Reptiles
Coast Horned Lizard
Phrynosoma blainvillii · also called California horned lizard
A coast horned lizard waits patiently beside what was once a reliable native harvester ant trail, but in growing parts of coastal Southern California, invasive Argentine ants have taken over instead, offering little of the nutrition the lizard actually needs to survive.
Overview
The coast horned lizard, Phrynosoma blainvillii, is a flattened, spiny lizard native to coastal and grassland habitat across California and Baja California. Its steep population decline, driven by the loss of native ant prey to an invasive species, makes it one of the more concerning conservation stories among North American horned lizards.
When the food supply changes beneath you
The coast horned lizard’s decline illustrates how a highly specialised diet can become a serious vulnerability, since the arrival of an unrelated invasive ant species was enough to undermine populations even in areas where the physical habitat itself remained largely undisturbed.
Status
Vulnerable — declining significantly across coastal Southern California due to urban development, habitat fragmentation, and displacement of native ant prey by invasive Argentine ants.
Coast Horned Lizard: common questions
Why has the coast horned lizard declined so much?
The coast horned lizard has experienced significant population declines across parts of coastal Southern California, driven by a combination of urban development, habitat fragmentation, and the spread of invasive Argentine ants, which have displaced the native harvester ants the lizard depends on heavily as its primary food source.
Why are Argentine ants such a problem for the coast horned lizard?
The spread of invasive Argentine ants across parts of the coast horned lizard's range has displaced native harvester ant colonies in many areas, and because the lizard depends so heavily on harvester ants specifically, this loss of its preferred prey has contributed significantly to regional population declines even where physical habitat otherwise remains intact.
Can the coast horned lizard defend itself like other horned lizards?
Yes, like several other horned lizard species, a coast horned lizard can squirt a thin stream of blood from vessels near its eyes as a startling defensive response when severely threatened, a dramatic last-resort tactic shared broadly across the horned lizard genus.
Where does the coast horned lizard live?
The coast horned lizard is native to coastal and adjacent grassland habitat across California and Baja California, generally favouring open, sandy or gravelly terrain, though suitable habitat has become increasingly fragmented by urban development across much of its historical Southern California range.