman Range, Punjab (Pakistan). Contr. Mus. Pal. Univ. Michigan 29(12): 331-357. [Protosiren sattaensis, new species]

Hasegawa, Y., T. Muramatsu, and Y. Miyazawa. 1995. A desmostylian tooth from the Tomikusa Group, Nagano Prefecture. Sci. Repts. Yokohama Natl. Univ., Sec. II, Biol. & Geol. No. 41/42: 1-11. [In Japanese; Engl. summ.]

Hasegawa, Y., Y. Taketani, H. Taru, O. Sakamoto, and M. Manabe. 1995. On sexual dimorphism in Paleoparadoxia tabatai. The Island Arc 3(4): 513-521.

Heizmann, E.P.J. 1992. Das Tertiär in Südwestdeutschland. Stuttgart Beitr. Naturk., Ser. C: Allg. Aufsätze 33: 1-61. [Mentions Halitherium.]

Inuzuka, N., D.P. Domning, and C.E. Ray. Summary of taxa and morphological adaptations of the Desmostylia. The Island Arc 3(4): 522-537.

Kamiya, T. 1994. [Steller's sea cow.] Toba Super Aquarium No. 12: 14-15. [In Japanese.]

Kataoka, T. 1987. "Sirenology" [general biology of the dugong]. Jour. Mie Prefecture Zool. Soc. No. 9: 3-7. [In Japanese.]

Kataoka, T., T. Mori, Y. Wakai, J.A.M. Palma, A.A.S.P. Yaptinchay, R.R. de Veyra, and R.B. Trono. 1995. Dugongs Dugong dugon (Müller, 1776) of the Philippines: A report of the joint dugong research and conservation program. Pawikan Conservation Project, Philippines, and Toba Aquarium, Japan: 1-168.

Kettembeil, S. 1995. Dugong vom Aussterben bedroht. Naturwiss. Rundschau 48(1): 29.

Kimura, M., H. Furusawa, T. Sagayama, Y. Igarashi, A. Suzuki, and H. Fukusawa. 1995. Geologic age and paleoenvironment of fossil sirenian-bearing deposits (Kinkomanai Formation) in the Shosambetsu region of northern Hokkaido, Japan. Jour. Geol. Soc. Japan 101(5): 345-352. [In Japanese; Engl. summ.]

Kobayashi, S., H. Horikawa, and S. Miyazaki. 1995. A new species of Sirenia (Mammalia: Hydrodamalinae) from the Shiotsubo Formation in Takasato, Aizu, Fukushima Prefecture, Japan. Jour. Vert. Pal. 15(4): 815-829. [Dusisiren takasatensis, n.sp.; Late Miocene]

Kraus, J. 1995. Florida manatee soft release. Endangered Species Tech. Bull. (U.S. Fish & Wildl. Serv.) 20(5): 8-9.

Lockett, J. 1996. Dugongs dine with the herd. BBC Wildlife 14(1): 20-21. [Popular account of cultivation grazing, based on Preen, 1995.]

Marmontel, M., T.J. O'Shea, H.I. Kochman, and S.R. Humphrey. 1996. Age determination in manatees using growth-layer-group counts in bone. Mar. Mamm. Sci. 12(1): 54-88.

O'Shea, T.J., B.B. Ackerman, and H.F. Percival (eds.). 1995. Population biology of the Florida manatee. Information & Technology Report (U.S. Dept. Interior, Natl. Biological Service) 1: vi + 289. [Comprises 18 articles resulting from the workshop on manatee population biology held at the University of Florida in 1992.]

Papastavrou, V. 1995. Gentle giant's furry fate: why the Steller's sea cow died out. BBC Wildlife 13(11): 26.

Pirika Sirenia Research Group. 1992. Report on excavation of sirenian fossil from Pirika Imakane, southwestern Hokkaido. Imakane (Japan), Imakane Township Board of Education: [vi] + 133. [In Japanese; Engl. summ. Concerns a Pleistocene skeleton of Hydrodamalis sp.]

Preen, A.R. 1995. Impacts of dugong foraging on seagrass habitats: observational and experimental evidence for cultivation grazing. Mar. Ecol. Prog. Ser. 124: 201-213.

Preen, A.R., and H. Marsh. 1995. Response of dugongs to large-scale loss of seagrass from Hervey Bay, Queensland, Australia. Wildl. Res. 22: 507-519.

Schindler, T., and K. Schindler. 1992. Ein Fund von Säugerzähnen im Oberen Meeressand (Rupelium, Oligozän) von Bad Kreuznach (Mainzer Becken, SW-Deutschland) mit Anmerkungen zum Aufschluss und zum sonstigen Fossilinhalt. Mainzer Geowiss. Mitt. 21: 35-40. [Engl. summ.; mentions Halitherium schinzii.]

Schiro, A., and D. Fertl. 1995. Mermaids sighted in Galveston Bay. Soundings (Galveston Bay Foundation) 7(3): 4-5. [Sightings of West Indian manatees in Texas.]

Schuhmann, H.-J. 1995. Der Manati, Trichechus senegalensis, im Rio Geba, Guinea-Bissau. Natur und Museum (Frankfurt a. M.) 125(12): 402-409.

Schwartz, F.J. 1995. Florida manatees, Trichechus manatus (Sirenia: Trichechidae) in North Carolina 1919-1994. Brimleyana No. 22: 53-60.

Takamura, N., and R. Sakai. 1994. [Stars of the Toba Aquarium: dugong.] Toba Super Aquarium No. 12: 10-13. [In Japanese.]

Wallace, R.L. 1994. The Florida manatee: organizational learning and a model for improving recovery programs. In: T.W. Clark, R.P. Reading, & A. Clarke (eds.), Endangered species recovery: finding the lessons, improving the process. Covelo (Calif.), Island Press: 131-155.

CHANGES OF ADDRESS

Benjamín Morales Vela, ECOSUR, Apdo. Postal 424, Chetumal, Quintana Roo 77000, MEXICO (fax: 983-20447)

Leslee Parr, Dept. of Biology, Portland State University, P.O. Box 751, Portland, Oregon 97207, USA

Patrick M. Rose, 2545 Blair Stone Pines Dr., Tallahassee, Florida 32301

Essam Samson, Forest Engineer, P. O. Box 11287, Yaounde, CAMEROON

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