Authors: Rafael Marquez, Jose Luis Olmo, And Jaime Bosch

Authors: Geoffrey R. Smith

Authors: Adrian Hailey And Michele Elliot

Abstract: The mean selected temperature of Zygaspis quadrifrons in a thermal gradient was 23 .1°C, similar to other amphisbaenians. Body temperatures of amphisbaenians are lower than those of other squamates, but are similar to those of fossorial snakes and lizards, apart from skinks. The precision of thermoregulation in Z. quadrifrons was low; body temperatures had a SD of 3.8°C and an interquartile range of 6.0°C.

Authors: Jacques Bons And Philippe Geniez

Abstract: We have analysed several scalation characters and the geographic distribution of lizards of the Acanthodactylus erythrurus group to verify the validity of these criteria. These data are collated with biogeography to demonstrate the existence of two distinct species within what are known as common fringe-toed lizards: Acanthodactylus erythrurus, consisting of three subspecies, and A canthodactylus lineomaculatus, monotypic and endemic to Morocco. Hypotheses concerning the population history of these animals are proposed.

Authors: Karen Tocque, Richard Tinsley & Tricia Lamb

Abstract: The ecology of the desert toad, Scaphiopus couchii, is very precisely regulated by summer rainfall, such that emergence may be less than 20 nights/year. There are estimates in the literature that, at best, S. couchii can obtain its entire annual energy requirement from a single, very large meal, comprising of 50% its body weight in lipid-rich termites. However, our field data from the San Simon Valley in southeast Arizona, show that the toads are generalist feeders, taking prey groups which appear in sequence during the short summer season, including a remarkable range of noxious animals (solpugids, scorpions, centipedes and pogonomyrmid ants). Alate termites emerged briefly after the first rains and seldom represented a major component of the diet. On the other hand, beetles and other hard-bodied insects formed a consistent food type throughout the season. Alate termites represented around 24% of the total food items ingested by S. couchii and when prey size (length) was taken into account their contribution to the annual intake was around 20%. Beetles, on the other hand, contributed (by size) around 33% to intake, with ants representing around 1 9% and all other items each representing less than 8%. Differences in prey type, total food ingested and temperature all significantly influenced the weight change of individual toads fed under controlled laboratory conditions. Animals which were fed more frequently grew more rapidly, since weight increases were correlated with food intake. However, for any given intake, increases in weight were significantly lower at high environmental temperatures (3 1 -33°C compared with 20-24°C), presumably due to increasing metabolic demands with temperature. The nutritional quality of the food significantly influenced body weight change and fat body accumulation: toads amassed excessively large fat bodies (representing up to 1 4% body weight) when fed with lipid-rich mealworms, compared with those fed crickets (fat bodies up to 1 0% body weight), and toads fed woodlice had virtually no fat bodies after eating an equivalent number of meals. These studies show that the natural prey range of S. couchii varies in time and space, and when toads consume high energy foods, weight increase and fat deposition are very efficient. However, the frequent ingestion of other foodstuffs, lower in calorific value, suggests that a greater number of meals are necessary to accumulate the total annual energy requirement. These other prey items may provide essential nutrients that are lacking from lipid-rich foods.

Authors: Werner Himstedt And Dietmar Simon

Abstract: The caecilian Ichthyophis kohtaoensis is able to localize prey objects by chemical cues only. On the surface of the ground I. kohtaoensis moves faster and on a more direct path towards prey than does the newt Triturus alpestris. Blocking the tentacles in the caecilian does not impair this ability. Within artificial tunnels, however, caecilians with blocked tentacles took longer to reach the prey than control animals did. Blocking the nostrils led to complete failure of prey localization on the surface of the ground.

Authors: José A. Díaz

Authors: Sergius L. Kuzmin

Abstract: Competition occurs when resources are limited and may be determined only by its effects on the component species. It must change the condition ofresources and the fitness of competitors (or at least part of them) so that both are negatively affected. Original data and analysis of the literature revealed that food competition in amphibians is usually discussed in terms of (1) negative interactions between individuals; (2) density-dependent responses of individuals; (3) density-dependent responses without estimation of food resources; (4) differences in the biology of syntopic species; (5) feeding rate variability; (6) the impact of amphibians on their food resources; and (7) density-dependent responses with estimation of food resources. Food competition can only be identified in the last case, where depletion of food resources is demonstrated together with negative interactions between species. Such events have been demonstrated in some laboratory or microcosm experiments, but not in nature. Food competition appears to be rather rare in natural guilds of amphibians.