Reptiles
Horned Lizard
Phrynosoma · also called horned toad, horny toad
A horned lizard looks like a small spiky pancake with a crown of horns, and its defences match. It holds still and disappears into the gravel. If found, it puffs up into a wide, prickly disc that a predator cannot swallow. And if a fox or coyote gets it in its mouth anyway, the lizard bursts blood vessels around its eyes and fires a jet of foul-tasting blood into the attacker’s face.
Overview
Horned lizards are the genus Phrynosoma, about 20 species across the arid parts of western North America and Mexico — desert flats, dunes, sagebrush, and dry grassland. They are ant specialists, especially of harvester ants, licked up one at a time from beside a foraging trail, which is why the big stomach and slow digestion. The names “horned toad” and “horny toad” come from the squat body, but it is a true lizard.
The defences
Camouflage first — the flat body and a fringe of scales hide its shadow. Then body-puffing into a spiny disc, horns tipped toward the threat. Then, in about eight species, the famous blood squirt from the eye sockets, up to 1.5 m, carrying an ant-derived compound that tastes vile to canids. The pancake shape also warms fast in the morning sun and presses flat to vanish, and the lizard drinks through its skin, channelling dew and rain along tiny grooves between the scales to its mouth.
Status
Least Concern overall but decreasing, with the Texas horned lizard gone from about half its Texas range. The main cause is the invasive red imported fire ant, which displaces the native harvester ants and kills hatchlings, plus broadcast ant poisons, habitat loss, and past collection for the pet and curio trade. Texas zoos now breed and release the species.
Horned Lizard: common questions
Do horned lizards really shoot blood from their eyes?
Yes, though not all species and not on every occasion. About eight of the roughly 20 horned lizard species can do it. When a predator, typically a member of the dog family, grabs the lizard, it restricts blood flow out of the head, which raises the pressure until small vessels in the sinuses around the eyes burst and send a fine jet of blood out through the eyelids, sometimes over a metre. The blood is not just startling, it also carries chemicals the lizard has taken up from eating harvester ants that taste extremely unpleasant to foxes, coyotes, and dogs, which usually release the lizard and shake their heads. It seems to have little effect on birds or snakes, which is why the lizard uses camouflage and body-puffing against those predators instead.
What do horned lizards eat, and can I keep one as a pet?
They are ant specialists, and this is the reason they make poor pets. A horned lizard needs to eat large quantities of ants, especially native harvester ants, every day, and it does not thrive on the crickets and mealworms that suit most pet lizards. Sourcing enough of the right ants year-round is impractical for a keeper, and captive horned lizards usually decline slowly from malnutrition. On top of that, several species are protected, so wild collection is illegal in Texas and restricted elsewhere. Horned lizards are best appreciated in the wild, and the conservation advice is to keep native ant populations healthy rather than to keep the lizards.
Why is the Texas horned lizard disappearing?
Mainly because of ants, in two ways. The invasive red imported fire ant has spread across the US Gulf states and displaces the large native harvester ants that are the Texas horned lizard's staple food, and fire ants also attack and kill the tiny hatchling lizards. At the same time, decades of broadcast insecticide use aimed at fire ants and other pests has wiped out harvester ant colonies over large areas. Add the conversion of native grassland to crops, pasture of introduced grasses, and housing, plus a long history of people collecting the lizards for pets and to sell as curios, and the species has been squeezed out of roughly half its Texas range. Zoos in Texas now breed and release horned lizards to try to re-establish populations.
What is the difference between a horned lizard and a thorny devil?
They look strikingly similar, both being small, flat, wide-bodied, ant-eating desert lizards covered in spines, but they are not closely related and live on opposite sides of the world, a clear case of convergent evolution. Horned lizards, genus Phrynosoma, are found only in the Americas and belong to the same broad group as fence lizards and iguanas. The thorny devil, Moloch horridus, lives only in the arid interior of Australia and is an agamid, related to the bearded dragons. Both eat almost nothing but ants, both collect water on the skin and channel it to the mouth, and both rely on camouflage and spines, but only the American horned lizards squirt blood from the eyes.