Tuesday, January 6, 2015

Really Weird Animals: Texas Horned Lizard

The Texas horned lizard (Phrynosoma cornutum) is found from the south-central United States to northern Mexico.  Their habitat is arid and semiarid open areas with limited plant cover.  They also require loose soil in order to burrow for hibernation, nesting, and insulation.
Notice how well this individual blends into the background (photo: the wikipedia files)

There are about fifteen species of horned lizards, eight being native to the United States.  They are often called “horny toads” or “horned frogs.”  However, they are neither a toad nor a frog but the name comes from the lizard’s rounded body and blunt snout, which resembles the amphibians.  The Texas Horned Lizard is the largest and most widely distributed of the horned lizards.
This lizard has two prominent horns towards the rear middle part of its head and then several smaller horns on the sides.  The protrusions on the head are true horns since they have a boney core.  However the horny spines on its sides and back are composed of modified scales.  Its scale coloration is a mixture of brown and gray earth tones, giving it excellent camouflage. 

Horned lizards mainly eat harvester ants, but will also include termites, grasshoppers, beetles, and beetle larvae in their diet

What makes the Texas horned lizard so strange is its defense mechanism.  Horned lizards mainly use their camouflage to avoid predation.  However, if found their horns and spines may act as a deterrent for many predators.  The lizard may also inflate its body to make itself look larger and less easy to swallow.  But finally, if all else fails, the lizard will violently excrete blood from its eyes!  This process is called autohaemorrhaging, or reflex bleeding.  It can squirt up to 1/3 of its volume in blood reaching up to a five-foot distance.  They do this by restricting the blood flow leaving the head, increasing the blood pressure and rupturing tiny vessels around the eyelids.  The blood is mixed with a chemical that makes it very foul tasting to canine and feline predators.  There are eight known species of horned lizards that have this defense mechanism.  The only other known animals that will expel blood as a defense is a genus of dwarf boas, Tropidophis, and the European grass snake, Natrix natrix.
The Texas horned lizard is listed as a threatened species in Texas and Oklahoma mainly due to loss of habitat, use of pesticides exterminating their food source, and the spread of an invasive species, the red fire ant.  The aggressive and territorial red fire ant destroys harvester ant colonies, the lizard’s main food source.  The Texas horned lizard is now a protected species and Texas Parks and Wildlife along with other conservation groups are studying the species in order to shield it from any further harmful human impact.

Submitted by Sara Oliver, World Bird Sanctuary Naturalist 

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