The reliability of basking counts as indices of relative abundance for Emys orbicularis was tested in a pond system in central Italy. For different field conditions  regression was carried out between basking indices and population size estimates obtained by capture and recapture methods. Regression was particularly significant in midday hours of sunny days from May to July, suggesting that in these conditions basking counts can be used as indices of population size.

Comparisons within and among populations offer important insights into variation in life-history traits and possible adaptive patterns to environmental conditions. We present the results of observed differences in body size, body shape and patterns of reproduction in four separate populations of the European pond turtle Emys orbicularis in central and southern Italy – coastal (n=3) and mountainous (n=1) sites and pond (n=2) and canal (n=2) habitats – to determine whether phenotypic plasticity affects reproductive output. Although we did not find any significant latitudinal variation in body size, we observed significant differences in body shape between canal (rounded body shape) and pond (elongated body shape) systems and smaller size with rounded shape in the mountainous population. Reproductive output is similar among populations (median=5 eggs per clutch), whereas reproductive investment (relative clutch mass to maternal body mass) is higher in the mountain population (one clutch per year) than in coastal populations (two clutches per year), suggesting differential trade-offs between geographic locality, elevation and habitat type. Turtle shell shape and geographic location together affect reproductive output in E. orbicularis in Italy.

The reproductive biology and ecology of the European pond turtle Emys orbicularis is little known, and available information was previously mainly anecdotal. Morphological data on E. orbicularis are now well than in southern populations. There are also indications that clutch size may be larger in northern than in documented in most of the known distribution area. Body size in northern populations tends to be larger southern European pond turtle populations. Clutch size and reproductive status of a central Italy population were detected by radiography and palpation, respectively, and comparative data were obtained by direct count of intact nest eggs. Reproductive females averaged 13.9 cm and rarely exceeded 15.5 cm carapace length. They produced a clutch size of six, the same number found in intact nests. Nest egg-size averaged 32 mm in length. Egg number was positively associated with female body size, and especially with carapace height.

The European pond turtle, Emys orbicularis (L., 1758), is threatened throughout its distribution, prompting management of habitats and populations for conservation. Quantitative data on habitat requirements for this species are needed to better evaluate which areas are the most suitable, or what actions can improve habitat suitability. We studied relationships between the distribution and abundance of E. orbicularis and the environment by analysing water quality and features of 39 wetland and upland habitats in the Po River delta of northern Italy; visual transects and point counts were used to determine turtle presence and relative abundance. Emys orbicularis occurs more frequently and abundantly in permanent wetlands surrounded by woodlands, and its presence does not appear to be related to water eutrophication. Woodlands strongly influence adjacent wetland features and may be important for turtles’ terrestrial activities such as nesting and dispersal. Habitat management and conservation plans for E. orbicularis should include protection of extensive terrestrial woodland habitat containing diverse wetland systems, to support turtle survival at different life-history stages. The requirements for wetlands and natural terrestrial habitat are difficult to meet in the currently human-dominated European lowlands; nevertheless, conservation plans for this species should take a broad-scale approach.

Our main objective was to establish the population size, density, body size, and sex ratio of a local Emys orbicularis population. We examined the population structure of E. orbicularis in Lake Yayla, Buldan (Denizli), Turkey, using capture-recapture methods. The population consisted of 54% males, 42% females, and 4% juveniles. The adult sex ratio was significantly skewed in favor of males. Using the Jolly program, the population size was estimated at 1,462 (95% CI = 1,161–1,763), corresponding to a density of 81 turtles per hectare of optimal habitat. Females were larger than males. In carapace length, the Lake Yayla population resembles other small-sized populations inhabiting the southern parts of the species’ range. The conservation status of the Turkish populations and their main threats are also discussed.