Straight-line Carapace Length Research Articles

Biology of the Forest Cane Turtle, Vijayachelys silvatica, in South India

A 2-year study was conducted on the forest cane turtle, Vijayachelys silvatica, in Chalakudy District, Kerala, South India. This is a poorly known species, endemic to the Western Ghats of Southern India. The aims of the study were to ascertain morphometrics, sex ratios, and reproductive data in the field. Female Vijayachelys were more massive than males and significantly larger in all the characters examined, except for straight-line carapace length. The sex ratio among adult individuals was 47 males to 36 females (1.31∶1), which did not differ significantly from 1∶1. The greatest number of turtles was found in October and the fewest in May. Mating was observed in the months of June, September, and November and oviposition in January and February. Clutch size was 2 eggs in most cases. Turtles were observed to feed on snails, mushrooms, centipedes, and beetles living in the molding leaf litter and humus. Almost all turtles had algae on their shells.

Comparative skeletochronological analysis of Kemp’s ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) humeri and scleral ossicles

Skeletochronological analysis of Kemp’s ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) sea turtle humeri and scleral ossicles was conducted to (1) describe the characteristics of scleral ossicles in these species, (2) determine whether the scleral ossicles contain annually deposited skeletal growth marks and (3) evaluate the potential for skeletochronological analysis of ossicles to obtain age data for size classes and species of sea turtles whose humeri exhibit prohibitive amounts of growth mark resorption. Humeri, entire eyes, and/or individual scleral ossicles were collected from stranded, dead sea turtles that were found along the coasts of Florida, North Carolina, Virginia, and Texas, USA. Samples were taken from a total of 77 neritic, juvenile Kemp’s ridleys ranging from 21.1 to 56.8 cm straightline carapace length (SCL), as well as two Kemp’s ridley hatchlings. For loggerheads, samples were obtained from 65 neritic juvenile and adult turtles ranging from 44.7 to 103.6 cm SCL and ten hatchlings. Examination of the ossicles revealed the presence of marks similar in appearance to those found in humeri. The number of marks in the ossicles and humeri of individual juvenile Kemp’s ridleys for which both structures were collected (n = 55) was equivalent, strongly indicating that the marks are annual. However, in large juvenile and adult loggerhead turtles (n = 65), some significant resorption of early growth marks was observed, suggesting that although ossicles might be useful for skeletochronological analysis of small juveniles, they may not provide a reasonable alternative to humeri for obtaining age estimates for older loggerhead sea turtles.

Characteristics of a Green Turtle (Chelonia mydas) Assemblage in Northwestern Florida Determined During a Hypothermic Stunning Event

A hypothermic stunning event (i.e., cold-stunning event) during late Dec. 2000 and early Jan. 2001 involving an unprecedented number of sea turtles provided an opportunity to characterize the green turtle (Chelonia mydas) assemblage in St. Joseph Bay (Gulf County, Florida). In addition to 388 green turtles, the 401 cold-stunned turtles comprised 10 Kemp's ridleys (Lepidochelys kempii) and three loggerheads (Caretta caretta). Most (337/401) of the turtles survived and were eventually released. To place this event in perspective, we categorize sea turtle cold-stunning events in the eastern United States as either acute or chronic. Acute cold-stunning events, like the one in St. Joseph Bay, occur only during unusually cold winters in shallow-water areas (< 2m), where sea turtles are year-round residents. These are short-lived (< 2 wk) events with low mortality rates (< 30%) that affect principally green turtles. Chronic cold-stunning events occur every winter in areas where sea turtles are seasonal residents. These are long-lived (1-3 mo) events with high mortality rates (> 60%) that affect primarily Kemp's ridleys. All of the green turtles from St. Joseph Bay were neritic-phase juveniles, and the mean straight-line carapace length of this group was 36.6 cm (range = 25.0-75.3 cm, SD = 8.9). This assemblage of juvenile green turtles is the first documented along the northern Gulf of Mexico. Sequencing of mtDNA (mitochondrial DNA) from tissue samples taken from 255 of the green turtles revealed that about 81% were from the nesting populations in the United States (Florida) and Mexico (Yucatan). This assemblage is unusual in the United States because it does not have a substantial representation from the nesting population in Costa Rica (Tortuguero), the Atlantic's largest green turtle nesting population. Based on necropsies of 51 of the green turtles, the sex ratio of this assemblage was female-biased (3.25 females: 1 male), which may be a result of warm incubation temperatures on the nesting beaches in Florida. The majority of the material found in the gastrointestinal tracts of the green turtles that died was turtle grass (Thalassia testudinum). This was the first time turtle grass has been identified as the primary diet of juvenile green turtles anywhere in the continental United States. Green turtles in St. Joseph Bay appear to have few direct threats, but the seagrass upon which these turtles primarily forage has suffered extensive damage from boat propellers.

REPRODUCTION OF THE SMALLEST TORTOISE, THE NAMAQUALAND SPECKLED PADLOPER, HOMOPUS SIGNATUS SIGNATUS

The smallest tortoise, Homopus signatus, is inadequately protected, and information on its reproductive ecology can facilitate effective conservation. We combined X-ray radiography and ultrasonography to assess the reproductive status of free-ranging female Homopus signatus signatus during August–September 2000 (n = 30) and September–October 2001 (n = 29). Females produced only single-egg clutches but can produce more than one clutch in a season. Most (ca. 75%) of the females were gravid each spring, so H. s. signatus probably has a seasonal pattern of egg production. This pattern may be related to the seasonal climate; summers are hot and dry, yet winter rainfall is moderately predictable. Females were gravid from August through October, but further analyses are necessary to characterize the entire reproductive season and quantify clutch frequency. Large females produced large eggs, compared to eggs of small females. The smallest gravid female had a straight-line carapace length of 84.1 mm while the largest female measured 110.0 mm. Compared to gravid females, nongravid females were in poorer body condition (body mass and mass relative to carapace length) only in 2000, when there was lower rainfall and plant availability than in 2001. The difference in body mass approximated the mass of one egg. The low clutch size and fecundity suggest that populations have low intrinsic rates of natural increase. This plus their limited range and specific habitat requirements make H. s. signatus vulnerable to anthropogenic impacts.

Heavy metals in tissues of loggerhead turtles ( Caretta caretta) from the northwestern Adriatic Sea

Thirty-five specimens of Caretta caretta were collected dead along the Adriatic Sea coast from the Po Delta to the Reno mouth (Italy). Turtles were classified into four size categories ranging from 24.5 to 74 cm, by measuring the minimum straight-line carapace length (MSCL). Cd, Cu, Fe, Mn, Ni, and Zn levels were assessed in liver, lung, muscle and adipose tissue. Cd, Cu and Fe mainly accumulated in the liver (8.9, 23.7 and 1180 mg/kg dry mass [d.w.], respectively), and Mn in the lung (29.5 mg/kg d.w.). Levels of Ni were higher in adipose (22 mg/kg d.w.) than other tissues, while Zn concentrations were higher in muscle (about 140 mg/kg d.w.). Negative correlations with size were established for Zn in liver and Cu in adipose tissue, while positive correlations were observed for Mn and Ni in adipose tissue. Metal concentrations did not differ between males and females, nor between individuals found stranded and those victims of by-catch. On average, Cd, Cu, Mn and Ni concentrations in our specimens were higher than in loggerhead turtles and other species living in other areas. We hypothesize that trace metals could be used as “acquired markers” to help investigate migration routes of C. caretta.

Immature Sea Turtles in Gullivan Bay, Ten Thousand Islands, Southwest Florida

An in-water survey for immature endangered and threatened sea turtles in the coastal waters of southwest Florida during 1997-2003 yielded 191 Kemp's ridley (Lepidochelys kempi), 15 loggerhead (Caretta caretta), 13 green (Chelonia mydas), and one hybrid hawksbill (Eretmochelys imbricata)-loggerhead turtle. Mean carapace lengths were 40.3 cm minimum straightline carapace length (MSCL) for Kemp's ridley, 65.5 cm MSCL for loggerhead, and 51.6 cm MSCL for green turtles. Fibropapilloma tumors were found on seven of the green turtles and one loggerhead turtle. The mean growth rate of recaptured Kemp's ridleys was 6.3 cm/yr. The nearshore waters of Gullivan Bay in the Ten Thousand Islands are an important developmental habitat for the highly endangered Kemp's ridley turtle, and to a lesser degree, immature loggerhead and green turtles.

Ecology and Distribution of the Pancake Tortoise, Malacochersus tornieri in Kenya

Field investigations on the ecology, distribution and conservation of the pancake tortoise Malacochersus tornieri in Kenya were conducted from September to December 1998 and from March 2001 to April 2002. This crevice-dwelling tortoise inhabits Precambrian rock outcrops and kopjes that are discontinuously distributed throughout the arid and semi-arid lands of Kenya and Tanzania. However, suitable micro habitats are sparse and this accounts for its patchy distribution. The pancake tortoise is more widespread in Kenya than previously thought, ranging from the South-east to the North. Two sub-populations South and North of the volcanic Nyambene Hills exist. Density between study sites differed significantly and abundance of particular age groups is dependent on season. Activity outside crevices is very limited, occurring mainly during the wet season. In the dry season individuals aestivate. There is no marked sexual dimorphism in terms of size and colouration, and no significant difference in mean body weight and straight-line carapace length between sexes. There is a significant positive linear correlation between straight-line carapace length and body weight. The observed sex ratio is 1:1. Movement is very limited and centred around rock refuges. Males are more wide ranging than females. Adults dominate the age structure of the pancake tortoise population. Shifting cultivation is the major threat for its survival other than illegal trade. In situ conservation through establishment of publicly and/or privately owned nature reserves is recommended.

Habitat effect on hawksbill turtle growth rates on feeding grounds at Mona and Monito Islands, Puerto Rico

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 234:301-309 (2002) - doi:10.3354/meps234301 Habitat effect on hawksbill turtle growth rates on feeding grounds at Mona and Monito Islands, Puerto Rico Carlos E. Diez1,*, Robert P. van Dam2 1Departamento de Recursos Naturales y Ambientales, PO Box 9066600, San Juan 00906-6600, Puerto Rico 2Chelonia Incorporated, PO Box 9020708, San Juan 00902-0708, Puerto Rico *E-mail: cediez@caribe.net ABSTRACT: Carapace length growth data were obtained from 197 hawksbill turtles Eretmochelys imbricata which were marked and recaptured from 1992 to 2000 at feeding grounds of Mona and Monito Islands, Puerto Rico. Straight-line carapace length (SCL) upon initial capture ranged from 20.0 to 84.5 cm. SCL growth rates ranged from -0.59 to 9.08 cm yr-1, were non-monotonic, and averaged highest in turtles measuring 34 to 35 cm. Somatic growth rates varied by site within the study area, with turtles from the aggregation at Monito Island growing on average 2.1 times faster than residents of Mona Island habitats. Aggregation density and body condition index (body mass SCL-3) were also highest at Monito Island. Hawksbills recruiting to Monito Island at 23 cm SCL are expected to reach maturity less than 14.7 yr later. Growth rates in the turtles studied are similar to those reported for other Caribbean localities, but faster than hawksbills of the southern Great Barrier Reef, Australia. Hawksbills appear capable of utilizing habitats of widely varying quality, with prey abundance exerting a strong effect on somatic growth rates. KEY WORDS: Hawksbill turtle · Eretmochelys imbricata · Growth rate · Carapace length · Habitat quality · Foraging ground · Puerto Rico Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 234. Online publication date: June 03, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Home range of immature hawksbill turtles ( Eretmochelys imbricata (Linnaeus)) at two Caribbean islands

Distances between capture and recapture locations of tagged immature hawksbill turtles Eretmochelys imbricata (Linnaeus) are analyzed for four near-shore survey sites at Mona and Monito Islands, Puerto Rico. Data were obtained for 87 turtles ranging in size from 20.0 to 56.7 cm straight-line carapace length. Net displacements by individual turtles averaged 0.45 km (S.D.=0.66, range 0.00–5.22) for mean inter-capture intervals of 465 days (S.D.=331, range 9–1118). Measured displacements were not correlated with turtle size and did not differ significantly between survey sites. Movements of three immature turtles fitted with sonic tags were monitored by acoustical tracking in reef habitats along the southwestern coast of Mona Island. The area utilized by the turtles during the 11–16 days of tracking measured 0.07–0.21 km 2. It is concluded that immature hawksbill turtles maintain a limited home range area and appear resident at the feeding grounds of Mona and Monito Islands for periods of at least several years.

Diet of the Pelomedusid Turtle Peltocephalus dumerilianus in the Venezuelan Amazon

Diet of the Pelomedusid Turtle Peltocephalus dumerilianus in the Venezuelan Amazon

Movements and Submergence Patterns of Kemp's Ridley Turtles (Lepidochelys kempii)

Four Kemp's ridley (Lepidochelys kempii) turtles, ranging in straight-line carapace length from 51 to 60 cm and in weight from 19 to 27 kg, were released in 12 to 19 m water depths off Florida, Texas, and North Carolina and tracked for 1.0 to 8.5 months. Movements up to 2600 km were observed. The number of submergences per day was inversely proportional to the duration of submergences per day. These ridleys spent 89% of their time submerged and frequented waters ranging in depth from 1-140 m. Turtles ranged from inshore to 77 km offshore. Mean swimming speeds of these turtles were from 0.7 to 1.3 km/h, with over 95% of the actual velocity values <5 km/h.

Size-Dependent, Sex-Dependent, and Seasonal Changes in Insulin-like Growth Factor I in the Loggerhead Sea Turtle (Caretta caretta)

This study examines size-dependent, sex-dependent, and seasonal fluctuations in plasma insulin-like growth factor-I (IGF-I) concentrations in loggerhead sea turtles (Caretta caretta). Loggerhead turtles (n = 158) were captured in shrimp trawler nets during a 12-month survey in Cape Canaveral Channel, Florida. Plasma samples were analyzed using a validated heterologous radioimmunoassay. Large turtles (>75 cm straight-line carapace length) had significantly higher plasma IGF-I concentrations than small turtles (⩽75 cm; P < 0.0001). Plasma IGF-I concentrations did not vary seasonally in small turtles, but large turtles had significantly higher plasma IGF-I concentrations during the spring and summer months (P < 0.005). Within the large turtles, adult males had significantly lower IGF-I concentrations than females and subadult males (P < 0.05). These results and a review of loggerhead turtle natural history suggest that the seasonal fluctuations in plasma IGF-I of adult turtles are due to elevated IGF-I levels in reproductively active female turtles. Further research is needed to examine correlations between reproductive activities and plasma IGF-I concentrations in reptiles.

Relative Abundance, Temporal Patterns, and Growth of Sea Turtles at the Mansfield Channel, Texas

Species composition, relative abundance, residency, seasonality, size classes, and growth of sea turtles at the Mansfield Channel, Texas were investigated from 1989-1992. Forty-three juvenile green turtles (Chelonia mydas) (N = 72 captures) and one juvenile hawksbill turtle (Eretmochelys imbricata) (N = 1 capture) were netted during 435 hours of year-round effort (1.38 turtles/km-h). Eighteen of the green turtles (42%) netted were subsequently recaptured, with a mean interval from first to last capture of 120 days (range 22-478 days). However, few of the individuals initially netted between September and February or measuring more than 35 cm straight-line carapace length at initial capture were recaptured. Collectively, green turtles were caught during all months except January. Catch-per-unit-effort was pos- itively correlated with water temperature, air temperature, and water salinity and most green turtles were captured during early morning and late afternoon hours. The Mansfield Channel may provide foraging and resting habitat for both itinerant and seasonally resident green turtles. Juvenile Kemp's ridley (Lepidochelys kempi), green (Chelonia mydas), and loggerhead (Caretta caretta) sea turtles are found within inshore wa- ters of New York, Virginia, and Florida, areas which may serve as important developmental habitats (Mendonca and Ehrhart, 1982; Lutca- vage and Musick, 1985; Byles, 1988; Withering- ton and Ehrhart, 1989; Burke and Standora,

Annual Occurrence and Winter Mortality of Marine Turtles in New York Waters

Cold-stunned sea turtles, both moribund and dead as a result of hypothermia, were collected along the shorelines of Long Island, New York, during three consecutive winters. A total of 130 juvenile Lepidochelys kempii, Caretta caretta, and Chelonia mydas was collected. Lepidochelys kempii represented 75% of all individuals encountered. The size distribution of L. kempii (straight-line carapace length 22.5 cm to 37.6 cm; i = 29.4 cm, SD = 3.1) was unlike any other assemblage reported within the species' range. The regular occurrence of relatively small turtles suggests that New York waters are utilized on an annual basis by L. kempii during early developmental stages. The numbers observed in this study, coupled with historical records, indicate that New York represents an important portion of the range of L. kempii. There is a continuous distribution of this species from the Gulf of Mexico to New England waters. Sea turtles are usually considered inhabitants of the tropics and the subtropics. However, in recent years it has become evident that many sea turtles also frequent northern temperate latitudes (Bleakney, 1965; Carr, 1980; Lazell, 1980; Shoop, 1987), where they may be exposed to very low temperatures. In transitional climates, there is evidence that both green turtles (Chelonia mydas) and loggerhead turtles (Caretta caretta) escape low winter temperatures by burying themselves in bottom sediments (Felger et al., 1976; Carr et al., 1980). However, unlike some freshwater turtles (Jackson and Ultsch, 1982) and some terrestrial turtles (Gatten, 1987; Claussen et al., 1991) that can withstand prolonged periods at very low temperatures of 3 C and 5 C, respectively, sea turtles have been reported to suffer from hypothermia, or coldstunning, at temperatures between 3.5 and 9 C in outdoor tanks (Schwartz, 1978) and below 8 C in the wild (Witherington and Ehrhart, 1989). The decline in water temperatures each year in northeastern U.S. waters raises some questions as to this region's suitability as habitat for marine turtles and as to the role of the area in life histories of certain species (Carr, 1980; Hendrickson, 1980; Lazell, 1980). Cold-stunning of sea turtles has provided valuable information from which we can approximate lower thermal tolerance limits and other physiological aspects of these reptiles. The most commonly observed response of sea turtles to very low temperatures is to become buoyant and float to the surface (Schwartz, 1978). This phenomenon makes it possible to sample large numbers of free-ranging, and otherwise healthy, sea turtles over a short time, and can provide new insight into the population structure and life history of species that are affected. Witherington and Ehrhart (1989) were able to describe some key demographic characteristics of green and loggerhead turtles in east-central Florida based on data collected from 467 coldstunned turtles over a 9 yr period. In the more northern waters of New York, four species of sea turtles, loggerheads, greens, Kemp's ridleys (Lepidochelys kempii), and leatherbacks (Dermochelys coriacea), have been repeatedly documented over the past century (Murphy, 1916; Babcock, 1919; DeSola, 1931; Brongersma, 1972). One specimen of a hawksbill turtle (Eretmochelys imbricata) was also collected in New York in 1938 (Morreale et al., 1989). Each autumn, temperatures in this region decline rapidly, and any sea turtles that remain through the winter must face water temperatures that drop below 1 C. In the winter of 1985, 56 cold-stunned sea turtles of three species were retrieved along New York's shoreline (Meylan, 1986). These observations initiated an effort to i vestigate the role of New York waters in the life history of sea turtles. The objective of this portion of the study was to examine demographic characteristics of sea turtles in New York waters based on cold-stunned animals collected

Growth Rates of Juvenile Loggerheads, Caretta caretta, in the Southern Bahamas

became clear that growth rates of wild turtles are much slower than those of captive sea turtles (Balazs, 1979; Limpus, 1979). Estimates of the age at which marine turtles attain sexual maturity based on captive growth rates have had to be revised. Knowledge of natural growth rates and age at sexual maturity are fundamental for understanding demography, assessing habitat quality, and designing appropriate management plans and conservation measures for these endangered species. Data on growth rates for non-captive loggerheads, Caretta caretta, have been limited to turtles larger than 50 cm straight-line carapace length (CL) (Limpus, 1979, 1985; Mendonca, 1981; Frazer and Ehrhart, 1985). Based on these studies, the age at sexual maturity has been estimated to be 10 to 50 years. Data on growth rates of 24 cm CL loggerheads are presented in this note. This size represents a transitional stage for loggerheads when they first leave the pelagic habitat and arrive at benthic feeding grounds (Carr, 1986). Growth rates of these smaller loggerheads are more rapid than those reported for larger turtles and result in significantly shorter estimates for the time necessary for loggerheads to grow from 25 to 75 cm and, thus, for a younger age at sexual maturity. In 1975, three loggerheads that had hatched from eggs collected in Florida and that had been raised in a laboratory at the University of Florida were taken to Union Creek, Great Inagua, Bahamas (with all necessary permits). Union Creek, protected by the Bahamas National Trust as a wildlife sanctuary, is a saltwater bay of approximately 20 km2 located on the north coast of Great Inagua, the southernmost island in the Bahamas. Union Creek is covered with seagrass beds (primarily Thalassia testudinum) and is surrounded by mangroves. These habitats support a rich invertebrate fauna on which loggerheads feed. Union Creek is a natural feeding area for all sizes of loggerheads, green turtles (Chelonia mydas), and hawksbills (Eretmochelys imbricata) (pers. observs. and pers. comms. from island inhabitants). In 1964, Union Creek was fenced off to provide a protected area in which sea turtles could be studied on natural feeding grounds. The loggerheads were tagged for identification and initially introduced into a confined area (approximately 2 ha) of Union Creek to monitor their adjustment to free-living conditions. Following an initial decrease in mass, the turtles regained their original mass at the end of three months and were judged to be ready for release into Union Creek. Measurements at the time of release were used as the initial values

Sea turtles nesting at Melbourne Beach, Florida, I. Size, growth and reproductive biology

From 1972 to 1978, 2910 loggerheads Caretta caretta and 18 green turtles Chelonia mydas were tagged as they came ashore to nest on Melbourne Beach, the area with the greatest density of sea turtle nesting in Florida. The nesting loggerheads averaged 92·0 cm in straight-line carapace length and grew at a mean rate of 0·57 cm per year. The most common remigration intervals observed for loggerheads were two and three years. In 46 cases, turtles tagged on Melbourne Beach moved to other beaches in later nesting seasons, and 82 Melbourne Beach turtles shifted to other beaches during the same season. Interseasonal nesting movements spanned 700 km of coastline; intraseasonal movements ranged over 290 km. The 18 green turtles nested from early June to late August. The mean straight-line carapace length was 110 cm. A two-year remigration interval predominated. No green turtle tagged on Melbourne Beach has been seen on other beaches.