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Reports of sexual dichromatism in salamanders are rare and have been generally restricted to a few species in the families Hynobiidae and Salamandridae. We used image analysis techniques to examine sexual dichromatism in the marbled salamander, Ambystoma opacum (Gravenhorst, 1807). We measured the average hue of white saddles on male and female marbled salamanders (n = 118), as well as the proportion of white dorsal surface area relative to the black dorsal surface area, to determine the extent of sexual dichromatism in this species. We also tested whether patterning and coloration were correlated with body size or relative body mass. Males had significantly whiter saddles and higher relative proportions of white coloration on their dorsal surfaces than did females. Furthermore, the relative proportion of white areas on the dorsum was positively correlated to body condition in both males and females. Body size was not correlated with hue or proportion of white area on the dorsum. To our knowledge, we report the first confirmation of sexually dimorphic coloration in the ambystomatid salamander family, extending the known distribution of sexual dichromatism in the order Caudata.

Pond-breeding amphibians from temperate regions undertake overland migrations to reproduce in aquatic habi- tats. In turn, their offspring metamorphose and emigrate to upland, terrestrial habitats. We examined the diel patterns and daily variability of migrations of adult and juvenile amphibians in response to climatic cues. Of the eight species ( Ambys- toma talpoideum (Holbrook, 1838), Ambystoma tigrinum(Green, 1825), Bufo terrestris (Bonnaterre, 1789), Hyla gratiosa LeConte, 1856, Pseudacris crucifer (Wied-Neuwid, 1838), Pseudacris ornata (Holbrook, 1836), Rana sphenocephala Cope, 1886, and Scaphiopus holbrookii (Harlan, 1935)) that we observed, all migrated almost exclusively at night except for the recently metamorphosed B. terrestris, which frequently migrated diurnally (>50% of captures). Additionally, we correlated daily captures of adult and juvenile A. talpoideum, A. tigrinum, B. terrestris, and R. sphenocephala to maximum and minimum daily temperatures, number of previous days without rain, total rainfall during the previous 24 h, and inter- actions of these variables. Rain was often the most important predictor of amphibian movements. However, species dif- fered in their response to climatic factors, with some species and age classes being more dependent on rain for migrations than others. Rapid changes in regional weather patterns may affect species' migrations differently, possibly altering arrival times of reproductive adults or affecting the likelihood of successful migrations. Resume ´ : Les amphibiens des regions temperees qui se reproduisent dans les etangs entreprennent des migrations ter- restres afin d'aller pondre dans les habitats aquatiques. Aleur tour, leurs rejetons se metamorphosent et migrent vers des habitats terrestres plus en altitude. Nous examinons les patrons diurnes et la variabilitejournaliere des migrations des am- phibiens adultes et des jeunes en reaction aux signaux climatiques. Les huit especes observees (Ambystoma talpoideum (Holbrook, 1838), Ambystoma tigrinum(Green, 1825), Bufo terrestris (Bonnaterre, 1789), Hyla gratiosa LeConte, 1856, Pseudacris crucifer (Wied-Neuwid, 1838), Pseudacris ornata (Holbrook, 1836), Rana sphenocephalaCope, 1886 et Sca- phiopus holbrookii (Harlan, 1935)) migrent toutes presque exclusivement la nuit, al'exception des B. terrestris frao ˆche- ment metamorphoses, qui migrent souvent (>50 % des captures) en plein jour. Il y a, de plus, une correlation entre les captures d'adultes et de jeunes d'A. talpoideum ,d 'A. tigrinum ,d eB. terrestris et de R. sphenocephala, d'une part, et, d'autre part, les temperatures journalieres minimales et maximales, le nombre de jours anterieurs sans pluie, les precipita- tions totales durant les 24 h precedentes et les interactions entre ces variables. La pluie est souvent la meilleure variable predictive des captures d'amphibiens. Cependant, les especes different dans leur reaction aux facteurs climatiques et cer- taines especes et certaines classes d'age sont plus dependantes de la pluie pour leur migration que d'autres. Les variations rapides des patrons climatiques regionaux peuvent affecter les migrations des diverses especes de facon differente, proba- blement en modifiant le moment d'arrivee des adultes reproducteurs et en affectant la probabilitedes migrations reussies. (Traduit par la Redaction)