A medium sized frog reaching a maximum length of ca. 6.2 cm (2 1/2 inches). Originally named for its hard, disproportionately wide head and shovel-like snout, the Northern Casque-headed frog is one of the most unique and tropical species found in Arizona. Although tropical in origin, in Arizona this species is most often associated with xeric environments.

The skin of the head is partially co-ossified and coupled with its specialized limbs has allowed this species to adapt to a fossorial existence. Dorsum color ranges from dark brown to light tan with large brown blotches outlined by pale yellow. Sexually mature males have dark throat patch, and large slightly bi-lobed vocal sac. Juvenile frogs may often have green dorsum ground color and will occasionally retain their appearance as adults.

Within the "100 mile circle" Pternohyla fodiens occurs in low desert mesquite grasslands of southwestern Arizona, usually associated with major washes and arroyos that help form the large mesquite bosques it seems to prefer. Nearly all of its range in Arizona is on the Tohono O’odham nation.

A shy and reclusive nocturnal frog. Were it not for its explosive breeding behavior, this frog would rarely be observed. After the first significant summer rain, males gather around rain filled pools and begin calling. The voice is an unmistakable loud honking metallic, duck-like quack. This species may vocalize from June through August to early September. An accomplished burrower and climber, by day it takes refuge in self-dug holes and rodent burrows in hard clay soils where humidity is high. Females have been found in trees as high as 5ft.

By Erik F. Enderson

Originally published in the Sonoran Herpetologist "Herpetofauna of the 100-mile Circle" 15 (09) 2002