Survival of the western pond turtle (Emys marmorata) in an urban California environment

The western pond turtle Emys (formerly Clemmys) marmorata is declining throughout its range, primarily due to loss of habitat via urbanization and conversion to agriculture. Urban waterways present several important challenges to freshwater turtle populations, but they also present an opportunity to maintain declining species in a ubiquitous habitat that has high public visibility. The arboretum waterway on the University of California, Davis campus is an example of an extensively altered urban habitat that supports a relatively large E. marmorata population. Over the last 6 years, we monitored the turtle population inhabiting the arboretum waterway to determine the demographic health of the population, and the challenges and opportunities that urban environments pose for pond turtles. Since 1993, the naturally existing arboretum pond turtle population has declined by approximately 40% and has shown little natural recruitment. During this time, we also introduced 31 headstarted turtles into the arboretum. Headstarting is the process of raising juveniles in captivity until they have outgrown their period of greatest vulnerability to predators, and then releasing them into the wild. Our headstarting results demonstrate that this contentious strategy is a viable option for adding young turtles to the population, although it does not address the causes of decline. Over the course of our study, we encountered nine species of non-native turtles in the waterway, and these appear to be a serious threat to the native species. As more habitat becomes urbanized, it is increasingly important to understand how freshwater turtles, such as E. marmorata, adapt to urban waterways and the impact of non-native turtles on native turtle species. Our strong feeling is that urban waterways can provide habitat for viable populations of freshwater turtles and showcase them to the public, but both the aquatic and terrestrial habitat must be managed according to the biological requirements of individual species.     

Market turtle mystery solved in Vietnam

Asian turtles are overharvested for food, medicinal purposes and pets, and most species are now at risk of extinction (‘Asian turtle crisis’). As a result of high levels of trade, some species of Asian turtles are known to science mostly or only from animals found in trade. The Vietnamese box turtle (Cuora picturata) was described in 1998 and is known only from markets. This species is likely to be highly threatened, and identifying the origin of this “market species” is imperative if it is to be conserved. We used evidence from phylogeny, biogeography and trade patterns to focus field searches for this species, and in July 2010–January 2011 found it in the wild at three localities on the Langbian Plateau of southern Vietnam. This discovery provides the first opportunity to conserve the Vietnamese box turtle, and provides hope for determining the wild origin of other rare Asian turtles that remain known only from commercial trade.     

Using long-term data and a stage-classified matrix to assess conservation strategies for an endangered turtle (Clemmys guttata)

Reptiles are in decline globally, and one-third of turtle species are considered endangered or vulnerable. Conservation of turtles presents special challenges, as turtles are long-lived, and have delayed sexual maturity, making long-term study necessary for accurate calculation of life history parameters. The spotted turtle (Clemmys guttata) is listed as an endangered species in Canada. A population in eastern Georgian Bay, Ontario has been the focus of the longest-running ecological study (30 years) on the species to date. The objective of the current project was to use the long-term demographic data to parameterize a stage-classified matrix and to use the model to asses several hypothetical management scenarios. Elasticity analyses and simulations indicated that small changes in adult survivorship would have the largest proportional effect on population growth rate, and that increasing survivorship of juveniles to 100% would result in the largest increase in population growth rate. Simulation of nest protection and headstarting scenarios indicated that these are inefficient conservation strategies for this species. We recommend that adults, and when possible, juveniles, be the stages targeted for conservation in spotted turtles and other long-lived iteroparous vertebrates.     

Long-term conservation efforts contribute to positive green turtle Chelonia mydas nesting trend at Tortuguero, Costa Rica

Worldwide, green turtle Chelonia mydas populations have declined and the species is classified as globally endangered. Tortuguero, Costa Rica, hosts the largest remaining green turtle rookery in the Atlantic basin. Tortuguero green turtles have been hunted since pre-Columbian times. Monitoring and conservation of the green turtle population began in 1955. The long-term efforts provide an excellent opportunity to evaluate the success of sea turtle conservation action and policies. Nest counts conducted 1971-2003 were analyzed to: (1) determine the nesting trend, (2) estimate rookery size and (3) identify events and policy decisions influencing the trend. A nonparametric regression model indicates a 417% increase in nesting over the study period. Rookery size was defined as the mean number of nests 1999-2003 and estimated at 104,411 nests year⁻¹, corresponding to 17,402-37,290 nesting females year⁻¹. A comparison with 34 index populations verifies Tortuguero as one of the two largest green turtle rookeries worldwide. Events and policy decisions in Costa Rica, Nicaragua, and Panama that comprise the main nesting, feeding and mating grounds for the Tortuguero population are likely to have had the greatest influence on green turtle survivorship. Conservation efforts and policies catalyzing increased hatchling production and decreased adult and juvenile mortality since 1963 have contributed to the positive nesting trend. The trend demonstrates that long-term conservation efforts can reverse nesting declines and offers hope that adequate management can result in recuperation of endangered sea turtle species.     

Estimates of sea turtle mortality from poaching and bycatch in Bahía Magdalena, Baja California Sur, Mexico

Bahia Magdalena on the Pacific coast of Baja California Sur, Mexico, is an important feeding and nursery ground for black turtles Chelonia mydas, loggerhead turtles Caretta caretta, olive ridley turtles Lepidochelys olivacea, and hawksbill turtles Eretmochelys imbricata. Despite international and national protection, sea turtles continue to be caught incidentally and hunted for consumption in large numbers. This study examines the mortality of sea turtles in Bahia Magdalena, focusing on (1) species distribution and number of carcasses found, (2) causes of death, (3) size frequency distribution and % juveniles in the catch, and (4) changes in average size over the past years. A total of 1945 turtle carcasses were found from April 2000 to July 2003 along beaches and in towns of the region with loggerhead (44.1%) and black turtles (36.9%) being the dominant species. Slaughter for human consumption was the primary cause of death of carcasses found in towns (95-100%), while carcasses on beaches mostly died of unknown causes (76-100%). Circumstantial evidence suggests however, that incidental bycatch was the main mortality cause on beaches. Black turtles suffered the highest consumption mortality overall (91%), followed by olive ridley (84%), hawksbill (83%) and loggerhead turtles (63%). Over 90% of all turtles found were juveniles or subadults. Carapace length of black turtles declined consistently over the sampling period, while that of loggerhead turtles increased. Our results strongly suggest that turtles are being taken at high and unsustainable rates; this may partially explain why the populations have not recovered despite widespread protection on nesting beaches.     

Pelagic longlines: A threat to sea turtles in the Equatorial Eastern Atlantic

Pelagic longlines are widely known to interact with several species of sea turtles, and there is an increasing concern about the by-catch of turtles in commercial fisheries and its impact on their populations. However, information on sea turtle by-catch in the South Atlantic Ocean is scarce, and there are no quantitative by-catch data available on olive ridleys for the Equatorial Eastern Atlantic. In this paper we analyze data collected by observers on board an Uruguayan long-liner targeting swordfish in two areas in the Equatorial Eastern Atlantic: off the Gulf of Guinea and north of Saint Helenaa Island. Specimens of Lepidochelys olivacea and Dermochelys coriacea were hooked or entangled in 26 longline sets. All registered interactions with olive ridleys took place off the The Gulf of Guinea, with captures ranging from 1 to 3 specimens in a single set. The captured specimens, though not measured directly, appeared to be juveniles. In addition, the examination of the stomach contents of one female mako shark showed dermal scutes, vertebrae and the complete head of a sea turtle identified as L. olivacea, allowing us to estimate its curved carapace length. In contrast, adult specimens of D. coriacea were caught in the two fishing areas. The capture of 10 individuals in a single set was recorded. Due to the high rate of sea turtle by-catch observed off the The Gulf of Guinea (1.02 ind/1000 hooks) conservation programs in the area should take into consideration the possible existence of a developmental and feeding area in this zone. Accordingly, longline fisheries in this area should be monitored and mitigation measures put in place to avoid or minimize damage to the pelagic phase of African populations of sea turtles.     

Road crossing structures for amphibians and reptiles: Informing design through behavioral analysis

Road traffic causes significant amphibian and reptile mortality, which could be mitigated through the installation of road crossing structures that facilitate safe passage, but only if reptiles and amphibians are willing to use them. Through a series of behavioral choice experiments with frogs and turtles, we examined how aperture diameter, substrate type, length, and light permeability influenced individuals’ preferences for specific attributes of crossing structures, and how individuals responded to various heights of barrier fences. Snapping turtles (Chelydra serpentina), green frogs (Rana clamitans), and leopard frogs (Rana pipiens) preferred larger diameter tunnels (>0.5 m) whereas painted turtles (Chrysemys picta) preferred tunnels of intermediate (0.5-0.6 m) diameter. Green frogs preferred soil- and gravel-lined tunnels to concrete- and PVC-lined tunnels. Painted turtles showed non-random choice of different lengths of tunnel, possibly indicating some avoidance of the longest tunnel (9.1 m); although no species preferred to exit via the longest tunnels (9.1 m), members of all four species used such tunnels. Green frogs preferred tunnels with the greatest light permeability. Fences 0.6 m in height were effective barriers to green frogs, leopard frogs, and snapping turtles, whereas 0.3 m fences excluded painted turtles. We conclude that tunnels > 0.5 m in diameter lined with soil or gravel and accompanied by 0.6-0.9 m high guide fencing would best facilitate road crossing for these and likely other frog and turtle species.     

Sea turtle by-catch in pelagic longline sets off southern Brazil

Results are presented on sea turtle by-catch observed in pelagic longline sets during research cruises in the south Atlantic in the vicinity of the shelf edge break in southern Brazil. The longline gear was set in a similar manner to that employed by the commercial longline fleet operating out of Santos, Brazil that targets swordfish, Xiphias gladius. Nineteen sea turtles were caught on 14 of 41 sets, which constituted a catch rate of 1.5 turtles per 1000 hooks. Thirty four percentage of all sets captured at least one turtle. The catch included loggerhead, Caretta caretta, leatherback, Dermochelys coriacea, and most likely olive ridley, Lepidochelys olivacea. All turtles, except one loggerhead, were captured live and released. Captures occurred during spring, summer and winter suggesting a year around presence and vulnerability. Given increased levels of longline effort directed at swordfish in the southeast Atlantic, substantial turtle by-catch can be expected. There is a critical need for additional information to be able to assess the potential impact on swordfish longline fisheries on sea turtle populations.     

Implications of conserving an ecosystem modifier: Increasing green turtle (Chelonia mydas) densities substantially alters seagrass meadows

Ecosystem modifiers have the ability to significantly alter the ecosystem they inhabit sometimes with serious consequences for their own populations. We evaluated the ability of green turtles (Chelonia mydas) to modify seagrass ecosystems by their foraging activity. This study was conducted in a seagrass-dominated lagoon in the Lakshadweep Islands, Indian Ocean, where a stable high-density congregation of green turtles is present. We determined a gradient of turtle density in the lagoon and measured the intensity of turtle herbivory across the gradient. We then measured the impact of increasing grazing on seagrass structural parameters, growth and flowering along this gradient. Our results indicate that turtles substantially change seagrass meadow structure (canopy height, shoot length, width and density), reduce flowering and can potentially even cause changes in the species composition of the meadow. We discuss the implications of these results for seagrass ecosystem function, green turtle movement and human attitudes. When conserving ecosystem modifiers like the green turtle, any management strategy needs to include a detailed knowledge of the roles these species play in the ecosystems they inhabit.     

Incidental capture of marine turtles by the Italian trawl fishery in the north Adriatic Sea

In the north Adriatic Sea on-board observations on midwater and bottom trawlers were carried out during years 1999 and 2000. Results indicate that the north Adriatic Sea, and especially the north-east part, is a very important foraging and overwintering habitat for loggerhead turtles (Caretta caretta). Since the distribution of fishing effort in the area is not known, the total turtle catch by the Italian bottom trawl fleet was conservatively estimated from the lower catch rate observed in the south-west sub-area: 4273 turtle captures/year (95% C.I.=2186-8546). The actual total catch in the whole north Adriatic is likely to be much higher, due both to an unknown Italian trawling effort in the south-west part with multi-gear vessels and to the Italian and Croatian trawling efforts in the north-east part, where catch rate was 15 times greater than in the south-west part. In the south-west sub-area 9.4% of captured turtles were dead and potential mortality (assuming that all comatose turtles would die too) was 43.8%. Hence, trawling in the north Adriatic is likely to represent a serious threat to the populations, and possible conservation measures are discussed.     

A review of sea turtle nesting activity along the Mediterranean coast of Turkey

Many parts of the Turkish coastline are important nesting grounds for sea turtles. The aim of this study was to assess the present state of sea turtle populations along the coastline of Turkey, by evaluating research conducted at various nesting grounds from 1979 to 2000. The results of the evaluation indicate that the Turkish coastline is the most important nesting area for Chelonia mydas, and the third most important nesting area for Caretta caretta after Greece and Libya (if nesting estimates for Libya are correct) in the entire Mediterranean. The most important C. caretta nesting beaches in Turkey are Dalyan (11.9%), Kumluca (11.3%), Belek (27.9%), Kizilot, (8.9%) and Anamur (8.8%), while those for C. mydas are Kazanli (24.1%) and Akyatan (54.4%). These sites are classified as “Nesting Areas of 1st Degree Importance”. Annual mean nest numbers along the coastline of Turkey are estimated to be ca. 2000 for C. caretta and 650 for C. mydas. Assuming that each adult female sea turtle nests three times per season, the annual numbers of nesting females along the beaches of Turkey range between about 500 and 800 for C. caretta and 130 and 300 for C. mydas. Annual nesting densities along the 204 km beach strip, which includes 17 important nesting grounds in Turkey, were 11.3 nests/km for C. caretta and 19.2 nests/km for C. mydas.     

Feral pig predation threatens the indigenous harvest and local persistence of snake-necked turtles in northern Australia

Northern snake-necked turtles (Chelodina rugosa) traditionally provided an important seasonal source of protein for indigenous communities in Arnhem Land, northern Australia. Harvest techniques today differ little from those used historically, harvesting being applied in the late dry season when ephemeral waters have drawn down and turtles are aestivating. Radio-telemetry was used to quantify survival rates of C. rugosa at a traditional turtle harvest site and relate them to harvest, predation by feral pigs (Sus scrofa) and environmental factors. Although turtle survival was positively correlated with body size, the survival of turtles of all sizes and stages of maturity was compromised by pig predation. Seasonal variation in the onset, duration and severity of rainfall and associated influences on periodic drying, are important for C. rugosa survival because such variation influences the timing and intensity of both Aboriginal harvest and pig predation. Contemporary harvest rates of C. rugosa in Arnhem Land by Aboriginal people are very low because pig predation depletes available stocks immediately before Aboriginal harvesting. Aboriginal harvest rates are regulated also by the frequency and timing of ceremonies and other cultural activities that interfere with harvests. Before the arrival of pigs, such relaxation of harvest pressure in years when harvest would otherwise be possible would have contributed to the local abundance and persistence of C. rugosa. In contrast, pig predation is unrelenting, and years of high turtle survival are now restricted only to years of high wet season rainfall.     

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.     

Migrations of green turtles in the central South Pacific

Migrations of seven post-nesting green turtles at Rose Atoll (American Samoa) were tracked by satellite transmitters in 1993-1995. Most turtles migrated 1600 km to foraging areas in Fiji and occupied home ranges averaging 27 km². Additional tag recaptures from other studies indicate a common pattern of turtle movement in the central South Pacific region. In total, the 26 recaptures of primarily post-nesting turtles from French Polynesia, American Samoa, and Cook Islands showed a similar course of direction and destination: 96% migrated westward after nesting, with 58% going specifically to Fiji. We propose that this pattern reflects the lower availability of turtle food east of Fiji where most islands are small, steep and have limited areas suitable for seagrass or algal growth. In contrast, Fiji's extensive pastures of seagrass and algae appear to be a significant resource for many green turtles in the region. These turtles apparently spend most of their adult life in Fijian waters, taking only brief migrations to other islands to nest.     

Sex ratio bias in hatchling sea turtles from artificially incubated eggs

Artificial incubation of eggs of green sea turtles, Chelonia mydas, above ground in styrofoam boxes results in a 23% drop in the number of hatchlings with ovaries, compared with samples from clutches left on the beach in natural conditions. This masculinization is consistent with the well-known effects of temperature on sexual differentiation in chelonians and with measurements showing that the styrofoam boxes were 1–1·5°C cooler than the sand on the beach at the depth of turtle nests. These findings verify previous suspicions about the use of styrofoam boxes in management programmes for sea turtles, and have implications for the conservation and husbandry of reptiles in general.     

Aerial surveying of the world’s largest leatherback turtle rookery: A more effective methodology for large-scale monitoring

For many marine megavertebrate species it is challenging to derive population estimates and knowledge on habitat use needed to inform conservation planning. For marine turtles, the logistics required to undertake comprehensive ground-based censuses, across wide spatial and temporal scales, are often insurmountable. This frequently leads to an approach where a limited number of index nesting beaches are monitored in great detail by foot. In this study we use nationwide aerial surveying interfaced with ground assessments across three seasons of leatherback turtle nesting in Gabon (Equatorial West Africa), highlighting the importance of a synoptic approach to marine turtle monitoring. These surveys allow the first complete population assessment of this nesting aggregation to be made, identifying it as the world’s largest for the species (36,185-126,480 clutches, approximating to 5865-20,499 breeding females per annum and a total estimate of 15,730 to 41,373 breeding females). Our approach also serendipitously provides insights into the spatial appropriateness of Gabon’s protected areas network, for example (mean ± 1SD) 79 ± 6% (range 67-86%) of leatherback turtle activities recorded during aerial surveys (n = 8) occurred within protected areas (345 km, 58%, of surveyed coastline). We identify and discuss sources of potential error in estimating total nesting effort from aerial surveying techniques and show that interannual variation in nesting is considerable, which has implications for the detection of statistically significant changes in population size. Despite its relative costliness per day, aerial surveying can play an important role in providing estimates of relative population abundance of large vertebrates dispersed over extensive areas. Furthermore, it can provide data on habitat use and deliver real-time information on the spatial efficacy of protected area networks.     

Reproductive biology and conservation implications of three endangered snapdragon species (Antirrhinum, Plantaginaceae)

About 32% of Antirrhinum species are considered to be endangered; however, no field studies have focused on their reproductive biology. In this work, several aspects of the reproductive biology (flowering phenology, floral biology, breeding system) and potential limits on seed quantity and quality (pollen limitation, inbreeding depression) were studied in natural populations of three endangered species of the genus (Antirrhinum charidemi, Antirrhinum subbaeticum, Antirrhinum valentinum). Results disclose that all three species need insect visitors for seed production since fruit set after autonomous self-pollination was lower than under hand cross-pollination. A. charidemi and A. valentinum were mainly self-incompatible, whereas A. subbaeticum was self-compatible but herkogamous. Supplementary pollination in open-pollinated flowers only increased fruit set and seed set relative to controls in a given population of A. valentinum. Preliminary data on inbreeding depression at early life-cycle stages of the self-compatible A. subbaeticum revealed that the cumulative level was low. Despite the three species being closely related and sharing many ecological characteristics, they show different mating systems, and different factors limit seed quantity and quality. Thus, caution should be taken when making a common conservation plan for a group of closely related taxa.     

Socio-economic importance, domestication trends and in situ conservation of wild Citrus species of Northeast India

Northeast India is rich in Citrus genetic diversity representing several wild and cultivated species. Besides commercially cultivated species, several wild, semi-wild and domesticated species namely Citrus indica, C. macroptera, C. ichangensis, C. latipes, C. megaloxycarpa and C. assamensis are found to grow in Northeast India. These species have great potential in improvement of Indian Citrus industry being source of genes for combating biotic and abiotic stresses. The natural diversity of these genetic resources is shrinking at alarming rate due to large scale deforestation, shifting cultivation practiced in these areas and climate change scenario in this important hotspot of biodiversity. Socio-economic importance of each species have been studied during surveys and interesting domestication trends were observed based on their cultural and economic significance, which led to “in situ on farm” conservation of C. indica, C. macroptera and threat to C. megaloxycarpa and C. ichangensis. Consequently, genetic resources of most of these species are facing severe threat of extinction necessitating policy interventions and adoption of dynamic conservation and management strategies. Species specific conservation strategy especially through “in situ on farm” conservation has been proposed with suitable sites in Northeastern Indian states based on population structure and suitability of habitat. Farmers’ support through “The Biological Diversity Act, 2002” and “The Protection of Plant Varieties and Farmers’ Rights Act, 2001” of India would bring the required impact on management of these complex genetic resources of Citrus. In the present study, we have documented the current status, socio-economic potential, domestication trends and associated traditional knowledge of these wild and semi-wild Citrus species occurring in Northeast India and enumerated suitable conservation strategies and desired policy interventions for their dynamic conservation and sustainable utilization.     

Terrestrial habitat requirements of nesting freshwater turtles

Because particular life history traits affect species vulnerability to development pressures, cross-species summaries of life history traits are useful for generating management guidelines. Conservation of aquatic turtles, many members of which are regionally or globally imperiled, requires knowing the extent of upland habitat used for nesting. Therefore, we compiled distances that nests and gravid females had been observed from wetlands. Based on records of > 8000 nests and gravid female records compiled for 31 species in the United States and Canada, the distances that encompass 95% of nests vary dramatically among genera and populations, from just 8 m for Malaclemys to nearly 1400 m for Trachemys. Widths of core areas to encompass varying fractions of nesting populations (based on mean maxima across all genera) were estimated as: 50% coverage = 93 m, 75% = 154 m, 90% = 198 m, 95% = 232 m, 100% = 942 m. Approximately 6–98 m is required to encompass each consecutive 10% segment of a nesting population up to 90% coverage; thereafter, ca. 424 m is required to encompass the remaining 10%. Many genera require modest terrestrial areas (<200 m zones) for 95% nest coverage (Actinemys, Apalone, Chelydra, Chrysemys, Clemmys, Glyptemys, Graptemys, Macrochelys, Malaclemys, Pseudemys, Sternotherus), whereas other genera require larger zones (Deirochelys, Emydoidea, Kinosternon, Trachemys). Our results represent planning targets for conserving sufficient areas of uplands around wetlands to ensure protection of turtle nesting sites, migrating adult female turtles, and dispersing turtle hatchlings.