Article

Determining home range, habitat use changes throughout time, and the threats of an endangered freshwater turtle (Rafetus euphraticus) in Turkey

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Abstract

1. The Euphrates Softshell Turtle (Rafetus euphraticus) is the most threatened chelonian species in the Middle East, where it is endemic of the Tigris and Euphrates basins. Since this species is ecologically little known it is difficult to plan any reliable action for its correct management and conservation. 2. In order to enhance the scientific knowledge on R. euphraticus, and to establish a science-based management strategy, a detailed investigation on the distribution, habitat, activity and home range of R. euphraticus individuals in Turkey was carried out. The previous distribution records in Turkey belonged to the 1990s. Thus, this study is the first comprehensive field research on the species after nearly three decades. 3. There was a significant sexual size dimorphism in the Turkish population, with males larger than females. 4. Four individuals were radiotracked for one year. The mean home range was highly variable depending on how it was calculated, but that of males was considerably greater than that of females by all methods employed. 5. A quantitative evaluation of habitat change throughout time was made. For the Euphrates River, the land cover classes potentially available to turtles increased over 100% between 1990s and 2018: 92% of this enhancement derived from water bodies and coastal lands. 6. Fifteen dams have been built in the lower part of the basins for 30 years. In addition, ongoing human interactions have caused the fragmentation and/or destruction of suitable habitats for the Euphrates Softshell Turtle. 7. The factors threatening the Euphrates Softshell Turtle were determined and a conservation action plan was developed. Some objectives such as monitoring and creating awareness of this action plan have been reached while others are still waiting to be achieved.

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The waters of the Euphrates and Tigris rivers have always been a vital resource in the water-food-energy nexus of the Middle East region. The currently ongoing Southeastern Anatolia Project (GAP) in Turkey aims to increase regional prosperity by optimizing the use of these waters for irrigation and hydropower. Since the beginning of the 1990s, the irrigation schemes and water management infrastructures within the scope of the GAP have caused significant land use and land cover (LULC) change in this semi-arid region. We employed a high resolution regional climate model to simulate the effects of irrigation induced LULC changes on the regional water and energy balances. For this purpose, historical simulations were conducted by using three land cover distributions which reflect the increase in irrigation and water surfaces. Our experiment reveals that water loss through evapotranspiration increases significantly with the areal expansion of irrigation. This increase is driven by the change in partitioning of the available energy at the surface between turbulent heat fluxes. On the one hand, a significant reduction in sensible heat flux causes local cooling by around 0.4 °C and 0.8 °C for the current and future irrigation conditions, respectively. On the other hand, the increase in latent heat flux enhances evapotranspiration and consequently atmospheric water vapor concentration. The moistening of a shallower boundary layer triggers the formation of convective clouds, which increases convective precipitation, most notably during the irrigation months. The enhanced water loss through evapotranspiration has potential to significantly alter the water budget of the GAP region. It seems that the water surplus of the headwaters region may not be enough to meet the water deficit of the GAP region in the future if the planned irrigation schemes are carried out to completion.
Article
1) Human recreational disturbance of riverine environments may be contributing to population declines of aquatic organisms worldwide. Aquatic turtles that are heavily dependent on basking in sunlight to maintain an optimal body temperature may abandon basking perches because they perceive humans as potential predators. 2) Impact of boat traffic, availability of basking structures, and various environmental factors on the basking behavior of ringed sawback (Graptemys oculifera) was assessed at two sites on the Pearl River, Mississippi, USA. We used this information to model the likely effects of human disturbance on the body temperature of large female turtles. 3) Both the duration of basking and the percentage of turtles in a basking group that abandoned their basking perch were influenced by the availability of alternative basking sites, frequency of boat traffic, boat speed enforcement zones (wake or no wake), boat type, air temperature, weather conditions, and Julian day. A simulation model of anthropogenically disturbed and undisturbed adult female ringed sawbacks showed that disturbance probably decreases mean daily body temperature, especially at higher disturbance probabilities and in May when air temperature is low. 4) Management recommendations are provided that minimize the negative effects of unintentional human disturbance of the ringed sawback to enable more effective conservation of this endangered, endemic species. Such methods will likely be useful elsewhere as recreational disturbance becomes a greater conservation issue worldwide.
Book
Although there has been a surge of interest in density estimation in recent years, much of the published research has been concerned with purely technical matters with insufficient emphasis given to the technique’s practical value. Furthermore, the subject has been rather inaccessible to the general statistician. The account presented in this book places emphasis on topics of methodological importance, in the hope that this will facilitate broader practical application of density estimation and also encourage research into relevant theoretical work. The book also provides an introduction to the subject for those with general interests in statistics. The important role of density estimation as a graphical technique is reflected by the inclusion of more than 50 graphs and figures throughout the text. Several contexts in which density estimation can be used are discussed, including the exploration and presentation of data, nonparametric discriminant analysis, cluster analysis, simulation and the bootstrap, bump hunting, projection pursuit, and the estimation of hazard rates and other quantities that depend on the density. This book includes general survey of methods available for density estimation. The Kernel method, both for univariate and multivariate data, is discussed in detail, with particular emphasis on ways of deciding how much to smooth and on computation aspects. Attention is also given to adaptive methods, which smooth to a greater degree in the tails of the distribution, and to methods based on the idea of penalized likelihood.
Article
Expanding the scope of landscape genetics beyond the level of single species can help to reveal how species traits influence responses to environmental change. Multispecies studies are particularly valuable in highly threatened taxa, such as turtles, in which the impacts of anthropogenic change are strongly influenced by interspecific differences in life-history strategies, habitat preferences, and mobility. We sampled approximately 1500 individuals of three co-occurring turtle species across a gradient of habitat change (including varying loss of wetlands and agricultural conversion of upland habitats) in the Midwestern USA. We used genetic clustering and multiple regression methods to identify associations between genetic structure and permanent landscape features, past landscape composition, and landscape change in each species. Two aquatic generalists (the painted turtle, Chrysemys picta, and the snapping turtle Chelydra serpentina) both exhibited population genetic structure consistent with isolation-by-distance, modulated by aquatic landscape features. Genetic divergence for the more terrestrial Blanding's turtle (Emydoidea blandingii), on the other hand, was not strongly associated with geographic distance or aquatic features, and Bayesian clustering analysis indicated that many Emydoidea populations were genetically isolated. Despite long generation times, all three species exhibited associations between genetic structure and post-settlement habitat change, indicating that long generation times may not be sufficient to delay genetic drift resulting from recent habitat fragmentation. The concordances in genetic structure observed between aquatic species, as well as isolation in the endangered, long-lived Emydoidea, reinforce the need to consider both landscape composition and demographic factors in assessing differential responses to habitat change in co-occurring species. This article is protected by copyright. All rights reserved.
Article
Observations on cranial morphology were made on Euphrates soft-shelled turtles, Rafetus euphraticus, sampled in the Euphrates and Tigris rivers and tributaries, Southeastern Anatolia. The vomer separates the maxillaries in half of the specimens, whereas the maxillae meet on the vomer in others. The parietal has no contribution in the formation of the foramen nervi trigemini due to the contact between the prootic and the epipterygoid. There are variations in the contacts of the basisphenoid and in the formation of the trigeminal region, a prootic-epipterygoid contact participates in the trigeminal region. The contacts of the vomer-pterygoid, the vomer-basisphenoid and the vomer-pterygoid-basisphenoid are observed in some specimens. In one specimen, the parietal contacts the opisthotic. All specimens have the symphyseal ridge, althought it is weak and barely discernible.
Article
In 1989, a total of 26 Euphrates Soft-shelled Turtles was recorded in the Tigris River in Turkey and a total of at least 55 individuals in the Euphrates between Al-Falluyah and Hawr-al-Hammar in Iraq. The Iraqi observations are the first to be published since the early 1960’s and increase our knowledge of the distribution and status of this species in Iraq. Kurzfassung 1989 wurden im Tigris in der Türkei insgesamt 26 Euphrat-Weichschildkröten beobachtet, im Euphrat im Irak zwischen Al-Falluyah und Hawr-al-Hammer mindestens 55 Individuen. Für den Irak Sind dies die ersten publizierten Nachweise dieser Art seit Begins der 1960er Jahre und erweitern unsere Kenntnis vom Status und vom Verbreitungsgebiet der Art.
Article
Exhaustive interview surveys were carried out on the upper Red River (Honghe) and nearby river systems of southwest China to characterize the distribution of Rafetus swinhoei, one of the rarest turtles in the world. The results show that the species once ranged strictly in the Red River system, apart from the lower Yangtze, and still existed in recent years, although it was on the brink of extinction due to overharvesting and habitat degradation. Further conservation efforts require monitoring of the hunting and trade of turtles in this region, public education, delaying the building of dams, setting up new protected areas, and international cooperation.
Article
Roads built through or near wetlands cause significant mortality of reptiles and amphibians and create bar- riers to migration and dispersal. I investigated the number of times turtles and other herpetofauna attempted to cross a 4-lane highway at Lake Jackson, Florida, USA, during a period of severe drought (Feb-Apr 2000). Levels of road mortality were so high that I designed and installed a temporary drift fence system to work with an existing drainage culvert and for the next 2.5 years I evaluated its effectiveness at reducing road mortality and facilitating migration. I monitored roads and fences several times per day for 44 months, during both drought and non-drought conditions. A total of 10,229 reptiles and amphibians of 44 species were found either road killed or alive behind drift fences: 8,842 turtles, 838 frogs, 363 snakes, 152 lizards, 32 alligators, and 2 salamanders. Drift fences combined with intensive monitoring greatly reduced turtle road kills and facilitated the use of an under-highway culvert. Along a 0.7-km section of the highway, turtle mortality before installation of the fence (11.9/km/day) was significantly greater than post-fence mortality (0.09/km/day) and only 84 of 8,475 turtles climbed or penetrated the drift fences. Pre-fence data provided strong evidence that turtles cannot successfully cross all 4 lanes of U.S. Highway 27, as 95% of 343 turtles were killed as they first entered the highway adjacent to the shoulder and the remaining 5% were killed in the first two traffic lanes. According to a probability model, the likelihood of a turtle successfully crossing U.S. Highway 27 decreased from 32% in 1977 to only 2% in 2001 due to a 162% increase in traffic volume. Therefore, at least 98% of turtles diverted by the fences probably would have been killed if fences were not in place. The results of this study represent the highest attempted road-crossing rate ever published for turtles (1,263/km/year). Because of demographic and life history constraints, turtle populations may incur irreversible declines in areas where road mortality is high, especially when mass migrations are triggered by periods of drought.
Article
Kernel methods for estimating home range are being used increasingly in wildlife research, but the effect of sample size on their accuracy is not known. We used computer simulations of 10-200 points/home range and compared accuracy of home range estimates produced by fixed and adaptive kernels with the reference (REF) and least-squares cross-validation (LSCV) methods for determining the amount of smoothing. Simulated home ranges varied from simple to complex shapes created by mixing bivariate normal distributions. We used the size of the 95% home range area and the relative mean squared error of the surface fit to assess the accuracy of the kernel home range estimates. For both measures, the bias and variance approached an asymptote at about 50 observations/home range. The fixed kernel with smoothing selected by LSCV provided the least-biased estimates of the 95% home range area. All kernel methods produced similar surface fit for most simulations, but the fixed kernel with LSCV had the lowest frequency and magnitude of very poor estimates. We reviewed 101 papers published in The Journal of Wildlife Management (JWM) between 1980 and 1997 that estimated animal home ranges. A minority of these papers used nonparametric utilization distribution (UD) estimators, and most did not adequately report sample sizes. We recommend that home range studies using kernel estimates use LSCV to determine the amount of smoothing, obtain a minimum of 30 observations per animal (but preferably ≥50), and report sample sizes in published results.
Article
Hydro-climatic effects of future climate change in the Euphrates-Tigris Basin are investigated using dynamically downscaled outputs of different GCM (ECHAM5, CCSM3 and HadCM3) - emissions scenario (A1FI, A2 and B1) simulations. The suite of simulations (total five) enables an analysis taking into account the A2 emission scenario simulations of three different GCMs and another analysis based on the three different emissions scenario (A1FI, A2 and B1) simulations of one GCM (CCSM3). All scenario simulations indicate winter surface temperature increases in the entire basin, however, the increase is larger in the highlands. The greatest increase in the annual temperature by the end of century belongs to the CCSM3 A1FI simulation with an increment of 6.1 oC in the highlands. There is a broad agreement amongst the simulations in terms of the winter precipitation decrease in the highlands and northern parts and increase in the southern parts of the basin. A remarkable impact of warming could be seen on the snow water equivalent in the highlands where each simulation points out statistically significant decreases ranging from 55% (lower emissions) to 87% (higher emissions). Statistically significant declines (25 to 55%) are found for the annual surface runoff of the main headwaters area. Moreover, significant temporal shifts to earlier days (between 18 and 39 days depending on the scenario) are projected to occur in the surface runoff timing in the headwaters region. Projected annual surface runoff changes in all simulations suggest that the territories of Turkey and Syria within the basin are most vulnerable to climate change as they will experience significant decreases in the annual surface runoff. Eventually, however, the downstream countries, especially Iraq, may suffer more as they rely primarily on the water released by the upstream countries. The substantial changes in the hydro-climate of the basin, therefore, are likely to increase the challenges associated with the management of several dam reservoirs and hydropower plants in the basin in addition to causing further impacts on physical and biological components of the ecosystems along these rivers.
Article
Observations on cranial morphology were made on Euphrates soft-shelled turtles, Rafetus euphraticus, sampled in the Euphrates and Tigris rivers and tributaries, Southeastern Anatolia. The vomer separates the maxillaries in half of the specimens, whereas the maxillae meet on the vomer in others. The parietal has no contribution in the formation of the foramen nervi trigemini due to the contact between the prootic and the epipterygoid. There are variations in the contacts of the basisphenoid and in the formation of the trigeminal region, a prootic-epipterygoid contact participates in the trigeminal region. The contacts of the vomer-pterygoid, the vomer-basisphenoid and the vomer-pterygoid-basisphenoid are observed in some specimens. In one specimen, the parietal contacts the opisthotic. All specimens have the symphyseal ridge, althought it is weak and barely discernible.
Article
We investigated predation of simulated turtle nests in an effort to understand how land-use patterns and the availability of nesting habitat may affect turtle recruitment in a region where human populations and associated development are increasing. Simulated nests were patterned after those created by painted turtles (Chrysemys picta), a common aquatic turtle in our study area, and distributed in four patterns (clustered and near pond, scattered and near pond, clustered and far from pond, and scattered and far from pond) around 36 ponds. Landscape composition (500–2000 m from pond perimeters) and habitats surrounding pond edges (an area extending 250 m from the shore of each pond) were then compared with rates of predation at each pond. Nest-site characteristics also were compared to the fate of individual nests. Landscape composition and habitats surrounding ponds apparently had little influence on predation rates. Nest distribution and the immediate habitat features associated with each nest did affect vulnerability to predation. Clumped nests were preyed upon at a higher rate than scattered nests, and nests close to ponds (within 50 m) were more vulnerable to predators than those created far (100–150 m) from a pond. Counter to our expectations, proximity to edge habitats (other than the shore of a pond) reduced the probability that a nest would be detected by predators. Also, nests placed near roads and suburban lawns had a reduced likelihood of predation whereas those placed in agricultural areas or disturbed sites had a greater probability of being preyed upon. Our results suggest that predation of simulated turtle nests may be a consequence of their distribution and location relative to the foraging activities of common nest predators, especially raccoons (Procyon lotor). Efforts to enhance recruitment among declining populations of turtles should consider the abundance and distribution of nesting habitat. Providing additional nesting sites away from predator foraging habitats may reduce nest predation and increase the recruitment of hatchlings into a population.