CHORUS ATTENDANCE BY MALE AND FEMALE PAINTED REED FROGS (HYPEROLIUS-MARMORATUS) - ENVIRONMENTAL-FACTORS AND SELECTION PRESSURES

1. The numbers of male and female Painted Reed Frogs (Hyperolius marmo ratus) were monitored over 28 consecutive nights at the height of the breeding season. Despite arguments that male and female numbers should be highly correlated we found that only 32% of the variance in female numbers was explained by the number of males present. 2. To assess ou r prediction that attendance was determined by considerations other th an optimal access to mates we modelled attendance patterns using a wid e range of environmental variables. 3. Male and female attendance patt erns were best described by different models. For males, 76.6% of the variance in nightly attendance was accounted for by the following vari ables: a constant, evaporation, pond depth on the previous night, rain fall, atmospheric pressure at 1400 h, wind on the previous day and the number of days since rain. The nature of the inter-relationships sugg est that males are primed to attend the chorus unless conditions are l iable to lead to increased evaporative water loss. 4. The female model accounted for 87.8% of the nightly variation in attendance and incorp orated the following variables: number of males present, number of hou rs of sunshine on the previous day, wind on the previous day, rainfall 2 days previously, humidity at 1900 h and minimum temperature. The da ta suggest that females are more selective about the timing of attenda nce than are males. Specifically, it appears that females attend when conditions favour the rapid development of larvae.