Influence of temperature, size and confinement on testosterone and corticosterone levels in breeding male spined toads (Bufo spinosus)
Résumé
Winter breeding amphibians opportunistically engage in reproductive behaviour when environmental conditions
become favourable. In such explosive breeding systems, males strongly compete for reproductive females.
Although most research has been oriented on species in which males use mating calls to attract females, many
high-density explosive breeding amphibians do not rely on mating calls. In such systems, larger and stronger
males are thought to have significant advantages to access reproductive females. Testosterone (T) is expected to
increase with the physical attributes that facilitate access to females, while increased corticosterone levels
(CORT) are needed to sustain the energetic requirements associated with mating behaviour. In this study, we
investigated how environmental temperature, and body size influence testosterone and corticosterone in males
of an explosive winter-breeding species with low investment in mating call, the spined toad (Bufo spinosus). We
found that both baseline CORT and T were positively correlated with environmental temperature. Interestingly,
despite a remarkable range of variation in CORT and T, there was no evidence that either hormone was correlated
with body size. Finally, we found no effect of confinement (13 h of captivity) on circulating CORT and T
levels. This suggests that breeding male toads may be relatively insensitive to stress in order to maintain reproductive
effort during their short mating period. Future studies should investigate both the influence of the
phenology of breeding and the social interactions on these hormonal levels.