Authors: Florentino Braña, Luis Frechilla And Germán Orizaola

Abstract: We have analyzed the effect of introduced fish on amphibian assemblages in mountain lakes of the Cantabrian range (Asturias and León; northern Spain), by comparing amphibian species richness, abundance and diversity in lakes occupied by introduced fish and in those without fish. Amphibian species numbers were significantly lower in lakes inhabited by fish, both considering the absolute number and the values corrected for the effect of the main correlates of the species richness (shore extent and altitude). Amphibian abundance (all species and stages pooled) and diversity also tended to be lower in lakes inhabited by fish as compared with the fishless ones. Direct predation by fish, for which we present evidence in our studied lakes, is likely to be the main cause for the reported amphibian depletion, although recognition by adult amphibians of chemical cues from predatory fish and subsequent avoidance of habitats with fish for reproduction could also be contributory.

Authors: Nora R. Ibargüengoytía And Victor E. Cussac

Abstract: Viviparity has been reached independently by different genera of reptiles. Synchronization of the reproductive style with the environment facilitates offspring birth  and survival. Several authors postulate a close relationship between reproductive mode and environmentaI conditions in these species. Liolaemus pictus is a viviparous medium-sized lizard that lives to temperate habitats up to moderate altitudes in the Andean-Patagonian forest. Sexual dimorphism, follicle number and size in relation to body size, date and locality, reproductive cycle and litter size were studied. In the light of our results we reject an annual reproductive cycle for female Liolaemus pictus in favour of a multiannual one. As a different reproductive style among viviparus lizards, biennial (or triennial) reproduction enlarges the known diversity of reptilian reproductive responses to short and cold activity seasons, such as those typical of the highlands of southern South America.

Authors: D. Bejakovic, I. Aleksic , A. Tarasjev , J. Crnobrnja-isailovic, G. Dzukic, M. L. Kalezic

Abstract: We compared life-history attributes of Algyroides nigropunctatus, Lacerta oxycephala, Podarcis melisellensis and Podarcis muralis populations in the Lake Skadar region (mainland and islands). These lacertids are moderately sized with differing morphology (flattened vs. cylindrical). They have similar duration of egg incubation, size at onset of sexual maturity, size of hatchlings, and rate of juvenile growth. Clutch size is variable between populations and species: P. muralis produced larger clutches than the other species, especially A. nigropunctatus and L. oxycephala. A significant difference in egg size was apparent at the population level only. Smaller clutch size and elongated eggs were associated with a flattened body in L. oxycephala. A canonical discriminant analysis of reproductive variables showed that species similarities in ecological characteristics reflect phylogenetic relationships.

Authors: Aurora M. Castilla

Abstract: This paper reports on the selection of substrate temperatures at oviposition sites by female lizards Podarcis hispanica atrata under laboratory conditions. Seven females deposited 11 clutches (a total of 34 eggs) in very small areas, representing 20% of the available surface. The mean temperature of the sites used for egg-laying was 25.7 °C. Results are compared with incubation temperatures of the same species under natural conditions (Columbretes islands, Mediterranean, Spain).

Authors: L. Vincent Fleming , Barbara Mearns And David Race

Abstract: Changes through time in a small, isolated population of natterjack toads on the Solway Firth are reported. The area and linear length of coastline occupied by the colony have declined since it was first described in 1849. The colony now occupies less than 20% of its former range. The rate of decline has increased since the 1960s and has continued into the present decade. This decline has been accompanied by losses of breeding pools and habitat which can be directly attributed to anthropogenic changes in land-use. Comparison of aerial photographs between 1 946 and 1 988 show, amongst other changes, a major loss (>60%) of coastal sandy grassland, favoured by natterjacks, to agricultural intensification and to the recreational development which now surrounds the colony. Recent population monitoring ( 1 986-1 995) shows a failure of recruitment in five of the six years before 1991. During this period the annual peak counts fluctuated between nine and thirty adult males, well below a previous estimate in 1976 of 100 males. Artificial excavation of breeding pools in 1991 resulted in the subsequent production annually of large numbers of toad lets. A peak count of 79 males in 1 995 probably reflects the recruitment to the breeding population of these cohorts and gives the first indication of recovery in this population. Re-occupation of the former range is no longer possible. The expansion of the colony to areas of suitable habitat away from the native site, but with no previous records of natterjacks, is discussed.

Authors: Sandra Aparecida Santos, Marcelo Stoll Nogueira, Max Silva Pinheiro, Zilca Campos, William E. Magnusson And Guilherme M. Mourao

Abstract: The diet of Caiman crocodilus yacare was investigated during the dry season in different habitats of the Pantanal, Brazil. Stomach contents of 196 animals were analysed by prey class, the total number of prey, and the number of caimans eating each prey type. C. c. yacare ate mostly insects and fish. The caimans' diets differed significantly among habitats but not among caiman size classes.

Authors: Jaime Bosch And Rafael Márquez

Abstract: Determining the sex of midwife toads in the field is not easy. Non-pregnant females and males not tending clutches are difficult to sex without dissection. We provide a method to determine the sex of individuals based on the study of linear variables. Fifteen morphological variables were measured from samples of two species of midwife toad in the Iberian Peninsula (Alytes obstetricans and Alytes cisternasii). Some variables, corrected for the size of the animal, show significant differences between sexes. A discriminant analysis between the sexes in both species shows a high power for discrimination (95% in A. obstetricans and 97.6% in A. cisternasii). The significant variables in A. obstetricans were: snout-urostyle length, distance between the nostrils, distance between the anterior end of the middle metacarpal tubercle and the tip of the third finger, and distance from elbow to third finger tip. The significant variables in A. cisternasii were: head width, jaw bottom length, vertical diameter of the tympanum, distance between the nostrils, and tibia-fibula length.