Bufo boreas boreas
- Yellowstone's only toad species which is confirmed to breed in the park.
- Adults range up to about 4 inches; juveniles just metamorphosed from tadpoles are only one inch long.
- Stocky body and blunt nose.
- Brown, gray, or olive green with irregular black spots, lots of "warts", and usually a white or cream colored stripe down the back.
- Tadpoles are usually black and often congregate in large groups.
- Once common throughout the park, now appear to be much rarer than spotted frogs and chorus frogs; scientists fear this species has experienced a decline in ecosystem.
- Adults can range far from wetlands because of their ability to soak up water from tiny puddles or moist areas.
- Lay eggs in shallow, sun-warmed water, such as ponds, lake edges, slow streams, and river backwaters.
- Tadpoles eat aquatic plants; adults eat insects, especially ants and beetles, worms, and other small invertebrates.
- Sometimes active at night.
- Defends itself against predators by secreting an irritating fluid from numerous glands on its back and behind its eyes.
- Eaten by snakes, mammals, ravens, and large wading birds.