In common with true toads (amphibians of the family Bufonidae), horned lizards tend to move sluggishly, often remain motionless, and rely on their remarkable camouflage to avoid detection by predators.

[2] At least eight species (P. asio, P. cornutum, P. coronatum, P. ditmarsi, P. hernandesi, P. orbiculare, P. solare, and P. taurus) are also able to squirt an aimed stream of blood from the corners of the eyes for a distance up to 5 ft (1.5 m).

Ocular autohemorrhaging has also been documented in other lizards,[7] which suggests blood-squirting could have evolved from a less extreme defense in the ancestral branch of the genus.

Recent phylogenic research supports this claim, so the species incapable of squirting blood apparently have lost the adaptation for reasons yet unstudied.

[citation needed] A University of Texas publication notes that horned lizard populations continue to disappear throughout their distribution despite protective legislation.

Population declines are attributed to a number of factors, including the fragmentation and loss of habitat from real estate development and road construction, the planting of non-native grasses (both suburban and rural), conversion of native land to pastureland and agricultural uses, and pesticides.

[9] Fire ants (Solenopsis invicta), introduced from South America via the nursery industry's potted plants, pose a significant threat to all wildlife including horned lizards.

The center said it may later seek protection for the animal on a federal level; it also said that reptiles in general are dying off at up to 10,000 times their historic extinction rate, greatly due to human influences.

This school is located in Western Central California and its arid region is home to the San Diego Horned Lizard, which is protected.