BULLETIN OF THE FLORIDA STATE MUSEUM BIOLOGICAL SCIENCES Volume 13 Number 2 SEA TURTLES OF THE GUIANAS Peter C. H. Pritchard UNIVERSITY OF FLORIDA Gainesville 1969 Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM are pub- lished at irregular intervals. Volumes contain about 800 pages and are not necessarily completed in any one calendar year. WALTER AUFFENBERG, Managing Editor OLIVER L. AUSTIN, JE., Editor Consultants for this issue: WALTER AUFFENBERG ARCHIE CARR Communications concerning purchase or exchange of the publication and all manuscripts should be addressed to the Managing Editor of the Bulletin, Florida State Museum, Seagle Building, Gainesville, Florida 32601. Published March 6, 1969 Price for this issue $.85 SEA TURTLES OF THE GUIANAS PETER C. H. PRITCHARDI SYNOPSIS: Summarizes investigations of turtle nesting beaches in Guyana during August 1964, August 1965, and April 1967, in Surinam during May to July 1966, May to July 1967, and June-July 1968, and in French Guiana in June and July 1967. Four species of sea turtles nest on beaches in Guyana, particularly Shell Beach: Chelonia mydas, Eret,nochetys imbricata, Dermochelys coriacea and Lepidochdys otiuacea. The same four species nest in Surinam, although Eretmochelys does so only rarely. Lepidochelys sometimes forms huge nesting aggregations at Eilanti, Surinam, and individuals have been shown to nest at the same place in successive years. Dermochetys, Chebnia, and probably Eret- mochetys all nest in large numbers in French Guiana, particularly at Si16bache Beach. Survival and conservation of sea turtles in northern South America are discussed. TABLE OF CONTENTS INTRODUCTION 86 ACKNOWLEDGEMENTS .....-........... 86 STUDY AREA 87 METHODS 88 SPECIES ACCOUNTS 89 Chelonia mydas 89 Lepidochelys otivacea 96 Dermochet!/8 coriacea 120 Eretmochelgs imbricata 132 Coretta caretta 186 ECONOMICS AND THE FUTURE 136 LrrERATURE CITED 189 iThe author is a graduate teaching assistant in the Department of Zoology, University of Florida, Gainesville, where he is working on the biology and systematics of sea turtles for his Ph.D. degree. Manuscript received 1 September 1968 - Ed. Pritchard, Peter C. H., Sea Turtles of the Guianas. Bull. Florida State Mus., vol. 18, Na. 2, pp 85-140. 86 BULLETIN FLORIDA STATE MUSEUM Vol. 13 INTRODUCHON Early accounts of sea turtles nesting in northeastern South America mention both Surinam ( Kappler, 1881) and Cayenne ( Lacepede, 1847). The occurrence of sea turtles in the waters and on the beach- es of the Guianas was known much earlier than this. A map of Suri- nam drawn by van Gerard of Keulen in 1670 indicates the area between Mot Creek and Wia-Wia Creek ( now known as Bigi Santi) as "Schildpad ( turtle) Bay". The same name appears on Reimer Ottens' map of 1740 Other than my own few receht notes ( Pritchard, 1964, 1966a and b) and the works of Schultz ( 1964) and Brongersma ( 1968), few modern references to the turtle populations nesting on this coast exist. ACKNOWLEDGEMENTS I wish to express my gratitude to the trustees of the Browne Fund of the Royal Society for a grant-in-aid covering the cost of the 1965 trip to Guyana. I am also most grateful to Hugh Popenoe of the Department of Tropical Agriculture, University of Florida, for a generous grant which, in conjunction with a grant from the Centre for Latin American Studies, financed the 1966 Surinam expedition. Conservation and scientific work in Surinam and French Guiana in 1967 and 1968 was financed entirely by the World Wildlife Fund. Many members of the Surinam Forest Service, especially J. P. Schultz, F. Bubberman,4 A. Voorheuven, G. Plak, A. Wolf, and E. Donner, were of inestimable help during my time in Surinam. My super- visor of studies, Archie Carr, was of help in many ways, and from his sources of research support - NSF Grant GB 3910; ONR Con- fract 580 ( 12) with the University of Florida; Caribbean Conserva- tion Corporation - furnished tagging equipment and funds for tag- return rewards. The ex-Governor-General of Guyana, H. E. Sir Richard Luyt, very kindly offered me accomodations and much assistance in Georgetown. A number of Guyana Government omcials, in particular Mrs. Winifred Gaskin, C. Mc. A. Ashley, M. L. Persaud and D. Shaw, were of invaluable help in different ways. Dennis Joaquin of the Waini River accompanied me to Shell Beach and took an active interest in the project. In French Guiana G. Grivaz of the Forestry Service and Pierre Fourmanoir were exceedingly helpful. P. W. Kent, my biochemistry supervisor at Oxford, was of great assis- tance with the original grant application. Archie Carr and David Ehrenfeld read the manuscript and made helpful criticisms. 1969 PRITCHARD: GUIANA SEA TURTLES 87 Finally I would like to thank my friends Tom Stubbs, Tom Lesure and Bill Greenhood who accompanied me on the Surinam expeditions and cheerfully joined in many hours of beach-walking at times when normal citizens were asleep. STUDY AREA The detailed studies summarized in this paper were conducted on three beaches: Shell Beach, Guyana; Bigi Santi, Surinam; and Eilanti, Surinam. Shell Beach, North-West District, Guyana - About 6 miles long and running northwest-southeast, this beach reaches its maximum width of about 250 yards about 1 mile from the northwestern tip. It is separated from the mainland by a large mud flat, much of which is exposed at low tide. The lagoon harbours many four-eyed fish (Anableps), sawfish (Pristis), and several unidentified species of sharks. In the open sea are larger sharks, including hammerheads. The most conspicuous birds of the beach are black vultures, spoonbills, scarlet ibis, flamingos and egrets. Beach and lagoon both become narrower southeastward, eventually becoming simply a continuation of the -- narrow barrier beach fringing much of the coast of the North-West District. * Shell Beach is mobile, having apparently moved 4 miles towards Venezuela in the last 3 years. Piles set in the beach when it was used as an emergency landing strip in 1939 now stand in the sea between 15 and 20 miles southeast of the beach's present location. The beach profile is inclined steeply just above the high tide mark. Much of this higher area is covered with a dense growth of beach morning glory, but this is sparse on the newly-deposited northwest end of the beach. Bigi Santi, Surinam - This name is applied to the stretch of beach between Matapica Creek and Wia-Wia Bank. The section on which the present study was conducted is about 40 miles east of the mouth *Some of the more clearly defined separate beaches between Shell Beach and the Essequibo Mouth have names, e.g. Papaya Beach, Father's Beach, Turtle Beach. Other beaches in Guyana used by turtles for nesting include Punta Playa on the Venezuelan border, 68 Beach near the mouth of the Corantijn River, Mahaica-Mahaicony Beach between Georgetown and the Berbice River, Suddie Beach on the west bank of the Essequibo, beaches on several of the Essequibo Islands, e.g. Zeelandia Beach on Wakenaam Island, Dauntless Point on Leguan Island; there is also an 8-mile stretch of good turtle beach on Tiger Island. 88 BULLETIN FLORIDA STATE MUSEUM Vol. 18 of the Surinam River. For detailed maps of this beach and also of Eilanti Beach see Schultz ( 1964). The beach is backed by extensive swampy areas, but not by open bodies of water. Like Shell Beach, Bigi Santi is rapidly moving westward. The changing coastline is exposing large expanses of previously suffocated forest, and the many dead tree trunks are so rotten that they can be pushed over with one hand. The beach material is sand and broken shell, in contrast to that of Shell Beach which is pure shell. The general aspect of the beach and its concomitant bird and fish fauna are similar to those of Shell Beach. Eitanti, Surinam - This is the name given to a small beach at the tip of a point of land on the west side of the mouth of the wide Marowijne River, which forms the border between French Guiana and Surinam. The b©ach is about 14 mile in length. A great mud bank has been deposited off the beach, about 1/2 mile of which is exposed at low tide. At 6ne time Eilanti was an island, but silting has reduced the original break with the mainland to a narrow inlet, 100 yards or so in length, at the west end of the beach, Schultz ( 1964) gives maps showing the progressive alteration of the beach. METHODS Lengths refered to in this paper refer to the straight-line shell length, measured from the nuchal lamina to the rearmost projection of the carapace. Plastral lengths are median; widths maximum. At first I measured the turtles with a caliper made from aluminum slats and a rollup metal tape, later I used a steel tree caliper. Weights were taken by turning the turtle and tying the flippers diagonally together and attaching a Salter's 10 ewt capacity self-recording dy- namometer, adjusted for use in a vertical position, to the intersection of the diagonal cords; a stick passed through the upper ring of the dynamometer is raised until the turtle is just lifted off the ground. In this way one man can weigh the largest ridley or hawksbill, but two or more are needed for a green turtle, and at least six for a leatherback. Turtles were tagged with Hasco brand cattle ear-tags clipped through the inner trailing edge of the front flipper. These tags are inscribed in Spanish and English, offering a reward for their return to the University of Florida. The tagging efforts of Carr and his co-workers at the University of Florida over the last 12 years have accustomed many of the turtle fishermen of the Caribbean, Gulf of 1969 PRITCHARD: GUIANA SEA TURTLES 89 Mexico, and South Atlantic to watch for the tags and to return them promptly. Shell terminology in this paper follows that used by Carr ( 1952). SPECIES ACCOUNTS Chelonia mydas GUYANA The green turtle, locally known as 'bettia', nests at Papaya Beach where fresh eggs and an adult carapace were seen 29 April 1967, on Turtle Beach where six shells were seen on the same date, and prob- ably at Dauntless Point, Leguan Island. According to N. 0. Poonai of the Guyana Museum, nesting also occurs on 63 Beach, Tiger Island Beach, Suddie Beach, Zeelandia Beach, and Mahaica-Mahaicony Beach. The most used nesting beach appears to be Shell Beach ( also called Kamwatta Beach) in the North-West District. Nesting season and periodicity: - In 1964 and 1965 visits were made to Shell Beach in August, which was probably near the peak of the hawksbill season but well after the green turtle peak; only 11 green turtles nested on Shell Beach between 6 and 27 August 1965. t Arawak turtle hunters, questioned about the peak and extent of green turtle nesting in Guyana, stated that the earliest appear in March and continue abundantly through July, with only stragglers there- after. This was corroborated by a third visit to Shell Beach in April 1967, when at least five or six green turtles, often more, nested each night. Parties of negroes and Amerindians on the beach were slaugh- tering virtually every turtle that nested. One green turtle, tagged while nesting 7 August, nested again 20 August, when it was caught by turtle hunters. This internesting period of 13 days is of the same order as that at Tortuguero ( M = 12.5 days, Carr & Ogren, 1960), Ascension ( M = 14.5 days, Carr & Hirth, 1962 ), and the Talang Islands off Sarawak (M = 10.5 days, Hendrickson, 1958). CARAPACE SIZE AND EGG DIMENSIONS: Carapace size and egg dimensions : For dimensions of some green turtle carapaces measured on Shell Beach see Table 1 and Figure 1. Six clutches of green turtle eggs from Shell Beach ranged in number from 106 to 138. Four random normal eggs had the following dimen- sions ( in mm.): 46 x 48; 47 x 49; 46 x 47; 46 x 48; one abnormal egg measured 56 x 44 mm. 90 BULLETIN FLORIDA STATE MUSEUM Vol. 18 Table 1. CARAPACE DIMENSIONS OF MATURE FEMALE Chelonia m~/das, SHELL BEACH, GuYANA ( IN INCHES) Length Width L ength Width 38 80% 42 34 291,5 3842 8134 421'4 82% 88% 82 4244 821/6 40 8242 4214 38 40% 29% 42% 8834 40 36 3136 42% 31 41 80% 4242 85 41 82 42% 30% 41 32% 42% 88% 411'4 321,4 42% 84 41;6 29 34 42% 841/2 4142 30% 43 88 41~ 31 43 38% 41 42 3134 48 88% 411/2 82% 43:~2 29% 41% 88 43% 82 41% 38 44% 3244 4142 33 44% 33 41 % 8042 45 84 42 8214 45% 34 42 82% 46 32 42 34 Nesting behavior: - Nesting of the green turtle in Guyana was, as far as could be discerned, identical to that Carr and Giovanolli ( 1957) describe for females from Tortuguero. According to Jerome da Silva, turtles nesting on the populated Essequibo Coast are much more easily disturbed than those on Shell Beach, where we were able to watch the whole nesting procedure from the stage of digging the body pit under continuous flashlight illumination. Green turtles in both Guyana and Surinam have the habit of making 'half-moons' ( non-nesting exploratory emergences) as they do at Tortuguero and on other mainland beaches. The rather charm- ing belief was expressed to me that these half-moons are made · by male turtles in search of a suitable place for their mates to nest. Trial nest excavation also occurs, a turtle sometimes digging in four or five places before actually nesting. Population structure: - That the Guyana green turtle population is composed at least in part of immature individuals is demonstrated by my receiving third-hand a 7-pound individual with a carapace measuring 11%" x 91/&,t with no other data than 'taken by a trawler off the Guyana coast' on 28 July. This is about as small as green turtles are found anywhere, apart from hatchlings on nesting beaches; 1969 PRITCHARD: GUIANA SEA TURTLES 91 BIG! SANTI, SURINAM 7- 6- 5- 4- FR E Q U E N C Y FR EQ U EN C Y FR EQ U EN C Y FR EQ UE NC Y 2- i- 39 40'41 42 43 4-4 45 46 47 48 ASCENSION ISLAND 25- 20 15- 0, r7 5- 33 34 35 36 37'38 394041 42 4344454e 47484950'51 52 53 5455 SHELL BEACH, GUYANA 16- 12- 8- 4- 38 39 40 41 42 43 44 45 46 TORTUGUERO, COSTA RICA45- 30- 15 - A-- -47 ''11,•it35 36 37 38 39 40 41 42 43 44 Carapace length (inches) Figure 1. Carapace lengths of mature female green turtles (Chelonia mydas) from four selected localities; Ascension Island data from field notes of H. Hirth; Tortuguero data from Carr and Ogren ( 1960). it was probably about 1 year oId and, as no turtle grass grows in this area, had probably not yet developed the herbivorous diet of the half- 92 BULLETIN FLORIDA STATE MUSEUM Vol. 13 grown and adult turtles. When I released the turtle, untagged. on the beach at Georgetown, its seaward orientation had not been disturbed by several days in a bathtub. i.'- Af.W .''I, --'0,1,~#A&.M~ill- Figure 2. Two types of green turtle skull from shell Beach, Guyana; left: large bulbous-topped type; right: flat-t<,pped, small type. SURINAM Here the local name of the green turtle is "krape". The species nests fairly abundantly on Bigi Santi and also on the beaches near and in the mouth of the Marou ijne River ( Eilanti, Tijger Bank, Babboon Santi). Nesting occurs on Marowijne beaches far enough upstream for the water to be fresh or only slightly brackish. Nesting season and periodicitu: - On Surinam beaches green tur- ties nest most abundantly in April and May, but a few stragglers persist until June or early July. We tagged 30 green turtles at Bigi Santi between 5 and 14 May, and between 24 May and 6 June 1966; about 30 more nests were discovered after the turtle returned to the sea. We tagged 44 more green turtles at Eilanti and Bigi Santi in May and June 1967. During the 2 months of the peak season an average of four or five green turtles nest each night at Eilanti. About this number also nested each night on Bigi Santi during the 1966 season, but in 1967 considerably more, occasionally zip to 15 or more per night, and in 1968 sometimes many more than this. The follow- 1969 PRITCHARD: GUIANA SEA TURTLES 98 ing individual internesting intervals ( in days) were recorded: 13, 13, 13, 15, 16, 21, 28, 29. Except for the 21 day record, these are com- mensurate with the average internesting period of other areas, 13 to 14 days. Size Of mature females: - Surinam green turtles are unusually large ( Table 2); the average length of 60 mature females was 44.02", nearly 2 inches longer than the average of the Ascension Island colony, previously thought to be the largest. Lengths ranged from 391/2 to 48 inches, and weights from 266 to 493 pounds. The only male measured had a carapace long and 32]~4" wide. Evidence of migration: - Only one tagged green turtle from Suri- nam has been recovered to date, a 45-inch individual which was Table 2. DIMENSIONS OF MATURE FEMALE Chetorua mydas FROM BIGI SANTI, SURINAM ( IN INCHES ) Carapace Carapace Plastron Head Weight length width length width ( Lbs.) 89 36 81% 88 51/2 812 41% 311/5 88% 6 829 41% 82 84 51/2 - 41% 339 82 6 344 421/2 821/5 3594 6% 840 4214 821/4 841/6 6 286 4234 881/2 84% 5% 850 48 32 84 5 % 266 48 36 34% 51/2 880 43% 34% - 59 - 431/& 841/2 37 6 855 44 38% 85% 6 879 44 34 8214 5% - 44 8494 - 5% - 441/6 831/6 34 5 94 405 44% 84 34% 6 359 44 % 86 86 6 394 44 % 34 861/5 6 462 45 85 35 14 614 450 45 8434 - 6 - 45 85% 87 6 - 45% 38 36 6 899 451/4 34% 36 6 417 45% 85% 37 61/2 892 45% 35% 86 6 - 46 34 37% 6 44 462 461/4 34 861/1 5% 896 46 35 34% - 6 - 47 88% 36% 6 - 47 44 84 841/6 6 892 48 87 8914 61/2 498 94 BULLETIN FLORIDA STATE MUSEUM Vol. 13 found, only 6 weeks after tagging at Bigi Santi, near Site Luis on the coast of Brazil ( Figure 3). This journey represents a swim of at least 1000 miles against the prevailing current. It will be interesting to see if more returns confirm this as a regular migration route. This is the first known case of a migrating turtle crossing the Equator. 600 W 55° W 56°w 45° W 100 N 113 0 100 200 300 400 soo 10°NMILES 2 ATLANTIC OCEAN VENEZUE 2 2 2 2 3 FRENCH GUYANA SURINAM GUIANA BRAZIL 1 1 60°W 55° W 50° W 450 W Figure 8. Recovery of tagged turtles: 1: Eretmochelys imbricata tagged at Shell Beach; 2: Lepidochelys otioacea tagged at Eilanti; 8: Chetonia m!/das tagged at Bigi Santi ( Arrows do not indicate actual routes traveled). Some of the green turtles at Bigi Santi have rather large barnacles on the carapace; green turtles in other areas remain almost free of barnacles throughout life, although hawksbills and loggerheads are often encrusted with them. The ridleys examined had only occasional · small barnacles on the head and shell, while leatherbacks were in- variably free of them. Clutch sizes and incubation periods: - Average number of eggs in 20 green turtle nests from Bigi Santi was 142.8 ( range 87-174); aver- age for 248 nests at Eilanti and a small neighboring beach ( Dapp Island) was 141.9, the largest number in one nest being 226. This numb6r was rechecked, and is apparently the largest number of eggs 1969 PRITCHARD: GUIANA SEA TURTLES 95 known to have been laid by any sea turtle, or indeed any amniote vertebrate, at one time. The average number of eggs per nest at Tortuguero is 110.0; at Ascension, 115.5; at the Sarawak Turtle Islands, 104.7 ( Carr and Hirth, 1962). In all cases samples were large enough for the difference in average clutch size to be highly signmcant. G. Plak gave me the following records of incubation time ( in days) for 40 undisturbed green turtle nests: 47,52, 54, 55, 55, 55, 55, 55,56,56,57,57,57,57,58,58,58,58,59,59,59,59,59,59,60,60,60, 60,60, 60, 60, 60, 61, 61,61, 61, 62, 63, 64, 64 (M - 58,25 days). The only definite information on fertility percentage is that a clutch of 169 eggs produced 162 viable hatchlings, 2 slow-developing embryos, and 5 infertile eggs ( i.e. 97 per cent fertility). Mr. Plak informs me that such percentages are normal for clutches on Bigi Santi where nests are not moved to protected sites after laying. Previously re- corded average fertility rates are around 50 per cent ( Carr and Hirth, 1962), but such data have always involved transferred nests. Their statement that 'removal of eggs from the nest and installation in artificial nests impose no additional mortality' is probably incorrect. Hendrickson ( 1958) tried to demonstrate that transfer of eggs imposed no additional mortality by transferring control clutches very carefully and other clutches rather roughly, but probably any moving of the eggs after they are laid will lower the hatching percentage. The hatchlings from one nest of 169 eggs ranged in carapace length from 51 to 55 mm (M- 5.35 mm; cf 3.17 at Ascension, 4.97 at Tortuguero). Abnormal green turtle eggs were rare, but one clutch contained a single large elongate egg and another contained four dumbell- shaped eggs. According to Mr. Plak, green turtles occasionally nest by day- light on Bigi Santi; he had seen emergences at 2:30 PM and at 4:30 PM. Medem ( 1962) reports a nesting emergence by this species at 10 AM in Colombia. I once saw green turtles mating at Bigi Santi; at 5 PM on 14 May a pair about 60 yards off the beach remained embraced for at least an hour, but I saw neither the start nor the finish. Population structure. - Green turtles intermediate in size between hatchling and adult· are rarely seen in Surinam, but Schultz ( 1967) figures a 35 cm specimen taken near the mouth of the Surinam River, and Brongersma ( 1968) mentions specimens measuring 28.8 and 37.9 cm respectively from the vicinity of the mouth of the Surinam 96 BULLETIN FLORIDA STATE MUSEUM VoI. 18 River, now in the Museum at Leiden ( RMNH 13934 and 13935). FRENCH GUIANA According to Lacepede ( 1847) green turtles used to nest in the vicinity of Cayenne between April and June; at the end of the 18th. century about 300 adults were taken there each year. They probably still nest on several beaches on the ile de Cayenne, in particular Mon- tabo Beach, Bourda Beach, and Montjoly Beach, judging by my in- terviews with the local people in 1967, although my informants were not very definite as to species. Green turtles are also said to nest on the beach near the mouth of the Mana River, and an aerial recon- naissance of this area in July 1968 showed that, although most of the nesting is unquestionably by leatherbacks, some green turtles also nest here. We could find no evidence of any turtle-nesting on the fine beach at Kourou. The best beach in French Guiana for green turtles is SilSbache Beach, a few miles west of the mouth of the Organabo River; it consists of extensive steep-sloping sandy stretches separated by huge deposits of hard, black mud. Mud flats exposed at low tide, similar to those at Eilanti Beach, Surinam, force the turtles to nest by mid- or high tide. I reconnoitered this beach in early June 1967 in the daytime and over a low tide period at night. Fresh tracks and nests of both green turtles and leatherbacks were plentiful, and it seems certain that at least several dozen green turtles nest on this 3-mile beach nightly at the peak of the season. I tagged one green turtle with a 451/2 inch carapace that was nesting despite the low tide. Lepidochelus olivacea The ridley turtle of the Guianas has been a curiously neglected and persistently misidentified animal. Almost a century ago Kappler ( 1881) wrote: ( quoted in translation from Schultz 1964) -In May and June a smaller turtle, weighing about 60-70 lbs, comes on shore in such numbers ( near the Marowijne River) that on some nights I about thirty can be caught, The Indians call them warana (Chelonia corticata). These turtles come on shore not only to lay their eggs; but still I never saw a male on land. The eggs are smaller than these of the former ( i.e. Chelonia mydas), better to eat, and with yellower yolks. The meat is not so good, and is not eaten." The name Chelonia corticata Strauch 1862 is customarily synonymized with Coretta caretta, but Kappler's statement that the breeding size of the animal is 60-70 lbs identifies the genus Lepidochelys unequivocally, As late as 1957 Carr summarized evidence for the occurance of Lepidochelys 1969 PRITCHARD: GUIANA SEA TURTLES 97 olivacea in the West Atlantic as a single adult from Gibara, Cuba, and rumors of the occasional capture of a turtle fitting the description of a ridley in Trinidad. Brongersma ( 1961) wrote that it is "likely that the species breeds somewhere in the Guianas, and indeed a further search along these coasts may yield interesting results." As proof of this, he records a hatchling collected in 1911 in Surinam, and he received one himself from a fisherman in Surinam in 1963 ( Bron- gersma 1968). Even Schulz ( 1964) in his excellent and detailed account of the sea turtles in Surinam misidentifies Lepidochelys as Caretta ( the true identity of the turtles is evident from the photo- graphs). That same year I ( Pritchard, 1964) was able definitely to associate the name Lepidochelys olioacea with a breeding population of turtles in the West Atlantic. GUYANA The ridley nests in reasonable numbers on Shell Beach, where it is known as -teracai" ( a name used for Podocnemis in Colombia), and also as "parrot-beak", "roach-turtle", and "hawksbill." It probably also nests on Waini Beach, Turtle Beach, and Dauntless Point, Leguan Island. I found 14 ridley shells on Shell Beach in August 1964, most of them reasonably intact, and 21 more in August 1965. Small turtles such as ridleys are frequently removed alive by turtle hunters, and probably many more nest without molestation. Therefore Shell Beach seems to be a site of considerable ridley nesting activity. The peak of the season probably lies in May and June; in August very little nesting occurred. Only three live animals were seen during the 3-week observation period. Turtle hunters caught two of these, while I tagged and released the third after watching it nest. Egg diameters on Shell Beach ranged from 39 to 40 mm; those of the hawksbill were similar ( 36-40 mm), but hawksbill eggs could be distinguished by the slight pinkish tinge showing through the shell, SURINAM "The local name in Surinam is warana . The species nests in moderate numbers on Bigi Santi; Schulz ( 1964) recorded 97 nesting emergences there between 29 April and 17 August 1964. Few ridleys nest in April and May when the leatherbacks and green turtles are nesting in numbers, but more do so in June and July, Between 5 May and 6 June 1966, we found only six ridleys on Bigi Santi. The first of the5e, an unusually heavy specimen (97 lbs) with a 2714 inch carapace, emerged from the sea at 5 PM on 10 May and carried 98 BULLETIN FLORIDA STATE MUSEUM Vol. 13 out its complete nesting process in daylight. Another daytime nest- ing record for this species is by Caldwell and Casebeer ( 1964), who found a ridley emerging in mid-afternoon on the Pacific Coast of Costa Rica. Aggregated emergences:-At Bigi Santi I was informed that the ridley nested in large numbers on certain days in June and July on ./Bil E 4. 4 ,$~ . »'. - 'f, - f. Figure 4. A substantial number of the ridleys nesting at Eilanti had shells and limbs damaged, presumably by shark bites. The raw stump of the hind foot of the lower turtle suggests that even adult turtles are vulnerable to shark attacks. 1969 PRITCHARD: GUIANA SEA TURTLES 99 a small beach called Eilanti, near the mouth of the Marowijne River on the French Guiana border. On a routine visit to the area Mr. Plak questioned the natives about this and learned that the first big *5 t -- , I.- -/74 Figure 5. General aspect of beach at Eilanti, Surinam. Note the Indian encamp- ments and the black vultures that eat any eggs the Indians break accidentally. J-L *y.*- Figure 6. Eilanti Beach, 8 June 1966. Note the tracks made by some of the 500 turtles that nested the night before. 100 BULLETIN FLORIDA STATE MUSEUM Vol. 18 Figure 7. Congestion of ridleys on Eilanti Beach. In the lower picture one turtle crawls back toward the sea over the carapace of another; it was restrained in that position until the camera was made ready. arrival of ridleys was expected 10 June. Accordingly we arrived at Eilanti a few days early, on 7 June, in the late afternoon, to find many Indians encamped on the beach, all certain that the big group of ridleys would come up that night. The first turtle emerged with the rising tide by daylight at 5:30 PM. Two more came out before dusk, and after the sun went down 1969 PRITCIIARD: GUIANA SEA TURTLES 101 they began to come ashore in large numbers. Nearly all the nesting was confined to a stretch about 230 yards long at the eastern end of the 1/z-mile beach. By 10:50 PM we had tagged 133 turtles and exhausted our supply of tags. At 11: 10 PM 97 turtles were nesting simultaneously on a 230-yard stretch, and 115 turtles were present on the entire beach. By 11:45 PM only six turtles were left. By mid- night no turtles remained on the beach, and the falling tide exposed extensive mud Hats, about 14 mile wide, crossed by the tracks of many turtles returning to sea in only a few inches of water. We estimated at least 400 turtles nested during the night. About 6 AM the next morning we found 16 more turtles nesting by the early morning light; 2 hours later one turtle was still poun(ling down the sand on its nest site on a very small beach just southwest of Eilanti, on which possibly as many as 100 ridleys had nested during the night. The following night ( 8 June) the first turtle was found nest- ing at 6:40 PM. At 7:30 there was again only one turtle on the beach, but at 10:00 PM 26 were nesting, and at 11:30 PM we found 37. An estimated total of between 80 and 100 turtles nested that night. On the night of 9 June we found four nesting at 7:45 PAL and 84 at 1:05 AM. The total for the night was probably near 300. Though we had to leave the beach the following day, we sub- sequently learned that after 9 June nesting declined to fewer than T I t- Figure 8. Eight mounds of eggs each of this size were accumulated during the night of 7 June at Eilanti. 102 BULLETIN FLORIDA STATE MUSEUM Vol. 18 15 per night. We did not witness the next big arrival that took place 24 June, but I was told that the numbers were comparable to those of 7 June. Only three turtles tagged on 7 June were reported in the later nesting period. The last major aggregation of the year was expected on 14 July. We arrived at Eilanti 12 July, but learned that the big group had nested on the 10th, and that not a single turtle had nested on 11 July About 10 ridleys nested the night of 12 July, and also a 64- inch leatherback, but the following night only two ridleys nested. The next day we left the beach. Table 3. N~MBERS OF Lepidochdys Olivacea NESTING EACH NIGHT DURING THE 1967 SEASON AT EILANT[ BEACH, SURINAM 25 April 0 15 May 8 4J une 8 24 J une 68 14 July 8 26 1 16 1 5 4 25 87 15 10 27 0 17 0 6 11 26 208 16 9 28 1 18 1 7 1 27 61 17 5 29 0 19 7 8 8 28 27 18 0 30 1 20 4 9 9 29 142 19 5 1 May 1 21 1 10 18 80 54 20 10 2 0 22 6 11 152 1 July 85 21 4 8 0 28 0 12 38 2 3 22 6 4 2 24 0 18 260 8 14 23 11 5 0 25 0 14 82 4 11 24 22 6 1 26 3 15 122 5 2 25 5 7 0 27 5 16 6 6 7 26 6 8 0 28 22 17 8 7 5 27 0 9 0 29 28 18 16 8 16 28 29 10 0 30 58 19 7 9 47 29 18 11 0 81 38 20 17 10 98 30 0 12 5 1J une 27 21 5 11 412 81 018 4 2 11 22 4 12 96 1 Aug. 0 14 1 3 12 28 22 18 4 2 0 In 1967 we carried out a more protracted study of ridley nesting at Eilanti; Table 3 shows the numbers of turtles nesting each night. These accurate figures were made possible by the cooperation of the Carib Indians of Christiaan Kondre village on the Marowijne River; each man occupied a few yards of the beach each night, marked all nests as they were made, and brought the eggs to our camp in the morning, where we bought them and re-buried them in an artificial hatchery. The Indians told me that the 1967 nesting was more diffuse than normal, and the periods of aggregated nesting occupied several days each instead of one or two days. Nevertheless a fairly well defined 1969 PRITCHARD: GUIANA SEA TURTLES 108 periodicity is evident, with peaks of nesting at approximately 14-day intervals. Thus the mid-point of the first small wave on 30 May was followed by a major aggregation centering on 13 June, another on 27 June, another on 11 July, and a small, tail-end peak centering around 25 July. It was noticeable that, even when a large group of turtles was expected, none materialized unless the wind was fairly strong onshore. A big group was expected 12 June, but there was no wind at all that night and relatively few turtles nested; these few were abnormally skittish and were easily frightened back into the sea. On the other hand, during a night of intensive nesting activity turtles could sometimes be tagged as they came out of the water; after a momentary flinching as the tag perforated the flesh, they continued up the beach and nested normally. On all nights of aggregated nesting in 1967, the tide was rising at dusk and falling at midnight. It was not unusual for one or two turtles to nest before dark, and moderate nesting took place until high tide was reached, but the turtles did not emerge en masse until much later, and indeed many were so late returning to the sea that they had to struggle through 1,5 mile of 2-inch deep water over the mud flat. Internesting intervals ( in days) are shown in Table 4. It may Table 4. INTERNESTING INTERVALS ( IN DAYS) FOR Lepidochdys olivacea AT EILANTI BEACH, SURINAM Interval Frequency Interval Frequency Interval Frequency 1 19 21 6 41 0 2 7 22 6 42 0 3 5 23 4 43 2 4 8 24 1 44 2 5 6 25 22 45 1 6 3 26 9 46 0 7 1 27 15 47 1 8 0 28 17 48 0 9 0 29 17 49 0 10 0 80 68 50 1 11 4 81 14 51 0 12 4 82 3 52 0 18 4 33 12 58 0 14 11 34 5 54 0 15 6 85 2 55 0 16 12 86 0 56 0 17 41 87 1 57 0 18 28 88 0 58 0 19 18 39 0 59 0 20 10 40 2 60 1 104 BULLETIN FLORIDA STATE MUSEUM Vol. 18 be seen that the most usual intervals occur around 17, 30, and pos- sibly 44 days, with a lone recovery after 60 days. Our immediate conclusion that the 30-day renesters had merely been missed the second time, and recorded the first and third times, is not supported by the small number of turtles found three times. Altogether 1060 turtles were tagged, of which 389 were found nesting twice in the same season, but only 11 were found three times ( except for a few cases in which one of the intervals was less than 7 days, when we assume that the turtle did not nest on its first appearance). These eleven nested at the following intervals ( in days): 20 & 11; 12 & 17; 12 & 30; 17 & 16; 17, 3 & 28; 18 & 19; 11 & 19; 17 & 16; 17 & 16; 18 & 16; 14 & 16. It seems most likely that Lepidochelys olivacea normally nests twice in a season, at intervals controlled more by external factors ( tide and weather) than by the internal factors that seem to control the green turtle's nesting. A particularly interesting finding was that no less than 39 of the 130 turtles tagged 7 June 1966 renested in 1967 between 31 May and 12 July, and 59, including 28 of the 39 from 1967, renested in 1968. Nine of these nested twice in 1967, on the following dates: 30 May and 28 June; 3 June and 9 June ( presumably disturbed the Brst time); 11 June and 11 July ( three individuals); 13 June and 9 July; 13 June and 11 July ( two individuals); 14 June and July 10, I have since heard from Rene Marquez that Lepidochelys kempi also sometimes nests in successive years, and recently these results have been published ( Chavez, 1968). On rare occasions Caretta caretta may nest in successive years on the coast of Natal ( Hughes et al, 1967). The local Carib Indians can predict with reasonable accuracy when large nesting aggregations of turtles are expected, and many of them move down to the beach to collect the eggs for the market. The village headman told me that he had been coming to Eilanti to raid ridley nests for 50 years, and that the numbers did not seem to be reduced from former times. This is hard to understand, as I estimated that fewer than 10% of nests on nights of aggregated nesting remained intact, and relatively few individuals nest on other nights. Possibly most of the turtles nesting today are old individuals hatched before systematic nest raiding began. Killing sea turtles is forbidden by Surinam Law, and indeed the Indians showed a solicitous regard for them and feared that I might damage or pos- 1969 PRITCHARD: GUIANA SEA TURTLES 105 sibly kill them by leaving them on their backs overnight to photo- graph in the morning. One of the ridleys tagged 7 June 1966 was recovered 17 Sep- tember 1966 near Cape Cassipore, Brazil, by a shrimp trawler. The turtle was taken in water 35 fathoms deep, having traveled about 300 miles upstream. Another was recovered 75 miles offshore from Paramaribo on 20 January 1967. Three of the 1967 group have been recovered, one from near the Orinoco Mouth, one off the coast of Surinam, and one from Brazil between the mouths of the Oyapoque and the Amazon ( see Figure 3). Nesting process. Several writers have hinted at the possibility that Lepidochel!/s oliuacea makes massed nesting emergences on Pacific shores of the Americas. Carr ( 1961) found the apparent scarcity of nesting ridleys on the Pacific coast of Mexico hard to reconcile with the large numbers of sexually mature individuals seen offshore, and concluded that they must be grouping up to nest in some remote, overlooked place. Caldwell ( 1966) mentions un- corroborated reports of large numbers of turtles nesting in the vicinity of Bahia Banderas, Jalisco, Mexico. Proof of aggregated nesting by the ridley of the East Pacific was not forthcoming until late 1967, when Carr received photographs from Antonio Montoya showing huge numbers of ridleys nesting together on a few kilometers of beach in northern Guerrero, Mexico, Montoya estimated that on one occasion 15,000 turtles nested in a 24-hour period, and on another occasion 30,000 nested in 18 hours. Nesting thus took place both by daylight, as is almost invariable with L. kempi, and by night, as is normal with Surinam L. olivacea. Similar large aggregations have since been found on the coasts of Jalisco and Oaxaca. Two questions arise: how do the turtles manage to synchronize and localize their nesting in this fashion, and why do they do it? The first question touches upon the larger and as yet unsolved prob- lems of sea turtle navigation, discussed at length by Carr ( 1964, 1967). The problem of synchronization of nesting, peculiar to the genus Lepidochelys, has yet to be discussed in the literature. It seems unlikely that eggs ripen within the body of the gravid female ridley in such perfect synchrony that the urge to lay, brought about by pres- sure of eggs from within, comes upon the whole population simul- taneously. It is more likely that the eggs ripen in approximate but not perfect synchrony, and that the female can hold the shelled eggs for a reasonably long period until the right combination of tide, moon, and wind brings about an independent urge to lay in all the 106 BULLETIN FLORIDA STATE MUSEUM Vol. 18 local turtles simultaneously. This theory must be viewed in the light of the common observation that a turtle frightened back to the sea before it nests will usually try to nest again either later the same night or the following night. It seems likely that, once a turtle comes voluntarily from the sea to nest, the eggs start moving towards the cloaca and produce a pressure that can be relieved only by laying the entire clutch. If the turtle has not yet tried to leave the sea, apparently the eggs may be held much longer. The advantage of massed nesting ( ambada formation) is simi- larly not obvious; some benefit must be gained, as the arriba(la is a highly organized trait, certainly not the result of random chance, and must require constant selective pressure to maintain. One of the reasons most commonly given is to overwhelm predators, par- ticularly predators on the eggs and hatchlings, with such a bewilder- ing abundance of prey, available for such a short time, that even though the predators eat all they can, large numbers will still sur- vive. It has now been shown that arribadas iii Surinam, Tamaulipas ( Carr 1963) and Guerrero all take place only during strong onshore winds and, even in Honduras where arribada formation is yet to be demonstrated, more turtles nest on windy nights than on calm nights. This too must have a reason, and it has been suggested that strong winds may in some way help the turtles to "ride the waves and be speeded on to the beach. Much more likely to me is the fact that a strong wind will help cover up the tracks and nests of the ridley and thus render them less conspicuous. Little short of a tornado will obliterate the tracks of a green turtle or leatherback, but the track of a ridley is so shallow that wind-blown sand can erase it quickly. William Greenhood has suggested that a strong wind helps to dislodge the mosquitoes that descend in clouds upon ridleys nest- ing in Surinam, and this reason too may have some substance. As no detailed account of the nesting of Let*dochelys olivacea in the Atlantic has been published, the following description of the nesting process of an Eilanti individual may be of interest. The turtle, found crawling up the beach with its carapace still wet, paused occasionally as she walked straight to the vegetation line, turned back a short way, and immediately began digging the body pit. Using rather disorganized strokes of all four flippers, the front ones usually working together ( Figure 9), the rear ones alternately, she completed the pit in 4 minutes. She started digging the nest cavity at the rear of the body pit with great energy, but soon be- came rather sluggish. Her shell moved from side to side through 1969 PRITCHARD: GUIANA SEA TURTLES 107 Figure 9. Ridley digging body pit with simultaneous strokes of the front flippers. a wide angle as she dipped her flippers alternately in the cavity. She jerked each Hipper forward sharply before re-inserting it in the hole. As the cavity deepened her shell dipped lower to let the Hipper scrape sand off the bottom. At first she moved the rear part of her carapace in a simple down-up movement, but towards the 41 Figure 10. Position of ridley during oviposition. Note the fore-flippers anchored in the sand and the widely-spaced hind flippers. 108 BULLETIN FLORIDA STATE MUSEUM Vol. 18 end of the excavation this movement became a little more compli- rated; she lowered the rear part of her shell to the full extent, the front of the shell raised high on the foreliinbs and the neck lowered. then she raised the rear a little, lowered it the same amount, and finally raised it fully before switching to the other flipper. When the egg cavity reached its final flask shape, she continued to jerk the flipper sharply for,vard as if about to re-iiisert it in the cavity, but instead she merely curled the Ripper and drew it under the overhanging rear marein of the carapace. There was no obvious reason for this movement, which she made al)out three times with each fiipper. Oviposition commenced with the foreflippers still braced in the sand and the hind Hippers splayed outwards (Figure 10). The sequence of movements preceding each deposition of one, two, three, or four eggs was as follows: 1) hunicral region drawn slightly in- rwards and head simultaneously slightly extended, 2) above move- Figure 11. As the eggs are laid the rear niargin of thi hind flippers curls upwards. 1969 PRITCIIARD: GUIANA SEA TURTLES 109 ments reversed, 3) rear part of shell moved up and down through a few millimeters with rear margins of hind flippers raised simultan- eously ( Figure 11),4) eggs deposited. Froin time to time during oviposition she raised her head considerably and took a deep breath. About a minute after laying the last egg, she pulled sand into the egg cavity by alternate movement of the hind flippers. As soon as the hole was filled she pounded the loose sand down with alternate sides of the carapace. During this movement she braced her front flippers in the sand with her head pointed down and almost resting on the sand but providing no anchorage. She thumped down the side of her carapace and the hind flipper on the same side almost simul- taneously ( Figure 12). After a few minutes she stopped pozinding 0...sq t C- e C ... r .El Figure 12. The sand over the nest site is porinded down with side-to-side movements of the shell; the turtle has just tilted sharply to the left, compressing the sand with the shell margin. and with the hind Hippers drew more sand into a small pile under the rear of her carapace. She then resumed thumping, always with a side-to-side rocking movement, never with the whole plastron. Then she began to throw sand backwards with one foreflipper and the opposite hind Ripper ( Figure 13 ). This movement generated a slight turning effect and a slight motion away from the nest site. After four or five swipes she counteracted the turning movement with a single quick step and repeated the maneuver with the opposite flippers. This 110 BULLETIN FLORIDA STATE MUSEUM Vol. 13 Figure 18. Sand is swept over the nest site with strokes of one foreftipper acting in conjunction with the opposite hind flipper, continued for a long time, while she moved about 5 feet awav, then turned round and returned toward the nest, possibly disoriented by the light. Into this movement she interposed a few simultaneous swipes of her fore flippers. Gradually the movement became the stand- ard walking which carried her part way to the sea. Shortly before she reached the sea she turned a tight circle and thereafter seemed completely disoriented, again possibly by the flashlight. Eventually it was necessary to help her into the sea. I timed another turtle as she went through the same motions as follows: 1:24 AM Emerged from sea. 1:26 Selected nest site and started body pit. 1:30 Started excavating nest cavity. 1:45 Changed digging movement to Ripper-curling move- ment ( see above). 1:46 Starting ovipositing. 1:55 Began to fill egg cavity. 1:56 Commenced sand pozin(ling. 2:00 First front Ripper movement. 2:09 Started moving towards sea. 2:10 Reached sea. 1969 PRITCHARD: GUIANA SEA TURTLES 111 15- 10 - - FR EQ UE NC Y 5- --1-1-7 25 26 27 28 29 CARAPACE LENGTH (INCHES) Figure 14. Overall carapace lengths of mature female ridley turtles (Lepidochelys olivacea) from Shell Beach, Guyana; Bigi Santi, Surinam; and Eilanti, Surinam. Although the Indians warned me that a flashlight would disturb the turtles, I found them remarkably oblivious to disturbances of this or other kinds, even before they had begun to nest. The whole process from emergence to reentry seemed completely automatic. Impatient Indians frequently dragged the turtle away from the nest as soon as the last egg was laid; the turtle went through the cover- ing-up and sand-pounding motions as if it had not been removed. Carapace measurements. - Mature female ridleys fall in a rather narrow size range, the vast majority having a carapace length between 26 and 28 inches. The smallest of 241 individuals measured had a carapace length of 24.5, the largest 29.125 inches. Figure 14 shows the carapace length distribution for 120 random adult female ridleys; Table 5 gives more detailed measurements for 21 individuals. Carr ( 1952) found the carapace length of mature female Lepido- chelys olivacea from Pacific Honduras to range from 25.4 to 27.2 inches. My own studies in this area show that some females reach maturity at as little as 23 inches, while- the largest of 100 individuals measured was 29.5 inches, which is larger than any known from Surinam. The species may reach a slightly larger size in the Indian Ocean than elsewhere; the record for the Species is apparently held by a 31.1 inch Ceylon female ( Deraniyagala, 1939). Clutch size. - Clutch size for 928 Surinam ridley nests ranged from 30 to 168 eggs; average was 116.072 eggs per nest, and only 4 1 112 BULLETIN FLORIDA STATE MUSEUM Vol 18 27- 0 26- e. . 0 00 0 CA RA PA CE W ID TH (IN C H ES ) .. 26- 0 0 0 . 0 0 1.0- .. 24- 0 040 0 0 0 ... 50 .. .. 23- 22 24 25 26 27 28 29 CARAPACE LENGTH (INCHES) Figure 15. Carapace width plotted against carapace length for 59 mature female Lepidochetys oliuacea from Guyana and Surinam and 5 mature female Lepidochetys kempi from the Gulf of Mexico. Closed circles: L. otivacea, open circles: L. kempi. nests contained less than 70 eggs, and only 4 more than 155. No data are available for Surinam ridleys for correlating shell length with clutch size, but out of 45 random Honduras ridleys the 20 that exceeded 26.25 inches in carapace length laid on average 123.8 eggs, while the remaining 25 turtles averaged only 95.9 eggs each. Carapace laminae . - Lepidochelys olivacea is unique among living turtles in showing a striking polymorphism of the carapace laminae. The lateral laminae average about 7 on each side, but vary from 10 to 18 or more for both sides. The central laminae also vary from 5 to 9 in number, although there seems to be only slight correlation between high central counts and high lateral counts ( Figure 16). 1969 PRITCHARD: GUIANA SEA TURTLES 118 Table 5. D~MENSIONS OF MATURE FEMALE Lepidochelys oltuacea FROM SURINAM C IN INCHES ) Carapace Carapace Plastron Head Weight' length widtli length width ( Lbs. ) 251/4 28 19:k 5 68 26 2414 20% 5 76 2644 28% 20 514 - 2614 28% 20% 5% 68 261/2 2214 20% 5~2 78 2642 28 21 5 71 2642 23% 21 5% 82 27 231/& 2014 5% - 27 24 21 % 5 76 27 2414 21 51,2 - 27 249 21 5 76 2714 28 21 % 5% 80 2731 24 44 20% 544 87 2744 24 34 21% 514 97 27% 281k 21% 5 77 27% 2414 21 514 - 27~2 24 12 21 5% 88 271/2 25% 201~2 5% _ 28 2414 21% 51% _ 28 25% 21 5% - 28 34 28 % 21 % 51,2 77 *All weights taken after oviposition. The marginals are reasonably constant at 12 on each side. The plastral laminae are much more stable than those of the carapace, but the intergular scute may be absent, single, or double. The lateral laminae of Lepidochelys olivacea are clearly divisible into whole laminae and half laminae, the whole laminae being homo- logous to the five laterals of L. kempi. Displacement of the homo- logues of the seams of L. kempi is usually slight, though in cases of extreme splitting to 8 or 9 laterals the seams become displaced to lessen the size of the small first lateral and the large last central. In almost every case division took place in the rearmost laterals; for example a 6-6 count is produced by division of the 5th laterals on each side, or an 8-8 count by division of laterals 3,4, and 5. One exception is a shell with a 7-6 count in which only lateral 4 on the right hand side was divided. It seems impossible to rationalize this multiscutate condition in terms of function; the extra seams in no way alter the hydrodynamic form of the animal, and the Iaminae are so thin that their precise arrangement could have no effect on the overall strength of the carapace. Nor could it have any signifi- cant disruptive or other effect on the animal's appearance, as one 114 BULLETIN FLORIDA STATE MUSEUM Vol. 18 8 9 20 7 1 NU M BE R O F C E N TR A LS ·6 9 8 7 3 '5 3 6 4 1 2 11 12 13 14 15 16 17 TOTAL NUMBER OF LATERALS Figure 16. Number of central laminae plotted against total number of lateral laminae for 88 sibling hatchling Lepidochelys otivacea from Bigi Santi, Surinam. usually has to look very closely at adult ridleys to see the lamina boundaries at all ( Figure 19). Carr ( 1957) suggests that the number of lateral laminae in Lepidochel!/s olivacea is geographically correlated. The present data suggest that this may be true on a broad, statistical basis, but cer- tainly no more than this ( Figure 17). It is nonetheless interesting to compare the frequency of occurrence of turtles with only five lateral scutes on each side in the Surinam and East Pacific popula- tions. This lamina count is of course the normal ( and very stable) one for the Atlantic ridley, Lepidochelus kempi and is the feature most commonly used for distinguishing the species, The only speci- mens of L. oliuacea with this count mentioned in the literature are two sibling hatchlings from the Cameroons ( Loveridge and Williams, 1957) and 3 out of 378 Ceylonese specimens ( Deraniyagala, 1939). Also an adult ridley shell from the Pacific coast of Mexico ( Chiapas) in the Chicago Natural History Museum has only five laterals on each side. In Surinam this low count was found to be rare indeed, 1969 PRITCHARD: GUIANA SEA TURTLES 115 A . 1 8 ' 9 10 11 12 13 14 15 16 17 18 20. B IS - 10- 5- , 1 1 1 ! ,1--1 , 89101112131415161718 20- - FR EQ UE NC Y 15- 1 , 5- 8 9 10 11 12 13 14 15 16 1718 100- 90- 80- D70- 60- 50- 46- 30- 20· lo· ---7 F- 8 9 10 1112 13 1415 16 9 18 TOTAL NUMBER OF LATERAL LAMINAE Figure 17. Histogram showing the lack of correlation of total number of lateral laminae of Lepidochetys dll>acea with locality; A: miscellaneous West African localities ( data from Carr, 1957 ); B: Shell Beach, Guyana; C: Eilanti, Surinam; D: Ceylon ( Data from Deraniyagala, 1939). shown by only 3 out of 762 individuals, but approximately 1 out of 5 adult Honduras ridleys had five laterals on each side, and one group of 126 hatchlings included 26 5-5 counts. Deraniyagala ( 1939) writes that a low average lamina count is a tendency of certain broods of hatehlings. This seems borne out 116 BULLETIN FLORIDA STATE MUSEUM Vol. 18 30- 20- 10- 7O,,F- . r-n , FR EQ UE NC Y 9 10 11 12 13 14 15 16 17 18 50- 40- 30- 20- 10- 0, 1 I 9 10 11 12 13 14 15 16 17 IS TOTAL LATERAL LAMINAE Figure 18. Histogram showing variation in total lateral lamina counts within two complete clutches of Lepidochelys olivacea from Big Santi, Surinam. by an analysis of three clutches of hatchlings from Isla de Ratones, Honduras, shown in Table 6, which were not hatched under natural conditions: brood 1 was hatched in Florida after the eggs had been brought back by car, and broods 2 and 3 were hatched in artificial nests 20 miles from the place of deposition. The extreme counts shown by broods 1 and 3 could well have been produced by trans- porting the eggs. Lynn and Ullrich ( 1950) produced hatchling Chrusemys and Citelydra with similar abnormalities experimentally by subjecting the eggs to suboptimal moisture conditions. The central laminae of L. olivacea show a variation in number in the same way as the Iaterals; of 474 Surinam specimens 72 had 5 centrals, 200 had 6, 185 had 7, 16 had 8, and 1 had 9. The marginals are less variable, about 90 per cent of specimens having 12 on each side ( not counting the paired supracaudals); other counts recorded 1969 PRITCI IARD: GUIANA SEA TURTLES 117 -.- -9 ··i. At: . -- 6- 0 2 - 4- C ~ 2- --1-0- ~-5- 32 32· 5 33 33·5 34 34·5 35 CARAPACE LENGTH (INCHES) Figure 28. Overall carapace lengths of adult female Eretmochet!/s imbricata from Shell Beach, Guyana. Table 8. DIMENSIONS OF MATURE FEMALE Eretmochelys imbricata, SHELL BEACH, GUYANA