Female Loggerhead Sea Turtles Research Articles

Hemograma e bioquímica sérica de tartarugas cabeçudas (Caretta caretta) de vida livre e mantidas em cativeiro, no litoral norte da Bahia

Com o objetivo de se obter dados que auxiliem na rotina clínica de tartarugas marinhas, realizou-se o hemograma e a determinação de alguns parâmetros bioquímicos séricos de fêmeas de tartarugas cabeçudas (Caretta caretta) de vida livre (n = 22), animais que desovam no Litoral Norte da Bahia, e em cativeiro (n = 5), animais mantidos no Centro de Visitantes do Projeto Tamar-ICMBio, na Praia do Forte, Brasil. Os valores obtidos para os dois grupos foram comparados, onde se observou diferença estatística significativa (p<0,05) para as contagens relativas e absolutas de eosinófilos e contagem relativa de monócitos dentre as variáveis do hemograma e, para a proteína total, globulina, glicose, colesterol e aspartato aminotransferase. Possivelmente, diferenças nas condições ambientais, nutricionais e reprodutivas, as quais estes animais foram submetidos, influenciaram nos resultados.

Smaller longer, larger shorter: energy budget calculations explain intrapopulation variation in remigration intervals for loggerhead sea turtles (Caretta caretta)

Adult female loggerhead sea turtles ( Caretta caretta (L., 1758)) show a size-related behavioural and trophic dichotomy within several populations: oceanic planktivory by small females and neritic benthivory by large females. Within a Japanese population, smaller females have longer remigration intervals (the intervals between successive nesting years) than larger females. We hypothesized that this is attributed to the size-related foraging dichotomy, and calculated energy budgets and food requirements for the small and large females. Total reproductive energy costs for the small and large females were 1003 and 434 MJ, equivalent to 4043 kg of planktonic items and 275 kg of benthic items, respectively. The minimum durations necessary for accumulating the total reproductive energy for the small and large females were 430 and 26 days, equivalent to remigration intervals of 2 years and 1 year taking into account the nesting and migration durations and seasonal reproduction. Therefore, it was theoretically demonstrated that the intrapopulation variation in remigration intervals for Japanese loggerheads could be caused by the difference in their feeding habits, implying that remigration dynamics in a sea turtle population that shows a foraging dichotomy is regulated by feeding conditions not in a single habitat but in multiple habitats.

Mating‐induced ovulation in loggerhead sea turtles, Caretta caretta

Mating-induced ovulation is common in mammals, but has been rarely described in other taxa. Observations of several mature female loggerhead sea turtles, Caretta caretta, held in captivity seemed to indicate that ovulation did not occur in the absence of a male. This study was designed to determine whether this was an effect of captivity or an effect of the absence of a male. Two mature female loggerheads were followed over six annual reproductive cycles. Ultrasound exams were performed approximately every 2 weeks to follow the development of follicles in the ovaries. During the first two seasons, no male was present, in the next two seasons, a mature male was present without mating, and in the final two seasons a mature male was present, mating with one or both females. When no male was present or when present without mating, ovarian follicles developed to full size, but ovulation did not occur and the follicles gradually began to decrease in diameter and undergo changes evident on ultrasound. In the fifth season, only one of the females mated, dropping two eggs after 7 days, and continued to oviposit throughout the following months (total 275 eggs). The unmated female did not ovulate, showing the same pattern as earlier seasons. In the final season, both females mated and ovulated, dropping eggs for the next four months (total 539 eggs). The following year, no males were present and neither female ovulated. This study provides clear evidence that ovulation in loggerhead sea turtles is induced by mating.

Bottom or midwater: alternative foraging behaviours in adult female loggerhead sea turtles

AbstractIntrapopulational polymorphism in habitat use is widely reported in many animal species. The phenomenon has recently also been recognized in adult female loggerhead sea turtles Caretta caretta, with small females tending to inhabit oceanic areas (where water depths are >200 m) while presumably feeding pelagically and large females tending to inhabit neritic areas (where depths are <200 m) while presumably feeding benthically. In this study, dive recording satellite telemetry units were used to verify their foraging and diving behaviours in these habitats. Two females that nested on Yakushima Island, Japan, were tracked for 124 and 197 days. The small female wandered in the oceanic Pacific, and spent most of the time at 0–25 m depths regardless of day or night, implying that she foraged pelagically at the surface and shallow depths. Her mean dive durations were significantly longer at night than during the day. The large female moved into the neritic East China Sea, and spent most of the time over the continental shelf at 100–150 m depths during the day and at 0–25 m depths at night, suggesting that she alternated between diurnal benthic foraging and nocturnal resting within the depths where she could attain neutral buoyancy. Her mean dive durations were not significantly different between day and night. The increase in dive duration for both turtles coincided with a seasonal decrease in water temperature. The small female sometimes showed midwater dormancy at 0–25 m depths with a duration of >5 h that was in contrast with bottom dormancy by sea turtles inhabiting other regions. The diving behaviours observed during this study were consistent with their estimated main feeding habits, which demonstrated resource polymorphism in a marine reptile.

Novel GPS tracking of sea turtles as a tool for conservation management

We used recently developed, low-powered, TrackTag™ GPS loggers to track the movements of female loggerhead sea turtles ( Caretta caretta) at the largest breeding population in the Mediterranean (Zakynthos, Greece). Three turtles were tracked for a total of 73 days in May and June 2006, during which time 3753 GPS locations were obtained after filtering outliers (51 per day per turtle). The diving behaviour of these three turtles and three others was also monitored using time–depth recorders (TDR). The GPS data revealed that all three turtles spent most of their time in shallow water (< 4 m sea bed depth) very close to the shore (< 200 m), primarily ranging along an 18.5 km section of coastline. These observations were corroborated by TDR data acquired from all six turtles and frequent first-hand sightings of turtles close to shore during the breeding period. Comparison with random crawl movement models indicated that two of the tracked turtles moved with a similar non-random pattern, suggesting common biophysical processes might be driving their movements. The movement and depth data that we collected both suggest that existing legislation to safeguard sea turtles within this protected region may not include the most critical habitats for female loggerhead sea turtles during the breeding period. Our study demonstrated the feasibility of using GPS tracking to investigate fine-scale movements of a marine vertebrate, illustrating the value of GPS tracking for wildlife conservation management.

Forage-diving behaviour of adult Japanese female loggerhead turtles (Caretta caretta) inferred from Argos location data

Adult female loggerhead sea turtles (Caretta caretta) nesting in Japan use different feeding habitats as a function of body size. The Argos location data of two females inhabiting either oceanic or neritic habitats were analysed to infer their foraging and diving behaviour. There were no significant differences in the number of transmissions received per satellite pass, the number of locations per day, and the frequency of location-accuracy classes between oceanic and neritic females, implying that there was little difference in the time these two turtles stayed at the sea surface. Two possible forage-diving behaviours are suggested for these turtles: (1) both dive duration and depth were not different between the two feeding habitats; or (2) although dive duration was not different between feeding habitats, dive depth was different.

Remigration and growth of loggerhead turtles ( Caretta caretta ) nesting on Senri Beach in Minabe, Japan: life-history polymorphism in a sea turtle population

There are size-related differences in the use of feeding habitats (planktonic or benthic; oceanic or neritic) by adult female loggerhead sea turtles (Caretta caretta) within Japanese populations. We thus hypothesized that the differences may be reflected in their remigration and growth patterns, and investigated the relationships between body size and remigration intervals, growth rates, and remigration percentages, for female loggerheads nesting on a Japanese beach between 1991 and 2001. Although remigration intervals, growth rates, and remigration percentages were not significantly different among females, there were trends for longer remigration intervals and lower remigration percentages in smaller females. All females grew little. Considering these results along with previous findings, we speculated on the life-history strategy of female Japanese loggerheads.

A "Good-Sperm" Model Can Explain the Evolution of Costly Multiple Mating by Females

A "Good-Sperm" Model Can Explain the Evolution of Costly Multiple Mating by Females

Satellite Telemetry of Loggerhead Sea Turtle Movement in the Georgia Bight

The movements of eight female loggerhead sea turtles in the Georgia Bight were monitored, using transmitters compatible with the NASA Nimbus 6 Satellite. The tracking sessions, lasting from as little as 14 hours to more than 34 days, were conducted between 1 June-14 July 1979, and 15 June-23 July 1980. The observations clearly demonstrate that satellite telemetry is a viable technique for monitoring the movements of larger marine turtles. The data collected during these two years suggest that the behavior of female loggerhead sea turtles is rather stereotypic between nesting attempts. Following nesting on Cumberland Island National Sea shore, Georgia, the turtles swam in a northerly direction and entered the estuarine waters behind the island. After one to three days, the turtles then left the estuary for the open seas of the Georgia Bight. They did not wander randomly while at sea, prior to renesting, but moved directly to small, isolated areas of stable substrate that may represent concentrated patches of abundant prey.