Nesting Frequency and Clutch Size in Dermochelys coriacea in Malaysia

Journal of Herpetology, Vol. 22, No. 2, pp. 208-218, 1988 Copyright 1988 Society for the Study of Amphibians and Reptiles

Nesting Frequency and Clutch Size in Dermochelys coriacea in Malaysia

TOCK H. CHUA AND J. I. FURTADO

Department of Zoology, University of Malaya, 59100 Kuala Lumpur, Malaysia

ABSTRACT. -Analysis of 37,654 leatherback visit records shows that a mean of 81% (range 51-95%) of visits resulted in successful nests every year at Rantau Abang beach, peninsular Malaysia. The internesting interval within a season (intraseasonal interval) varied from 0-49 days, but the highest mode (polymodal histogram) was 9-10 days. The percentage of tagged turtles returning to breed in consecutive years and once in 2 years was 48.9 and 24.6, respectively. Few turtles returned after a long absence (e.g., 4 after 8

years). On average, each turtle returns to breed after an interval of 1.95 years (interseasonal interval). Most turtles (38% of the daily total) arrived at the beach at 0100-0300 hours, and laid at 0200-0400 hours. Mean clutch size for those turtles with only one clutch per season was 83 normal and 20 yolkless eggs. For those with more than one clutch, the mean total clutch of normal and yolkless eggs varied little (range 100-105)

although yolkless eggs may be fewer in the later clutches (e.g., 11th and 12th). The major difference was in variation in the maximum and minimum number of normal and yolkless eggs in later clutches. For 3 clutches, the minimum-maximum normal and yolkless egg numbers were 84-85 and 18-22, respectively, while for 12 clutches the corresponding figures were 75-96 and 8-29. The number of yolkless eggs depended on the number of normal eggs laid (y = 47.13 - 0.34x [P < 0.001]. Clutch size was also found to vary with the beach sector where the eggs were laid.

Four species of sea turtles are known to nest in peninsular Malaysia; they are the leatherback turtle, Dermochelys coriacea, the green turtle, Chelonia mydas, and the Ridley turtle, Lepidochelys olivacea, which nest mostly on the east coast, mainly in Te- rengganu State (Hendrickson, 1961; Hen- drickson and Alfred, 1961). The hawksbill turtle, Eretmochelys imbricata, nests on the west coast in Melaka State (Kiew, 1975a; Chua, 1979). The leatherback turtle has the largest rookery here by far and has been studied for over three decades (Tweedie, 1953).

The leatherback turtle has a special place in Malaysia. It is mentioned in some Ma- laysian folklores, and provides a cheap source of protein to the local villagers in the form of eggs. Thus, it is not surprising that it is protected by law in the three states where it is found. These regulations are essentially the same: they prohibit the taking and possession of turtles, and the taking (without license) or destruction of eggs, and specify the areas where eggs may be collected.

To help conserve the turtle population, a hatchery was first set up in 1961 after much hard work by J. R. Hendrickson and

his colleagues in persuading the state gov- ernment of Terengganu. Hendrickson (1962) discussed the historical background of the hatchery. Regular reports have been made subsequently by various people: Anonymous, 1964; Balasingam, 1965,1967a, b; Balasingam and Tho, 1972; Kiew, 1975b; and Siow, 1982. The eggs are purchased from the licensed egg collectors and trans- planted at the hatchery. Information from earlier experiments on the hatching of turtle eggs done by Hendrickson and Win- terflood (1961) proved to be useful in run- ning the hatchery. The methods presently used may be attributed to Hendrickson and Winterflood (1961), Balasingam (1967a) and Siow (1982).

Briefly, every year in May or June a 65 m long beach is fenced off and one m2 areas pegged out. Mature eggs collected at night are then buried in holes of 60 cm deep and 25 cm diameter. The natural clutch is usually placed in one or two holes so that each contains about 80 eggs or fewer (Siow, 1982). About 45 days later, the area around each hole is fenced off to contain the hatchlings. Hatchlings are released at regular intervals (2000, midnight, and 0600). Be- tween the years 1961 and 1976, a total of

NESTING FREQUENCY IN DERMOCHELYS

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70 73 76

100

50

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Year FIG. 1. Number (x 1000) (histogram) and percentage (graph) of leather-back turtle visits to Rantau Abang

beach, Malaysia, with nesting observed.

633,740 eggs was used in the hatchery and 329,437 hatchlings were released. The mean percentage of successful hatching is 52% (Siow, 1982).

In conjunction with the hatchery, a tagging program was first tried in 1966 (Ba- lasingam and Tho, 1972) and later carried on for the next 10 years until 1976. Be- tween May and September each year, tagging was conducted by 24 licensed egg collectors, who patrolled the rookery nightly. Other information was also collected on each turtle encountered on the beach. This is the second report from the analysis of the data collected between the years 1967 and 1976, made available through the cour- tesy of the Fisheries Department of Te- rengganu.

MATERIALS AND METHODS

Details of the tagging and data gathering program are presented by Chua (1988). Briefly, 24 taggers were employed to work on the rookery at Rantau Abang. They patrolled the beach nightly during the nesting season and if any turtle was spotted, the following information was recorded: date, time, and beach sector where the turtle was first observed; part of the beach profile where observed; turtle's activity

when first observed, whether tagged or not; tag number; whether nested or not; number of both normal and yolkless eggs; sur- face length and breadth of carapace (maximum straight-line distance along the midline, from the anteriormost margin of the cervical scute to the posteriormost edge of the marginal scale); and other remarks. If the turtle was not tagged, then a new tag was applied.

For the purpose of data collection, the beach was divided into 15 sectors, each about 1.3 km. On the other hand, the beach

TABLE 1. Number and percentage of leatherback turtle visits to Rantau Abang beach with nesting observed or confirmed.

% of annual Year Total visits No. of visits total

1967 2822 1869 66.23 1968 6721 3391 50.45 1969 5064 4259 84.10 1970 3458 3126 90.40 1971 4188 3732 89.11 1972 6471 5717 88.35 1973 2767 2541 91.80 1974 2048 1889 92.24 1975 2153 2048 95.12 1976 1962 1845 93.99 Total 37,654 30,417 80.78

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a season).

profile was divided into 5 parts: the lowest part being the water level, and the highest part the area where the bushes and shrubs were. In between these two lay 3 equal, intermediate parts.

For convenience, the nesting activity was divided into seven distinct parts by the observer. They are: ascent to the beach, digging the body pit, digging the egg hole, egg laying, covering up hole, making decoy tracks, and descent back to sea. The whole activity may last for about 140 minutes, of which actual egg laying takes only 9 minutes while making the decoy tracks takes 50 minutes (about 30% of the total nesting time).

For the ten year period, a total of 37,654 turtle sightings or records were made, and the data were analyzed using a UNIVAC

mainframe computer at the University of Malaya.

RESULTS

Number of Nestings.-The number of cases in which turtles visiting the beach were observed laying eggs or confirmed having laid eggs (even with the nest holes cov- ered, in which case, the presence of eggs was determined by digging) ranged from 1845 (in 1976; 94%) to 5717 (in 1972; 88%) (Table 1). In terms of percentage, however, the figure varied from 50.5% (in 1968) to 95.2% (in 1975), with a mean for the ten year period of 81%. Except for the years 1967 and 1968, the percentage for the other years is normally high, i.e., in excess of 84%. In fact, for the years 1970-1976, the percentage stayed almost stable (Fig. 1).

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Interseasonat interval FIG. 3. Histogram of total number of leatherback

turtles (x 100) from 1967-1976 against breeding (interseasonal) interval (years) at Rantau Abang beach, Malaysia. The percentages of turtles with intervals of 1-8 years are 48.9, 24.6, 15.2, 7.3, 2.8, 0.9, 0.2, and

0.1%, respectively.

Inter-nesting Interval.-For this analysis, only the records which show the same individual turtles (identified by the tag) having returned to the beach successively within the same year were considered. The histogram of number of individual turtles

against interval (days; intraseasonal interval) between visits, with nesting observed and/or recorded, indicates a polymodal structure with a long tail towards the longer interval (Fig. 2). The number of turtles returning to nest fluctuates cyclically with the increase in interval. Some turtles were recorded to return to nest the next day after the first clutch, while very few returned after 49 days. There are at least four distinct peaks, at days 1, 9, 19, and 28. At the right end of the histogram, minor peaks at days 36 and 45 may be discernible. This is roughly equivalent to a peak every 9-10 days, meaning that most turtles are ready to lay eggs every 9-10 days. However, this does not necessarily imply that every turtle would renest on this schedule, nor even

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Time ( hours) FIG. 4. Histogram of mean number of nestings per

year (x 100) against time of day when egg laying was observed. The mean is based on data for the years 1968-1969, 1971-1974 and 1976.

that every turtle would nest more than once in the same breeding season. Based on the height of the peak, it appears that more turtles returned on the 9th day to nest again than on any other day.

Inter-breeding Interval.-Since not all turtles return to Rantau Abang every year to nest, it is useful to determine what the inter-breeding interval (interseasonal interval) is between successive visits by the same turtle. The number of visits (whether with nesting observed or not) made by the same turtle within the same year is not taken into consideration in the analysis. Only those visit records with nesting observed or confirmed by other means (e.g., by find- ing the nest) were analyzed. It is possible that some returning turtles were missed; however, such misses were probably neg- ligible (since the sectors under surveil- lance by 2 adjacent taggers overlapped) and do not influence the analysis significantly.

It would seem that most turtles (48.9% of those which returned at least once) revisited the Malaysian beach to breed after an interval of one year (Fig. 3), while another 24.6% returned after two years. Very few turtles revisited the beach after a long interval; 26 turtles returned after 6

211

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TABLE 2. Time of day when visiting turtles were observed laying eggs at the beach at Rantau Abang for the years 1968-1969, 1971-1974, and 1976.

Year Estimated time

Time (hr) '68 '69 '71 '72 '73 '74 '76 Total Mean % ascending

1800-2000 2 3 1 5 2 2 6 21 3 0.1 1700-1900 2000-2200 132 170 95 210 206 143 85 1041 149 5.0 1900-2100 2200-2400 309 611 413 578 423 265 232 2831 404 13.5 2100-2300 0000-0200 432 824 568 1272 607 400 397 4500 643 21.5 2300-0100 0200-0400 504 1511 1694 2023 826 717 621 7896 1128 37.7 0100-0300 0400-0600 243 1010 668 1141 415 331 446 4254 608 20.3 0300-0500 0600-0800 14 89 70 146 35 14 42 410 59 2.0 0500-0700

Total 1636 4218 3509 5375 2514 1872 1829 20,953 - - -

years, 8 after 7 years, and 4 after 8 years. Based on these revisiting data, the calculated average interseasonal nesting interval was 1.95 years.

Egg Laying Times. -Only the data for the years 1968-1969, 1971-1974, and 1976 were analyzed. In 1967, the time of egg laying was not recorded, while some unsolved technical problems with the computer tape prevented the use of the data for 1970 and 1975. However, it may be assumed that 7 years' data provides a reasonably accurate picture of the general trend.

The number of turtles observed to lay eggs increases as the day cools from 1800 h, and reaches a peak at 0200-0400 h (Fig. 4). Only 23 turtles were observed in the early evening (1800-2000 h) while a mean of 1264 turtles (or 38% of those visiting the beach daily) were recorded to lay eggs in the early morning (0200-0400 h; Table 2). From 0400 h onwards, the number decreases again.

On average, observations have shown that the turtles take a total of 52 minutes to ascend the beach and to dig a body pit and an egg hole before laying the eggs. Therefore, if an hour is deducted from the egg laying time observed, we should get an estimate of the ascending time of the turtles. The turtles are thus calculated to ascend the beach in large numbers just before midnight (2300-0100 h: 22% of daily total number), the number peaks at 0100- 0300 h (38%) and tapers off at 0300-0500 h (20%).

Clutch Size in Relation to Nesting Frequen- cy.-The difficulty with analyzing variation in clutch size with nesting frequency

is that sometimes the clutch size was not recorded, resulting in some gaps in the data. It should be noted that the mean clutch size was calculated from known clutch sizes only. The mean values were calculated from the data for the years 1967 to 1976 (Fig. 5; except for 1968, see reasons below).

There are two types of eggs: the normal, usually fertile eggs, and the smaller, yolkless eggs. The yolkless eggs are laid towards the end of the clutch and consist of albumin only. It is possible that some normal eggs are unusually small and could be mistaken for yolkless eggs during the count at night.

For turtles which made only one visit to the beach (and hence had only one clutch), the mean number of eggs laid is 83.1 normal and 19.1 yolkless. For all years exam- ined, it is clear that the total clutch size (including yolkless eggs) is less variable if the number of visits or clutches laid is 7 or fewer (Fig. 5). For example, in 1967, for 1 to 7 clutches laid, the total normal eggs per clutch varied from 83 to 92, while the yolkless eggs varied from 18 per clutch to 32. For the total of 10 clutches, the maximum total clutch size is 110 and the minimum, 68.

In 1968, the number of yolkless eggs was unexplicably low, either absent, or per- haps, not recorded in many cases. The normal eggs per clutch varied from 63 to 130. Because of this, the average was calculated using only the data of 1967 and 1969-1976 (Fig. 5).

Based on the nine year average for 1 to 4 clutches laid (Fig. 5; Table 3), the number of normal eggs seemed almost constant

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No. of clutches laid by a turtle FIG. 5. Variation of clutch size in relation to number of clutches laid. The histogram represents mean

values for the years 1967 and 1969-1976. Stippled area = yolkless eggs; hatched area = normal eggs.

(about 84), while the yolkless eggs varied only slightly, from 20 to 22. It may be noted that the variation in yolkless eggs occurred almost in a step-wise fashion, increasing slightly in number for the later clutches. When 5-8 clutches were laid, the number of eggs laid varied more, being 81 to 87 for

the normal eggs and 15 to 23 for the yolkless eggs. The variation was even greater when 9 to 12 clutches were laid. In these cases the normal eggs ranged from 80 to 96 while the yolkless eggs were 8 to 29. Two peaks are discernible, one at clutches 5 to 7 and the other at clutches 9 to 11.

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TABLE 3. Details of variation in egg number with respect to number of nestings recorded. The data represent the mean for the years 1967 and 1969-1976. The number within parentheses represents clutch number. Data for number of clutches greater than 12 are not analyzed, as they are few in number. N = normal, Y = yolkless.

Per visit

Normal eggs Yolkless eggs Total eggs Mean No. of clutches Max. Min. Max. Min. Max. Min. N Y Total

1 83.1 19.7 83.1 19.7 83.1 19.7 102.8 2 84.3 (1) 83.7 (2) 21.7 (2) 19.6 (1) 168.0 42.2 84.0 20.6 104.6 3 84.7 (3) 83.6 (1) 21.6 (3) 18.2 (1) 251.5 59.7 83.8 19.9 103.7 4 85.0 (2) 82.5 (1) 22.1 (4) 19.3 (1) 334.6 82.9 83.7 20.7 104.4 5 86.4 (3) 83.0 (1) 22.2 (4) 17.9 (1) 421.8 102.3 84.4 20.5 104.9 6 86.0 (3) 83.8 (6) 22.7 (6) 16.5 (1) 510.1 120.9 85.0 20.2 105.2 7 86.6 (3) 83.3 (6) 21.8 (6) 16.4 (1) 595.7 139.5 85.1 19.9 105.0 8 86.8 (2) 81.2 (1) 21.6 (7) 15.5 (2) 683.0 152.2 85.4 19.0 104.4 9 89.5 (6) 83.1 (8) 22.4 (8) 14.3 (1) 763.0 171.4 84.8 19.0 103.8

10 94.7 (5) 79.6 (1) 22.9 (7) 17.0 (1) 863.4 197.6 86.3 19.8 106.1 92.9 (9)*

11 91.6 (7) 81.5 (9) 28.1 (3) 9.9 (7) 946.3 191.2 86.0 17.4 103.4 86.7 (11)*

12 95.6 (5) 75.4 (8) 28.8 (9) 7.9 (2) 1033.2 166.4 86.1 13.9 100.0 90.6(11)*

*Value for second peak.

Therefore, it would appear that if a turtle nests on the beach more frequently within a season, the clutch size is more variable, resulting in greater differences between the maximum and minimum clutches recorded. The total number of eggs comprising 12 sequential clutches amounted to 1033 normal and 166 yolkless eggs (Table 3). The mean number of eggs per clutch in- creased slightly from 83 (1 clutch) to 86 (10 clutches or more) for normal eggs. The yolkless eggs varied very little, around 19 to 20 eggs, except for the 11th and 12th clutches which had only 17 and 14, respectively.

Variation in Clutch Size with Beach Sector. - There appear to be three areas where the mean number of normal eggs laid by an individual was higher (85 or more). These are the sectors 1, 5, 6, and 12 (Fig. 6). In the first two years of research, the number of yolkless eggs recorded appeared to be zero, but this is because most of the work- ers did not record them. Therefore, the mean calculated was based on the data of 1969-1976. The mean was also not calculated for sectors 13-15 because the number of clutches recorded there was relatively rather small and might give a biased view.

The highest number of normal eggs recorded was 87 at sector 12, while the lowest

number was at sector 4, with 78 eggs. How- ever, in terms of total clutch size (including yolkless eggs), the highest was recorded at sector 1 (105), while the lowest was at sector 11 (96). There also appeared to be a trend that when the number of normal eggs was higher, there was a corresponding lower number of yolkless eggs. This trend is more discernible if the number of yolkless eggs is plotted against normal eggs (Fig. 7). The resulting regression is y = 0.34x + 47.13 (F = 18.91, P < 0.001), where y is the number of yolkless eggs.

DISCUSSION

In an earlier report, Chua (1988) showed that the turtles mostly nested (at least 57% of the turtles recorded yearly) on the higher part of the beach. This would reduce embryonic mortality, as Whitmore and Dut- ton (1985) showed that washover by waves increases mortality. The sand texture is im-

portant too as Hendrickson and Balasin- gam (1966) found that Dermochelys prefers sand which has 10-20% fine sand (<353 ,A) and 80-90% coarse sand (> 500 j,). A greater proportion of fine sand (e.g., 52%) would result in low hatching success (15%) of the

eggs, as reported by Limpus et al. (1984) for leatherback turtles in Australia.

The percentage of turtles visiting the

214


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Beach Sector FIG. 6. Variation in number of normal and yolkless eggs in relation to the beach sector where the eggs

were laid. The data represent the mean clutch size per turtle for the years 1969-1976. The left scale is for normal eggs while the right scale is for yolkless eggs.

beach which had been observed to nest successfully or which showed signs of having nested was high and varied between 88% (1972) and 94% (1976). This might in- dicate the high efficiency of the taggers, especially when the turtles were laying (considering that egg laying takes only 9 minutes or 6% of the time each turtle spends on the beach), and/or the low percentage of failures of turtles to lay eggs. If the latter was true, it is unfortunately not so any longer as more hotels and shops have sprung up on the beach, and an increasing number of visitors come and watch the turtles. As many as 4000 watchers were recorded one night in 1976 by Moll (1976).

Within a nesting season (within the same year), some turtles were recorded to return to lay eggs again the next day, although others nested again after an interval of between one and 49 days. However, it is doubtful that a turtle is able to lay two full clutches on consecutive days. What could

have happened was that the turtle was dis- turbed (e.g., by torches of turtle watchers) and did not lay a full clutch the first time. It would come back later that night or the next night to finish laying the eggs some- where else (Frazer, pers. comm.). For the turtles which nested more than once, the majority of them were recorded to do so on the 9th day. For those which had 3 or more clutches, they were found to nest once every 9 or 10 days. This could imply that it takes about 9 to 10 days for the eggs to be ready to be laid. This is consistent with the findings of Pritchard (1971), who noted an internesting interval of 9 to 11 days with an average of 10.33 days. Slow (1982) also noted that some of the leatherback turtles in Malaysia return to lay additional eggs after an interval of 9 to 14 days.

Hirth (1980) has systematically compiled useful data for the reproductive biology of marine turtles, from which I have calculated the overall internesting (or renest-

215


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Normal eggs FIG. 7. Relationship between yolkless and normal eggs. Each point gives the mean (of 1967-1976) number

of yolkless and normal eggs for a turtle at a particular sector.

ing) intervals (actually the average of the mean values given). These are leatherback, 9.6 days (range not given); green turtles, 12.3 days (2-21); loggerhead turtles, 14.5 days (13-19); hawksbill turtles, 18.6 days (13-28); and olive Ridley turtles, 28.5 days (17-45). Thus, it appears that the leatherbacks have the shortest mean internesting interval and also the maximum interval (49 days, present results). Overall mean carapace lengths for these species have also been calculated from Hirth's data (1980) and they are: 150.6, 99.4, 90.5, 78.1, and 65.6 cm, respectively. It is clear, therefore, that the internesting interval (y) is dependent on the body size as measured by the carapace length (x), with a curvilinear relationship of y = 4569.83x- '25(r2 = 0.89, P <

0.01). It is possible that a larger body would be able to contain more immature eggs which could become mature within a short time, resulting in a shorter internesting interval. However, for intraspecies compar-

ison, it is likely that the nesting frequency depends more on resource availability and energy acquisition than on body size, especially during the period between nesting seasons. This has been found to be true, at least for loggerhead turtles at Little Cumberland Island (Frazer and Richard- son, 1985b). The nesting frequency of leatherback turtles also depends on the month, as Chua (1988) has shown, with the peak (2.20 nestings/turtle) occurring in July. This could mean that in July the nesting interval would be shorter, while longer in other months, especially May and September.

It was found that 48.9% of the tagged turtles returned to nest once in consecutive years; 21.3% returned once every 2 years. Few turtles made return visits after a long interval; only four turtles were recorded to return in 8 years. These data also indi- cate that the monel tags applied to the turtles could last as long as 8 years, compared

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to the retention of slightly over 4 years reported by Carr and Meylan (1984). On average, each turtle was calculated to breed once in 1.95 years (interseasonal interval). This supports the conclusion of Hirth (1980) that individual female marine turtles usually do not reproduce on an annual basis, with the exception of Lepidochelys olivacea and L. kempi. This appears to be true also for freshwater turtles. For example, Tinkle et al. (1981) estimated that between 30-50% of the female painted turtles (Chrysemys picta) in the population studied possibly do not reproduce every year. It would be interesting to find out whether this is a result of infrequent mating, or is a result of their nesting on other beaches, or that a long period is needed for sufficient energy acquisition. Cooperative research on an international level is needed to answer these questions.

The peak egg laying time was recorded in the early morning (0200-0400 h), which contrasts with the observation of Pritchard (1971), who found the daily peak of turtle nesting in French Guiana taking place in the middle hours of the night (0000-0115 h). This could be due to local environment conditions.

The mean clutch size for the turtles nesting on the beach once in a year is 83.1 normal eggs and 19.7 yolkless eggs (total clutch = 103 eggs). The yolkless eggs con- stitute about 23.7% of the number of normal eggs. Hirth (1980) also provided very similar figures. He estimated a mean of 83.5 fertile eggs and an additional 10-33% yolkless eggs. In Australia, the leatherbacks were reported to lay comparatively more yolkless eggs: 46.5 yolkless, about 56.2% of the normal eggs (82.8; N = 14 clutches) (Limpus et al., 1984). The relatively large number of yolkless eggs compared to other sea turtle species, appears to be character- istic of leatherback and hawksbill turtles (Hirth, 1980). As noted by Pritchard (1971), the clutch size given here is more similar to that recorded for the French Guiana population than to the geographically clos- er Tonga population. The overall maximum and minimum size for a particular clutch was not determined, although it is believed that they would not differ very

much from those recorded by Balasingam (1967a), a maximum of 140 and minimum of 33 normal eggs. Further analysis on the variation of clutch size with different sectors is not possible at the moment, as the environmental factors were not moni- tored. However, proportion of coarse sand, relative abundance of vegetation and differences in beach profile could be impor- tant.

The variation in clutch size with the number of clutches is not significant and discernible only when more than 4 clutches had been laid in the same season. How- ever, there is no definite trend as to how the clutch size changes with the number of clutches. Nevertheless, the peak clutch appears to have moved from the second or third clutch (for 8 clutches or less) to the 5th-7th clutch (for 9 clutches or more) (Ta- ble 3). Furthermore, the number of normal eggs tend to increase slightly, while the yolkless egg number decreases with greater number of clutches. If it could be considered that the clutches were laid during the course of the season (this is especially true for the larger number of clutches, e.g., 10), then it would seem that there is no significant change in clutch size over the course of the nesting season. Frazer and Richardson (1985a, b) also arrived at a similar conclusion for the loggerhead turtle after some vigorous statistical tests.

Hirth (1980) has shown significant lin- ear regression of clutch size on carapace length (straight-line measurements) for green and hawksbill turtles, while Frazer and Richardson (1986) found a similar, significant regression for loggerhead turtles. Furthermore, Frazer and Richardson (1986) have also statistically proven that there is no significant relationship between body size and the number of clutches laid in a given season in loggerhead turtles. Similar analyses on the leatherback will be at- tempted later and discussed in a future ar- ticle.

Acknowledgments. -We wish to thank the Universiti Malaya and the Fauna Preser- vation Society for financing the research. We are also grateful to the Director of Fish- eries, Terengganu State, who has kindly

217


allowed use of the data. The first author thanks N. Mrosovsky for his challenge to finish this analysis. We are indebted to N. Frazer for valuable comments on an earlier manuscript. This paper is dedicated to J. R. Hendrickson and the late E. Balasingam, who were the pioneers of leatherback turtle research in Malaysia.

LITERATURE CITED

ANONYMOUS. 1964. Conservation programme of the giant leathery turtles. Malay. Nat. J. 18:64.

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Accepted: 28 April 1987.

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Nesting Frequency and Clutch Size in Dermochelys coriacea in Malaysia

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