SEASON OF CALUNG AND BREEDING AND ASSOCIATED CONTROL FACTORS OF A NORTHERN TRANSVAAL ANURAN POPULATION

Abstract

Four species viz. Tomoptema cryptotis, Ptychadena anchietae, Kassina senegalensis and Phrynomerus bifasciatus were studied during the 1987/88 breeding season. Observations included estimates of mating calls on an index scale of 0–4 and the recording of eggs and young tadpoles during subsequent days. Relations between calling and spawning and the control thereof by climatic and environmental factors were investigated. Multiple regression analysis was employed to compile prediction models calling and spawning from climatological and environmental data. Distinct inter-species differences in the period and season of calling and breeding were found. T. cryptotis and P. anchietae had extended calling and breeding seasons that included most of the summer rainfall period. The calling seasons of P. bifasciatus and K. senegalensis were shorter and breeding ceased earlier than calling. Breeding mostly took place during nights with a call index of 4. The total number of nights the different species called differed significantly, but there was no significant difference between number of nights spawning took place (9 to 11 nights). Several climatological and environmental variables were found to contribute significantly towards the regression models explaining calling and spawning of the different species. Rainfall was the most important, followed by temperature (at 8.00 pm, as well as maximum and minimum temperatures) and relative humidity. The level of water in rain pools also proved to be important, while atmospheric pressure had no effect. The prediction models had coefficients of determination that ranged from 0,62 to 0,45.