In anuran amphibians migratory behaviour is constrained by the demands of water balance and thermoregulation. Therefore, the migratory range of anurans amounts to 15 km at most. Adult anurans perform migrations, if important habitat resources (e.g. sites for reproduction, nutrition and hibernation) are spatially separated. Site fidelity to these spatial units is a common feature of most anurans. These general considerations are exemplified in the common European toad Bufo bufo. Directed movements such as migrations towards a breeding or home site require mechanisms of orientation. The spatial range of the homing ability coincides widely with the natural migratory range of each species. Many sensory systems are involved in the perception of orientation stimuli: the auditory, the olfactory and the visual system as well as the still unidentified system of magneto-perception. Vocalization of conspecifics, odours of ponds, landmarks, the positions of sun, moon and stars, polarization patterns of the sky and th...

Migration and orientation in anuran amphibians

The phenology of calling activity and reproduction of a neotropical anuran community in French Guiana was studied during one rainy season. We investigated the correlation between calling activity, rainfall, temperature and water level in two ponds and recorded the occurrence of tadpoles of pond-breeding species. The study site contained 31 calling frog species, which were divided into groups according to reproductive mode. Increased rainfall was associated with increased reproductive activity in all groups, but temporal patterns in calling activity varied significantly between groups. Species with aquatic oviposition exhibited sporadic acoustic activity, aggregating into explosive breeding events following heavy rainfall. Species laying eggs in foam nests had the peak of calling activity at the start of the rainy season. Taxa with embryonic development on vegetation called mainly from middle to late wet season, being the only group which showed a significant correlation of calling with increasing water level. Dendrobatids with terrestrial oviposition and subsequent parental tadpole transportation were continuously active. Species with direct development or with non-feeding larvae were mainly active at the beginning of the rainy season. It is concluded that phenologies of calling activity in South American tropical anuran species are strongly influenced by abiotic factors like rainfall and availability of breeding sites. The temporal limitation of the rainy season forces species to adjust calling and reproductive activity according to their reproductive modes.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0266467403001172

Temporal partitioning of reproductive activity in a neotropical anuran community

The migratory behaviour of the toad Bufo bufo was studied from February 1985 to April 1986 in the submontane region of Bavaria, West Germany. Toads were fitted with a mechanical tracking device to record individual paths of migration. Three aspects of migratory behaviour were quantified: orientation in relation to the breeding site, straightness of path, and locomotory activity. The annual activity period began with migration from the hibernation sites to the breeding pond in April. The paths went straight towards the breeding pond independent of the distance (70–420 m). During the period of oviposition the preference for the breeding site direction vanished and toads moved away from the breeding pond, but in less straight paths than before. In summer migratory activity decreased considerably and was restricted to small areas, the home ranges, at distances of 55–1600 m from the natal breeding pond. The straightness of path was rather low, because toads often returned to their starting points. During rainy nights toads occasionally left their home ranges for extensive excursions. In autumn most toads again migrated towards the breeding pond, but paths were significantly less straight and direct than in spring. However, toads stopped before reaching the breeding pond and hibernated in holes or under the leaf layer. The mortality rate of tracked toads was about 45%. The relative influence of 17 environmental variables on locomotory activity was evaluated by principal component analysis and stepwise multiple regression. Temperature at night and rainfall variables accounted for significant amounts of variance, whereas temperature by day, air humidity, and atmospheric pressure showed no correlation. Activity decreased if temperature approached 0° C or after long periods without rainfall. Within a certain range of tolerance, however, the locomotory activity of the toads was widely independent of environmental factors, indicating that endogeneous factors are more important sources of variation in the migratory behaviour of these toads than commonly assumed.

Seasonal changes in the migratory behaviour of the toad Bufo bufo: direction and magnitude of movements.

Blanket mires extend over approximately 22,500 km2 of the north and west of the British Isles, and are of both national and international importance. Blanket peat started to form locally in some re...

Growth and degradation of British and Irish blanket mires.

The breeding behaviour ofa Common toad (Bufo bufo) population was studied at a breeding pond on Portland, Dorset. Major toad movements towards the breeding pond occurred on warm, wet nights when the temperature did not fall below 6°C. Males arrived earlier than females resulting in an initially exaggerated sex ratio which then slowly reduced as the breeding season progressed. No size assortative pairing was found although large males were more successful at mating than small males. Although males demonstrated no ESS (evolutionary stable strategy) in searching for a female between sites within the pond evidence suggesting the existence of one between the pond and an undefined area surrounding it was found.

P. J. Wisniewski

Papers

The effects of temperature on the breeding migration and spawning of the common toad (Bufo bufo)

Studies on the breeding migration and intramigratory movements of the common toad (Bufo bufo) using panjet dye-marking techniques

The extractive potential of peats in mid-wales with particular reference to the county of powys

The emergence of young common toads from a mid-Wales lake

Patterns of erosion in the blanket peats of mid-Wales