Abstract
Amphibians are considered to be the most threa- tened group of vertebrates. Among the multiple factors in- volved in their decline, habitat loss and alteration as a result of human activities is a major threat. At the individual level the effects of habitat alteration are potentially multiple, in- cluding a range of morphological and physiological re- sponses. Analysing and understanding these responses is therefore a critical challenge for amphibian conservation. We examined the influence of intensive vehicle traffic (mo- torbikes and trucks on unpaved pathways) on the body size and condition and on the production of glucocorticoids (i.e. corticosterone) in the yellow-bellied toad Bombina variegata. In particular, we tested the hypothesis that intensive vehicle traffic has a negative influence on body size and body con- dition, and postulated that it also increases corticosterone production. Using morphometric data and saliva samples collected from four populations in France, we found that intensive vehicle traffic is associated with a decrease in body size and body condition in both males and females. Furthermore, our analysis revealed that corticosterone pro- duction was lower in both sexes in populations experiencing intensive vehicle traffic. We suggest that measures should be applied to reduce vehicle traffic intensity on unpaved pathways during toad breeding activity. This is critical for B. variegata, for which man-made ruts and residual puddles could mitigate the loss of natural habitats.