Annual variation of breeding patterns of the toad, Melanophryniscus rubriventris (Vellard, 1947)

Climate may play a direct role in determining patterns of reproductive activity in anurans. Investigating the responses of males and females attending a breeding site to environmental variation are of particular interest regardless the possible effect of climate change on the decline of populations. I studied annual variation over two years in the breeding population size and breeding phenology of the diurnal toad, Melanophryniscus rubriventris, in a seasonal environment characterized by temporal and spatial uncertainty due to climatic conditions. Breeding activity of this toad was opportunistic throughout a prolonged spring-summer breeding season. Direct influence of rainfall on the onset and extent of breeding activity was detected in both years. Spawning activity showed a clear pattern of two three-day peaks mostly related to heavy rainfall events. Males always significantly outnumbered females at breeding sites. The disparity of rainy season extent between the two breeding seasons studied resulted in different annual patterns of arrival and length of residence of adults. Males and females remained several days longer during the second year than during the first year. Because adults showed highly variable annual patterns of breeding activity studies involving only a few years may yield misleading results concerning the nature and extent of the decline of the species or populations. Future studies on the ecology and conservation of the species should include long-term monitoring.