Overview
The Coast Horned Lizard (Phrynosoma blainvillii), affectionately celebrated throughout California history as the ‘horny toad’, is a flat, spiky, and iconic desert-and-chaparral reptile belonging to the family Phrynosomatidae. Once an abundant and beloved inhabitant of southern California’s valleys, coastal dunes, and chaparral hillsides, this gentle, armored reptile is famous for its crown of sharp occipital horns and rough, prickly skin.
Despite its intimidating, prehistoric dragon-like appearance, Phrynosoma blainvillii is a harmless, slow-moving ant specialist that relies entirely on cryptic camouflage to avoid predators. When pushed to extreme distress by canid predators, it performs one of the most astonishing, bizarre physiological defense mechanisms in nature: auto-hemorrhaging, squirting a stream of foul-tasting, pressurized blood directly from its eye sockets over a distance of several feet.
AT A GLANCE
- Common Name: Coast Horned Lizard
- Scientific Name: Phrynosoma blainvillii
- Category: Reptiles
- Subcategory: Lizards
- Size: 6.5 to 11 cm (2.5 to 4.5 in) snout-vent length, excluding short tail
- Weight: 20 to 50 g (0.7 to 1.8 oz)
- Lifespan: 5 to 8 years in the wild
- Diet: Insectivorous/Myrmecophage Specialist: native harvester ants (Pogonomyrmex), beetles, termites, and small grasshoppers
- Habitat: Coastal sage scrub, chaparral, sandy washes, alluvial fans, open oak savannas, and arid sand dunes with abundant native harvester ant colonies.
- Range: Native to western North America, ranging from the San Francisco Bay Area and Central Valley of California south through southern California into Baja California, Mexico.
- Conservation Status: Near Threatened (IUCN Red List)
Biology and Physical Characteristics
Phrynosoma blainvillii possesses an exceptionally flattened, pancake-like oval body covered in rough, keeled scales and fringe-like spines running along the margins of its flanks. Its crown is armed with a formidable ring of true bony horns extending from the parietal and squamosal bones of the skull, with two prominent, sharp horns pointing backward from the center of the head. Its dorsal coloration is mottled grey, tan, and reddish-brown, mimicking gravel and granite sand.
The lizard has an astounding cardiovascular adaptation: when attacked by canids like coyotes or foxes, muscular sphincters restrict venous blood flow returning from the head, dramatically elevating blood pressure in the ocular sinuses until thin membranes in the corners of the eye rupture. The lizard squirts a thin jet of pressurized blood up to 1.5 meters (5 feet) directly into the predator’s mouth. The blood is laced with pungent, bitter compounds that canines find violently repulsive.
Behavior and Ecology
Coast horned lizards are diurnal ambush foragers with an extreme dietary specialization: over 90 percent of their natural diet consists of native harvester ants (*Pogonomyrmex* species). The lizard parks itself beside an active ant trail and uses its sticky, muscular tongue to lap up dozens of stinging ants without moving. Its digestive tract produces specialized mucus that neutralizes the painful formic acid and stings of harvester ants.
When basking in the morning sun, it tilts its flattened body toward the light to absorb heat rapidly. If a predator approaches, it flattens itself into the sand, wriggling its body side-to-side until sand covers its flanks, leaving it virtually invisible. Mating occurs in late spring; females lay clutches of 6 to 21 white eggs in moist subterranean sand burrows, which hatch after two months.
Conservation and Human Impact
The Coast Horned Lizard is classified as Near Threatened on the IUCN Red List and is a California Species of Special Concern, having disappeared from over 80 percent of its historical range in coastal southern California. The primary driver has been catastrophic urban sprawl, commercial agriculture, and coastal golf course development.
Even more devastating is the invasion of non-native Argentine ants (*Linepithema humile*): these aggressive invasive ants displace and eradicate native harvester ant colonies, but because Argentine ants are too small and chemically unpalatable for horned lizards to eat, horned lizards rapidly starve to death in invaded habitats. Conservation efforts focus on protecting large, intact chaparral reserves free from Argentine ants.
Interesting Factoid
When cornered by a coyote or dog, the coast horned lizard can shoot a jet of foul-tasting, toxic blood directly out of the corners of its eyes for up to five feet.