Wednesday Wildlife: Greater short-horned lizard

Beneath the sun-baked coulees of southeastern Alberta, a tiny spiked reptile lies nearly invisible against the dusty ground. The greater short-horned lizard, often known by the misnomer of the “horny toad,” is the only lizard species native to Alberta. Sighting one is a rare treat; with its camouflaged scales and secretive nature, this little reptile easily evades the notice of predators and people alike.

The greater short-horned lizard, Alberta’s only native lizard, is a tiny prairie survivor armed with camouflage, spines, and surprising defences.

These lizards are small, only about 5-12 cm long, and they vanish into their surroundings with remarkable ease. Their colours range from dusty grey and sandy beige to warm rust-brown, blending perfectly with prairie soils and rock. Often, the only way to find one is if it moves, but movement is rare. Greater short-horned lizards are ambush predators, preferring to remain motionless until an ant, beetle, cricket, or spider strays too close, when they strike in a sudden flicker of motion. Ants in particular make up much of their diet, and their sit-and-wait hunting style makes them masters of patience.

Camouflage is their first line of defence, but not their only one. If discovered by a predator, the lizard inflates its body into a spiny ball, making itself look larger and less appealing to swallow. It may also angle its horned head toward the threat like a tiny shield. When these tactics fail, the lizard turns to its strangest weapon: the ability to squirt blood from the corners of its eyes. The sudden blood spurt can reach nearly a metre, startling predators into retreat, and the bitter, foul taste of the blood often deters mammalian predators like coyotes. Yet the tactic is not without risk: forcing blood from the eye sockets is stressful and leaves the lizard briefly weakened. For that reason, it is a weapon of last resort; bizarre, unsettling, risky, but effective.

The eroded coulees and sunbaked slopes of Alberta’s badlands provide perfect habitat for the greater short-horned lizard. Sparse vegetation, friable soils, and south-facing exposures create the warm, open ground this species and its prey depend on.

Considering its desert-like appearance, one might be surprised that this reptile survives Canadian winters at all. Each year, the greater short-horned lizard digs a shallow burrow, often around 10 cm deep, and waits out the long, cold months safely below the frost line, emerging again in April when the prairie sun returns. This resilience makes them unique: they are the most cold-tolerant of all horned lizards, thriving at higher elevations and in cooler climates than their relatives. For a long time, they were thought to be the same species as the pygmy short-horned lizard, which ranges farther south in the United States. Only in recent decades did genetic studies reveal that the two are distinct, with the pygmy being smaller and more southerly, and the greater short-horned lizard possessing special adaptations that allow it to endure the harsher conditions of Canada’s badlands.

 A pygmy short-horned lizard, nearly identical in appearance to the greater short-horned lizard but smaller in size. So well camouflaged that it is difficult to spot, this species is less cold-tolerant than the greater short-horned lizard and occurs farther south in the United States. They are not found in Alberta.

Unlike many reptiles, these lizards do not lay eggs in soil. Instead, they are what is known as viviparous. Females retain the eggs within their bodies until they hatch, then give birth to live young in late summer. A single brood may be just a few offspring or more than two dozen tiny replicas of the adults. By carrying the eggs internally, the mother shields them from the cold prairie ground, where external nests would struggle to survive.

For decades, wildlife biologists have worried about the future of the greater short-horned lizard in Canada. The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) first listed the species as Special Concern in 1992. By 2007, mounting evidence of habitat loss and population decline led to an uplisting to Endangered (COSEWIC, 2018). Later surveys uncovered new populations and revealed that the lizards were less fragmented than once believed. In 2018, COSEWIC down-listed the species back to Special Concern, a hopeful sign that conservation measures and habitat protection are making a difference (COSEWIC, 2018). Alberta, however, continues to list the lizard as Endangered under its Wildlife Act, reflecting its precarious situation in the province (Government of Alberta, 2013).

Rolling prairie grasslands in Grasslands National Park, Saskatchewan, where most of Canada’s greater short-horned lizards are found.

The challenges remain stark. Because this species occupies such a small and specialized range, any disturbance can be devastating. Roughly 70 percent of Canada’s short-horned lizards live inside Grasslands National Park in Saskatchewan, where their habitat benefits from federal protection (COSEWIC, 2018). Even there, invasive plants and increasingly extreme weather, including summer droughts and winter freeze-thaw cycles, are taking a toll (COSEWIC, 2018). Outside the park, every remaining population, including all those in Alberta, is exposed to additional pressures. Conversion of native prairie to cropland, oil and gas activity, road building, irrigation projects, and even off-road recreation all damage the fragile soils that the lizards need (COSEWIC, 2018; Environment and Climate Change Canada, 2015). With such a patchy distribution, a single poorly placed development could wipe out an entire local colony (COSEWIC, 2018).

There is good news, however. The greater short-horned lizard is protected under both Alberta law and the federal Species at Risk Act, making it illegal to harm, harass, or possess them, or to destroy their burrows (Government of Alberta, 2013; Environment and Climate Change Canada, 2015). Researchers and conservation groups continue to study these elusive reptiles and safeguard the habitat pockets they depend on. Still, the push to protect Alberta’s only lizard is far from finished. By learning about this extraordinary species and sharing its story, we can help ensure that this tiny “prairie dragon” continues to endure on our wild grasslands for generations to come.

For assistance with injured and orphaned wildlife, please contact the Calgary Wildlife Rehabilitation Society at 403-214-1312.

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The greater short-horned lizard is tiny, rare, and at risk. Its future depends on protecting the shrinking prairie landscapes it calls home. Image credit: https://phenology.mwparc.org

References: 

• COSEWIC. (2018). COSEWIC assessment and status report on the Greater Short-horned Lizard (Phrynosoma hernandesi) in Canada. Committee on the Status of Endangered Wildlife in Canada. https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/greater-short-horned-lizard-2018.html

• Environment and Climate Change Canada. (2015). Recovery strategy for the Greater Short-horned Lizard (Phrynosoma hernandesi) in Canada. Species at Risk Act Recovery Strategy Series. Ottawa: Government of Canada. https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/recovery-strategies/greater-short-horned-lizard-2015.html

• Government of Alberta. (2013). Wildlife Act: Wildlife Regulation, Alta Reg 143/1997, Schedule 6 — Endangered wildlife. Edmonton, AB: Alberta Queen’s Printer.