Lizards are a highly diverse group of reptiles, with over 6,000 species inhabiting nearly every environment across the globe, from scorching deserts to humid rainforests. This immense variety means there is no single answer to what they eat. Their diet depends significantly on the individual species, its size, its stage of life, and the specific ecosystem it occupies. Understanding the dietary needs of these animals begins with classifying them by their primary food source.
Categorizing Lizard Diets
Lizards are broadly categorized into three main feeding groups: carnivores, herbivores, and omnivores, each requiring a distinct nutritional profile.
Carnivores primarily consume animal protein. Insectivores, such as leopard geckos, chameleons, and anoles, rely on invertebrates like crickets, mealworms, and Dubia roaches. Larger carnivorous lizards, including monitor lizards, expand their diet to include vertebrate prey such as rodents, birds, eggs, and other lizards.
Herbivorous lizards consume plant matter and require diets rich in fiber to support their specialized digestive systems. Species like the green iguana and Uromastyx ferment plant fiber in an enlarged hindgut using gut microbes. Their diet must consist predominantly of leafy greens like collard, dandelion, and mustard greens. Vegetables like squash and carrots make up a smaller portion, and fruits should be offered sparingly due to their high sugar content and poor calcium-to-phosphorus ratio.
Omnivorous lizards, such as the bearded dragon and many skinks, maintain a flexible diet incorporating both animal and plant material. These species need a careful balance, consuming insects and small vertebrates alongside fresh vegetables and greens. Juvenile omnivores require a much higher ratio of protein-rich insects to support rapid growth before transitioning to a more vegetable-heavy diet as adults.
Essential Nutritional Components
All lizards require certain micronutrients to maintain health, regardless of their dietary classification. Calcium is an important mineral, serving as the building block for strong bones and playing a role in muscle function and nerve transmission. A deficiency in calcium is a common problem in captive lizards and can lead to Metabolic Bone Disease (MBD).
Calcium metabolism is linked to Vitamin D3, which helps the body absorb and utilize calcium effectively. In the wild, most lizards synthesize Vitamin D3 naturally through exposure to ultraviolet B (UVB) light from the sun. Without adequate UVB exposure or dietary supplementation, a lizard cannot absorb calcium, rendering a calcium-rich diet ineffective.
Protein and fat serve as primary sources of energy and materials for growth and repair. Protein supplies the amino acids necessary for developing muscle and tissue, making it important for young, growing lizards and breeding females. Fats provide concentrated energy, supporting healthy skin, immunity, and the absorption of fat-soluble vitamins like A and D3.
Hydration is also necessary, though the method of water intake varies widely between species. Some lizards drink readily from standing water bowls, while others in arid or arboreal environments rely on water droplets, known as hygroscopic drinking. Water intake is also secured through the consumption of moisture-rich food items, such as fresh vegetables or hydrated insects.
Feeding Practices for Captive Lizards
Providing a complete diet for a captive lizard requires specific husbandry practices to ensure adequate nutrient delivery. Since most commercially available feeder insects are nutritionally deficient, gut-loading is necessary. This involves feeding the prey insects a highly nutritious diet for 12 to 48 hours before they are offered, turning the insect into a delivery system for vitamins and minerals.
Supplementation is required to correct nutritional imbalances found in captive diets. Feeder insects or plant matter must be lightly dusted with powdered calcium supplements to boost mineral content. Calcium powder without Vitamin D3 is used for lizards with proper UVB lighting, while a calcium with D3 supplement is utilized for those with limited light exposure.
Multivitamin powders, containing essential vitamins like A and E, are administered less frequently, typically once or twice a week for adults. Feeding frequency depends on the lizard’s life stage; juveniles need to be fed daily to support rapid growth. Adult lizards have slower metabolisms and often require meals only every other day or a few times per week.
Food preparation is important, especially for herbivorous and omnivorous species. Vegetables and greens should be finely chopped to an appropriate size, ensuring they are easily digestible. The use of wild-caught insects is discouraged due to the risk of pesticide contamination or parasite transmission.