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OF PLANNING AND NATURAL DIVISION OF FISH AND WILDLIFE RESOURCES May 1997 Volume 9 Number 8

SAGA OF A SPONGIVORE: The Ecology and Conservation of the Hawksbill Turtle

The hawksbill is the largest spongivore(sponge populations on the reef but they enable other eater) and the only reptile known to feed almost animals to prey on sponges.As the turtle eats the exclusively on sponges.Fewer than a dozenverte- sponge,it exposesthe soft inner parts of the sponge brate animals are known to be dedicated which are fed on by other fish. This also exposes spongivoresand those are predominantly angelfish many organisms that live within the spongewhich (including the gray; French; and queen angelfish), then are also preyed upon. filefish; trunkfish; and the Moorish idol. Just as hawksbills affect life on the reef, the Dr. Anne Meylan is one of the world's foremost quality of the reef habitat affects them. Hawksbills authorities on hawksbill turtles. Her studies indi- require a vibrant spongecommunity on which to cate that more than 95 percent of the stomach feed. Unfortunately, coral reefs worldwide are contents of hawksbills consist of sponges.Dr. deteriorating as a result of marine pollution, the Meylan's research and subsequentexperim-ents by collection of reef life forms, other human distur- other scientists indicate that male and female bances,and natural catastrophes. If the conditions hawksbills of all sizes dependon spongesas their of reefs and the food provided by reefs continue to primary food source. decline, the hawksbill will be affected. To better understand the "uniqueness" of a As grim as the situation is for hawksbills, there spongeeater, you need to consider the structure, is hope. Legal international trade of tortoiseshell defensesand nutritional qualities of sponges. has declined dramatically, although illegal trade Spongesare multicelled animals which belong to probably still continues. In 1992, Japan, histori- the phylum Porifera. cally the largest importer of tortoiseshell, agreedto Most spongeseaten by hawksbills are charac- end its importation of tortoiseshell under the terized by a dense matrix of spongin fibers and Convention on International Trade of Endangered siliceous spicules. Spicules resembleneedle-thin Species(CITES). As recently as 1990, tortoiseshell slivers of glass, many with multiple, hooklike tips. from some 12,200 hawksbills was exported from Spicules are unaffected by the digestive processes the Caribbean into Japan. According to a report of hawksbills or other spongivoresfor that matter. published by Anne Meylan in 1989, the turtles Somesponges consumed by hawksbills possess were taken from a region for which the maximum noxious or toxic chemical compoundsthat in most estimate of nesting females is 5,000 each year. casesare effective deterrents against potential Only through stringent enforcement of bans predators. No one is sure how hawksbills overcome on tortoiseshell trade, protection of coral reefs and the toxins that may be present in their prey conservation of the beacheson which hawksbills sponges. nest do we stand a chance to save this species.Loss Given the questionable gastronomic character of of the hawksbill turtle would be a terrible loss to sponges,why would hawksbills, angelfish, and the biodiversity of the world's oceans. other spongivoreswant to eat sponges?Some Article partially excerptedfrom original story by Jeff scientist have suggestedthat spongivory evolvedin Ripple, OceanRealm Magazine. responseto increased competition for food among animals on coral reefs. Spongesrepresent a wide- spread, abundant, relatively underexploited food Quote sourcefor any predator able to eat glass and not Like winds and sunsets, wild things were taken becomepoisoned by toxins in the sponge.Little for granted until progress began to do away with information is available on how spongivoresdigest them. Now we face the question whether a still their prey. higher "standard of living" is worth its costsin Hawksbills are influential inhabitants of coral. things natural, wild and free. reefs. They not only maintain the size of spong-e - f.lrl" T ~~~~1.J A Record Year At Sandy Point thousand eggslaid survives the perils of life and lives long enough to reach maturity. When you The Sandy Point leatherback turtle project has figure that half are probably males, it means that a been running since 1981.Before the project was lot of eggshave to be protected to see one turtle started by the Division, nearly 50% of all nests laid comeback. Each turtle lays an average of 5.3 nests were lost to beacherosion each year. Thosethat per year, and 80 eggsper nest. If we exceed100 remained suffered poaching by humans. This left turtles this year, which we easily may, we could very few nests to hatch and maintain the species. have over 500 nests and 40,000 eggson the beach As a result, numbers of turtles nesting each year at this year, a monumental record for Sandy Point! Sandy Point was around 20 and probably declining. Article by RalfH. Boulon, Jr., Chief of Environ- For the first eight years of the project, we had an mental Education Program. averageof 28 turtles nesting each year. For the last eight years, we have averaged41 turtles per year with a high of 55 turtles in 1992 and 1994. Turtle Video now available Starting in 1981, we began moving nests that Just as promised, our latest video is now avail- were laid in erosion prone parts of the beach to able. Third in the series, Our Natural Virgin Is- "safe zones"We began patrolling the beach at lands: Sea Turtles: Our Endangered Mariners, is night, every night, from April 1 to the end of Au- really a treat for the sea turtle enthusiast. "Tessa gust to try to encounter each and every turtle that the Turtle", an animated turtle, shares interesting nested.As a result of these activities, poaching has information about her species.The 9.5 minute droppedto zero and loss to beach erosion is less video discussesVirgin Islands sea turtles; Leather- than 3% each year. This means more hatchlings backs, Green, and Hawksbills. The video is avail- are successfullyleaving Sandy Point than at any able at both DFW Offices in Redhook,St. Thomas time in the recent past. From genetic work we (809 775 6762) and Lagoon Street, St. Croix Office know that the hatchlings return to Sandy Point to (8097721955). Please give us a call if you are nest oncethey mature. It is believed that leather- interested. We request a $2.00 fee for postageper backs take from ten to fifteen years to reach matu- video. rity. This year we may be seeing someexciting re- Trees were saved by printing on recycled paper sults of our nest protection efforts. As of the 18th of May we have 100 individual turtles nesting on Sandy Point. Thirty six of those are new, untagged ~\9\"'I:f,. . This newsletter was funded by the US turtles, presumably young turtles coming to nest Fish and Wildlife Service,Sport Fish and ~,p;~~Wildlife Restoration Acts, the Caribbean for the first time. These may be turtles that ~..~l~;r, ~D ~'{\O~ Fishery Management Council and the hatched from protected nests on Sandy Point ten to ~~~- G<>vernmentof the VI. fifteen years ago and have survived to maturity. It Donna M. Griffin - Editor is estimated that only about one in one- cont'd RalfH. Boulon Jr. - Chief of Environmental Education

GOVERNMENT OF nm VIRGIN ISLANDS BULK RA1E OF nm UNITED STATES U.S. POSTAGEPAID ****** CHARLOTm AMALIE, V, Departmentof Planningand Natural Resources PERMIT NO. 35 Division of Fish and Wildlife 6291 EstateNazareth 101 St Thomas,USVI 00802-1104 (809)775-6762(ST .T.), (809)772-1955(ST.X.)

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