Horned lizards, often called "horned toads" or "horned frogs" though they are neither, are fascinating reptiles with unique dietary needs and feeding strategies. These spiky-bodied creatures, known for their docile nature and camouflage abilities, primarily consume ants but may supplement their diet with other insects and invertebrates. This article explores the diet and feeding habits of horned lizards, with a focus on the Texas horned lizard (Phrynosoma cornutum) and the Hernandez’s short-horned lizard, also known as the greater short-horned lizard, examining what they eat, how they hunt, and the factors that influence their dietary choices.
Horned Lizard Species and Their Habitat
Horned lizards belong to the genus Phrynosoma, which includes several species distributed across North America. The Texas horned lizard, a particularly well-known species, ranges from Colorado and Kansas to northern Mexico, and from southeastern Arizona to Texas. Isolated, introduced populations can also be found in the Carolinas, Georgia, and northern Florida. Hernandez’s short-horned lizard is widely distributed in North America and can be found as far north as southern Saskatchewan and Alberta and south into the Texas Panhandle and central Mexico.
These lizards prefer hot, dry, sandy habitats that are mostly open. These areas include semiarid plains, shortgrass prairies, pinyon-juniper forests, and montane regions. Coloration varies depending on the environment in order to blend in with the color of the ground, ranging from a yellow or reddish-brown for deserts to a tannish brown for prairies.
Physical Characteristics and Behavior
Texas horned lizards are flat-bodied reptiles with characteristic horns spanning across their body, the two largest crowning its head, two more on its brows and jawline respectively, as well as lines of spikes spanning the lateral parts of the torso and dorsal ridges of the back. They typically range from 2.5 to 7 inches in length. The Texas horned lizard is a stocky, short-tailed lizard with several large “horns” protruding from the back of the head. Its general color is tan, grayish brown, or reddish brown. There are two large, dark brown spots behind the head and a series of brown markings on the back. A white or yellow line extends down the center of the back.
Despite their fierce appearance, Texas horned lizards are extremely docile creatures. They lead a solitary life and interact with each other only during the mating season. They are diurnal and spend their time feeding, resting in the shade, or sunbathing along the side of roads or other open, rocky areas. At night, they bury themselves in the sand and sleep. During the winter Texas horned lizards hibernate under soil or foliage. These horned lizards prefer to move very little, however, they can move quite fast if they feel a predator is in the area, and dart into thick grass and foliage to escape. Horned lizards are also excellent diggers, and can quickly burrow underground to escape threats.
Read also: Diet of the Colorado River Toad
Hernandez’s short-horned lizards are flat-bodied and squat with scales around the top of their head. They have snub noses, short legs, fringes near pointed scales on the trunk, smooth bellies, and short tails. They are gray, yellowish, orange-brown, or reddish-brown with dark spots on the back. Adult Hernandez’s short-horned lizards are diurnal, being most active during the evening and burrowing at night. However, these lizards may be active during the day when the weather is good from March to October. In general, they hibernate from late fall to early spring.
Primary Diet: Ants
Horned lizards are primarily myrmecophagous, meaning that their diet mainly consists of ants. About 70% of the Texas horned lizard's diet is made up of Harvester ants; this way they keep ant populations under control. They play a crucial role in regulating ant populations in their ecosystems.
Secondary Diet: Insects and Invertebrates
While ants form the bulk of their diet, horned lizards are also known to consume other insects and invertebrates when necessary. This includes grasshoppers, beetles, spiders, young snakes, snails, sowbugs, and a variety of invertebrates. This dietary flexibility allows them to adapt to varying environmental conditions and food availability.
Hunting and Feeding Strategies
Horned lizards are masters of camouflage, generally relying on their coloration for protection and sometimes even partially burying themselves in sand. They are considered to be “sit-and-wait” predators, though they can run in short bursts. They usually stand still and blend in with their environment, waiting for prey to come within range. Horned lizards usually capture their prey with their sticky tongues rather than grabbing it with their mouth.
Defense Mechanisms Related to Diet
Texas horned lizards also have the ability to squirt an aimed stream of blood from the corners of the eyes and sometimes from their mouth for a distance up to 5 ft (1.5 m). They do this by restricting the blood flow leaving the head, thereby increasing blood pressure and rupturing tiny vessels around the eyelids. This not only confuses predators, but also the blood is mixed with a chemical that is foul-tasting to canine predators such as wolves, coyotes, and domestic dogs. When threatened by a predator, a horned lizard puffs up and appears very fat, which causes its body scales to protrude, making it difficult to swallow. When inflated, their protruding horns make an unappetizing meal.
Read also: The Hoxsey Diet
Factors Affecting Diet
Several factors influence the diet of horned lizards, including habitat, prey availability, and environmental conditions.
- Habitat: The specific habitat in which a horned lizard lives determines the types of prey available. For example, lizards in grasslands may have access to a wider variety of insects compared to those in deserts.
- Prey Availability: The abundance and distribution of ants and other insects vary depending on the season and environmental conditions. Horned lizards must adapt their feeding habits to take advantage of available prey.
- Environmental Conditions: Temperature and rainfall can affect the activity levels of both horned lizards and their prey. During periods of drought or extreme heat, prey may become scarce, forcing lizards to rely on alternative food sources.
Conservation Status and Threats
Texas horned lizards have disappeared from almost half of their geographic range. Population declines are attributed to the loss of habitat, human eradication of the ant populations upon which the lizards prey, displacement of native ant populations by invading fire ants, and predation by domestic dogs and cats. The IUCN Red List and other sources don’t provide the number of the Texas horned lizard total population size.
Diet of Frogs and Toads
While horned lizards are reptiles, it's interesting to briefly consider the diet of amphibians like frogs and toads for comparison. Frogs and toads are opportunistic feeders, eating bugs small enough to fit in their mouths. Their well-being depends on diversity. Large frogs and toads (Anurans) can eat small fish, lizards, snakes, mice, crayfish, and other amphibians.
In captivity, frogs and toads do not have access to a large array of bugs. They’re limited to what their keeper acquires at the local pet store or cultivates independently. They need live insects.
Frogs eat the following:
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- Butterflies, Moths, Flies (Lepidoptera and Diptera)
- Wasps, Bees, Ants (Hymenoptera)
- True Bugs, Cockroaches, Grasshoppers, Locusts, Crickets
- Beetles (Coleoptera)
- Worms, Millipede, Centipedes, Slugs, Snails
- Springtails, Termites, Isopods
- Spiders, Scorpions
Large frogs can eat:
- Snakes, lizards
- Fish, Crayfish, Crustaceans
- Frogs, Salamanders, Caecilians
- Mice and other small mammals
Feeding Frogs and Toads in Captivity
Feeding frogs and toads can be tricky. It’s not as simple as filling a bowl with kibble. As we learned in the last section, frogs need live insects.
Use a variety of insects. The larger the variety, the better. Pet stores offer crickets, mealworms, dubia roaches, wax worms, wingless fruit flies, and more. When possible, offer different bugs to your frog rather than just crickets, for example. Feeders should be appropriately-sized. The insect size should not be so large that your pet chokes or hurts itself while eating. Monitor for overeating and undereating. Some species are prone to overeating, while others need food available 24/7. Research your frog’s requirements, watch their weight, and pay attention to their health so you can adjust their feeding as needed.
Gut-loading feeder insects. Feeders are low in nutritional value. Due to this, most hobbyists give their feeders a nutrient-rich diet 48 hours before feeding them to their pets. UVB or supplements. Captive frogs are prone to MBD (Metabolic Bone Disease) due to low calcium. Either a UVB light or supplements are recommended. Most hobbyists opt for dusting their feeder insects with a calcium powder supplement. Wild caught insects are frowned upon. If your pet doesn’t come from your part of the world, it might not be adapted to handle little parasites found in the local insect population. For this reason, hobbyists prefer to use feeder insects.