Body Condition Of Turtles Research Articles

Variations in body condition of green turtles (Chelonia mydas) in two nearby foraging grounds indicate their sensitivity to foraging habitats

Abstract Coastal seagrass habitats are critical foraging grounds for endangered green turtles (Chelonia mydas). However, these habitats are vulnerable to anthropogenic effects, potentially leading to their degradation with consequent impacts on the health status of foraging green turtles. Two foraging habitats of green turtles in Tun Mustapha Park, Sabah, Malaysia were surveyed: Kudat Mainland and Balambangan Island, by capturing green turtles and evaluating their physical body condition as well as assessing seagrass cover. Despite having similar genetic compositions, the Kudat Mainland aggregation had significantly higher body size (curved carapace length: 61.7 ± 14.5 cm, body weight: 30.0 ± 22.2 kg), Fulton's body condition index (BCI: 1.49 ± 0.13), barnacle (Chelonibia testudinaria) occurrence (78.8%) and barnacle abundance (5.46 ± 9.90 barnacles/turtle) than the Balambangan Island aggregation (curved carapace length: 51.6 ± 8.1 cm, body weight: 17.3 ± 7.7 kg, BCI: 1.40 ± 0.09, barnacle occurrence: 31.0%, barnacle abundance: 0.50 ± 0.92 barnacles/turtle). The differences in BCI between the nearby aggregations could not be attributed to size and barnacle occurrence differences, suggesting the foraging habitat is the primary factor affecting the body condition of green turtles. Seagrass cover at Kudat Mainland was only slightly higher than at Balambangan Island. These findings suggest that the body condition of green turtles is potentially sensitive to the quality of foraging habitats such as nutrients and water quality. It is crucial to monitor the health of foraging habitats and their impact on the body condition of turtles. It is recommended that habitat‐turtle dynamics are given conservation priority, in parallel to water quality monitoring – with action taken to reduce pollution if necessary. A holistic approach to turtle conservation is therefore required.

Wind farm and wildfire: spatial ecology of an endangered freshwater turtle in a recovering landscape

Wind energy presents many advantages, but wind farms pose risks to wildlife and habitats. We hypothesized that habitat changes caused by the impacts of wind farm construction and wildfire would alter the spatial ecology of Spotted Turtles ( Clemmys guttata (Schneider, 1792)). In a space-for-time study design, we outfitted 28 turtles with radio transmitters in three treatments (Control n = 10, Wind farm n = 9, and Windburn (wind farm and wildfire n = 9)) and located turtles every 3–5 days throughout the active season. We did not detect any significant differences in turtle body condition, home range size, minimum daily distance moved, or microhabitat selection among treatments. Macrohabitat selection differed slightly among treatments; only Windburn turtles used wet depressions on rock barrens, which may indicate that turtles exploited early successional habitats created by wildfire. Turtles did not avoid habitats near wind farm infrastructure yet did not cross service roads unless a culvert was present, highlighting the need to maintain habitat connectivity in modified landscapes. Our findings suggest that Spotted Turtles that survived the acute impacts of the wildfire and wind farm construction were able to navigate the recovering landscape, but a before–after–control–impact study is required to understand the acute and long-term impacts of wind farms and wildfires on turtles.

A half-century of demographic changes in a green turtle (Chelonia mydas) foraging aggregation during an era of seagrass decline

To understand the demographic responses of green turtles to seagrass decline, we examined a data set from study of a mixed-stock foraging aggregation of immature green turtles, Chelonia mydas, collected in Bermuda (32o18’N, − 64o46’W) over five decades. Average turtle size (SCLmin) and mass declined by 22.3% and 58.2%, respectively. Aggregation size structure shifted to smaller sizes and now consists of more small turtles and fewer large turtles. Density (turtles ha−1) increased significantly but biomass (kg ha−1) remained unchanged and low compared to C. mydas biomass observed elsewhere. Green turtles exhibited reduced site fidelity during two portions of the study period, suggesting increased foraging effort. Reduction in turtle body condition index and seagrass coverage occurred from offshore to inshore. Changes in aggregation composition and behavior were consistent with expectations given a documented decline in seagrass availability, combined with increased output from source rookeries. Apparent response to resource decline is traced back to 1976, well before seagrass loss was first documented. Green turtles and their primary food source (Thalassia testudinum) are at the northern limit of their range in Bermuda, where seagrasses would be expected to have a reduced tolerance for natural grazing pressure and increased susceptibility to synergistic stressors, especially temperature, bioturbation and phosphorus limitation. Our results suggest that synergistic stressors, and not green turtles alone, have produced the observed reduction in seagrasses on the Bermuda Platform. Given that seagrass declines have been reported worldwide, our findings may suggest how green turtles will respond elsewhere.

Stable isotopes and epibiont communities reveal foraging habitats of nesting loggerhead turtles in the South West Indian Ocean

Loggerhead sea turtles (Caretta caretta) occupy an array of marine habitats throughout their lives and understanding how this threatened species utilizes these habitats can help guide conservation efforts. This study used a combination of isotopic analysis (δ13C; δ15N) of turtle epidermis and epibiotic community composition to examine habitat-use patterns of nesting loggerheads from the South West Indian Ocean and related these to turtle body condition. First, we identified two foraging groups using relative changes in the turtle’s epidermis δ13C isotope values (of 170 individuals). Second, we show that epibiont communities (of 80 turtles) differed significantly between the two foraging groups, with oceanic/pelagic and neritic/benthic species occurring in higher abundances on turtles with depleted and enriched δ13C values, respectively. The complementary evidence from isotope and epibiont data thus indicates that nesting loggerheads of this population exhibit a bimodal foraging strategy. The relatively high variability in δ13C and δ15N values of the turtles’ tissue showed that they have a broad isotopic niche. While isotopic niches overlapped among turtles with different body conditions, very healthy individuals had a significantly narrower isotopic niche width than those in poorer condition. This suggests that turtles in very good condition are food specialists, and individuals with suboptimal body conditions utilise a wider range of food items and are more generalist foragers. These results show the value of using a combination of stable isotopes and epibiont communities as cost-effective tools that can be applied effectively to derive information on habitat-use patterns of migratory species.

Host-parasite association of Placobdella costata (Glossiphoniidae: Hirudinea) and Mauremys leprosa (Geoemydidae: Testudinoidea) in aquatic ecosystems of Morocco.

Emys orbicularis (Linnaeus, 1758) was considered as a specific host of Placobdella costata (Fr. Mûller, 1846). However, since the parasite was recorded from outside the distribution area of its host, some authors suggested a possible relationship with other hosts. Although two accidental associations were found with another turtle, Mauremys leprosa (Schweigger, 1812), the obtained data remain insufficient to better understand this discovered host-parasite ecological system. In this context, the present study was carried out to evaluate the relationship between the Mediterranean pond turtle, M. leprosa, and the freshwater rhynchobdellid leech, P. costata (Hirudinida: Glossiphoniidae), in aquatic ecosystems of Morocco. During the period from April to June 2018, we found leeches attached to turtles in five out of 30 populations sampled with a prevalence of infection significantly higher in adult than that in juvenile turtles. Moreover, the males are the most infested with 51% of the total, followed by females (33.3%) and juveniles (15.7%). The obtained results indicated that 51 turtles were infested by 139 leeches with a mean intensity of infestation of 4.17 ± 0.47 leeches/turtle (up to 10 leeches/turtle). It was higher in males than that in females in almost all sites. The posterior limbs are the most preferred attachment site, and the body condition of turtles was not affected by the intensity of infestation but it is rather a function of altitude. Our findings proved that M. leprosa-P. costata association is more than accidental and that M. leprosa is rather the main host of P. costata in aquatic ecosystems of Morocco.

Determining body condition of nesting loggerhead sea turtles (Caretta caretta) in the South-west Indian Ocean

AbstractSea turtles are long-lived migratory species that are sensitive to anthropogenic impacts. Their condition reflects that of marine ecosystems and can serve as an indicator for environmental monitoring. However, evaluating body condition parameters, as a proxy for health, is challenging and often overlooked. The purpose of this study was to validate a straightforward method for assessing the body condition of nesting loggerhead sea turtles (Caretta caretta), and to investigate whether body condition was correlated with epibiont loading. To achieve this, 60 nesting loggerhead sea turtles were sampled and categorized into five body conditions ranging from very poor to very good. Injuries, skin deformities and plastron shape were used for this classification. Epibionts were collected from the same turtles and identified, with species richness, diversity, community structure and barnacle loading compared among body conditions. Epibiont communities were correlated with body condition as both species richness and abundance increased with a decline in turtle body condition. Barnacle epibionts showed great variation among different body conditions, having significantly higher numbers on turtles in poor condition. All parameters in this study showed similar distinctive relationships with body condition of loggerhead turtles from poor to very good body condition. The body condition index used in this study can be applied readily and, along with barnacle counts, can provide basic baseline information on turtle health.

A novel technique to measure chronic levels of corticosterone in turtles living around a major roadway.

Conservation biology integrates multiple disciplines to expand the ability to identify threats to populations and develop mitigation for these threats. Road ecology is a branch of conservation biology that examines interactions between wildlife and roadways. Although the direct threats of road mortality and habitat fragmentation posed by roads have received much attention, a clear understanding of the indirect physiological effects of roads on wildlife is lacking. Chronic physiological stress can lower immune function, affect reproductive rates and reduce life expectancy; thus, it has the potential to induce long-lasting effects on populations. Reptiles are globally in decline, and roads are known to have negative effects on reptile populations; however, it is unknown whether individual responses to roads and traffic result in chronic stress that creates an additional threat to population viability. We successfully extracted reliable measures of corticosterone (CORT), a known, commonly used biomarker for physiological stress, from claw trimmings from painted turtles (Chrysemys picta) captured at three study sites (road-impacted site, control site and validation site). Corticosterone levels in claws were evaluated as a measure of chronic stress in turtles because CORT is deposited during growth of the claw and could provide an opportunity to examine past long-term stress levels. While male turtles had higher CORT levels on average than females, there was no difference in the level of CORT between the road-impacted and control site, nor was there a relationship between CORT and turtle body condition. In validating a novel approach for non-invasive measurement of long-term CORT levels in a keratinized tissue in wild reptiles, our study provides a new avenue for research in the field of stress physiology.

A bloom of Lyngbya majuscula in Shoalwater Bay, Queensland, Australia: An important feeding ground for the green turtle ( Chelonia mydas)

Lyngbya majuscula, a toxic cyanobacterium, was observed blooming during June–July (winter) 2002 in Shoalwater Bay, Queensland, Australia, an important feeding area for a large population of green turtles ( Chelonia mydas). The bloom was mapped and extensive mats of L. majuscula were observed overgrowing seagrass beds along at least 18 km of coast, and covering a surface area of more than 11 km 2. Higher than average rainfall preceded the bloom and high water temperatures in the preceding summer may have contributed to the bloom. In bloom samples, lyngbyatoxin A (LA) was found to be present in low concentration (26 μg kg −1 (dry weight)), but debromoaplysiatoxin (DAT) was not detected. The diet of 46 green turtles was assessed during the bloom and L. majuscula was found in 51% of the samples, however, overall it contributed only 2% of the animals’ diets. L. majuscula contribution to turtle diet was found to increase as the availability of the cyanobacterium increased. The bloom appeared to have no immediate impact on turtle body condition, however, the presence of a greater proportion of damaged seagrass leaves in diet in conjunction with decreases in plasma concentrations of sodium and glucose could suggest that the turtles may have been exposed to a substandard diet as a result of the bloom. This is the first confirmed report of L. majuscula blooming in winter in Shoalwater Bay, Queensland, Australia and demonstrates that turtles consume the toxic cyanobacterium in the wild, and that they are potentially exposed to tumour promoting compounds produced by this organism.