Field Notes on Frogs and Toads

When visiting Anson B. Nixon Park, you may be fortunate enough to spot one of four species of frogs or the American Toad. The fifth species of frog is one you'll more likely hear than see, the Spring Peeper; look for a separate post about them in the future.

If you see a frog in or on the water, it is either a Green Frog (Lithobates clamitans) or an American Bullfrog (Lithobates catesbeianus). To tell them apart, look just behind the eye; green frogs have a ridge leading from the eye down the back on each side. In bullfrogs, the ridge curves down and around their ear. This is the dorsolateral ridge or dorsolateral fold.

To tell them apart look just behind the eye, green frogs have a ridge leading from the eye down the back on each side. In bullfrogs the ridge curves down and around their ear. This is the dorsolateral ridge or dorsolateral fold.

Frogs that you'll typically see out of the water in the grass around the pond or in the forest are the Pickerel Frog (Lithobates palustris) and Wood Frog (Lithobates sylvaticus).

Pickerel frogs can secrete irritating fluid from their skin, a defense allowing them to move around out of the water more safely than other frogs.

After the spring breeding season, pickerel frogs migrate away from ponds and streams to damp meadows, grassy fields, and forest edges to forage for insects. Pickerel frogs have rectangular spots running down a tan or light brown back and yellow undersides.

Wood Frog

Wood frogs live on the forest floor, visiting temporary pools during their breeding period in winter or early spring; otherwise, they will often be spotted far away from the water. The most distinct feature is a dark mask from their snout through the eye to the shoulder. They range from pinkish-tan to dark brown to match the leaf litter.

The American Toad is a familiar sight in forests, fields, and gardens. They have dry, warty skin ranging from brown to gray or olive in color.

Evolutionary History

Toads (Bufonidae) and Frogs (Ranidae) are two families in the scientific order Anura. Over millions of years these families branched by natural selection to live in different environments.

Frogs evolved a body plan for speed and defense. They launch into high-velocity leaps to avoid predators on long, powerful hind legs and their streamlined, moist skin supplements breathing while underwater.

Toads evolution adapted them to a terrestrial life. Their thicker, warty skin prevents drying out. Rather than the speed defense they evolved large toxin secreting glands behind their eyes to deter enemies.