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FISH: Pennsylvania Frog and Toad Breeding Phenology

During the First Investigation of Stream Health (FISH) activity, one optional data field records the number of frogs and toads observed or heard. Different species are active during different months in Pennsylvania.

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Updated:

February 11, 2026

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Breeding American toads surrounded by strings of eggs. Photo: Natalie Marioni

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Phenology is the study of the timing of observable events in nature, such as when flowers bloom, birds migrate, frogs begin their breeding calls, and leaves change colors and drop in the fall. A combination of factors, including rainfall, soil, water and air temperature, moisture levels, and photoperiod, can influence the timing of these events. In Pennsylvania, there are distinct periods in which potential species can be expected to begin breeding and when they are most easily observed or heard. These periods and the species that breed in them are as follows.

Frog and Toad Phenology Chart
Frog/Toad	Feb	Mar	Apr	May	Jun	Jul	Aug	Sept
Wood Frog	Peak	Peak	Maybe
Mountain Chorus Frog	Peak	Peak	Maybe
Western Chorus Frog	Peak	Peak	Peak	Maybe	Maybe
Northern Leopard Frog		Peak	Peak	Peak	Maybe
Spring Peeper		Peak	Peak	Maybe	Maybe
Eastern Spadefoot		Peak	Maybe	Maybe	Maybe	Maybe	Maybe	Maybe
Eastern American Toad		Maybe	Peak	Peak	Peak	Peak
Fowler's Toad		Maybe	Maybe	Peak	Maybe	Maybe	Maybe
Pickerel Frog			Peak	Peak
Eastern Cricket Frog			Maybe	Maybe	Peak	Peak	Maybe
Gray Treefrog			Maybe	Maybe	Maybe	Peak	Peak
Cope's Gray Treefrog			Maybe	Maybe	Maybe	Peak	Peak
Green Frog				Peak	Peak	Peak	Peak
American Bullfrog				Maybe	Maybe	Peak	Peak

This phenology chart shows the months when breeding activity occurs for Pennsylvania frog and toad species. These are the times when observing or hearing them is easiest.