Over a five year period, breeding biology of the Great Plains toad (Bufo cognatus) was studied in central Oklahoma. Breeding activity was closely associated with precipitation. Consequently, the number of nights when breeding occurred during spring varied considerably from year to year. Breeding occurred for 14 consecutive nights during March 1985, up to six consecutive nights after rainstorms in April and early May but for only one or two nights after June rains. Breeding activity was greatest during the first three hours after sunset and typically during the first two nights after a rainstorm. Regardless of when females entered the breeding pool and paired, egg laying began at sunrise and lasted until mid-morning with amplexus averaging 803 minutes. Bufo cognatus exhibited communal egg laying at seven different breeding sites that characteristically had large breeding choruses. Eighty-eight percent of all females in those pools laid eggs at a 1 m<sup>2</sup> to 4 m<sup>2</sup> area specific in each pool. These areas were used from rain to rain and from year to year. It is not clear why these exact locations were repeatedly chosen or why communal egg laying was so prevalent. Females exhibited size-related fecundity with clutches ranging from 1342-45,054 eggs. Larval period also varied greatly ranging from 45 days in April to 18 days in June. Finally, mean size of breeding males and females increased markedly over the course of the 1985 breeding season and individually marked adults captured over three years exhibited a wide range of growth rates.
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