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Claude Miaud

Abstract

Oviposition site selection in Triturus helveticus, T. alpestris and T. cristatus was studied both in natural and laboratory situations. In a natural breeding site, eggs of the three species were not laid equally on several plants: T. cristatus laid practically all their egges on only one plant (Nasturtium officinale) while T. helveticus eggs were collected on four plant species. In laboratory experiments, plastic and cotton fabric supports made it possible to test ovipositing female selectivity according to flexibility and shape of support and egg-laying distance below the surface. In all three species, a high proportion of eggs were laid on supports of linear shape (as opposed to arborescent shape) and egg frequency decreased as a function of depth (from 0 to 40 cm below the surface). Selection according to flexibility was also observed, the smallest species (T. helveticus) laying more eggs on the thinner supports. The role of support selectivity during oviposition in Triturus is discussed, in term of proximate (i.e. female protection against predators, breathing necessity) and ultimate (i.e. egg survival) factors, and related to new ecology.

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Claude Miaud and Delfi Sanuy

Abstract

Nineteen adult toads equipped with transmitters were followed during and after the breeding period (January to September) in order to estimate their home range area and habitat use in a landscape of cereal agriculture. Median home range area was 0.5 ha (range 0.1-11 ha) during the breeding season (January-April). Home range areas increase during the post-breeding season (April-September) e.g., median minimum concave polygon of 4.1 ha. No relation between home range and toads' body size was observed. Six habitat types were described in the studied area. The proportion of habitats used (i.e. proportion of the pooled positions of 11 toads during the post-breeding season in each habitat) was significantly different from the proportion of available habitats: while crops represented 85% of the available habitat, only 43% of the toads' positions were recorded in this type of habitat. A compositional analysis of habitat preference was performed. At both landscape and individual home range levels, the toads preferred the stone embankments and ditches above all, while the crops were the least preferred habitat. This study highlights the role of habitat linkage and marginal habitats for the persistence of amphibian populations in intensive agricultural and arid landscapes.

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Delfi Sanuy, Jean-Noël Avrillier and Claude Miaud

Abstract

The movements of 19 natterjack toads (Bufo calamita) were monitored by telemetry in a semi-arid agricultural landscape in NE Spain. Toads reproduced in two water pools in fields of barley and an ancient clayquarrying zone filled by rainfall. Thirteen toads were followed during the breeding season (weeks 5-17 of 1997) and 11 toads were followed after reproduction (weeks 18 to 46). During the breeding season four toads moved distances of up to 500 m between breeding sites. No significant differences in movement patterns were found between the sexes, but a tendency was observed for males to show higher terrestrial site fidelity than females. Distances moved after the breeding season were substantial. The distance between the furthest positions recorded was from 164 to 1201 m, the maximum distance observed between daily recordings ranged from 125 to 353 m and the maximum overall distances ranged from 567 to 4411 m. No significant differences were observed between males and females or between small and large toads. The movements of these toads in a semi-arid agricultural landscape in Spain are compared with those observed in England and Germany.

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Jean Clobert, Aurélie Husté and Claude Miaud

Abstract

The isolation of animal populations due to urban activities provides a useful framework for studying the consequences of landscape fragmentation. We studied a population of natterjack toads (Bufo calamita) in an urban park near Paris, France. In 2001 and 2002 we used radio-tracking to estimate the terrestrial movements of adults around their breeding sites. Twenty-four toads were equipped with internal transmitters in 2001 to record movements during and after the breeding period. In 2002, 19 males were released at 300 and 380 meters from their breeding ponds. Natterjack toad movements around and outside their breeding ponds were reduced compared to previous observations on this species. The only exchanges that were observed occurred between closely neighbouring breeding sites. During a translocation experiment in 2002, 58% of the displaced males returned to their site of capture and this happened mainly during the breeding period. The remaining 42% stayed close to the release site. There was no exchange of males between distant breeding sites. Natterjack toad conservation needs to take into account the high fidelity to a breeding site and the reduced breeding dispersal and homing ability of these animals. Conservation biology in urban landscapes constitutes a specific urban ecology with specific concepts such as 'population area'. Information from this study can assist land managers in establishing protected areas of high habitat quality around breeding ponds in urban areas, and managing parks for the protection of amphibian populations, particularly by facilitating exchanges between available areas.

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Christiane Jakob, Alfred Seitz, Claude Miaud and Alain Crivelli

Abstract

We studied growth patterns within a marbled newt population (Triturus marmoratus, Urodela) at the southeastern limit of its geographical range by skeletochronology of the phalanges and humeri. Seasonal and annual changes in growth rates were assessed through the analyses of 56 females, 66 males and 34 juveniles sampled in different seasons and years. Age and growth cycles were estimated by cross sections of the diaphyseal region of the bone. These analyses revealed a clear line of metamorphosis caused by the metamorphic process itself and the transition to the terrestrial environment. A line of arrested growth (LAG) was observed in winter in both juveniles and adults. Another LAG was recorded in summer among adults. These growth patterns corroborated field observations on life-history traits of the population under study, but differ from those reported for the marbled newt in other environments.

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Kurtulus Olgun, Azız Avci, Nazan Uzum and Claude Miaud

Abstract

We studied the characteristics of bone growth assessed by skeletochronology in a southern crested newt Triturus karelinii (Urodela) population from Western Turkey. The timing and patterns of bone arrested growth were observed using the phalanges of juveniles and adults that were caught in spring at a breeding site. A metamorphosis line was found in the juveniles. In some adults, a classical succession of single lines of arrested growth was observed in about 50% of the cross sections. However, the other adults exhibited a succession of double lines of arrested growth in their phalanges. Due to the arid summer and cold winter climate in the Bozdag region (1200 m a.s.l.), we argue that in this last case, the lines of arrested growth were deposited during both the summer (aestivation) and winter (wintering). Body length, age and growth were similar in males and females. The age of maturity was 3 to 4 years old and longevity was 8 and 11 years in males and females respectively. Body length and age among taxonomically related large bodied newts of the T. cristatus complex were reported from populations experiencing various environmental conditions. Body length and age at maturity were similar to that observed in other newt species. However, longevity seems to be lower than expected in the T. karelinii studied population. We hypothesized that the arid climate of Bozdag could cause a higher mortality risk during the terrestrial phase of the life cycle. Studying more populations exposed to various conditions is clearly needed to assess interpopulational variation of these life-history traits in this newt species.

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Jean Secondi, Tony Dejean, Alice Valentini, Benjamin Audebaud and Claude Miaud

Detection is crucial in the study and control of invasive species but it may be limited by methodological issues. In amphibians, classical survey techniques exhibit variable detection probability depending on species and are often constrained by climatic conditions often requiring several site visits. Furthermore, detection may be reduced at low density because probability capture (passive traps), or activity (acoustic surveys) drop. Such limits may impair the study of invasive species because low density is typical of the onset of colonisation on a site. In the last few years, environmental DNA (eDNA) methods have proved their ability to detect the presence of aquatic species. We developed here an eDNA method to detect Xenopus laevis in ponds. This austral African species is now present worldwide because of its use in biology and as a pet. Populations have settled and expanded on several continents so that it is now considered as one of the major invasive amphibians in the World. We detected the presence of X. laevis at density as low as 1 ind/100 m2 and found a positive relationship between density in ponds and rate of DNA amplification. Results show that eDNA can be successfully applied to survey invasive populations of X. laevis even at low density in order to confirm suspected cases of introduction, delimit the expansion of a colonized range, or monitor the efficiency of a control program.

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Olivier Marquis, Sylvie Guittonneau, Annie Millery and Claude Miaud

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are damaging for aquatic organisms such as amphibians. In this study, toxicity of a mixture of three PAHs (naphthalene (2 rings), phenanthrene (3 rings) and pyrene (4 rings)) was tested on Common frog (Rana temporaria) embryos. The protective role of the jelly coat surrounding the eggs was studied by exposing embryos with and without jelly coat to PAHs dissolved in an aqueous solution without organic solvent. Results showed that the mixture of these three PAHs significantly increase embryonic mortality rate after a few hours of exposure. Embryos with jelly coat tend to suffer a lower mortality rate than embryos without jelly. The jelly surrounding eggs is filled by water of the breeding site, which can contain pollutants. Because jelly characteristics vary among species, sensitivity to environmental pollutants and levels of embryonic protection could be different among amphibian species.