The horned frog, despite its common name, is not an amphibian but a type of lizard, scientifically known as a horned lizard (genus Phrynosoma). These reptiles are recognized for their flattened bodies and spiky heads. Found predominantly across North and Central America, horned lizards possess unique characteristics and behaviors.
Physical Characteristics
Horned lizards have a squat, broad, and flattened body, which helps them blend with the ground. Their most striking feature is the crown of thorn-like projections, or “horns,” on the back of their heads, extensions of their cranium. They also display rows of fringe-like scales along their torso. Their coloration mirrors the local soil, ranging from sandy yellow to reddish-brown or gray, allowing for effective camouflage. Adult Texas horned lizards measure between 2.5 to 5 inches (6.4 to 13 cm) in snout-vent length, with females usually larger than males.
Natural Habitat and Lifestyle
Horned lizards inhabit arid and semi-arid regions across the southwestern United States and northern Mexico. These environments include prairies, deserts, and grasslands, often characterized by loose, sandy, or loamy soils. The sandy substrate benefits their burrowing habits. Horned lizards are diurnal, meaning they are active during the day, using the sun for thermoregulation. They bask in open areas during cooler mornings and evenings, then retreat into burrows, under rocks, or shaded vegetation during the hottest parts of the day to avoid overheating.
Diet and Feeding Habits
The diet of horned lizards consists predominantly of ants. Harvester ants, in particular, often make up over 70% of their food intake. These lizards employ a “sit-and-wait” predatory strategy, remaining motionless near ant trails or colony entrances. When an ant comes within range, the horned lizard quickly extends its sticky tongue to capture the prey. Some species can eat up to 70-100 harvester ants per day. Occasionally, they supplement their diet with other insects like beetles, termites, and grasshoppers.
Distinctive Defenses
Horned lizards possess several defense mechanisms. Their primary defense is effective camouflage; their mottled skin and flattened bodies allow them to blend with their surroundings. If detected, they may remain motionless, relying on their appearance to evade predators. They can also inflate their bodies with air, causing their spiky scales to protrude, making them appear larger and more difficult for a predator to swallow.
Their most unique defense is squirting a stream of blood from their eyes. When threatened, particularly by canine predators like coyotes, foxes, or domestic dogs, they restrict blood flow from their head, increasing blood pressure in specialized sinuses around their eyes. This pressure causes tiny blood vessels to burst, expelling a stream of blood that can reach up to five feet. The blood contains compounds noxious to canids, causing them to shake their heads and retreat. This response is believed to be enhanced by chemicals derived from their ant-based diet.
Conservation and Threats
Horned lizard populations have faced declines across much of their historical range. Habitat loss and fragmentation, due to urbanization, agricultural expansion, and other human development, pose a threat. The decline of their main food source, harvester ants, largely due to widespread pesticide use and the introduction of invasive fire ants, also impacts their survival. Horned lizards are susceptible to predation by domestic animals like cats and dogs, and illegal collection for the pet trade has also contributed to their population decline. Conservation efforts focus on habitat protection, managing ant populations, and addressing the impact of invasive species.