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Variations in anuran movements and habitat use: Implications for conservation
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Anurans (frogs and toads) have suffered recent notable declines, and many species for long-term conservation may need protection from environmental disturbances. Protective measures depend on conserving areas actually used, and habitat use by anurans is poorly known. A total of 68 studies covering 50 species provided information used in this review. Eighteen studies (15 species) documenting post-breeding movement distances found frogs remained at their breeding site year-round, six studies (five species) recorded movements to new riparian areas and 33 studies (24 species) found frogs used separate terrestrial post-breeding sites. Mean movements to new riparian sites ranged from 38 to 700 m and terrestrial sites from 385 to 1810 m. With values varying greatly, movement for an average species was difficult to predict. Individual movement within studies also varied widely, resulting in wide scatter of study populations. When separate non-breeding sites were used, bufonid populations (range 30-800 m; n = 9) appeared to move further than hylids (35-594 m; n = 9). Maximum distances followed similar patterns. Body size was not a significant predictor of overall movement distance, but this was significantly greater in bufonids as adult size increased. Values were not apparently affected by breeding habit or study method. Frogs often overwintered at their post-breeding activity site (16 studies), but in 10 studies, at least some frogs moved to distinct and often protective overwintering areas. Mean home range was from 6.3 to 5099 m2 (mean 1773 m2; n = 18), and was not significantlyinfluenced by body size. Bufonids' habits wererelatively consistent, whereas these were more diverse in ranids and hylids. The wide scatter of data indicated that protective measures applied are uncertain to protect all or even most of a target population; detailed biological studies remain important to ensure conservation of populations.
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Effects of a low intensity fire on populations of pond breeding anurans in mid-northern New South Wales, Australia
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Low intensity burns within and adjacent to Chaelundi State Forest prompted comparisons of pre- and post-fire frog counts for six burnt and six unburnt pond areas. We used a before-and-after control/impact (BACI) approach to assess whether changes in total frog numbers, number of species and numbers of individuals of five common species varied significantly between the burnt and unburnt sites. Additionally, time since last fire, fire scar height from last fire and maximum fire scar height from any fire were scored for the vegetation surrounding 17 ponds in the area, and compared to frog counts obtained in November 2001. In the BACI study, the only significant source of variation for all analyses was found between the within-season counts, which could be extremely variable. Season, fire and the season × fire interaction were not significant. A Spearman Rank Correlation found no significant associations between counts and fire measurements for the 17 ponds. A review of the confidence intervals of our data revealed a low power to detect any effects because within-season counts varied so greatly. We estimate that a change of six species or 12 frogs per site would be needed to obtain a statistically significant result with the type of data collected. We recommend that effort in any future studies be directed to obtaining a much greater number of repeat counts per site/replicate sites, if such variation were to occur. Another possibility may be the strict control of the timing of surveys to within specific environmental conditions (e.g., temperatures between 18 and 22°C, and/or rainfall between 10 and 30 mm in the previous 72 hours). Such an approach may reduce variation to more manageable levels. The low intensity fire studied did not result in severe changes in frog numbers, but the presence of moderate changes or more subtle long-term changes cannot be discounted.
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Dispersal, home range establishment, survival, and reproduction of translocated eastern box turtles, Terrapene c. carolina
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The feasibility of translocation to establish a population of the eastern box turtle (Terrapene c. carolina) was studied at Floyd Bennett Field, Brooklyn, New York, USA. The 579 ha site,originally salt marsh, was filled during the 1920's to construct a now-abandoned airport. It consists primarily of grasslands, native shrub thickets and woodlands, and mixed stands dominated by giant reed (Phragmites australis). These human-created uplands are managed by the U.S. National Park Service for recreation and ecological restoration. Prior to this work, the site did not support a population of this species, but it is historically native to adjacent uplands. T. c. carolina were collected from sites on Long Island, New York, that were undergoing development, and released after data on size, mass, age, and sex were recorded. From 1987 through 1990, 335 individuals were released into developing woodlands. To provide data on dispersal, home range establishment, and initial survival, fifty-three of these were radio-tracked for up to seven years. Though individually variable, the T. carolina dispersed homeward. Of the 53 radio-tagged individuals, 13 (24.6%) left the site, 25 (47.2%) established home ranges, and 15 (28.3%) died before determination of home range establishment could be made. Most individuals established home ranges within a kilometer of the release point. However, some dispersed greater distances. Of the 25 individuals that established home ranges, 17 (68%) did so in the release year, two (8%) in outyear 1, three (12%) in outyear 2, and three (12%) in outyear 3. Annual known survival over five years post-release was 71%. Though not statistically significant, annual survival was 64% over the first two years and 84% over the final three. Principal causes of "mortality" were dispersal from the site and pneumonia, both of which were greatest initially, plus winter kill, a random event. Patterns of growth, home range size, activity season, habitat use, annual reproductive output, and production of young were generally comparable to natural populations of T. carolina. These results suggest that translocation may have potential for establishing new populations of T. carolina, though long term viability is still uncertain. However, any contemplated translocation would need to address the initially high loss to dispersal and disease. Moreover, since there are few sites of adequate size and quality, at least 500 ha of predominantly woody habitat, lacking populations of this species, its appropriateness is very limited.
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Morphological abnormalities and heavy metal concentrations in anurans of contaminated areas, eastern Ukraine
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High incidences of morphological abnormalities (mostly of limbs) and tumor-like dysplasias were recorded in three species of anurans (Bombina bombina, Bufo viridis, and Rana ridibunda) over 5 years in three areas of Dnepropetrovsk Province, eastern Ukraine. Wedescribe changes across years, and differences between species and developmental stages, in the frequency and types of deformity. The content of seven heavy metals (Fe, Zn, Mn, Cu, Pb, Ni and Cd) was also analyzed in water bodies and in R. ridibunda (separately for 11 organs). Four main factors were discussed as possible causes of morphological abnormalities; biogeography (edge of range); hybridization; infection; environmental contamination. The latter was the most likely cause, with significant correlations between frequencies of deformities and levels of environmental contamination. There was substantial variation among organs in the levels of heavy metals in R. ridibunda, as found in other anurans. Highest values were most common in the spleen and fat bodies, organs neglected in previous studies of this type. The ranking and accumulation of heavy metals, as well as their toxic/teratogenic effects, were reviewed. An interaction between heavy metals, organic contaminants, and water acidity was the most likely cause of mass abnormalities observed in anurans in eastern Ukraine.
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No effect of nitrate on gray treefrog (Hyla versicolor) tadpoles
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Frog farming: Investigation of biological and mechanical agents to increase the consumption of pelleted food by adult Rana temporaria
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The requirement of moving prey for eliciting feeding behaviour is typical of anurans, and is one of the major difficulties of rearing frogs. This difficulty can potentially be solved by using mechanical devices to move the food, or by mixing inert food with live prey. This study investigated consumption of pelleted food by adult common frogs, Rana temporaria, when moved by a mechanical stirrer or by fly larvae. The mechanical device did not produce higher consumption than inert pellets alone. Fly larvae significantly increased consumption of food pellets, whether these were mixed together, or the larvae were isolated below the pellets by a flexible membrane. Consumption was similar whether the membrane was sealed or perforated, so that movement of the pellets, rather than the scent of the fly larvae, was the stimulus that increased pellet consumption. Frogs did not apparently learn to feed on pellets, with no increase in consumption through the experiment of either control inert pellets or of pellets moved by fly larvae. Consumption (of dry mass) of pellets was similar to that of live crickets by frogs in the same conditions. Frogs consumed significantly more xenopus pellets (produced for aquatic Xenopus toads) than trout pellets from an equal mixture, both by number and mass. The two types of pellet had similar nutritional composition but differed in texture, smell, size and mass, and colour; xenopus pellets being larger (82 mg and 50 mg, respectively) and darker. Any combination of these differences could have caused the difference in consumption, with colour being most likely, darker pellets presenting greater contrast against the white background of the feeding dishes. The difference in consumption shows that optimisation of pellet characteristics, such as the incorporation of a dark dye, could be important in large-scale frog culture.
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Understanding the relationship between body temperature and activity patterns in the giant Solomon Island skink, Corucia zebrata, as a contribution to the effectiveness of captive breeding programmes
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The behaviour and body temperatures of the Giant Solomon Islands skink, Corucia zebrata, have been observed in a semi-naturalistic enclosure. Corucia zebrata is a non-basker that thermoregulates by selecting microhabitats where operative temperatures enable body temperatures of around 30°C to be maintained. Body temperatures were significantly higher during sunny weather, but there was no significant difference in body temperature variance. Body temperatures were significantly lower than operative temperatures in open locations or dappled sunlight, but higher than operative temperatures in shaded locations. Coefficients of determination (r2) showed that lizard body temperatures had less association with operative temperatures during sunny weather. The frequency of activity was greater in sunny weather, but the distances travelled during locomotory activity were not significantly different between weather conditions. The lizards were observed less frequently at the upper levels of the canopy during sunny weather. Enclosure design for captive animals should reflect both thermal and structural diversity to enable target body temperatures and appropriate levels of activity to be achieved. Captive breeding programmes may be the only means left for conserving C. zebrata, and information on the relationship between activity and thermal biology is crucial for effective captive breeding programmes.
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Incubation of alligator snapping turtle (Macrochelys temminckii) eggs in natural and agricultural soils
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Physicochemical properties of incubation substrates may affect embryonic growth, development, and sexual differentiation in oviparous species with temperature-dependent sex determination. Thus, the physicochemical modification of incubation substrates associated with anthropogenic activities may pose a risk to normal embryonic and hatchling development in the alligator snapping turtle (Macrochelys temminckii), an oviparous species with temperature-dependent sex determination. The present study evaluated the development of alligator snapping turtle embryos and hatchlings incubated in vermiculite, and in Tunica Soils Series from a natural nesting area and from a cotton farm. Differences between agricultural and natural soils included particle size composition, concentrations of phosphorus, nitrates (NO3), magnesium, manganese, potassium, calcium, sodium, and copper concentrations, salinity, and cation exchange capacity (CEC). Soil pH, and iron, boron and sulfate (SO4) concentrations were similar. Agricultural soils received applications of herbicides (glyphosate, fluometuron, pyrithiobac sodium, 2,4-D, trifluralin) and insecticides (methyl parathion, dicrotophos), and natural soils did not. No significant differences were detected in incubation period, clutch success, hatchling mass, sex ratio, or frequency of abnormalities in offspring from the different incubation substrates. Increases over a four-month period in mass and tail length of hatchlings incubated in natural soils were, however, significantly greater than in hatchlings incubated in other substrates. We therefore suggest that future studies should examine how physicochemical factors of incubation substrate affect hatchling growth.
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