American bullfrog

Lithobates catesbeianus · Aquatic life

In the water · Photo: Blake Ross / CC BY

InvasiveOther organism

Also called Bullfrog tadpoles, Rana catesbeiana, Bullfrog

State listing

Idaho: Prohibited invasive species
Oregon: Controlled

How to identify American bullfrog

Largest frog in the region, body up to about 6 to 8 inches
Green to olive brown, often with darker blotches; yellowish to white belly
Large round eardrum with a skin fold that curves around it, but no ridges down the back
Deep, booming jug o rum call on summer nights
Big tadpoles up to about 6 inches that take one to two or more years to change

Similar species

Native frogs such as Columbia spotted frogs, northern leopard frogs and red legged frogs are smaller and have ridges (dorsolateral folds) running down each side of the back. Green frogs, also introduced, have those ridges too.

Profile

Season	Calling and breeding late spring through summer; tadpoles present all year.
Starts	Breeding begins when water warms to about 70 F
Depth	Shallow edges and plant beds
How it spreads or reproduces	Adults hop between nearby waters; tadpoles moved with fish stocking, bait and pond plants; deliberately introduced in the past
Habitat	Warm, permanent ponds, lakes, irrigation reservoirs, canals and wetlands with plant cover, especially in low elevation valleys.

Why it matters in a lake

Introduced to the West and now a major threat to native frogs, turtles, snakes and young waterfowl, which they eat. Idaho lists it as an invasive species and Oregon classifies it as controlled, so live bullfrogs and tadpoles should not be moved or stocked.