Lizards are a diverse group of reptiles found across nearly every continent, and their diets reflect this global distribution. Ranging from tiny geckos to massive monitor lizards, their feeding habits span the full spectrum of available food sources, including insects, plants, and small vertebrates. A lizard’s diet depends heavily on its species, size, and habitat, making a single, universal feeding guide impossible. Understanding these variations is necessary for providing appropriate care and nutrition.
The Three Primary Dietary Types
Lizard diets are broadly categorized into three main types, each requiring a specific nutrient balance for long-term health.
Carnivorous and insectivorous lizards include the majority of smaller species, such as geckos and anoles, which primarily consume invertebrates like crickets and roaches. Larger carnivorous species, like Monitor Lizards, expand this diet to include small mammals, birds, and eggs. These diets are naturally rich in protein and fat, but require supplementation to balance the low calcium content typically found in feeder insects.
Herbivorous lizards consume plant matter, including leaves, flowers, and fruits. Their digestive systems are specialized for processing high amounts of fibrous material, relying on fermentation in the hindgut to break down cellulose. Species such as Green Iguanas and Uromastyx fall into this category. This plant-based diet must be rich in calcium and low in phosphorus to support bone structure.
Omnivorous lizards maintain the most flexible diet, consuming a balanced mix of both animal and plant matter. The Bearded Dragon is a well-known omnivore, eating a combination of insects and fresh vegetables throughout its life. This mixed feeding strategy ensures a wider intake of nutrients but requires careful management to prevent excess fat or insufficient mineral intake.
Essential Nutritional Needs and Supplementation
All lizards require two specific micronutrients for proper physiological function: calcium and Vitamin D3. Calcium is necessary for bone density, muscle function, and nerve transmission. A deficiency can result in Metabolic Bone Disease (MBD), which causes skeletal deformities and fractures and is a leading health concern for captive lizards.
Vitamin D3 regulates the absorption of calcium from the digestive tract into the bloodstream. Many lizards synthesize Vitamin D3 when their skin is exposed to UVB light. Those without adequate exposure must receive it through supplementation. A target Calcium-to-Phosphorus ratio of approximately 2:1 is recommended in the overall diet to ensure sufficient calcium is available and absorbed.
Hydration is also a nutritional consideration, as many species do not drink from a standing water bowl. Lizards from humid environments, such as chameleons, often prefer to lick water droplets from leaves or cage surfaces. Providing clean, fresh water in a manner appropriate to the species’ natural history is necessary for metabolic processes and successful skin shedding.
How Diet Changes with Species and Age
The dietary needs of a lizard are not static, often undergoing a significant change as the animal matures, known as an ontogenetic dietary shift. Many species, particularly those that grow large, are primarily insectivorous as juveniles to support rapid growth with high-protein intake. For example, Green Iguanas begin life as insectivores and gradually transition to an almost exclusively herbivorous diet as adults.
The adult body size of a lizard is a strong predictor of its natural diet, with most herbivorous species being significantly larger than their insectivorous counterparts. Plant material provides fewer calories per volume than insects, meaning a large lizard must consume a greater quantity of food. Some lizards exhibit extreme dietary specialization, such as the Marine Iguana, which feeds almost entirely on underwater algae.
Practical Feeding Guidelines
For lizards that consume invertebrates, the nutritional value of the prey must be enhanced through a two-step process: gut-loading and dusting.
Gut-loading involves feeding the feeder insects a nutritious, calcium-rich diet for 12 to 48 hours before they are offered to the lizard. This process ensures the lizard consumes the beneficial contents of the insect’s gut, increasing the overall nutrient delivery.
Dusting involves lightly coating the insects or plant material with a commercial calcium or multivitamin powder just before feeding. This technique directly delivers necessary supplements, which are often insufficient in commercially raised insects. Juveniles, which are undergoing rapid growth, typically require daily feeding, while adult lizards may be fed less frequently, depending on the species.
Certain human foods and plant items are unsafe and must be avoided in a lizard’s diet. Foods like avocado contain compounds that can be toxic to reptiles. Items high in oxalates, such as spinach, can bind calcium and prevent its absorption. Citrus fruits and processed foods should also be avoided, as they lack the appropriate nutritional profile and can cause digestive upset.