Horned lizards, often called "horny toads" despite not being frogs or toads, are reptiles characterized by their flattened bodies and distinctive crown of spines. These lizards, masters of camouflage, inhabit arid and semi-arid environments across North America and Mexico. This article explores the diverse feeding habits and dietary preferences of horned lizards, highlighting their adaptations and ecological roles.
Physical Characteristics and Distribution
Horned lizards are exotic reptiles with a flat body and a fierce appearance, ranging from 2.5 to 7 inches in length. The Texas horned lizard, Phrynosoma cornutum, has a prominent crown of spines on its head, with the two center spines being the longest. Two rows of fringed scales run down each side of the lizard. Their coloration is generally brownish or sandy, with dark spots that help them blend into their environment. Dark lines radiate from the eye.
Naturally occurring from Louisiana to Arizona, they have also been introduced in several locations in the Southeast due to the pet trade. Their North American distribution extends from southeastern Arizona east to south-central Arkansas and north from central Kansas south into Mexico. These lizards are adaptable to a wide range of conditions.
These lizards prefer hot, dry, sandy habitats that are mostly open. Like all reptiles, horned lizards depend primarily on their environment to control their body temperature, often seen basking in the morning sun. They live in a variety of arid and semi-arid environments from oak-pine woodland to thorn scrub deserts.
Dietary Specialization: Myrmecophagy
Horned lizards are primarily myrmecophagous, meaning their diet consists almost exclusively of ants. They are masters of camouflage, generally relying on their coloration for protection and sometimes even partially burying themselves in sand.
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The Texas horned lizard's diet consists mostly of harvester ants. Parker (1975) examined the stomach contents of 351 Texas horned lizards. A single Texas horned lizard can consume from about 30 to over 100 ants per day. This specialized diet plays a crucial role in maintaining the balance of ant populations within their ecosystems. A Texas horned lizard can consume from about 30 to over 100 ants per day, which gives their prey a chance to replenish their populations.
Supplemental Diet: Other Invertebrates
While ants form the cornerstone of their diet, horned lizards are opportunistic feeders. If necessary, they may supplement their diet with other small insects such as grasshoppers, beetles, and spiders. They will also eat many other types of invertebrates, such as grasshoppers, beetles and spiders, to supplement their diet. They may also consume young snakes, snails, and sowbugs.
Foraging Behavior and Predation Risks
Horned lizards typically search for prey in open areas, moving quietly or waiting for an unsuspecting ant or other food item to come into view. Usually, they search for prey in open areas, moving quietly searching or waiting for an unsuspecting ant or other food item to come into view. When an ant approaches, the lizard takes a few quick steps forward, flicks out its tongue, captures its prey and swallows it whole. When a prey animal passes by, the lizard quickly snaps it up with a flick of its tongue and swallows it whole. Horned lizards usually capture their prey with their sticky tongues rather than grabbing it with their mouth.
This foraging behavior puts them at risk of predation. Horned lizards' foraging behavior puts them in danger of being eaten themselves. They are preyed upon by a variety of animals, including hawks, roadrunners, snakes, lizards, coyotes, ground squirrels, mice, cats, and dogs.
Defense Mechanisms
To avoid predators, horned lizards employ several unique tactics. Horned lizards attempt to avoid predators by using various tactics, some of which are quite unique. Their most unusual tactic is the ability to squirt a stream of blood from the corner of their eyes. This stream may be directed with limited accuracy at the predator's eyes and mouth and is probably a last resort. Experiments have shown that the blood is distasteful and repels some predators, canids (coyotes) in particular. Chemicals in the blood that produce the bitter taste may be derived from the ants they eat.
Read also: Feeding Habits of Horned Lizards
Another behavior horned lizards exhibit is the ability to inflate their bodies until they look like spiny balloons. When grasped, they close their eyes and the eyelids appear to inflate. They then squirt a directed stream of blood from the sinuses in their eye cavity toward the would-be predator. However, they most effectively avoid predators by simply holding still, relying on their camouflage. Horned lizards' color patterns closely match the soil on which they live and they can eliminate their shadows by flattening against the ground. If forced to move, a horned lizard runs only a short distance, stopping unexpectedly. The horned lizard lies flat, blending into its surroundings, and the predator is left chasing nothing. They will roll onto their backs and play dead to escape becoming prey.
Daily Activities and Habitat
Texas horned lizards are active in Oklahoma from early April through September. In October, they burrow underground to begin their winter hibernation. During the active season, they are usually found in open areas with sandy soil. During spring and early summer, Texas horned lizards can be observed in their habitat by slowly driving paved and unpaved roads in mid- to late morning. The lizards frequently bask in the sun on roads. During much of the summer, they can be found by walking on unpaved roads or in open areas either early in the morning or late in the afternoon when the sun is close to the horizon. Because they are cryptically colored and usually do not move, Texas horned lizards are often difficult to detect.
They are often seen basking in the morning sun on a summer day. Even so, they are susceptible to overheating, so as the day gets warmer, the lizards move into the shade and may even go into burrows to stay cool in the long summer afternoons. Their bodies elevated to survey their environment for prey or predators. ; however, if the opportunity arises, they will consume other insects.
Reproduction
Horned lizards occur from southern Canada to southernmost Mexico. Seven species reproduce by laying eggs (oviparous) and six species give birth to live young (viviparous).
Female Texas horned lizards are larger than the males. reportedly grow until they become 144 mm in length, while males grow to 94 mm. From mid-April and continues until mid-June. Females deposit clutches of eggs (that vary in number with size of the female) in a slanted tunnel approximately 6-8 inches into the ground. Smaller females may produce clutches with more than 40 eggs. Hatching occurs in August, and hatchlings are about the size of a quarter when they emerge from eggs. The female provides no further care for her eggs or young and is not likely to lay more eggs that year. Individuals reach sexual maturity in the second year of life.
Read also: Diet and Feeding: Armadillo Girdled Lizard
Conservation Status and Threats
Populations of the Texas Horned Lizard have disappeared in East and Central Texas, and are decreasing in North Texas as well. A decline and disappearance of them in Oklahoma and New Mexico has been noted. Other species of horned lizards throughout the Southwest are also in trouble including the Pacific Coast Horned Lizard and the Flat-tailed Horned Lizard. The primary cause for population decline is the loss of habitat by agricultural and urban conversion. Other causes also have lead to declining populations including over-harvesting for the pet trade and curio trade and the invasion of exotic species, particularly exotic ants which the lizards can not survive on and out-compete their preferred ant. Also introduction of dogs and cats to areas where they were once abundant has caused the horned lizards to disappear.
Many species are state listed as Protected: which means it is illegal for anyone to take, pick up, possess, transport or sell them without a special permit. Not only is it illegal to keep many horned lizard species, but they are difficult to care for in captivity, and most captured ones eventually die from improper care.