Basic and Applied Herpetology

Reduction of amphibian roadkill by one-side barriers

2024-04-06T12:04:11+00:00

Amphibians are the most affected vertebrates by roadkill. Often, to minimise this problem mitigation barriers are installed. While two-side barriers effectiveness is well described in the literature, one-side barriers are poorly studied. The present study aimed to evaluate the effectiveness of one-side barriers installed by LIFE LINES project along the EM535 road in south-east Portugal. Two types of one-side barriers (one permanent and another temporary one made from tarp) were monitored through road surveys. For each barrier, the influence of interaction between the period (before and after the barrier installation) and road sector (control-no barrier, permanent or temporary barrier installed) on the number of amphibians was evaluated. The result showed that, contrary to the temporary barrier, the permanent one-side barrier appeared to be effective. Thus, the ineffectiveness of the temporary barrier may be related to (i) the tarp material that allows some amphibians to escape, (ii) the presence of vegetation that goes over the top of the barrier, or (iii) increased fence-end effects due to its short length. Even though less effective than two-side barriers, one-side barriers could be installed when there is budget limitation in conservation projects or if land use conflicts exist. Given that our study was the first to evaluate the effectiveness of one-side barriers, we discuss the potential constrains that may have affected our results.

Comparative acute toxicity of pesticides to tadpoles of a tropical anuran (Epipedobates anthonyi), a North American native anuran (Lithobates sphenocephalus) and a standard fish species

2024-03-27T11:52:29+00:00

Global amphibian declines have the highest incidence in tropical regions, but most of the ecotoxicological data on amphibians is collected on temperate northern hemisphere anuran species. We tested the hypothesis that tropical anuran larvae (Epipedobates anthonyi) would be more sensitive to pesticides than a North American native species (Lithobates sphenocephalus). For 12 pesticides, 96-hr range-finding acute toxicity tests were conducted to determine if mortality occurred at environmentally relevant levels. Based on those studies, two substances were selected for additional time-to-event analyses in both species as well as median lethal concentration (LC50) calculations. Time-to-event results indicated that the two species appear to be roughly equivalent in their sensitivity to the two tested pesticides. Significant differences between species were not consistent across concentrations for either the insecticide terbufos or the herbicide pendimethalin. The utility of LC50 data was mixed with one LC50 providing an arbitrarily large standard error around the LC50 precluding informative comparisons across species. However, standard LC50 methods allowed data collection that continues to contribute to our understanding of the protectiveness of fish as surrogates for anuran larvae. While our data set is limited, it appears that testing temperate species would be protective for tropical species in ecological risk assessments. Our data also support the continued use of fish as surrogates for amphibian larvae as none of the species were more sensitive to the tested pesticides than rainbow trout (Oncorhynchus mykiss), the standard sensitive fish species used for acute toxicity testing.

Is the Pyrenean newt (Calotriton asper) a thermoconformer? Cloacal and water temperature in two different thermal periods in a Pre-Pyrenean stream population

2024-03-27T11:52:41+00:00

In ectothermic animals, heat seems to be a determining factor because it influences many vital activities such as locomotion, the ability to escape, feeding, and reproduction, among others. In aquatic environments, physical characteristics of water prevent small ectotherms from thermoregulating and therefore it is expected that their body temperature remains similar to water temperature. Throughout its distribution and annual cycle, the Pyrenean newt (Calotriton asper) is exposed to a wide range of water temperatures that affect its biological and ecological traits like the standard metabolic rate, oxygen consumption, activity period and growth pattern. This study analyses the relationship between the cloacal and water temperatures in a Pre-Pyrenean population of C. asper in two periods with well differentiated water temperatures (July and September). The aims are to establish if there are differences between sexes in cloacal temperature, whether reproductive activity modifies cloacal temperature, and to analyse the degree of thermoconformity of the species. The results indicate that cloacal temperature depends on the water temperature, corroborating the idea that C. asper is mainly a thermoconformer, as it corresponds to an aquatic ectotherm. However, the cloacal temperature of newts was slightly higher than water temperature. In individuals in amplexus, cloacal temperature was significantly higher than in specimens that are not in this mating position, and in July, females showed much greater dispersion in cloacal temperature than males, which is probably related to spawning behaviour.