Lizards are opportunistic predators that often include caterpillars in their diet. The consumption of caterpillars, which are high in protein and fat, is common for many lizard species, especially smaller ones and juveniles. However, certain defensive traits can make caterpillars unappealing or even dangerous prey. This leads to a nuanced predator-prey relationship and plays a significant role in how lizards function as natural control agents for insect populations.
Lizards as Generalist Insectivores
Most lizard species are classified as generalist predators, meaning they consume a wide variety of prey rather than specializing in one type of food. Insects form the bulk of the diet for the majority of small to medium-sized species globally. This includes soft-bodied insect larvae, such as caterpillars, which offer a substantial caloric reward. Juvenile lizards of even larger species, which may become herbivorous as adults, are often insectivorous early in life to meet their high metabolic demands for growth.
Caterpillars are slow-moving and nutrient-dense, making them attractive targets for lizards employing different hunting strategies. Lizards that use a “sit-and-wait” approach, like many anoles, readily ambush passing caterpillars. Conversely, “active foragers,” such as many skinks, deliberately search ground cover and vegetation where these larvae are commonly found.
Specific Lizard Species Known to Consume Caterpillars
Many common lizard groups include caterpillars in their foraging repertoire. Geckos, found globally, frequently prey on a wide range of soft-bodied invertebrates, including caterpillars. The New Zealand common gecko demonstrates the widespread acceptance of these larvae as a food source across different lizard families.
Skinks, often ground-dwelling, are effective caterpillar predators due to their active foraging behavior. Rooting through dense vegetation and debris brings them into frequent contact with ground-level caterpillars. Arboreal species, like the Jackson’s chameleon, also consume caterpillars, utilizing their prehensile tails and specialized vision to hunt among the branches. The size of the lizard limits prey selection; larger lizards eat larger caterpillars, while smaller species focus on smaller larvae.
When Caterpillars Are Off-Limits: Defensive Strategies
Not all caterpillars are safe for a lizard to consume, as many have evolved sophisticated defense mechanisms. The most common defense is the sequestration of toxins, where the caterpillar ingests poisonous compounds from its host plant, making its body toxic to the predator. Monarch butterfly caterpillars, for example, feed on milkweed and accumulate cardiac glycosides, which are highly repulsive and often cause a predator to vomit, creating a powerful negative association.
These chemically defended caterpillars frequently advertise their toxicity with bright, contrasting coloration, a phenomenon known as aposematism. A lizard encountering a brightly colored larva, like the monarch, learns to associate that visual warning signal with a bad experience. This leads to the rejection of similarly patterned prey in the future.
Other physical defenses also deter predation, including dense, irritating hairs or urticating spines that can cause discomfort or injury to a lizard’s mouth and throat. Lizards prioritize safety and energy conservation, often bypassing a potentially dangerous meal if less problematic prey is readily available.
Ecological Significance in Controlling Insect Populations
Lizards serve an important ecological function as natural biological control agents, particularly in gardens and agricultural areas. By feeding on a broad spectrum of invertebrates, including the larval stages of moths and butterflies, they help regulate insect populations that can become pests. Their predation on caterpillars directly limits the number of herbivorous insects that cause damage to cultivated plants.
A healthy local lizard population can noticeably limit pest multiplication, benefiting both natural ecosystems and human agriculture. Larger lizard species, like some of the Uta genus, are often observed in high densities in areas of insect abundance, demonstrating their ability to capitalize on readily available prey. Maintaining suitable habitat and avoiding broad-spectrum pesticides supports these lizard populations, allowing them to continue their role in natural pest management.