Effects of climatic conditions
From these patterns it is clear that size and complexity of parental investment reflects clutch size. Another trend is that development time appears to reflect climatic conditions. Frogs within tropical regions develop relatively rapidly, sometimes spending only two or three weeks in the tadpole stage, whereas those living in cool temperate climates develop much more slowly. One such species is the spotted frog, Rana pretiosa, which lives in the cold streams that cascade down the Rocky Mountains. Because the cold water in which the frogs live slows their metabolism, more than one year is needed to produce fully yolked eggs, and the females lay eggs only once every two or three years. Tadpoles also metamorphose more slowly in cooler areas. For example bull frogs in northern USA (Rana catesbeiana) typically spend two years in the tadpole stage and another species Ascaphus truei needs three years to reach adulthood.