Though they are infamous for their ability to squirt blood from their eyes to deter predators, it is their thick skin that allows horned lizards to thrive amid the harsh conditions and plentiful predators of the desert. In addition to providing protection in the form of camouflage and spikes, the thick skin of horned lizards allows them to conserve enough water to survive in the desert ecosystem.
Approximately 17 species of horned lizards live throughout the southwestern United States and Mexico. Most -- including the desert horned lizard (Phrynosoma platyrhinos ssp.) -- are small, ant-eating lizards that have evolved to live very sedentary lifestyles. Horned lizards have longer activity periods than most lizards, and are among the first to emerge in the morning and the last to retire in the evening. Because they have large body cavities and sedentary lifestyles, horned lizards produce and deposit relatively large clutches of eggs.
Desert horned lizards and their kin rely heavily on their skin and scales for protection from predators. The thickness of their scales helps to prevent the teeth of would-be predators from penetrating their skin. Additionally, many of the thick scales on horned lizards have evolved into sharp horns or spikes, further deterring predators. When attacked by a predator, horned lizards will jab attackers with the large spines on their heads.
Disappearing into the Desert
Camouflage is incredibly important for the survival of desert horned lizards. Though they can run quickly for short distances, horned lizards try to evade detection rather than outrun their enemies. Their skin color -- which varies greatly to match the substrate of their habitat -- makes them very difficult to see, but the shape and texture of their scales further their efforts to hide. Along the sides and edges of their body, desert horned lizards have rows of jagged scales that break up their outline and make them blend seamlessly into the sandy desert ground.
Like most animals living in deserts, horned lizards opportunistically drink water in the form of rain, dewdrops and temporary puddles. When they can, horned lizards collect rainwater by arching their back, lowering their heads and letting the rain run down the scales of their back, eventually dripping into their mouths. Horned lizards conserve the water that they drink, and their thick scales prevent the water inside their bodies from evaporating into the environment.
- University of Texas: Horned Lizards, Part 2
- CaliforniaHerps.com: Phrynosoma Platyrhinos Calidiarum - Southern Desert Horned Lizard
- Reptiles and Amphibians of Arizona: Desert Horned Lizard
- Reptile Database: Search -- Genus: Phrynosoma
- Oklahoma Department of Wildlife Conservation: The Texas Horned Lizard
- Biological Journal of the Linnean Society: Morphological Correlates of Ant Eating in Horned Lizards (Phrynosoma)
- Journal of Experimental Zoology: Horned Lizards (Phrynosoma) Incapacitate Dangerous Ant Prey With Mucus
- Copeia: The Detoxification of Ant (Pogonomyrmex) Venom by a Blood Factor in Horned Lizards (Phrynosoma)