River Turtle Research Articles

Embryonic development of the Giant South American River Turtle, Podocnemis expansa (Testudines: Podocnemididae)

Knowledge of embryonic development is important for choosing strategies for nest conservation, and reducing negative effects on eggs and embryos of turtle species subject to human and natural interference, as is the case of Podocnemis expansa in the Amazon. Nine P. expansa nests located in Balbina, Amazonia, Brazil, were used to describe embryonic development. An embryo was collected each day, totaling 240 embryos. The specimens were fixed in Bouin’s and Karnovsky’s solutions for macroscopic analysis and scanning electron microscopy, respectively. The incubation period lasted between 58 and 64 days with a mean nest incubation temperature of 30.3 °C. The main characteristics used for description and comparison of embryonic development were: development of the eyes, the mandibular process, limbs, carapace and plastron. We found that the timing of appearance and disappearance of structures in P. expansa were more advanced than in other turtle species. Furthermore, P. expansa displays some unique characteristics during its normal development, such as craniofacial morphology, frontonasal groove and carapace and plastron characteristics.

Primer registro de la tortuga de río Kinosternon leucostomum (DUMERIL & BIBRON, 1851), para las estribaciones de la Sierra Nevada de Santa Marta en la Guajira colombiana

La tortuga de río (K. leucostomum), fue registrada por primera vez en 2011 para el departamento de Guajira, dentro de la franja baja de la Serranía de Perijá (GALVIS-PEÑUELA et al., 2011). Nuestras observaciones constituyen el primer registro de esta especie para las estribaciones de la Sierra nevada de Santa Marta, y el segundo registro para el departamento de la Guajira, Caribe colombiano.

Orientation in Five Species of Hatchling River Turtles Dispersing from Experimental Nests

Abstract Hatchling river turtles (Smooth Softshell Turtles, Apalone mutica; Spiny Softshell Turtles, Apalone spinifera; Northern Map Turtles, Graptemys geographica; False Map Turtles, Graptemys pseudogeographica; and Ouachita Map Turtles, Graptemys ouachitensis) were released in a variety of settings to help place orientation and dispersal from nests in the context of nest site selection by females and juvenile recruitment habitat. Visual cues associated with near open or far dark horizons were the primary environmental cues used during initial orientation and dispersal of the hatchling river turtles. On a river beach, hatchlings of both species of Softshell Turtles dispersed toward the open horizon of the nearby river. In contrast, hatchlings of all 3 species of Map Turtles on the same beach dispersed toward the near dark horizons of a forest that led them away from the river. Hatchling Map Turtles of all 3 species released in autumn and Northern Map Turtles also released in spring at a field arena dispe...

Identifying Critical Habitat for Australian Freshwater Turtles in a Large Regulated Floodplain: Implications for Environmental Water Management.

Freshwater turtles face many threats, including habitat loss and river regulation reducing occupancy and contributing to population decline. Limited knowledge of hydrological conditions required to maintain viable turtle populations in large floodplain wetlands hinders effective adaptive management of environmental water in regulated rivers. We surveyed three turtle species over 4 years across the Lower Murrumbidgee River floodplain, a large wetland complex with a long history of water resource development. Using site and floodplain metrics and generalized linear models, within a Bayesian Model Averaging framework, we quantified the main drivers affecting turtle abundance. We also used a hierarchical modeling approach, requiring large sample sizes, quantifying possible environmental effects while accounting for detection probabilities of the eastern long-necked turtle (Chelodina longicollis). The three species varied in their responses to hydrological conditions and connectivity to the main river channel. Broad-shelled turtles (Chelodina expansa) and Macquarie River turtles (Emydura macquarii macquarii) had restricted distributions, centered on frequently inundated wetlands close to the river, whereas the eastern long-necked turtles were more widely distributed, indicating an ability to exploit variable habitats. We conclude that turtle communities would benefit from long-term management strategies that maintain a spatiotemporal mosaic of hydrological conditions. More specifically, we identified characteristics of refuge habitats and stress the importance of maintaining their integrity during dry periods. Neighboring habitats can be targeted during increased water availability years to enhance feeding and dispersal opportunities for freshwater turtles.

Distribution and Abundance of the Central American River Turtle, Dermatemys Mawii, in Southern Quintana Roo, Mexico: Implications for a Regional Conservation Strategy

We estimated the distribution and abundance of the Central American River Turtle, Dermatemys mawii, in four aquatic systems in southern Quintana Roo, Mexico. Using nets and free diving we captured 52 individuals D. mawii among the winter, dry and rainy seasons. We recorded 12 variables to characterize the habitat and correlated these with the abundance of D. mawii. Using catching per unit effort, we evaluated the species’ relative abundance for each aquatic system. Using Maxent, we modeled the potential distribution of D. mawii using historical and present locality data. We recorded 81 D. mawii individuals using systematic sampling and casual observations. La Union was the site with the highest relative abundance (~4 ind.-net). We found a negative correlation between D. mawii abundance and salinity. The model of potential distribution identified sites with ecological conditions suitable for the species where it is undocumented. Information about the ecology of this species remains scarce, but we propose that identifying management units could improve conservation of the species at local and regional levels.

Polyandrous behavior in an overexploited giant South American turtle (Podocnemis expansa) population in Central Amazon, Brazil.

The aim of the present study was to investigate the reproductive behavior of the giant Amazon River turtle (Podocnemis expansa) in the Amazon. This was carried out by estimating the degree of polymorphism in five DNA microsatellites in a sample of 359 hatchlings from 12 nests in the Mamirauá Sustainable Development Reserve in the municipality of Tefé, state of Amazonas, Brazil. An analysis of allele frequency and variation in the five microsatellite loci allowed for determination of multiple paternity in all nests sampled. Contributions of at least four male turtles to one nest, three male turtles to six nests, and two male turtles to five nests were identified. Knowledge on the reproductive behavior of P. expansa can assist in the establishment of management and conservation strategies for the population in the Mamirauá Reserve.

Abundance and harvest proportion of river turtles in Missouri

ABSTRACTFreshwater turtle populations are declining worldwide, yet managers have little information about the effects of commercial turtle harvests. In Missouri, the snapping turtle (Chelydra serpentina), smooth softshell (Apalone mutica), and spiny softshell (Apalone spinifera) are harvested commercially in the Missouri River. In 2011 and 2012, we conducted mark–recapture of these species to estimate abundance on the Missouri River and two unharvested tributaries, the Osage and Gasconade Rivers. We conducted mock harvests, applying capture methods of the state's primary commercial harvester, to estimate plausible expected harvest proportions. Snapping turtle abundance per 2 km was lower at harvested units ( = 15; SE = 7.1; unharvested: = 90; SE = 40.3). Smooth softshell abundance was greater at harvested units ( = 59; SE = 7.9; unharvested: = 14; SE = 28.1), although the difference was not significant. Mean unique spiny softshell captures were similar at harvested ( = 18; SE = 4.3) and unharvested ( = 17; SE = 9.7) units. Expected harvest proportions averaged 23% across species (SE = 5%; range = 6%–79%), exceeding sustainable rates reported for turtles. Our results suggest that on a small scale, using these methods, harvesters can remove a substantial portion of river turtle populations.

Reproductive aspects of the Chocoan River turtle (Rhinoclemmys nasuta, Geoemydidae) along the Colombian Pacific coast

We collected data on several aspects of the reproductive biology of the Chocoan River Turtle (Rhinoclemmys nasuta) as part of a long-term demographic study (2005-2015), along the Pacific coast of the department of Valle del Cauca in Colombia. We palpated 659 females and found 77 gravid, with two peaks in the proportion of females gravid, one between May and June, and another from October to December; there was a significant correlation between the monthly proportion gravid and the monthly amount of precipitation (Spearman rank correlation , ). We obtained 13 eggs (mean length = 63.8 mm, mean width = 35.4 mm, mean weight = 45.8 g). Using egg volume as a general indicator of size, there was no significant relationship with female size. To induce oviposition, oxytocin, prostaglandin, or a combination of the two was injected into 37 gravid females with a success rate of 48.6%. We determined the duration of incubation for two individuals as 133 and 135 days. With this information, we fill some gaps in the knowledge of reproductive ecology of this species; however, the sample size is very low and primarily comes from a single insular population and therefore it is important to continue studies on aspects of reproductive ecology such as those evaluated in this study and other topics like sex determination.

Effect of diet on growth in captive Podocnemis unifilis: assessing optimal diets for turtles in head-starting programs

Because turtles have come under increasing pressures from habitat loss and over-exploitation as food sources and traditional medicine, efforts have focused on options for conservation, including head-starting programs. Success of head-starting programs depends on establishing economical means of rearing hatchlings over relatively short time frames to sizes resistant to predation. We examined effects of three different diets on growth of a clutch of captive Yellow-spotted Amazon River Turtles (Podocnemis unifilis) over a two-year period in a Florida zoo. Rates of growth differed among the three treatment groups; relationships between morphological variables were not affected by diet. Results indicate that turtles fed on a commercial gel diet may exceed growth rates of animals fed on a more natural, vegetarian diet by more than 15% as measured by straight-line carapace length, or by more than 50% in body mass. Use of a vegetarian diet reduced costs to less than 10% of the cost of a commercial gel diet. Choice of diets for turtles in head-starting programs is a variable that should be weighed against other conservation objectives such as captive duration and intended sizes attained.

Avaliação de parâmetros bioquímicos séricos em Tartarugas-da-Amazônia (Podocnemis expansa) mantidas em cativeiro

RESUMO: Amostras de sangue de Tartaruga-da-Amazônia mantidas em cativeiro foram analisadas com o propósito de avaliar os constituintes bioquímicos séricos e de relacionar ao que já foi relatado por outros pesquisadores, além de gerar mais informações, tendo em vista a escassez de dados envolvendo a espécie estudada. Foram utilizados 35 animais, com idade entre 3 e 7 meses, os quais foram contidos fisicamente para coleta de sangue em tubo sem anticoagulante. As análises bioquímicas foram processadas através de métodos cinéticos (enzimas) e colorimétricos (demais análises), e os valores médios obtidos foram: cálcio 7,0±1,9mg/dL, fóforo 2,8±1,2mg/dL, ácido úrico 1,8±0,8mg/dL, uréia 10,4±3,9mg/dL, alanina aminotransferase (AST) 75,5±33,6 UI/L, proteína total 1,9±0,8g/dL, triglicerídeos 22,9±9,8mg/dL e colesterol 45,3±19,7mg/dL. Observou-se que os valores dos componentes séricos avaliados assemelham-se aos que foram encontrados por outros pesquisadores em estudos bioquímicos séricos com Podocnemis expansa e outras tartarugas de água doce. Importante ressaltar que, no decorrer deste estudo observou-se a escassez de dados publicados sobre parâmetros sanguíneos de tartarugas do gênero Podocnemis, especialmente a espécie Podocnemis expansa, o que corroborou a alta relevância do desenvolvimento de mais pesquisas que envolvam a questão.

Research and Conservation Priorities for Tortoises and Freshwater Turtles of Colombia

The objective of our study was to review and quantify the level of knowledge of the biology of tortoise and freshwater turtle species of Colombia based on studies conducted in the country. We used the resulting rankings in knowledge, in combination with IUCN threat category, presence in protected areas, and endemism, to propose conservation priorities. This process also allowed us to evaluate which aspects of turtle biology have been least studied. Four species obtained total values of zero or one over the 21 knowledge criteria employed, so they were ranked as the highest priority for research based on the lack of knowledge of their biology: Black-lined Toad-headed Turtle ( Mesoclemmys raniceps), Amazon Toad-headed Turtle ( Mesoclemmys heliostemma), Gibba Toad-headed Turtle ( Mesoclemmys gibba), and Dunn’s Mud Turtle ( Kinosternon dunni). Moreover, species in the family Chelidae in general were found to have limited levels of knowledge, which makes this group a priority for investigation. Evaluation of the distinct criteria used in the knowledge assessment revealed that the best-known criteria were geographic distribution (modeled), presence or absence in protected areas, and clutch size. The most poorly known biological characteristics, which constitute research priorities, are the frequency of nesting, longevity and generation time, and population parameters. According to the criteria used, the priority species for conservation were the Magdalena River Turtle ( Podocnemis lewyana), Dahl’s Toad-headed Turtle ( Mesoclemmys dahli), K. dunni, and Maracaibo Wood Turtle ( Rhinoclemmys diademata), three of which are endemic or semiendemic ( R. diademata only occurs in Colombia and Venezuela), followed by two species of Mesoclemmys.

Effects of Incubation Temperature on Sex Determination in the Endangered Magdalena River Turtle,Podocnemis lewyana

Abstract In species with temperature-dependent sex determination, the embryo commits to its sexual fate during a time window called the thermosensitive period (TSP). Although substantial research has focused on the effect of the temperature during this canonical TSP, the effect of temperatures experienced before this time (pre-TSP) on the onset and duration of the TSP is less understood. Here, we incubated eggs of the endangered Magdalena River turtle, Podocnemis lewyana, under 3 relatively constant temperatures and 6 shift-twice treatments. Constant treatments included two 100% masculinizing temperatures that fostered a relatively slower and faster embryo development and one 100% feminizing temperature. The shift treatments included a masculinizing temperature and later a feminizing temperature for a period of time at different incubation stages. Sex ratios were determined by a geometric-morphometric sexing approach developed for this species and validated by gonadal histology. This technique is a nonlet...

Testing the Effects of Barriers on the Genetic Connectivity inPodocnemis erythrocephala(Red-Headed Amazon River Turtle): Implications for Management and Conservation

Abstract In contrast to the other Podocnemis species, Podocnemis erythrocephala (Pleurodira: Podocnemididae) is restricted to blackwater and clearwater rivers and lakes, including the Negro River basin, and several other tributaries of the eastern Amazon River basin. In order to test the effects of geographic barriers on genetic connectivity of P. erythrocephala, 10 localities sampled throughout the Brazilian Amazon basin were studied. Two hundred and forty-six specimens were sequenced for the mitochondrial control region. Analysis of molecular variance confirmed the existence of population subdivision (ΦST = 0.28, p < 0.001). In pairwise comparisons, the values of the fixation index ΦST were significant in almost all comparisons involving the Sao Gabriel da Cachoeira (Negro River), Jau National Park (Jau River), and Barreirinha (Andira River), indicating that these populations are genetically differentiated. Genetic differentiation is most likely explained by the presence of rapids and waterfalls separat...

Bigger clutch sizes save offspring energy during nest escapes

Hatchling turtles typically emerge from underground nests in groups, so the nest escape process may represent another example of animals sharing a task (in this case, digging out of a nest) to save on individual energy expenditure. Previous studies have reported the energetic cost of embryonic development across chelonian taxa, but none has quantified the extra amount of energy needed to escape the nest. Brisbane river turtle (Emydura macquarii signata) hatchlings were found to fuel this activity by using approximately 50 % of their residual yolk energy content. An open-flow respirometry system was used to quantify the effect of clutch size on an individual’s energetic cost while digging out of the nest. The energetic cost of nest escaping 15 cm upward in the fine moist sand was calculated to be between 0.34 and 2.32 kJ per individual depending upon the number of hatchlings digging together. The energetic cost decreased as the number of individuals digging together increased and thus supports the ‘social facilitation’ hypothesis which suggests hatchlings cooperate to share the workload of digging out of the nest amongst clutch mates to reduce individual energy expenditure. The reduced energetic cost associated with large cohorts was chiefly caused by the shorter time taken to dig out of the nest by larger numbers of individuals. We conclude that synchronous digging activity of many individuals during nest escape evolved not only to facilitate quicker nest emergence but also reduce the energetic cost to individuals.

Complete mitochondrial genome of the endangered Mary River turtle (Elusor macrurus) and low mtDNA variation across the species' range

Elusor macrurus is an endangered short-necked turtle restricted to the Mary River catchment in south-eastern Queensland. Shotgun sequencing of genomic DNA was used to generate a complete mitochondrial genome sequence for E. macrurus using the Illumina MiSeq platform. The mitogenome is 16 499 base pairs (bp) long with 37 genes arranged in the typical vertebrate order and a relatively short 918-bp control region, which does not feature extensive tandem repeats as observed in some turtles. Primers were designed to amplify a 1270-bp region that includes 81% of the typically hypervariable control region. Two haplotypes were detected in a sample of 22 wild-caught individuals from eight sites across its natural range. The Mary River turtle is a species with low mtDNA nucleotide variability relative to other Chelidae. The combination of a very restricted distribution and dramatic reduction in population size due to exploitation for the pet trade are the conditions likely to have led to very low mtDNA variability in this endangered species.

Biology of the Hicatee: A Critically Endangered River Turtle of Belize

The hicatee (Dermatemys mawii) is a Central American river turtle and one of the 25 most endangered turtle species in the world. Over-hunting for meat, eggs, and shells is driving the turtles toward extinction. This 3-page fact sheet about the hicatee includes its natural history, reproductive habits, and ecology and describes the international conservation efforts to save the fascinating but fast-disappearing turtle. Written by Venetia Briggs-Gonzalez, Nathan Schwartz, Rebecca G. Harvey, and Frank J. Mazzotti and published in November 2015 by the Wildlife Ecology and Conservation Department.

A Plea to Redirect and Evaluate Conservation Programs for South America’s Podocnemidid River Turtles

Abstract We review the current practices of podocnemidid turtle conservation programs in South America and summarize the direct and indirect negative consequences that some of these practices may have on the populations we are attempting to manage. We argue that programs that only focus on nest transfer and head-starting as their conservation strategies would be better served by redirecting their efforts toward the protection of subadults and adults and in conducting monitoring programs designed to evaluate the impact of their management practices. Also, we make suggestions for other ways that the management of podocnemidid populations may be improved without resorting to manipulative ex situ practices that may well do more harm than good.

Population structure and allometry of Podocnemis unifilis (Testudines, Podocnemididae) in a protected area upstream Belo Monte dam in Xingu River, Brazil.

Amazon river turtles are increasingly threatened by habitat loss and alteration due to the Brazilian energy policy based on construction of hydroelectric dams, meanwhile, populational studies remain scarce. We described the population structure, and established body allometric relationships of Podocnemis unifilis in the Terra do Meio Ecological Station in the Iriri River, tributary of the Xingu River upstream the Belo Monte dam under construction Turtles were captured by hand net and diving in 2012 and 2013 dry seasons, and 2013 rainy season. A total of 728 males, 296 females and four juveniles were captured. Adult sex ratio was male-biased by 9.15 ♂:1 ♀. Females were significantly larger than males. Mean straight carapace length was 268.9 ± 46.7 mm (165 - 403) for females; and 232.7 ± 24.8 mm (167 - 303) for males. The sexes were morphologically distinct in function of a proportionally larger plastron, and higher carapace, on females. Allometric relationships between straight carapace length and other morphometric traits were strong for males (R2 range = 0.87 - 0.96 and females (R2 range =0.79 - 0.98. Exploitation of P. unifilis in biomass extirpated from the Middle Xingu River may be estimated from body parts found post-consumption by the presented regressions.

The conservation status of the freshwater and terrestrial turtles of Mexico: a critical review of biodiversity conservation strategies

The continental turtle fauna of Mexico is composed of 7 families, 13 genera, and 45 species; when subspecies are included, a total of 61 distinct taxa are recognized. We searched for the imperiled level or protection status of each taxon according to the IUCN Red List, CITES appendices, the 25 most endangered freshwater turtles and tortoises, and the protection lists issued by the Mexican Government. We explored the overlap of conservation status between Mexican and international agencies by comparing listing status. Among the 61 taxa, 37 were in the IUCN Red List, 16 taxa were listed on CITES appendices, 39 taxa were in NOM-059 (Mexican Government list), 4 taxa were in Conabio's list (Mexican Government list), and only 1 species was included in the world's 25 most endangered freshwater turtles and tortoises. The Central American river turtle (Dermatemys mawii), the desert tortoises (Gopherus spp.) and the black soft shell turtle (Apalone atra) were the only taxa included in all the lists surveyed. Our comparison of the lists indicates that at least 25 taxa of Mexican turtles are lacking basic information and require further study to inform their comprehensive conservation status. Further, we detected a noteworthy discrepancy between international and Mexican conservation priorities for turtle conservation.

Anesthesia of the giant amazon river turtle Podocnemis expansa (Schweigger, 1812 -Testudines, Podocnemididae), with combination of ketamine and propofol

The aim of this study was to analyze the effects of the combination of the ketamine and the propofol anesthetics in Podocnemis expansa (giant amazon river turtle). Were used 20 turtle, which were divided into two groups of ten animals each. The first group received ketamine 20mg/kg/IM and propofol 10mg/kg/IV and the second group received ketamine 60mg/kg/IM and propofol 10mg/kg/IV. The animals were weighed and identified. The cardiac frequency of each animal was monitored before running the anesthesia and at 10, 30, 60, 120 and 180 minutes after administration of anesthetics. The applications of anesthetics occurred in the left forelimb (ketamine) and in the cervical vertebral sinus (propofol). Was assessed the degree of movement, muscle relaxation, ease of handling and response to painful stimulus in the thoracic limbs and pelvic, after administration of anesthetics. All animals entered in the surgical anesthesia plan before one minute after application of the anesthetic and remained in this condition by 180 minutes during the turtle’s evaluation