Lizards are a highly diverse group of reptiles, with over 6,000 different species found across nearly every continent. Their immense variety, ranging from tiny, insect-eating geckos to massive monitor lizards, means their diets are equally varied. The question of what lizards eat has no single answer, as their food source is linked to their size, habitat, and evolutionary adaptations. Understanding their feeding ecology requires looking beyond a simple list of prey and examining their specialized nutritional needs and unique hunting strategies.
The Three Primary Diet Types
Lizards can be broadly categorized into three groups based on their primary food source: herbivores, carnivores, and omnivores. Herbivorous lizards subsist almost entirely on plant matter, including leaves, flowers, and fruits, and represent a small minority of all species. Examples of plant-eaters are the Green Iguana and the Uromastyx, which rely on fibrous vegetation.
Carnivorous lizards, including insectivores, are the most common dietary group, especially among smaller species. These lizards feed on insects, arthropods, and other invertebrates, such as many geckos and chameleons. Larger carnivores, like monitor lizards and Gila monsters, consume small vertebrates, eggs, and carrion.
Omnivorous lizards maintain a flexible diet incorporating both animal and plant material, allowing them to take advantage of seasonal food availability. The Bearded Dragon is a well-known omnivore, consuming a mix of insects and fresh vegetables. Many young lizards begin as strict insectivores to fuel rapid growth before shifting to a more omnivorous or herbivorous diet as they mature.
Specialized Feeding Strategies
Many lizards employ specialized methods to capture and process their meals. The chameleon’s projectile tongue is a remarkable example of a high-power feeding mechanism that relies on elastic energy storage rather than muscle force. The tongue can be launched at a speed accelerating at over 264 times the force of gravity, preloaded into specialized connective tissue sheaths. This quick, ballistic strike allows them to capture prey in as little as 20 milliseconds, a speed muscle contraction alone could not achieve.
Large carnivorous lizards, such as the Komodo Dragon, utilize an approach relying on powerful jaws and a specific hunting technique. While their maximum bite force is not exceptionally high for their size, they compensate by using a slashing bite and pulling motions to tear flesh from large prey. Their skull structure is adapted to withstand significant forces generated by this caudal (rearward) pulling motion.
Herbivorous lizards, like the Green Iguana, have developed an enlarged hindgut where symbiotic microbes perform fermentation. This process breaks down tough plant fiber (cellulose). Hindgut fermentation provides a significant portion of their energy requirements, sometimes supplying 30 to 40% of their metabolic needs.
Nutritional Requirements and Hydration
A lizard’s diet must provide specific chemical components to ensure long-term health, particularly the correct balance of calcium and phosphorus. The ideal ratio of Calcium (Ca) to Phosphorus (P) is approximately 2:1. When phosphorus levels are disproportionately high, the body cannot absorb enough calcium, leading to metabolic bone disease (MBD).
Vitamin D3 plays a direct role in this process, as it is necessary for the lizard to absorb calcium from its digestive tract. Lizards that do not receive adequate exposure to ultraviolet B (UVB) light, which is needed to synthesize their own Vitamin D3, require this vitamin through supplementation. Without sufficient calcium and Vitamin D3, the body begins to draw calcium from the bones, weakening the skeletal structure.
Hydration involves specialized biological mechanisms, especially for lizards in arid environments. The Thorny Devil, native to Australian deserts, can absorb water through its skin using a network of tiny capillary channels between its overlapping scales. This micro-structured surface collects moisture from dew, rain, or moist sand and passively transports it to the lizard’s mouth. Other species, such as the Crested Gecko, hydrate by licking water droplets from leaves, requiring caretakers to mist their enclosures to mimic the natural environment.
Diet in Captivity vs. the Wild
The dietary needs of a lizard in a managed environment present unique challenges compared to its natural foraging habits. A wild lizard’s diet offers a wide variety of prey and plant matter, ensuring a broad spectrum of micronutrients that are difficult to replicate. Captive diets must be carefully managed to prevent nutritional deficiencies.
Two standard husbandry practices help compensate for this difference: supplementation and “gut loading.”
Supplementation
Supplementation involves dusting feeder insects or plant material with a fine calcium powder, often with pre-formed Vitamin D3, to achieve the necessary Ca:P ratio.
Gut Loading
Gut loading is the practice of feeding nutritious, high-calcium food to feeder insects for 24 to 48 hours before they are offered to the lizard. This process boosts the nutritional value of the insect, transferring essential vitamins and minerals to the lizard upon consumption. Owners must also avoid inappropriate human foods that lack proper nutrition or contain toxic compounds, as the captive environment removes the lizard’s ability to instinctively select a balanced diet.