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ISLAND RESOURCES FOUNDATION Can'bbean Headquarters RED HOOK BOX 33. ST. THOMAS U.S. VIRGIN ISLANDS 00802 (809) 775·6225 Heport on Washington, D. C. Office 1718 P STREET. N.W .. SUITE T4 WASHINGTON. D.C. 20036 (202) 265-971 2 Sea Turtle Nesting, Sighting, Eggs and Hatchlings for 1978 in the U. S. Virgin Islands and a recommended research methodology for dealing with hatchling disorientation on the beach (with specific reference to leatherback nests at Sandy Point St. Croix) Pursuant to NOAA/NMFS Purchase Order #01- 8-D08-00187 Submitted for Island Hesources Foundation (a non-profit research organization) October 30, 1978 by Dr. Edward L. Towle Executive Director with the assistance of Dr. David Olsen1 U. S. National Park Service, VINP Mr. William Hainey1 Mitll [' H 6 he:rt I '.T·e.:yt 9- Ud~i.~l· Mr. Michael Kenned~2 Mr. Hichard Dewey Mr. Theodore Skov2 Dr. Caroline Hogers3 Virgin Is lands Fishermen 1 Island Hesources Foundation 2 Virgin Islands Department of Conservation and Cultural Affairs 3 West Indies Laboratories i TABLE OF CONTENTS 1. Survey of Available St. Croix Data on Sea Turtle Nesting Beaches and Offshore Sightings 2. Summary of Available Data on 1977-78 Turtle Nesting Beaches in St. Thomas-St. John 3. Disorientation and Related Mortality in Leather- back (Dermocrelys coriacea) Hatchlings at Sandy Point, St. Croix, U. S. Virgin Islands LIST OF TABLES TABLE A - Turtle Nesting Beaches, St. Croix, U. S. Page No. 1 - 13 14 - 22 23 - 28 Virgin Islands 6 - 7 TABLE B - National Park Service, Buck Island 9 TABLE C - West Indies Laboratory Sightings Since 6/15/78 (Dr. Caroline Rogers) 12 TABLE D - Summary of Interviews Reporting Turtle Nesting Activity for Leatherback and Hawksbill Turtles in St. Thomas and St. John, U. S. Virgin Islands TABLE E - Summary of Reported Recent Turtle Nest- ing Activities in St. Thomas, U. S. V. 1., Listed by Nesting Beach 17 - 19 20 ii LIST OF FIGURES FIGURE I - Turtle Nesting Beaches. St. Croix 1976 - 1978 FIGURE II - 1978 Turtle Sightings/Fishermen FIGURE III - Turtle Sightings/Charter Captains- Divers FIGURE IV - 1978 Turtle Sightings. Dr. Caroline Rodgers. WIL FIGURE V - Summary of 109 Hawksbill and Leather.,- back Turtle Nesting Reports for 1978 in St. Thomas and St. John. U. S. Virgin Is lands FIGURE VI - Location of St. Thomas and St. John Turtle Nesting Beaches Page, No. 8 10 11 13 21 22 -1- SURVEY OF AVAILABLE ST. CROIX DATA ON SEA TURTLE NESTING BEACHES AND OFFSHORE SIGHTINGS This summary c'ontains information derived from personal records of Michael Kennedy and Theodore Skov, records kept by Dr. Caroline Rogers of West Indies Laboratory at Kennedy's request, records of the National Park Service, and interviews by Kennedy with 9 divers and dive-tour operators, 3 charter- boat operators, and 10 fishermen. A. Nesting Beaches (1) Data from personal records of T. Skov and M. Kennedy, DCCA conservation enforcement officers, are presented in Table A. Numbers represent their best estimates of numbers of nests per year, as recorded from their incidental (i.e., non-systematic) observations between 1976 to the present. Note that the species in most cases were inferred from such indications as size of tracks, size and location of nest pits, etc. Figure I shows the location of these beaches on a map of St. Croix. If one lists as "major" nesting beaches those areas where 10 or more nests are observed per year, the following ranking is obtained: Major leatherback nesting beaches: l. Sandy Point - tip and Northwest 2. Punnett Bay (Shoy's) 3. Coakley Bay 4 • Sandy Point - Southeast 5. Manchioneel Bay 6. Prune Bay - (actually only 9/year listed) -2 - Major Hawksbill nesting beaches: 1. Jack Bay 2. Green Cay Beach 3. Manchioneel Bay 4. Coakley Bay Major Green Nesting Beaches: 1. Manchioneel Bay One should keep in mind the "softness" of the above data and use caution in drawing conclusions from it, but it is felt that it does give a fairly reliable indication of which beaches are most heavily nested. Kennedy sighted a group of 27 leatherbacks of the NW corner of St. Croix, and 10 turtles of undetermined species along the south shore from Turner Hole to Watch Ho while making a circuit of the island by helicopter on May 23, 1978. These sightings are indicated on Figure II by the symbols Kl and K2 , respectively. (2) Data on Buck Island from records of Robert Thomas, National Park Service ranger, are presented in Table B. Since the park service rangers attempt to erase the tracks of nesting turtles so the nests will not be poached, no species data is available. Diedrich's Point on the south shore appears to be the major nesting beach with 19 recorded nests, followed by the west end beach with 12 nests, and the north shore with 7 nests. -3 - B. Offshore Sightings (1) Data from interviews with fishermen are plotted as Figure II and summarized below; all data are fo'r 1978: Fishermen 1. Robert Vertichio (vessel, capt. Ross) - saw about 7 good-sized turtles (3'-4') on Lang Bank, 3-6 miles due east of East Point. Saw about the same number (7) on southern part of bank (good-sized) from Great Pond eastwards. 2. Jim Vertichio (vessel, Capt. Ross) (not interviewed personally, communication with Robert V., above) - saw mating just off reef at Yellowcliff Bay. Also saw a couple of small turtles inside reef. 3. Joe Christmas (vessel, Capt. Ross) - has seen all kinds including loggerhead. About 50 between Estate Anquilla and Texaco storage tanks west of airport. 4. Teddy Skov - saw about 100-150 turtles all along south shore from East Point to Sandy Point, hawksbills and greens 18"-4'. Hawksbills seen between Salt River and Cane Bay, unidentified species north point of Lang Bank. Saw 3 greens mating east of Buck Island, 1 hawksbill mating SE of Lang Bank. 5. Robert MacAuliffe (vessel, Miss Bertha) - saw 150-200 greens and hawksbills on Lang Bank east of Buck Island around to Grapetree Bay. All sizes; no mating. 6. Michael Lombard (vessel, Kali) - has seen about 200 greens and hawksbills, primarily on southern half of Lang Bank - 18" - 3'; no mating. 7. Vladimir Prince - saw about 1 or 2 green or hawksbills each trip on Bayside of Sandy Point; no mating. 8. Valentino Lugo, Jr. - saw between 50-100 what he called whitebacks (greens) by bank south of Sandy Point. Sizes range from hatchlings to 3'-4'; no mating. About 5 years ago, he saw about 2000 leather- back hatchlings just offshore (1/2 mile south side of Sandy Point). 9. Hank Jones - saw 30-40 hawksbills from Butler Bay around to Ham's Bluff, Mostly NW of (3-6 miles) Ham's Bluff; no mating. -4- 10. Jay Huber (Captain, C-J) - has seen a few (3-5) green turtles west of NW corner of Buck Island in deep water. (2) Data from interviews with charter-boat captains and divers are shown on Figure III and summarized below; data are for 1978: Dive Operators/Charter Boat Captains 1. Brian Friedman (Operator, Pressure Ltd. Dive Charters) - has seen about 30 turtles that looked like greens, sizes from 18" to 4', between the North Cut and the trail at Buck Island. Also saw about 30 on Scotch Bank. No matings this year, 1 mating last year east of White Horse. 2. Brian Bishop (Diver, Aqua Engineers) - has seen about 6 hawksbill from 1'-3' long on Lang Bank, southern side. Also saw 8 leatherbacks off Mannings Bay. No mating. Saw 1 green about 3' at Anally Bay. 3. Don Bishop (Diver, Aqua Engineers) - has seen about 6 hawksbill off East Point around to Jack's Bay, 1'-3'. No mating. 4. Michelle Pugh (VI Divers) - has seen more than 30 hawksbill between North Star and Cane Bay; usually only sees' l' or 3' turtles. Not many in-between gizes. Has seen a hawksbill on Buck Island trail at night. Some of the large turtles had barnacles. No mating. 5. Bill Walker (Diving Manager, VI Divers) - has seen about 10 at Cane Bay, all near shore inside of dropoff. No mating. 6. Junie Bomba (Capt. of vessel North Star) - has seen between 150-200 greens or hawksbills. Says there seems to be two main groups: one north of Green Cay on the dropoff, and one south of Dietrich's Point Buck Island. Also 1 leatherback west of Buck Island in deep water. Has seen newly-born leatherbacks in trail at Buck Island. Saw 1 mating north of Green Cay. 7. Teddy Clark (Teddy's Charter Service) - has seen 150-200 between C'sted Harbor and Buck Island. Heaviest north of Green Cay and south of Buck Island. Seen especially when it's calm. Mostly large (3'); Saw about 12 newborn leatherbacks inshore near beach on north side of Buck Islanq at· one time. Has seen 3-4 matings in past 5 years.' 8. -5- Edward Wendt (Co-operator, Above & has seen about 100 turtles, mostly Kings' Reef (SW of F'sted Pier) to 1 big 5' hawksbill at Butler Bay. No mating, Below Dive Shop) - hawksbill, from Butler Bay, 18"-4', No leatherbacks. 9. Gene Tepe (Co-operator, Above & Below Dive Shop) - has seen about 50 green and hawksbills at Cane Bay. About 10 greens by sunken barge off F'sted Pier. No mating. 10. Peter Winnicki (Diver) - has seen about 30 green or hawksbills, mostly hawksbill, 18"-4'. No mating. Sighted at Butler Bay and along west coast from F'sted Pier north. 11. Robert Butcher (Diver, Carribean Sea Adventures) - saw 20-30 turtles this year off Pull Point, about 5 off Scotch Bank. 1-2 matings last year. A group off Diedrich's Point and a group off Pull Point. (3) Data on turtle sightings by West Indies Lab personnel have been collected by Dr. Caroline Rogers since July 15, 1978, and are presented in Table C and Figure IV. About 10 turtles of undetermined species were sighted during a flight between Christiansted and the eastern tip of the island on August 15, 1978. (4) The only data available (for St. Croix) from the Department of Conservation and Cultural Affairs for 1978, is for the one week period, July ~4-20, dur~ng which DCCA officers and National Marine Fishery Service agents mounted a turtle sur- veillance at Sandy Point, Shoy's Beach and Prune Bay. No nesting females or hatchlings were seen. Aside from this joint operation, no official DCCA nesting surveillance has been carried out on St. Croix during 1978 -6- TABLE A - Turtle Nesting Beaches, st. Croix, u.s. Virgin Islands l Location 1. New Fort 2. Beauregard Bay 3. Shoy's Point 4. Punnett Bay (Shoy's Beach) 5. Green Cay Beach 6. Prune Bay (Pull Point) 7. Coakley Bay 8. Roebuck's Beach (Solitude) 9. Teagues Bay (West) 10. Smuggler's Cove 11. Knight Bay 12. Boiler Bay 13. Teytaud's Beach 14. East End Bay 15. Isaac Bay 16. Jack Bay 17. Grapetree Bay 18. Turner Hole 19. Rod Bay 20. Robin Bay 21. H' Penny Bay 22. Manchioneel Bay 23. Cane garden Bay 24. Manning's Bay 25. Hope & Carlton Land 26. Sandy Point (Southeast) 27. Sandy Point (tip & NW) 28. La Grange 29. Prosperity to Sprat Hall 30. Sprat Hole 31. Butler Bay 32. Ham's Bay 33. Maroon Hole Approximate No. Nests/Year 3 Green and 2-3 Leatherback Historical Green and Hawksbill 1-2 Leatherback 25 Leatherback, 2-3 Green or Hawksbil 15 Hawksbill and 2 Leatherback 9 Leatherback and 2-3 Hawksbi11 15-20 Leatherbacks and 5-10 Hawksbil1 3 Green 2-3 Hawksbill 2-3 Green and 2-3 Hawksbil1 3-5 Green 1-3 Hawksbill 1-3 Hawksbill 3 Hawksbill 7-8 Hawksbi11 and 1-2 Leatherback 25 Hawksbi11 and 1-2 Leatherback 3J..i5 Hawksbil1 and 3-5 Green 1-2 Hawksbill and 1-2 Green 5 Hawksbil1 and Green 5 Hawksbi11 and Green 5 Hawksbill 10 each Hawksbi11, Green & Leatherbac 4-5 Hawksbill 1-2 Green 2-3 Hawksbill 15 Leatherback and 3-4 Hawksbill 80 Leatherback and 3-5 Green and Hawksbill 3-5 Green 5 Green 1-2 Hawksbi11 1-2 Hawksbill 1-2 Hawksbil1 5 Hawksbill and 5 Green -7- Table A - Turtle Nesting Beaches, St. Croix - Cont. Location 34. Annaly Bay 35. Davis Bay 36. North Star 37. Cane Bay 38. Rust Op Twist 39. Salt River (West point) 40. Tourquoise Bay 4l. Judith's Fancy (St. John) 42. Buck Island 2 Approximate No. Nests/Yr. 1-3 Green 3 Hawksbill, 3 Leatherback, 4 Green 5 Hawksbill 3 Hawksbill 3 Hawksbill 3-5 Hawksbill or Green 5 Hawksbill or Green 5 Hawksbill or Green 49 (no species given) lSource: M. Kennedy & T. Skov, incidental observations between 1976-1978. Species inferred from size of tracks and characteristics of nest pit. 2Buck Island data from National Park Service, for 1978 only. FIGURE I TURTLE NESTING BEACHES, ST. CROIX 1976-1978 4{? 3 r '--'"'-' ~ Js Q ./ 20 19 I ro I ) IJ~~ 27\ ~ ...........--14 26 NOTE: NUMBERS CORESPOND TO BEACHES LISTED ON TABLE I Source: M. Kennedy, T. Skov, N.P.S. -9- . TABLE B - NATIONAL PARK SERVICE, BUCK ISLAND July 1978 17 new nests 1 recorded hatch - hawksbill 3 nests destroyed by poachers August 1978 12 new nests 2 recorded hatches - green 2 nests destroyed by poachers 1 nest destroyed by mongoose September 1978 9 new nests 2 recorded hatches 2 nests destroyed by unknown sources i *" \ \ *&~ *.---- * KEY * SIGHTINGS # MATINGS SIGHTED L IGUl:<E II 1978 Turtle Sightings/F~sherrnen * ~ *----------~---- _.* *~. *-----* SIGHTINGS OVER AN AREA ,t * * * C? U#~ i /*/. --./ ./" I ./ ..... Q----/ ~ -----*? K2 ':::--- # * -----------/* * FIGURE III 1978 TURTLE ST~HTINGS/CHARTER CAPT~INS-DIVERS *C ** ~ *.1 KEY . * SIGHTINGS * * SIGHTINGS OVER AN AREA *A,*B,*C GROUPS OF TURTLES # MATINGS 9 * * ~ ~ -12- TABLE C - WEST INDIES LABORATORY SIGHTINGS SINCE 6/15/78 (Dr. Caroline Rogers) Date 6/15 6/19 6/21 6/29 6/30 7/13 7/14 7/15 7/19 7/22 7/21 7/16 7/25 8/4 8/4 8/5 8/12 8/13 8/15 8/18 8/15 8/20 9/6 9/16 9/29 No. 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10 1 1 1 1 1 1 Location Smuggler's Cove Patch Reef #1 White Horse Smuggler's Cove Boiler Bay Boiler Bay Buck Island Salt River Buck Island North Star Outside Jacks Bay Grapetree Bay Grapetree Bay Buck Island Judith's Fancy NorthEast Cane Bay West End Buck Island Approx. Kind Size ? 12" Green 18" Hawksbi11 2' Gr. or Hawks. 2' Hawksbi11 3' Gr. or Hawks. 2' Gr. or Hawks. 2' Gr. or Hawks. 4' Hawksbi11 18" Hawksbi11 3' ? 3'-4' ? 3' ? 1'-11/2 , Hawksbi11 11/2' Hawksbi11 11/21 Hawksbi11 2' Green North Shore,Buck Island Hawksbill 3' I' C'sted to East Point (flight) ? West Wall, Salt River Cnyn. ? North Shore, Buck Island ? North Star ? East Shore, Buck Island Hawksbil1 East Buck Island Hawksbill North Cut Buck Island Hawksbi11 ? 3' 21/2' 2' 18" 10" 18" * PIGURE IV 1978 TURTLE SIGHTINGS 1 * /t1 ~~Q KEY * SIGHTINGS 1 * * AERIAL FLIGHT 8/15/78 * SOURCE: DR. CAROLINE ROGERS , Data on incidental sightings since 6/15/78 ** *-** , * C?* ** * I - w -14- SUMMARY OF AVAILABLE DATA ON 1977-78 TURTLE NESTING BEACHES IN ST. THOMAS-ST. JOHN Data for this summary of sea turtle nesting and sightings on st. Thomas and St. John was acquired through interviewing 63 commercial fishermen and 6 recreational fishermen, one Park Ranger, and one government Shoreline Management staff member. Most of the fishermen were not aware of any turtle nesting activities since most of their fishing activities took place offshore. In all we had 15 respondents who had observed some sort of nesting related activity. The results presented contain several possible biases which must be considered. The first bias involves the failure of most of the fishermen to remember anything but recent nesting activity within the 4 months pre- ceeding the interview. Only one fisherman had any information for the 1977 nesting year. There were several cases where dates were obviously confused (for example "end of April, first of October" was given for a nesting observation which later was described as about 2 weeks ago). There were also several cases where the same nesting activity was reported by different respon- dents so that the results may reflect slight redundancy of nesting activity. Therefore, these data are probably over-estimates of the turtle population in that multiple reporting of the same nesting activity and mUltiple nestings by the same turtle are not dis- tinguished. The final bias in the results came from an obvious reluctance to admit any predation. One of the respondents admitted 'to catching one of the nesting turtles but there may have been additional unreported predation. -15- Five respondents reported that mongooses (Herpestes auropunctatus ) prey on the nests. Dr. David Nellis of the Department of Conservation and Cultural Affairs, who has undertaken research on mongooses says that they would be secondary predators in that they would not dig the eggs from the sand, but would prey on already opened nexts. Ten different respondents said that turtles are not nesting as frequently as before because there are too many lights around the nesting beaches. At least 35 of the fishermen interviewed said that there were more turtles in the waters than in previous years. Turtle sightings covered most of the inshore from Lameshur Bay on St. John, to Savanna Island, west of St. Thomas. Turtles were sighted on the Atlantic side of the islands from west Cay.to Leinster Bay on st. John. Turtles are frequently sighted throughout the bays and waters comprising Pillsbury Sound. The absence of reports from outside the previously described areas is probably a function of the fact that the persons interviewed don't fish outside of these areas. For example, the author has seen turtles (Hawksbills and Greens) in Coral Bay, although none were reported during the interviewing process. Most of the fishermen agreed that Hawksbills were more abundant than Green turtles although no quantitative data could be derived from the interviews. No one reported any other species except for the leatherback nesting in Magen's Bay. One of the fishermen interviewed reported butchering one turtle. There were two additional reports of turtles being -16- butchered and one nest opening reported. Curiously, most of the fishermen stated that they did not care for turtle products. -17- TABLE D. Summary of Interviews Reporting Turtle Nesting Activity for Leatherback and Hawksbill Turtles in St. Thomas and St. John, u.S. Virgin Islands. INTERVIEW: Place #1 Little Hans Lol1ik Big Hans Lol1ik (Dry Bays) Inner Brass Caret Bay Nel tj eberg Bay Mermaid's Chair Salt Cay West Cay Magens Bay Little Hans Lollik #2 Little Hans Lollik Big Hans Lol1ik Magen's Bay West Cay Inner Brass Little Hans Lol1ik Big Hans Lollik Frenchman's Bay Penn Bay Bordeaux Beach Caret Bay Neltjeborg Bay Magen's Bay Bordeaux Inner Brass Caret Bay Caret Bay #3 Salt Cay #4 Little Hans Lollik Inner Brass Salt Cay Date August 2~-25, 1978 August 23-30, 1978 August 23-30, 1978 August 23-30, 1978 September 1-6,1978 September 1-6,1978 September 1-6, 1978 September 1-6, 1978 October 9, 1978 October 27, 1978 October 2, 1977, October 2, 1977 May 5, 1978 July ]3, 1978 July 19-22, 1978 July 19-27, 1978 July 19-27, 1978 July 19, 1978 July 20, 1978 July 19-28, 1978 July 21" 1978 August 3, 1978 August 19, 1978 August 19, 1978 August 22, 1978 August 22, 1978 October 18, 1978 August, 1978 October 18, 1978 October 18, 1978 October 18, 1978 Nesting 4 Hawksbills 6 Hawksbills 3 Hawksbills 6 Hawksbills (1 butchered, 1 nest opened) 1 Hawksbill (1 butchered) 1 Hawksbill 1 Hawksbil1, no sand on beach, didn't nes' 2 Hawksbills 1 Hawksbill 4 Hawksbills 5 Hawksbi11s 9 Hawksbills 1 Leatherback 1 Hawksbil1 2 Hawksbills 6 Hawksbills 7 Hawksbills 1 Hawksbill 1 Hawksbil1 4 Hawksbills 2 Hawksbi11s 2 Hawksbil1s 1 Hawksbil1 2 Hawksbills 2 Hawksbills 2 Hawksbi11s 1 Hawksbil1 (butcher, 1 Hawksbi11 1 Hawksbill 2 or 3 Hawksbi11s 2 Hawksbills (mating observed) TABLE D. Continued. INTERVIEW: Place #5 Pelican Beach Smith Bay Great Bay Grass Cay (South Side) Mingo Cay (Southwest End) #6 Little Coculus Bay Fortuna Bay #7 Mingo Cay (Southwest End) #8 Sandy Cay (BVI) #9 Sandy Cay (BVI) #]0 Great St. James (Bare Ass Bay) #11 Trunk Bay (St. John) Hawksnest Bay (St. John) #12 Trunk Bay Trunk Bay #13 Bordeaux Caret Bay Dog Island Little Coculus -18- Date ? (in past) ? (in past) ? (in past) October 2-5, 1978 September 30, 1978 September, 1978 September, 1978 End of September, 1978 August, 1978 September, 1978 August, 1978 late summer, 1977 summer, 1978 summer, 1978 June, 1978 July-August, 1977 September 10-20, 1978 September 10-20, 1978 September 10-20, 1978 September 10-20, 1978 Nesting 1 Hawksbill 1 Hawksbill 1 Hawksbill 1 Hawksbill 1 Hawksbill numerous numerous numerous nest hatching observe nest hatching observe nest hatching observe 1 set tracks observed 8-10 tracks observed 3 Hawksbills 2 Hawksbills 4 Hawksbills 1 Hawksbill -19- TABLE D. Continued. INTERVIEW: Place #14 Bordeaux Caret Bay Hans Lollik (either) Stumpy Bay #15 Jumbi Bay, St. John Date October 20, 1978 October, 1978 Late October, 1978 Late October, 1978 Late July, 1978 Nesting 2 Hawksbills 1 Hawksbill several 2 Hawksbills 2 Hawksbills -20- TABLE E. Summary of Reported Recent Turtle Nesting Activities in St. Thomas, U.S.V.I., Listed by Nesting Beach. Nesting Beach Number of Nestings Little Hans Lollik 15 (5 in 1977) Big Hans Lollik 13 (9 in 1977) Inner Brass 10 Caret Bay 14 Neltjeberg Bay 3 Salt Cay 2 West Cay 3 Magen's Bay 2 Penn Bay 1 Frenchman's Bay 1 Bordeaux Beach 11 Grass Cay 1 Mingo Cay 2 Little Coculus Bay 2 Fortuna Bay 1 Sandy Cay (BVI) numerous Great St. James nest hatching Trunk Bay, St. John nest hatching Hawk's Nest, St. John nest hatching Fish Bay, St. John reported (time indefinite) Dog Island 4 Mermaid's Chair 1 Stumpy Bay 2 Jumbi Bay, St. John 2 (8-10 in 1977) 60 kj ••• ···.~ •• J·.· •. i~.~ .. ; .:=J:~~i-:~f·~ ••. L~~i-=IJit~.~i· .•..... , 50 40 CJ) 30 19 Z H E--< CJ) 20 fl..1 Z / .. -----_._ .. q ~ 1 0 . l~ .. ___ (._ ~ \ --'-:1-: '. o ~ ... _ P-. fl..1 0 I Feb. ~ Jan. 19l"i3.._ .," . -'-'.-'" ····-·l , ., .••••• ---.----j •. - -- '·"1 -----...j._- .- .. Dec. .•....... j J ------i I -I .. _. __ .-1 I ! ___ ..I FIGURE V. Summary of 109 Hawksbill and Leatherback Turtle Nesting Reports for 1978 in St. Thomas and St. John, U. S. Virgin Islands. I t-.:) - I ~ 1978 nesting activity on previously reported beaches. n~ 1978 nesting activity on previously unreported beache~ P~Previous1y reported beaches (Rainey, 1976) not reported in 1978. r~Reported beaches used in past. Year not given by interviewee. h~~atching observed in 1978. D - ~ 6 1:"tf FIGURE VI. Location of St. Thomas and St. John Turtle Nesting Beaches. 4iI -23- DISORIENTATION AND RELATED MORTALITY IN LEATHERBACK (Dermoch~lys coriacea) HATCHLINGS AT SANDY POINT, ST. CROIX, U.S. VIRGIN ISLANDS A. Background and Statement of the Problem: Information regarding the mortality of hatchling sea turtles is crucial to any proposed management program, yet it is not available for any population in the Virgin Islands. There is some evidence that at Sandy Point a significant number of leatherback hatchlings may fail to locate the sea after emerging from the nest and die on the beach, either by predation or as a result of dessication. In order to find the most direct route to the sea, hatchlings depend on a tropotactic visual orientation system that has been well described by Mrosovsky (1,2,3), Mrosovsky and Carr (4), Mrosovsky and Shettleworth (5), Ehrenfeld (6), and Ehrenfeld and Carr (7) for the Green and Hawksbill turtles. Mrosovsky and Shettleworth (8) studied the significance of circling movements observed in leatherback hatchlings, and Mrosovsky (11) reported on individual differences in their sea-finding mechanism. Aside from these two studies, there seems to be little quantitative experimental work on the water-finding orientation of leatherback hatchlings. It is generally assumed that the orientation system of leatherbacks is similar to that described for green turtles. In all cases studied, sea-finding orientation seems to depend on the fact that there is nearly always a massive bright- ness differential between the seaward and landward horizons under natural conditions, with the seaward horizon being the brighter. -24- During the 1977 surveillance of the nesting beach at Sandy Point by NMFS and DCCA it was observed that sometimes entire groups of leatherback hatchlings would leave the nest pit and travel parallel to the surf line for long distances, or even go inland, instead of going to the water by the shortest route. Many became entangled in the underbrush and died of dessication. No data is available on the percentage of hatchlings displaying this aberrant behavior, but the problem was felt to be so serious that the NMFS and DCCA officers took to collecting all the hatchlings they could find and hand carrying them to the water's edge. Those present soon became convinced that the hatchlings were being attracted to the sky glow created by the lights of Hess Oil Refinery and the lights of the town of Frederiksted, which quite noticeably brighten the horizon in a landward direction. This hypothesis is supported by the observation of MacFarlane (9), who reported disorientation in loggerhead hatchlings as a result of artificial lights near the nesting beach in Florida, and by the fact that green turtle hatchlings can be attracted by handheld lanterns (5). On one occasion, Hawksbill hatchlings in St. Croix were found crossing a road near the nesting beach and heading towards a nearby ballpark where a game was in progress under the lights (10). A similiar event has been reported at Bolongo Beach on St. Thomas where Hawks- bill hatchlings headed for lighted tennis courts adjacent to the beach. -25- Any attempt to assess leatherback hatchling mortality on the beach at Sandy Point must therefore take into account the possibility that a major contributing factor in mortality may be a tropotactic response to artificial lights. This response could prove to be very damaging to the stock because: (a) a rigidly programmed piece of behavior which evolved under natural conditions as an effective survival response is perverted so that the behavior becomes anti-survival, (b) the severity of the problem is expected to increase over time as development proceeds, and (c) it is difficult to find an effective solution for management. It is proposed to establish a critical habitat for the leatherback at Sandy Point, which would extend two-tenths of a mile inland. However, should development take place on Sandy Point itself (and at present this seems very likely) then an increased amount of artificial light from, say, a condominium development, could well precipitate mass mortalities of hatchlings with possibly serious impact on the viability of the stock. A first approach to assessing the significance of dis- orientation as a factor in beach mortality of the hatchlings at Sandy Point could be made by combining an experimental analysis of orientation with measurements of the horizontal radiance distribution. This data would be augmented by observations of actual mortality. Such information would be useful in designing a management strategy for the stock, and it would also serve as a benchmark by which to guage the effects of the ,"- anticipated increase in artificial lighting in the future. -26- Various courses of action to ameliorate the problem could then be explored in the light of this study. B. Suggested Experimental Approach Hatchlings would be collected at Sandy Point as they emerge from the nest, given various orientation tests, and then released into the sea on the same night. Orientation arenas as described in (4) and (5) would be used to quantify the responses of the turtles. Before each test the radiance distribution of the horizon from hatchling-eye-Ievel at the center of the arena would be quantified by suitable instrumenta- tion. An attempt would be made to relate the preferred orientation direction of hatchlings under various experimental and control procedures to the radiance distribution recorded by instrument. Brightness cues could be manipulated during experimental runs by screening various portions of the horizon (from the viewpoint of the hatchlings) with black plastic, in a manner similar to the methods of Mrosovsky and Shettleworth ( 5) • Since leatherbacks nest in two different situations at Sandy Point (a) on the lower beach, and (b) on top of the berm, it would probably be necessary to replicate each experiment at both locations. "Dry runs" using this experimental procedure have been carried out at Sandy Point, and it is estimated that a team of 4-5 persons could collect-enough data for statistically -27- significant results in a total of about 100 hours of field work, (400 to 500 man hours) provided that the nest locations and the approximate date of hatching were determined ahead of time by a daily nesting survey in the peak of the nesting season. If no nesting survey were undertaken, then collection of adequate numbers of hatchlings would be much more of a hit-or- miss procedure, and the estimated time in the field for the entire team would have to be significantly increased. It would be more economical to employ one person to make a daily nest count throughout the nesting season, thereby enabling the team to predict the approximate dates of hatchling emergence. As the opportunity arose, naturalistic observations would be made of the orientation of undisturbed hatchlings as they emerged from the nest, for comparison with the experimental data. Observations on predation of hatchlings on the beach would also be made. It is sometimes possible to deduce the paths taken by hatchlings even when the actual emergence was not observed, from the tracks which they make in the sand, and it may be possible to estimate the relative numbers involved. Finally, a special effort should be made by the person doing the daily nest count to find evidence of the fate of dis- oriented hatchlings in order to get some idea of the numbers which actually succumb, and the causes of death. Using these methods, one can extrapolate from the experi- mental data the percentage of hatchlings which under "normal" conditions would be expected to @rient in a direction that would -28- lead them away from the sea. Combined with opportunistic observations on the orientation of undisturbed hatchlings and by actual counts of dead ones, it should be possible to arrive at a first approximation of beach mortality due to artificial-light orientation at Sandy Point. C. Options for Management Action Since it is not feasible to physically screen off the entire beach from the offending lights, it would appear that the options for management action are three: (a) do nothing, and accept the additional hatchling mortality resulting from artificial-light disorientation, (b) establish a nightly patrol during the hatching season to collect disoriented hatchlings and hand-carry them to the water's edge. (It may be possible to enlist volunteer help to aid in such an effort) • (c) conduct experiments with erecting a number of artificial lights at the water's edge along the entire beach, in order to attract hatchlings in the seaward direction. Such lights would have to be specially designed so that they would not exert a trapping effect on the hatchlings and increase their exposure to predators, and also so that they would not prevent females from corning ashore to nest -- it is not easy to see how this could be accomplished. -29- LITERATURE CITED (1) Mrosovsky, N. 1967. How turtles find the sea. Sci. J. 3: 52-57. (2) 1970~ The influence of the sun's position and elevated cues on the orientation of hatchling sea turtles. Anim. Behav. 18: 648-651. (3) 1972. The waterfinding ability of sea turtles. Brain, Behav., Evo1. 5: 202-225. (4) and A. Carr. 1967. Preference for light of short wavelengths in hatchling green sea turtles ... Behavior 28: 2]7. (5) and S. J. Shett1eworth. 1968. Wave-length preferences and brightness cues in the waterfinding behavior of sea turtles. Behavior ~ (4): 2]]-257. (6) Ehrenfeld, D.W. 1968. The role of vision in the sea- finding orientation of the green turtle (Chelonia mydas) . II. Orientation mechanism and range of spectral sensitivity. Anim. Behav. ]6: 28]-287. (7) and A. Carr. 1967. The role of vision in the sea-finding orientation of the green turtle (Chelonia mydas). Anim. Behav. ]5: 25-36. (8) Mrosovsky, N. and S. J. Shettleworth. 1975. On the orientation circle of the leatherback. Anim. Behav., 23: 588-593. (9) McFarlane, R.W. 1963. Disorientation of Loggerhead Hatchlings by Artificial Road Lighting. Copeia, 1963:]53. (10) Philibosian, R. 1976. Disorientation of hawksbi11 hatchlings, Eretmoche1ys i~bricata, by stadium lights. Copeia, no.4, 824. (11) Mrosovsky, N. 1977. Individual differences in the sea-finding mechanism of hatchling leatherback turtle. Brain, Behav. and Evo1. 14: 261-273.