Authors: Marco A. L. Zuffi

Authors: A. KUPFER AND S. F. M. TEUNIS

Authors: Xin Lu

Authors: Toshiaki Hirai And Masafumi Matsui

Abstract: Rana nigromaculata and R. rugosa consumed different food resources when they coexisted in Japanese rice fields. Rana nigromaculata consumed prey from many taxa including a small proportion of ants (16% in number of the total prey items), while R. rugosa ate mainly ants (56%). However, presence of the same terrestrial prey types in the bulk of their diets suggests that the frogs forage on the ground syntopically, and do not partition their feeding sites. Moreover, the comparatively wider mouth of R. rugosa (relative to similiar sized R. nigromaculata), suggests that R. rugosa does not eat more ants because of morphological constraints. This dissimilar pattern of food resource utilization seems to have resulted from selection of different prey, as indicated by the stronger avoidance of ants by R. nigromaculata compared to R. rugosa. This food partitioning may be facilitating their coexistence in rice fields.

Keywords: Rana nigromaculata, R. rugosa, food partitioning, prey selection, syntopic foraging

Authors: El Hassan El Mouden , Mohammed Znari And Claude Pieau

Abstract: The effects of temperature on incubation time, embryo survival, sex ratio , embryo growth and size at hatching were investigated in the north African Agamid lizard, Agama impalearis. Seven constant temperature treatments (spanning 20-36°C) were employed and a split clutch design was used to assign eggs from the same clutch to the different treatments. Incubation time varied significantly with temperature treatments. Embryos incubated at 32°C, 34°C and 36°C hatched between 41 and 46 days, whereas embryos incubated at 26°C and 28°C hatched at 83 and 67 days respectively. Hatching success was higher at 28°C, 30°C, 32°C and 34°C, but much lower at 26°C and 36°C; hatching did not occur at 20°C. Eggs incubated at 26°C and 36°C produced only females. At 28°C, 30°C, 32°C and 34°C, the percentages of males were 9%, 53. 5%, 32%, and 58% respectively. These sex ratios can be explained by a temperature-dependent mechanism of sex determination. The relative growth rates are highest early in incubation and lower for several days prior to hatching. The relationship between snout-to-vent length and age of embryos seems to be best described by a polynomial fitted regression. Growth rates at 26°C were much lower than those at 34°C. Constant incubation temperatures affected both snout-to-vent length and body mass at hatching, with maximum body size occurring at intermediate constant incubation temperatures (30°C, 32°C and 28°C). According to this study, the optimal temperatures of embryonic development probably lies within the range 28-34 °C. The possible adaptive significance of incubation temperature effects on some life history characteristics of A. impalearis is discussed.

Keywords: incubation temperature, embryonic development, sex determination, Agama

Authors: J. R. Downie, S. R. Livingstone And J. R. Cormack

Abstract: Trinidad's only dendrobatid frog, Mannophryne (=Colostethus) trinitatis, lives by the small streams draining the slopes of the Northern Range mountains and at Tamana Hill in the Central Range. Adults are often very abundant, but tadpoles are found patchily in the streams. In the absence of two potential predators - the fish Rivulus hartii and shrimps of the genus Macrobrachium - tadpoles are abundant in pools. Where the predators are present, tadpoles are uncommon or absent. Tadpoles may also be found in small, isolated bodies of water at some distance from streams. Males carrying tadpoles retained them for 3-4 days, in the absence of suitable pools. When presented with a choice of pools, males preferred to deposit their tadpoles in pools lacking predators. There were differences in behaviour between males from the northern and southern slopes of the Northern Range. For example, north coast males deposited tadpoles in pools containing other conspecific tadpoles in preference to empty pools, whereas males from southern slopes made the opposite choice. When presented only with pools containing predators (i.e. shrimps or fish), north coast males shed their tadpoles in damp leaf litter rather than in the pools, while males from the southern slopes deposited tadpoles in pools with shrimps - predators uncommon in the southern slopes streams. The results indicate that male frogs spend some time searching for predator-free pools in which to deposit their tadpoles. These results are discussed in the context of other examples of anti-predator reproductive behaviour in frogs, and of life history evolution under the influence of different selective pressures.

Keywords:  Dendrobatids, Trinidad, tadpole-deposition, predator-avoidance, Rivulus

Authors: F. Sequeira, H. Gonçalves, M. M. Faria, V. Meneses And J. W. Arntzen

Abstract: We studied the activity pattern and small-scale spatial distribution of the golden-striped salamander, Chioglossa lusitanica, in a forest plot in northwestern Portugal. A large proportion of the local population inhabited an underground watercourse and foraged in the woodland, leaving and entering the underground shelter through three holes. Surface activity - measured as the number of salamanders out in the open and their distance from the inferred shelter- was positively associated with relative humidity and precipitation. A negative relationship between dispersion distance and temperature was found in females. Distances moved were higher for adult salamanders than for juveniles. Spatial models indicated that males, females and juveniles differed in habitat utilization. The frequency of occurrence of salamanders at the surface was highest in the area of the stream (adults andjuveniles), near dry-stone wal ls (males andjuveniles), in areas with a higher than average density of trees (adults) and in areas of dense undergrowth (females). The results suggested that (I) the underground watercourse served as a retreat from which the salamanders would visit the surface, (2) dry stone walls functioned as retreats ratherthan as foraging grounds, and (3) trees and dense vegetation served as shelter for foraging salamanders. The results are compared with those for phylogenetically related and morphologically similar species.

Keywords: Chioglossa lusitanica, distribution, habitat, spatial model, Portugal