Authors: José Martín, Pilar López And Andrés Barbosa

Abstract: Morphological adaptations ofamphisbaenians to fossorial life may affect their anti-predator behaviour and escape decisions. Amphisbaenians exposed on the soil surface by a predator may decide to escape either by burrowing immediately or by using alternative defensive behaviours. This decision may depend on the internal state (body temperature and associated burrowing performance) but, because anti-predator behaviours may be costly, an optimal response should also be sensitive to risk and vary according to the threat of predator attack. In a laboratory experiment we simulated predatory attack on individual amphisbaenians of the species Blanus cinereus, and specifically examined the effects of temperature (warm vs. cold) and predation threat (low vs. high) on escape decisions. Amphisbaenians showed significantly longer episodes of an alternative anti-predator behaviour on the soil surface (coiling) when the predation threat was high and when the temperature was low. The time to burrow until half of the body was buried was significantly longer when the temperature was low and was significantly shorter when the threat was high. The variations observed in anti-predator behaviours may reflect the choice of the optimal response under each circumstance, taking into account the estimated predation risk, which is dependent on the characteristics of the initial attack, and potential burrowing performance, which is dependent on body temperature.

Keywords: predation, escape behaviour, fossorial reptile, Blanus cinereus

Authors: Alfredo Ortega-rubio, Gonzalo Halffter And Robert Barbault

Abstract: We studied the population dynamics of Sceloporus scalaris from 1 979 to 1 982 using mark-recapture methods. The estimated population density was 50 adults per hectare. The sex ratio was approximately 1:1, with females slightly predominating at older ages. Based on morphological data, four well-differentiated age classes were established - juveniles, sub-adults, adults < 1  yr and adults > 1yr. The mean clutch size was 8.8 eggs per female, but varied widely (5 to 12) in relation to female body size. The estimated number of hatchlings in 10 hectares was 2245 and embryo mortality was 13.89%. After hatching, the average mortality was higher than 76% for all ages and both sexes. The population life table indicates a Slobodkin Type IV survivorship curve, with a net reproductive rate of 1 .059. The average generation time for this population was 1.2 years.

Keywords: lizard, Mexico, population dynamics, Sceloporus scalaris

Authors: Marisa Esteban And Borja Sanchiz

Abstract: Age, body size and histological bone growth were analysed in two populations of Rana iberica that were genetically similar and which represented the attitudinal extremes of the species range. In spite of having a much longer hibernation, mountain frogs were significantly bigger (snout-vent lengths) for all ages, with the exception of the pre-maturity period. Mountain frogs were longer-lived (oldest females 6 years, males 5 years, one male outlier 9 years) than lowland frogs, where at most only one individual of each sex attained the age of 4 years. The minimum age at sexual maturity was 2 years for both sexes and populations. For both sexes, and using different assumptions about the duration of the period of seasonal activity, the relative contribution of the growth rate component seems slightly higher ( 46-75 % for females, 60-82 % for males) than differences in I ife span (i.e. total days of activity: 25-54 % for females, 1 8- 40 % ) in accounting for the overall size differences found between populations.

Keywords: age, altitude, Anura, growth, skeletochronology

Authors: Xiang Ji And Ping-yue Sun

Abstract: Female Ptyas korros from a population on Dinghai, Zhoushan Islands, in eastern China, produced one clutch per breeding season. Clutch size varied from 7 to 1 4, and was positively correlated with female SVL. The duration of incubation at 30 ± 0. 5 °C averaged 54. 7 days. Dried shells from freshly laid eggs averaged 30.0% of the entire egg dry mass. Egg contents of the freshly laid egg contained higher quantities of dry material, non-polar lipids and energy than did newly hatched hatchlings. Shells from freshly laid eggs contained higher quantities of ash than did those from hatched eggs. During incubation, approximately 77% of dry material, 54% of non-polar lipids and 69% of energy in the egg contents of freshly laid eggs were transferred to the hatchling. There were inverse relationships between carcass dry mass, post-hatching yolk dry mass and fat body dry mass for hatchlings sampled immediately after hatching. Post hatching yolk could be used to support subsequent growth of newly emerged young, as indicated by significant increases in the carcass dry mass and SVL of hatchlings during their first days of life, following the depletion of post-hatching yolk

Keywords: Colubridae, Ptyas korros, incubation, egg, hatchling, post-hatching

Authors: Paulo Sá-sousa

Abstract: The geographic distributions of two forms of the Iberian wall lizard (Podarcis hispanicus) in Portugal were determined through extensive field surveys. Predictive models of probability of occurrence were developed for both forms of P. hispanicus, based on multivariate logistic regression of environmental variables. On a coarse scale, the best-fit models suggested that the distribution of the north-western form of P. hispanicus can be largely explained by environmental variables such as altitude, mean annual temperature and number of frost days per year. The distribution of the south-western form of P. hispanicus is also explained by altitude and temperature, but the type of climate also appears important. Predicted probabilities of occurrence broadly match the known distributions range of the two forms. Where predicted distributions are not confirmed by field surveys, historical and/or interspecific factors may be more important than environmental variables in influencing the distribution of the lizard.

Keywords: Podarcis, wall lizard, distribution, GIS

Authors: Rafael Marquez , Ignacio De La Riva , And Jaime Bosch