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Amphibian conservation studies often rely on auditory call surveys to determine distribution, abundance, and habitat associations of anuran species. Call surveys omit important life stages, however, and conservation recommendations from call surveys alone risk creating population sinks or ecological traps. To more effectively determine the effects of a catastrophic flood on an amphibian community, we surveyed tadpoles and metamorphs of six anuran species in the Missouri River floodplain in 2012 and 2013. Inference gleaned from these surveys was compared to inference from previous work with call surveys. For 8 of 10 species-years, extinction probabilities were >0 for tadpole and metamorph stages, indicating there may be habitat factors affecting tadpoles and metamorphs beyond those affecting calling adult males. In several cases we discovered habitat associations for tadpoles and metamorphs that were not present during call surveys. We had previously recommended shallow slopes for Blanchard's Cricket Frog, but we found slopes that were too shallow were detrimental for metamorph emergence. Woodhouse's Toad metamorphs had opposite preferences for slope than adults and preferred larger wetlands with less emergent vegetation. Gray Treefrog tadpoles had preferences for emergent vegetation that differed from adult requirements. Our work highlights the need to consider habitat factors affecting life stages beyond calling adult males. Amphibian conservation and management should proceed with sufficient information on critical aquatic life stages.
Sea turtles use beaches that are suitable for the successful development of embryos. Heavy nesting on beaches may have detrimental effects on the survival of embryos as the result of the destruction of nests by conspecifics and physiological stress of the incubation substrate. We studied nesting space dynamics and the impacts of nesting Olive Ridley Sea Turtle (Lepidochelys olivacea) females on the hatching success in Gahirmatha rookery, along east coast of India. A reduction in beach area following a recent post super-cyclone presented an opportunity to test the hypothesis predicting that nest density would negatively affect nest and hatching success. The average calculated area was 475.4 cm2 for one nest cavity; therefore, the nest capacity of the beach was estimated to be 85,176 clutches. The high degree of nest overlap resulted in relatively low hatching success. We expect, however, that if erosion is arrested, the nesting space is likely to expand and thereby increase long-term hatching success at Gahirmatha.
Destruction and fragmentation of wildlife habitat often results in small, isolated populations that are highly susceptible to extirpation. In many cases, however, estimates of population size are lacking, precluding accurate assessments of population viability and sound conservation management recommendations. The Eastern Massasauga (Sistrurus catenatus) is a federally threatened pitviper species that has been extirpated throughout much of its historic range attributable to agricultural conversion of wetland habitat and other synergistic threats. Population size is generally unknown among extant massasauga populations, making site-specific management difficult. In this study, we estimated genetic effective population size (Ne) and census population size (Nc) for Eastern Massasaugas at two sites in southwest Michigan. For each population, we used mark–recapture models to estimate Nc and the linkage disequilibrium method to estimate Ne. Our results revealed small Nc, with approximately 108 (95% CI = 87–165) and 148 (95% CI = 102–295) adults estimated at our study sites in Cass County and Barry County, respectively. Estimates of Ne were even smaller: approximately 29.5 (95% CI = 21.2–43.1) for Cass County and 44.2 (95% CI = 30.8–69.3) for Barry County. Additionally, Ne/Nc ratios were similar across study sites, suggesting some stability in this ratio for Eastern Massasaugas, at least for populations in close proximity. Although we did not detect high levels of inbreeding or relatedness in either population, we caution that these small populations could become increasingly vulnerable to extirpation from unpredictable threats such as disease and climate change.
Anecdotal observations suggest that visual obstruction after capture will calm crocodilians, leading many to hypothesize that eye covering reduces physiological stress. However, this has yet to be tested empirically. To investigate this, we randomly divided 20 juvenile American Alligators (Alligator mississippiensis) into two treatments (visual obstruction [VO] and no obstruction [NO]) and took blood samples immediately after capture (baseline) and 30 min after treatment to determine the effects of visual obstruction on alligator corticosterone (CORT) levels. We found that baseline and post treatment CORT levels were similar between both NO-treated and VO-treated alligators; however, CORT levels were significantly elevated 30 min after capture relative to baseline in both NO and VO alligators. Our results indicate that visual obstruction does not prevent or reduce handling stress after capture in crocodilians and that any observed behavioral alterations are independent of changes in CORT levels.
Many turtle species, including Diamond-Backed Terrapins (Malaclemys terrapin), often nest shortly before and during rainstorms. We tested the hypothesis that rain can decrease the likelihood that nests will be depredated, presumably by reducing the chemical, tactile, or visual cues that predators use to locate turtle nests. We analyzed the impact of rainfall on predation rates of Diamond-Backed Terrapin nests in Jamaica Bay Wildlife Refuge, NY, USA from June–July 2016. Natural and artificial nests built on days with no rain or varying amounts of rain were monitored for 5 d after oviposition/construction. Predation rates were similar for both artificial and natural nests and decreased when nests were laid on rainy days. For artificial nests, that decrease was significant, and for natural nests the decrease was nearly significant. Predation rates on natural and artificial nests were inversely correlated with the amount of rain on the day nests were laid or constructed. These results indicate that selection may favor turtles that nest soon before or during rainfall.
Anthropogenic disturbances can have negative effects on species assemblages. This study was established to form baseline data on the environmental structure and reptile assemblages within a planned energy corridor in Pinal County, Arizona, prior to construction. We emphasized evaluating the differences in reptile assemblages in two subdivisions of the Sonoran Desertscrub, the Lower Colorado River Valley (LCV) and Arizona Uplands (AZU). Surveys were conducted on 50 sites (LCV = 15; AZU = 35) along the proposed 67.1-km long energy corridor through environmental surveys and 50 drift-fence trapping arrays with 400 box funnel traps. Vegetation height, number of burrows, and percent rock, ground cover, and coarse woody debris were significantly higher in the AZU than in LCV. Eighteen reptile species (n = 995 captures) were detected on the energy corridor including 8 lizard species (n = 952 captures) and 10 snake species (n = 43 captures). Species richness, evenness, and capture rates were not significantly different between the LCV and AZU; however, species diversity was significantly higher in the LCV. Reptile abundance (LCV = 281; AZU = 714) differed in the two subdivisions, yet rank-abundance curves revealed no difference in dominance of species. Post hoc examination revealed that the geographic separation of sites within the LCV and the location of the study area (along the ecotone) may have contributed to our results. We conclude that both subdivisions are equally important to the maintenance of local biotic diversity and recommend that any future land set-asides consider both subdivisions.
Occupancy models provide a reliable method of estimating species distributions while accounting for imperfect detectability. The cost of accounting for false absences is that detection and nondetection surveys typically require repeated visits to a site or multiple-observer techniques. More efficient methods of collecting data to estimate detection probabilities would allow additional sites to be surveyed for the same amount of effort, which would support more precise estimation of covariate effects to improve inference about underlying ecological processes. Time-to-detection surveys allow the estimation of detection probability based on a single site visit by one observer, and therefore might be an efficient technique for herpetological occupancy studies. We evaluated the use of time-to-detection surveys to estimate the occupancy of pond-breeding amphibians at Point Reyes National Seashore, California, USA, including variables that affected detection rates and the probability of occurrence. We found that detection times were short enough, and occupancy was high enough, to estimate reliably the probability of occurrence of three pond-breeding amphibians at Point Reyes National Seashore, and that survey and site conditions had species-specific effects on detection rates. In particular, pond characteristics affected detection times of all commonly detected species. Probability of occurrence of Sierran Treefrogs (Hyliola sierra) and Rough-Skinned Newts (Taricha granulosa) was negatively related to the detection of fish and pond area. Time-to-detection surveys can provide an efficient method for estimating detection probabilities and accounting for false absences in occupancy studies of reptiles and amphibians.
Studies of the structures that limit gape size in snakes contribute to the understanding of the function and evolution of the ophidian feeding apparatus. Although recent papers have investigated which morphological characteristics are important to gape in macrostomatans, such studies have yet to determine the contributors to gape size in nonmacrostomatans. I directly measured gape circumference by pushing a cone through the buccal cavity of 10 deceased Red-Tailed Pipe Snakes (Cylindrophis ruffus). For each individual, I measured snout–vent length (SVL), several external head dimensions, and the distance between the mandibles while distended on the cone. The soft tissue was removed from the skull to collect osteological measurements. External and osteological measurements were separately modeled with the use of the Akaike Information Criterion to determine which morphometrics were the best predictors of gape circumference. Like other snakes, gape circumference was negatively allometric with both SVL and cranium length. With the use of line equations from similar studies, C. ruffus exhibited a relatively smaller gape circumference than Crotalus atrox and Nerodia fasciata, but similar to Farancia abacura. Of the external measurements, cranium length and head width were the strongest predictors of gape circumference for Cylindrophis. No single osteological dimension was most important among the tested models, as five metrics ranked equally as the strongest predictors of gape circumference. The relatively small gape and stout skull of C. ruffus are likely adaptations for specialization on narrow, elongate prey and a fossorial lifestyle.
I describe a new species of Emoia that is the sixth member in the E. cyanogaster group. It differs from all other Emoia species in its distinctive pattern of serrated black stripes on an emerald-green ground color. Further distinguishing features include its relatively small size, long and narrow snout, large number of toe lamellae, and lack of a distinct interparietal. Specimens of the new species had previously been assigned to E tetrataenia, but the more elongated snout and unique color pattern easily distinguish it from the latter, which is restricted to the D'Entrecasteaux Islands. The new species is known only from Rossel Island in the Louisiade Archipelago, the southeasternmost island of Papua New Guinea, and it is likely endemic to that island. A combination of morphological and distributional evidence suggests that the new species, E. tetrataenia, and E kordoana are probably each other's closest relatives.
Green Salamanders, Aneides aeneus, are habitat specialists found in narrow crevices of rock outcrops and under flaky bark of trees. The species has a high conservation priority throughout its range and has been negatively affected by habitat loss, climate change, disease, and overcollection. In portions of the Blue Ridge Escarpment population, many historical locations for this species have not been visited since the 1980s or earlier. Across three counties in South Carolina, we conducted visual encounter surveys of known rock outcrops that were accessible, and used binoculars to conduct arboreal surveys in the adjacent forest. We detected Green Salamanders at 30 of the 61 sites surveyed (49.2%). We collected a variety of habitat variables and compared a suite of N-mixture models using an Akaike information criterion framework. Detection probability was positively influenced by time of day. A model of abundance that included aspect, habitat size, and elevation had the most support. Specifically, Green Salamanders were more abundant at larger sites at lower elevations with south-facing slopes. Knowledge of factors that influence population abundance will help guide future efforts to protect the species in the southern portion of its range.
Island ecosystems provide habitat for many endemic species that may be threatened by nonnative species introductions. We examined nonnative freshwater turtle occurrences and diets to examine potential predation effects on native species in Kawai Nui Marsh, Oahu, Hawaii. No freshwater turtles are native to the Hawaiian Archipelago. The Pond Slider (Trachemys scripta) and Chinese Softshell (Pelodiscus sinensis) were the only turtles found in the marsh after 767 trap days. Trachemys scripta stomachs (n = 50) contained mostly the nonnative plant Commelina diffusa and nonnative snails (Pomacea sp.), whereas Pelodiscus sinensis stomachs (n = 5) contained mostly snails. Interspecific dietary overlap was low and intersexual dietary overlap in the sliders was high, with more diverse female diets. Small, medium, and large size classes of T. scripta stomachs contained different proportions of plant and animal matter, with the small size class containing less plant matter than the medium size class, and the large size class containing a greater volume of animal than plant matter. No native species were found in the stomach contents of the turtles sampled except a freshwater sponge (Heteromyenia baileyi). This lack of native species in their diets may have more to do with the degraded state of the marsh and lack of native taxa than with a preference for nonnative taxa. A potential concern could be nonnative freshwater turtle presence in pristine wetland habitats in Hawaii, because of the higher abundances of native species in those areas.
The effect of temperature on embryonic development and offspring phenotype has received increasing attention. Most of these studies are based on constant-temperature incubations, however, rather than on fluctuating temperatures that mimic nest temperatures. In this study, we conducted a common garden incubation experiment on Asian Yellow Pond Turtles (Mauremys mutica), with a 2 (populations) × 2 (nest temperatures) factorial design, to identify the phenotypic consequence of embryonic responses to latitudinal variation in developmental temperatures. The embryos of the low-latitude population developed faster than those of the high-latitude population; hatching success and hatchling mass did not differ between populations or temperatures. The carapace length and width were not affected by incubation temperature but were greater in hatchlings from the low-latitude population than from the high-latitude population. The offspring from the high-latitude population had better righting ability (despite smaller body size) than those from the low-latitude population. Our results did not show a significant interaction between population origin and nest temperature on embryonic development, which contradicts the conclusion from the constant-temperature incubation experiments for this species. This highlights the importance of fluctuating-temperature effects (mimicking field nests) on the embryonic development in understanding the developmental plasticity of reptiles.
A new genus and species of colubroid snake is described from the isolated highlands of western Chiapas. This enigmatic little snake possesses a unique suite of characters that defies placing it in any known genus and clearly distinguishes it from all known genera. Several of the most unusual features include subcaudals undivided throughout the length of the tail and a simple hemipenis completely adorned with calyces and having a sulcus spermaticus that remains unbifurcated until the apical portion of the organ. Neither of these characteristics is known for any other colubroid of the Western Hemisphere. Consideration of morphology places the new snake in the Dipsadidae and suggests that Adelphicos, Atractus, Geophis, and Chapinophis are among its closest relatives.
We describe a new small species of Scinax from the rain forests on the interfluve between Purus and Madeira Rivers, Brazilian Amazonia. The new species is diagnosed by snout–vent length 20.2−22.5 mm in males; a yellowish-bronze dorsum showing small spots along the body and limbs; a red stripe horizontally extended on the medial portion of the iris; posterior surface of thigh brown, in both live and preserved specimens. The advertisement call consists of two types: type A represents a series of multipulsed notes (note duration 0.097−0.115 sec, dominant frequency 2,541−3,015 Hz); type B consists of a single tonal note (note duration 0.015–0.019 sec, dominant frequency 2,584–2,950 Hz).
The focus of amphibian conservation has recently shifted towards the establishment of genetic resource banks that, in association with assisted reproductive technologies (ARTs), can potentially function as a means of securing anuran biodiversity at risk of extinction. Gamete cryopreservation is one such technology that provides a mechanism for sustaining the genetic viability of small fragmented populations, and, therefore, has been championed as an important component of endangered amphibian conservation. Current technologies for gamete cryopreservation, however, are not without their adverse effects on cellular functions, and although there is an increasing body of literature regarding possible effects on traditional sperm parameters (such as motility and plasma membrane integrity), biologists know little about the effect of the freeze–thaw process on sperm DNA integrity. In addition, despite extensive literature detailing sperm chromatin organization and DNA fragmentation in mammalian species, current knowledge pertaining to amphibian sperm DNA is limited. Consequently, this review assembles current information on amphibian sperm chromatin organization and explores the effects of cryopreservation on DNA integrity; it is designed to prompt those working in the field of amphibian ART to consider the potential significance of sperm DNA damage as it relates to the assessment of amphibian spermatogenesis and sperm preservation procedures.