Observations and collections on the breeding biology and life history of Rana pretiosa pretiosa Baird and Girard have been made in central Utah from 1962 to 1967. The frogs' activities were followed from their spring emergence untril the tadpoles metamorphosed and hibernated in the fall. Collections and observations were made at regular intervals through the entire period of summer activity. Data were gathered at the ponds and samples of the life history stages were taken to the laboratory where they were analyzed and studied. Emergence is normally during the middle of March. The males precede the larger females by three or four days. Immature frogs emerge approximately two weeks later. In Utah this species prefers small ponds of standing water grown thick with stonewort, Chara sp., and possessing a deep muck bottom from which cattails emerge. The males congregate in small areas of the pond as breeding choruses where they outnumber the females five to one. The male's call is weak and can be heard for approximately 6 to 10 meters. The eggs are laid shortly after the arrival of the females and vary in number from 147 to 1160 per clutch, the average being approximately 750 per clutch. The average size of individual eggs are as follows: Egg 2.5 mm, inner gelatinous envelope 5.0 mm, and outer envelope 10.0 mm. Hatching requires about two weeks in nature and varies between 7 and 23 days, depending upon temperature. Several factors noted which affect the frog's growth and behavior are temperature, crowding, and dissolved minerals in the water. Metamorphosis required from 122 to 209 days following ovulation. Hibernation took place during the middle of October approximately to weeks after the first freezing temperatures.



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Plant and Wildlife Sciences



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