A small spiny lizard that's rapidly evolving longer legs and new behaviors in response to invasive fire ants — one of the fastest-documented evolutionary changes in any vertebrate.

Also called: Swift, Pine Lizard, Prairie Lizard

Native status: Native to eastern + southern US

§ Quick facts

SizeTotal length 10–18 cm (4–7 in)
Weight10–20 g
LifespanWild typically 3–4 years; captive 5–7
OrderSquamata
FamilyPhrynosomatidae

§ Encyclopedia

The eastern fence lizard is a medium-sized species of lizard in the family Phrynosomatidae. The species is found along forest edges, rock piles, and rotting logs or stumps in the eastern United States. It is sometimes referred to as the fence swift, gray lizard, gravid lizard, northern fence lizard or pine lizard. It is also referred to colloquially as the horn-billed lizard. One of its most notable behaviors is that of its escape behavior when encountering fire ants, which have been known to invade and negatively affect many of their populations.

Source: Wikipedia — Eastern fence lizard Licensed under CC BY-SA 4.0

§ Identification

Field marks. Small spiny gray-brown lizard with rough keeled scales; males have bright blue throat and belly patches; females and juveniles duller with crossbands.

Similar species. Texas Spiny Lizard (larger, range overlap). Plateau Spiny Lizard (different range). Side-blotched Lizards (western, smaller).

Voice. N/A; push-up displays are primary communication.

§ Diet & behavior

Diet. Small invertebrates: ants, beetles, spiders, caterpillars, stinkbugs.

Behavior. Spiny "swift" lizard common in eastern open woodlands and rocky areas. Males do conspicuous push-up displays with brilliant blue throat and belly patches to defend territory. Populations in fire ant-invaded areas have evolved longer legs and faster escape behavior over just 70 years — a documented example of contemporary evolution in response to invasive predators.

§ Range

Eastern US from New York to Florida and west to Texas

§ Habitat

Open pine forests, rocky slopes, fence posts

§ Threats

Habitat loss to development, fire ant predation, fire suppression in pine forests.

§ Conservation status

According to the IUCN Red List, the eastern fence lizard is currently classified as Least Concern.

§ What helps

Support fire-managed pine restoration. Avoid pesticide drift. Don't kill native lizards.

Support our work More ways to help

§ Further reading

§ Sources cited

  • Penn State University fire-ant evolution studies
  • Virginia Herpetological Society
  • iNaturalist
  • IUCN Red List 2007