The reptile diet: every species is a world of its own

With reptiles, the first lesson about feeding is this: there is no such thing as "the reptile diet". That word covers animals as different as a herbivorous tortoise and a carnivorous snake. Feeding a reptile the wrong diet is one of the most common causes of illness — and one of the most avoidable.

There is no single reptile diet

Before adopting a reptile, the question is not "what do reptiles eat", but "what exactly does this species eat". The diet of a leopard gecko, a bearded dragon and a tortoise have nothing in common.

This guide walks you through the major groups so you understand the general framework, but the specific diet — what, how much and how often — has to be tailored to your species and, ideally, with an exotics vet.

Herbivorous reptiles

Tortoises are the classic example. Their diet is based on a good variety of grasses and leaves suited to their species. Key points:

• Variety of safe plants and leaves; don't base the diet on a single food.
• Fruit, very little or none · its sugar upsets a herbivore's digestion.
• No animal protein · feeding dog or cat food to a herbivorous tortoise causes serious long-term harm.
• Calcium supplementation as directed by the vet.

Insectivorous reptiles

The leopard gecko is a strict insectivore. They eat live insects bred as feeders — crickets, cockroaches, various worms depending on the species and age:

• Farmed insects, never wild ones (pesticides, parasites).
• Insects of a size appropriate to the reptile.
• "Gut-loaded" insects dusted with supplement (see below).
• Some insects are fattier and are used only as an occasional treat; the vet will guide you.

Omnivores and carnivores

The bearded dragon is an omnivore: it combines insects and vegetables, and the ratio changes with age — as a youngster it needs more animal protein to grow, and as an adult the diet becomes more plant-based. Other species are strict carnivores. In every case, the rule is the same: research the specific diet of the species and life stage, don't improvise.

Calcium, vitamin D3 and UVB

This is one of the most important and most misunderstood points. Many reptiles need a proper supply of calcium and vitamin D3, because D3 is what allows calcium to be absorbed. And D3 is linked to UVB light.

• Calcium is usually provided by dusting the food with a specific supplement.
• Vitamin D3 is synthesised by many reptiles thanks to the UVB light in the vivarium.
• A lack of calcium, D3 or UVB causes metabolic bone disease: deformities, weak bones, fractures — serious and very common in poorly kept reptiles.

Diet, supplementation and UVB go hand in hand: that's why the vivarium and feeding are inseparable. The exact plan is set by the exotics vet according to the species.

Gut-loading: feeding the insects

"Gut-loading" is a simple and very important concept for insectivorous reptiles: before giving the insects to the reptile, you feed those insects well with vegetables and nutritious foods.

The logic: an empty insect provides little; a freshly fed insect carries those nutrients "inside" and passes them on to the reptile. Proper gut-loading, together with calcium dusting, is the difference between a poor diet and a complete one.

Frequency, water and mistakes

A few final pointers:

• Frequency · young reptiles tend to eat more often than adults; many species eat considerably less than a mammal. Adjust with the vet.
• Water and hydration · needs vary greatly by species (some drink from a bowl, others lap up droplets, others hydrate in baths). Find out about yours.
• Temperature rules · a cold reptile doesn't digest well. If it isn't eating, first check the vivarium temperatures.
• Serious mistakes · a monotonous diet, too much fruit for herbivores, animal protein for herbivores, wild insects, skipping calcium and UVB, and improvising instead of researching the species.

In short: a reptile's diet depends entirely on its species — herbivore, insectivore or omnivore. Research thoroughly what your particular reptile eats, ensure a supply of calcium and vitamin D3 (linked to UVB) to prevent metabolic bone disease, gut-load the insects, and adjust frequency and hydration with an exotics vet. With reptiles, feeding well is preventing illness.