Variable reproductive strategies of an African savanna frog, Phrynomantis microps (Amphibia, Anura, Microhylidae)

Abstract

Abstract:West African savannas are habitats with unpredictable rainfall. Species with varying life-history traits may be more successful in these environments than species with fixed traits. We studied the reproduction strategies of the microhylid frog Phrynomantis microps in different savanna types, a humid savanna in Ivory Coast and a drier one in Benin. We recorded 5437 clutches in eight ponds in the humid savanna during five consecutive rainy seasons. A further 694 clutches were investigated in 10 ponds in Benin in one rainy season. For each clutch, we recorded egg numbers, deposition time, location within the pond and rainfall. Precipitation was important in triggering reproduction. However, the amount of rainfall needed differed in relation to rainy season length and total annual rainfall. Especially in years and regions with a late rainy season a threshold of minimum precipitation was needed to initiate spawning, indicating a trade-off between the need to reproduce and the survival probabilities of offspring in ponds with a high desiccation risk. Egg numbers per clutch further differed between pond sizes, breeding season length, as well as to time within the rainy season. Potential explanations for these differences, in particular desiccation and predation risks are discussed, but need further experimental support.