Search

Thermal tolerances are affected by the range of temperatures that species encounter in their habitat. Daniel Janzen hypothesized in his “Why mountain passes are higher in the tropics” that temperature gradients were effective barriers to animal movements where climatic uniformity was high. Sea turtles bury their eggs providing some thermal stability that varies with depth. We assessed the relationship between thermal uniformity and thermal tolerance in nests of three species of sea turtles. We considered that barriers were “high” when small thermal changes had comparatively large effects and “low” when the effects were small. Mean temperature was lower and fluctuated less in species that dig deeper nests. Thermal barriers were comparatively “higher” in leatherback turtle (Dermochelys coriacea) nests, which were the deepest, as embryo mortality increased at lower “high” temperatures than in olive ridley (Lepidochelys olivacea) and green turtle (Chelonia mydas) nests. Sea turtles have temperature-dependent sex determination (TSD) and embryo mortality increased as temperature approached the upper end of the transitional range of temperatures (TRT) that produces both sexes (temperature producing 100% female offspring) in leatherback and olive ridley turtles. As thermal barriers are “higher” in some species than in others, the effects of climate warming on embryo mortality is likely to vary among sea turtles. Population resilience to climate warming may also depend on the balance between temperatures that produce female offspring and those that reduce embryo survival. [ABSTRACT FROM AUTHOR]

The red panda (Ailurus fulgens) has a similar diet, primarily bamboo, and shares the same habitat as the giant panda, Ailuropoda melanoleuca. There are considerable efforts underway to understand the ecology of the red panda and to increase its populations in natural reserves. Yet it is difficult to design an effective strategy for red panda reintroduction if we do not understand its basic biology. Here we report the resting metabolic rate of the red panda and find that it is higher than previously measured on animals from a zoo. The resting metabolic rate was 0.290 ml/g/h (range 0.204–0.342) in summer and 0.361 ml/g/h in winter (range 0.331–0.406), with a statistically significant difference due to season and test temperature. Temperatures in summer were probably within the thermal neutral zone for metabolism but winter temperatures were below the thermal neutral zone. There was no difference in metabolic rate between male and female red pandas and no difference due to mass. Our values for metabolic rate were much higher than those measured by McNab for 2 red pandas from a zoo. The larger sample size (17), more natural conditions at the Panda Base and improved accuracy of the metabolic instruments provided more accurate metabolism measurements. Contrary to our expectations based on their low quality bamboo diet, the metabolic rates of red pandas were similar to mammals of the same size. Based on their metabolic rates red pandas would not be limited by their food supply in natural reserves. [ABSTRACT FROM AUTHOR]

Sea turtles are vulnerable to climate change impacts in both their terrestrial (nesting beach) and oceanic habitats. From 1982 to 2012, air and sea surface temperatures at major high use foraging and nesting regions (n = 5) of loggerhead turtles (Caretta caretta) nesting in Greece have steadily increased. Here, we update the established relationships between sea surface temperature and nesting data from Zakynthos (latitude: 37.7°N), a major nesting beach, while also expanding these analyses to include precipitation and air temperature and additional nesting data from two other key beaches in Greece: Kyparissia Bay (latitude: 37.3°N) and Rethymno, Crete (latitude: 35.4°N). We confirmed that nesting phenology at Zakynthos has continued to be impacted by breeding season temperature; however, temperature has no consistent relationship with nest numbers, which are declining on Zakynthos and Crete but increasing at Kyparissia. Then using statistically downscaled outputs of 14 climate models assessed by the Intergovernmental Panel on Climate Change (IPCC), we projected future shifts in nesting for these populations. Based on the climate models, we projected that temperature at the key foraging and breeding sites (Adriatic Sea, Aegean Sea, Crete, Gulf of Gabès and Zakynthos/Kyparissia Bay; overall latitudinal range: 33.0°—45.8°N) for loggerhead turtles nesting in Greece will rise by 3–5°C by 2100. Our calculations indicate that the projected rise in air and ocean temperature at Zakynthos could cause the nesting season in this major rookery to shift to an earlier date by as much as 50–74 days by 2100. Although an earlier onset of the nesting season may provide minor relief for nest success as temperatures rise, the overall climatic changes to the various important habitats will most likely have an overall negative impact on this population. [ABSTRACT FROM AUTHOR]

The decline in snake populations has been attributed primarily to anthropogenic disturbances, including habitat destruction and fragmentation. We radio-tracked Northern Pinesnakes ( Pituophis m. melanoleucus) in a military Target Zone and in the surrounding undisturbed buffer zone at the Warren Grove Gunnery Range in the New Jersey Pine Barrens, USA, to examine differences in spatial movement patterns and behavior. There were no differences in home range size ( X¯ = 60.0 ± 32.7 ha), core activity area ( X¯ = 10.6 ± 8.2 ha), range length ( X¯ = 1294.8 ± 32.7 m), or mean distance traveled per day ( X¯ = 65.2 ± 30.1 m) across all snakes, or between sexes (male n = 13, female n = 11), or location within ( n = 13) or outside ( n = 11) of the Target Zone. However, there were differences between tracking years. Northern Pinesnakes in 2005 and 2006 ( n = 13) traveled greater total distance and mean distance per day and had larger home ranges compared to snakes radio-tracked in 2003 and 2004 ( n = 11). In 2005 and 2006, snakes in the Target Zone traveled longer distances compared to snakes outside the Target Zone. Pinesnakes used both the Target Zone and undisturbed buffer zone for mating, nesting, foraging, and hibernating. Although the Target Zone was disturbed regularly, the open-canopied landscape, cover availability, and sandy soils maintained habitat for Northern Pinesnakes. Our data indicate that the military disturbance had little impact on the spatial ecology of Northern Pinesnakes; the disturbed area supported enough natural habitat features used by Northern Pinesnakes and was surrounded by a large tract of undisturbed landscape. These data can aid in developing mitigation and conservation strategies where the habitat of Northern Pinesnakes is threatened by development, in particular, across other military installations, which commonly overlap with the occurance of Northern Pinesnakes. [ABSTRACT FROM AUTHOR]

Habitat degradation and species introductions are two of the leading causes of species declines on a global scale. Invasive species negatively impact native species through predation and competition for limited resources. The impacts of invasive species may be increased in habitats where habitat degradation is higher due to reductions of prey abundance and distribution. Using stable isotope analyses and extensive measurements of resource availability we determined how resource availability impacts the long term carbon and nitrogen assimilation of the invasive red-eared slider turtle (Trachemys scripta elegans) and a native, threatened species, the red-bellied turtle (Pseudemys rubriventris) at two different freshwater wetland complexes in Pennsylvania, USA. At a larger wetland complex with greater vegetative species richness and diversity, our stable isotope analyses showed dietary niche partitioning between species, whereas analyses from a smaller wetland complex with lower vegetative species richness and diversity showed significant dietary niche overlap. Determining the potential for competition between these two turtle species is important to understanding the ecological impacts of red-eared slider turtles in wetland habitats. In smaller wetlands with increased potential for competition between native turtles and invasive red-eared slider turtles we expect that when shared resources become limited, red-eared slider turtles will negatively impact native turtle species leading to long term population declines. Protection of intact wetland complexes and the reduction of introduced species populations are paramount to preserving populations of native species. [ABSTRACT FROM AUTHOR]

We compared small mammal community composition among undisturbed habitats and habitats disturbed by military operations on Warren Grove Gunnery Range (WGR) in the New Jersey Pinelands. WGR is one of the largest tracts of protected land within this globally rare ecosystem. Disturbance in the form of fire, mowing, soil disruption and logging has had a large effect on small mammal occurrence and distribution. Of the 14 small mammal species that occur in the Pinelands, 9 live on WGR, including large populations of the southern bog lemming ( Synaptomys cooperi Baird, 1858) and meadow jumping mouse [ Zapus hudsonius (Zimmermann, 1780)]. Simpson's Index of Diversity was 0 for most disturbed sites and was generally greater in wetlands than in uplands. White-footed mouse [ Peromyscus leucopus (Rafinesque, 1818)] was the most common species on WGR and had a dominant effect on species diversity and community similarity indices. It dominated upland habitats and was the only species to occur in several disturbed habitats, whereas all 9 species occurred in wetlands. Principal components analysis indicated that most variation in species diversity was explained by disturbance and differences between upland and wetland habitats, due to presence of white-footed mice in disturbed and upland sites. Meadow jumping mice, southern bog lemmings and red-back voles [ Myodes gapperi (Vigors, 1830)] were positively correlated with wetland habitats, and pine voles [ Microtus pinetorum (Le Conte, 1830)], short-tail shrews [ Blarina brevicauda (Say, 1823)] and eastern chipmunks [ Tamias striatus (Linnaeus, 1758)] were associated with uplands. Habitat heterogeneity at WGR, including extensive undisturbed wetlands and uplands supported a rich diversity of small mammal species. [ABSTRACT FROM AUTHOR]

The hypothesis that low skin reflectance (melanism) provides an advantage for thermoregulation under cold conditions has received mixed support in ectothermic vertebrates. We selected a model system, three allopatric closely related species of cordylid lizards that differ in skin reflectance, to test this hypothesis. Cordylus niger and Cordylus oelofseni are melanistic and inhabit peninsular and montane areas, respectively, whereas Cordylus cordylus is more widespread and inhabits low inland areas. By combining theoretical, experimental, and field data on these species, we demonstrate that the difference in body temperature (Tb) between melanistic and non-melanistic lizards under ecologically relevant climate variation ranged from 0° to 2°C. Despite its small magnitude, however, the faster heating rate and higher Tb of melanistic species relative to non-melanistic species conferred an advantage under cold conditions. Comparison of habitat thermal quality (de) and thermal accuracy (db) across species indicated that, in winter, melanism conferred the greatest advantage during small windows of thermal opportunity. This finding was most pronounced for C. oelofseni, which is most constrained by cold temperatures in its habitat. By contrast, due to their rock-dwelling habits, melanistic and non-melanistic species benefited from rock refugia in summer, giving similar levels of thermoregulatory effectiveness across species, regardless of skin reflectance. This study therefore demonstrates that skin reflectance variation across cordylids has significant effects on their thermal balance. Furthermore, studies investigating the role of varying skin reflectance in field populations and species should incorporate fine and broad temporal scales (daily, monthly, and seasonal), environmental variability, and cost-benefit trade-offs of thermoregulation. [ABSTRACT FROM AUTHOR]

Preferred body temperatures (Tsel) of ectotherms are important for ecological and evolutionary studies. In lizards, the measurement of Tsel is controversial for several reasons, generally related to hypotheses addressing how Tsel may evolve in the wild. Although seldom explicitly tested, evolutionary hypotheses of adaptation to local climate require that Tsel meets the conditions of natural selection, which include repeatability, heritability and a link to fitness. Here, we investigated repeatability (τ, intra-class correlation coefficient) of Tsel at several time-scales using four Cordylid species from heterogeneous thermal habitats. Although there was significant inter-individual variation within days (P < 0.005 in most cases), there was no significant inter-individual variation when calculated across several days (P > 0.05). Repeatability was low in all species investigated (from 0 to 0.482) when compared against other estimates of repeatability of Tsel in the literature. Irrespective of how Tsel was calculated, it showed inconsistent and variable temporal effects across species. Furthermore, repeatability of Tsel did not change with acclimation to laboratory conditions. These data have implications for understanding the evolution of thermoregulation in these and other ectotherms. [ABSTRACT FROM AUTHOR]

Sea turtles bury their eggs in nests at depths ranging from 25 to 100 cm. After hatching, turtles crawl up to the surface and emerge over several days. Some hatchlings fail to emerge and die in the sand column. In this study, we investigated the effect of the depth of the drying front (the region separating saturated and partially dry sand), number of hatchlings emerging, depth of nest and temperature on the emergence of hatchling leatherback turtles (Dermochelys coriacea) over the course of three nesting seasons (2008-2009, 2011-2012 and 2012-2013) at Playa Grande, Costa Rica. The depth of the drying front affected the number of hatchlings that failed to emerge in all years and high temperature reduced emergence rate in 2008-2009 and 2012-2013, but not in 2011-2012. Most of the variability in emergence rate was explained by the number of hatchlings emerging and the depth of the drying front. The number of dead hatchlings was mainly explained by the depth of the drying front and temperature. Depth zones within the sand column that included the drying front and the egg chamber registered the greatest number of dead hatchlings. The depth of the drying front, temperature and number of hatchlings remaining in the sand column increased and the emergence rate decreased as the season progressed. Leatherback turtles are critically endangered in the eastern Pacific Ocean. Conservation strategies towards improving the conditions in the nest environment (i.e. nest irrigation and shading to decrease the depth of the drying front and temperature) could boost hatchling production and contribute to revert declining population trends. [ABSTRACT FROM AUTHOR]

Anthropogenic stressors such as habitat loss are a global problem for wildlife. Coastal development in the United States has replaced estuary shorelines with hard erosion barriers. In Barnegat Bay, New Jersey, the diamondback terrapin ( Malaclemys terrapin ) encounters these barriers when approaching upland beaches for nesting. To determine the effects of shoreline barriers on this threatened species’ nesting abilities, we measured adrenocortical response (i.e., stress response) by comparing natural corticosterone and testosterone levels of 91 terrapins following in situ exposure to either an experimentally blocked, or open nesting beach. In addition, we exposed 15 individuals, from various nesting beaches, to handling stress to identify acute corticosterone secretion, finding a significant increase over 60 min to 8 ng/ml. Corticosterone did not reach this level in terrapins exposed to barriers. Corticosterone and testosterone levels were not significantly higher among terrapins exposed to barriers compared to those at open reference beaches. This lack of a stress response suggests that terrapins do not physiologically respond to barriers when they approach nesting beaches and thus are not stressed. This may be due to an adaptive trait to help female turtles complete the nesting process despite the natural stresses inherent to coming on land. Our study suggests that this lack of stress response is also applied to non-natural, human made nesting barriers. If terrapins are not physiologically capable of adapting to shoreline barriers, future erosion control structures could support terrapin nesting with periodic upland access points. This endocrinological study provides a more quantitative approach to guiding management of anthropogenic stressors upon wildlife. [ABSTRACT FROM AUTHOR]

Although there has been a global decline in herpetofaunal species, populations in some areas have been more impacted than others while other areas show no decline. Therefore, it is important to establish baseline data and monitor existing populations to determine whether herpetofaunal declines are a natural fluctuation or a result of anthropogenic impacts. The spatial and temporal heterogeneity of habitats within the New Jersey Pinelands support a diverse assemblage of herpetofaunal species (39 native and 23 non-native species). The Warren Grove Range (WGR) occupies 3810 hectares of upland pine-oak forests, wetlands, and disturbed sites created by military operations. We conducted a study during 2002-2005 at WGR to develop baseline data and assess whether military operations are having an impact on species composition. We identified 29 native species of herpetofauna from ten different habitats, including thirteen snake, six anuran, six turtle, three salamander, and one lizard species. Native species were widely distributed throughout WGR. Of the 593 captures 57.2% were anurans, 24.6% were snakes, 8.9% were lizards, 7.3% were turtles, and 2% were salamanders. Species richness (n = 29) represented 74% of native Pinelands species. Habitat integrity at WGR supports a significant herpetofauna population including nine species with New Jersey state status. We did not inventory any nonnative species and military operations do not appear to be negatively impacting species composition. While native species impacts associated with development and forest fragmentation have increased throughout the Pinelands, the WGR remains an important refuge and contiguous tract of land for native Pinelands species. [ABSTRACT FROM AUTHOR]

Crotalus horridus is a state-endangered species and occurs as a disjunct population in the Pinelands of southern New Jersey. The Warren Grove Gunnery Range (WGR) occupies 3810 hectares of upland pine-oak forests, wetlands, and disturbed sites created by military operations. During fall 2002-fall 2004, we used radio telemetry to monitor the home range and movements of three female and six male C. horridus. Radio-tracked snakes did not enter the immediate vicinity of the target zone. Incidentally captured and radio-tracked snakes exhibited an affinity for wetland habitats compared to upland habitats. There were no significant differences in home range size, seasonal activity, core activity area, range length, distance traveled per day, or seasonal differences in movements between male and female snakes. Crotalus horridus utilized hardwood swamp habitat proportionately more than six other habitat types at WGR. In addition to quantifying movement behavior we found 12 hibernacula in undisturbed wetland habitats and we observed C. horridus mating and reproducing. It appears that military operations are not significantly impacting the C. horridus population at WGR. The population of C. horridus and military operations coexist on WGR because they occur in different areas. Our results suggest that WGR is an important refuge for C. horridus in the Pinelands. [ABSTRACT FROM AUTHOR]