Cranwell’s horned frog

Cranwell’s horned frogs have large, wide, flat heads with unusually large mouths and a set of “horned” ridges above each eye. Small skin bumps cover the top portion of its body, with mottled colors that range from bright green and yellow to dark brown in splotchy patterns that help it camouflage among leaf litter and undergrowth.

Hefty for an amphibian, this species grows between 3.1–5.1 inches (8–13 cm) long and can weigh up to 1.1 pounds (0.5 kg).

These frogs are found only in the Gran Chaco, a sprawling region of South America that covers parts of Argentina, Paraguay, Bolivia and Brazil. The land includes a mix of dry thorny forests, palm savannas and seasonal wetlands, and these frogs’ life cycles revolve around rainy seasons.

Most only live around 1-4 years in the wild, although individuals can live quite a bit longer in human care.

Males call out to females during the breeding season using a repeating call that sounds somewhat like a bass horn.

These frogs are sit-and-wait predators that hide in vegetation, staying motionless for hours at a time until an unsuspecting insect or other small animal passes nearby. When they strike, a set of hooked teeth running along the upper jaw and a pair of bony fang-like protrusions on the lower jaw help them grab and hold prey to prevent escape. Highly carnivorous, even their own species is on the menu: this frog will cannibalize other Cranwell's horned frogs as well as other prey.

Nocturnal. This frog is most active at nighttime in the rainy season near ephemeral ponds, which fill up with water for part of the year. During the cold and dry months when these ponds disappear, the frogs will spend months buried underground in a hibernation-like state called estivation until the rains return.

These frogs time their reproductive cycles to the rainy season, breeding in early November through April, which is the Southern Hemisphere’s summer. After mating, females deposit their eggs in temporary pools filled by the seasonal rains. These eggs hatch into tadpoles, which are carnivorous and feast on insects, small aquatic invertebrates, and sometimes each other. 

This species is not considered to be at immediate risk of extinction, although its numbers appear to be declining. The frogs’ native ecoregion, the Gran Chaco of South America, is one of the world’s most severely threatened natural places. Over the last few decades, rampant habitat loss and destruction have led to the clearing of natural spaces to make way for ranches and soybean farms, which has had a devastating effect on the hundreds of animal and plant species native to this region. 

Cranwell’s horned frog is also popular among the pet trade, which can threaten amphibians and reptile populations if overharvested from the wild. Also, these frogs are sometimes persecuted and killed by humans due to the mistaken belief that they are venomous.