Merck Manual

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Providing a Home for a Reptile


Roger J. Klingenberg


Last full review/revision Jul 2011 | Content last modified Nov 2016
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Among the most important considerations for any pet are its housing and dietary requirements. Because reptiles cannot regulate their body temperature in the same way mammals can, they have stricter requirements for housing than many other pets, particularly regarding temperature and sanitation. Dietary needs vary widely by species.


Housing requirements for reptiles include an appropriate enclosure and sources of light, heat, and water. Be sure to have the habitat completely ready and secure before bringing your pet home.

Enclosure Design

Many reptiles appear nervous and insecure in captivity. This can be reduced by providing appropriate cage “furniture” and hiding spaces. Arboreal species (those that live in trees) should be provided with horizontal and vertical tree branches or other appropriate climbing material. Terrestrial species (those that live on the ground) usually require more horizontal space. Many terrestrial species, as well as those that like to dig or burrow, require hiding places such as boxes, tree trunks, rocks, or other objects. For some species, a solid black border painted on the glass wall 8 inches (20 centimeters) from the cage bottom provides added security.

Some species of reptiles are solitary and prefer to be housed alone. Housing animals of the same species together may sometimes be possible; however, groups should not include more than 1 male, as males of the same species may become aggressive toward each other. For experienced reptile owners, it may be possible to create an enclosure suitable for housing several compatible species together. Community housing of highly social species that are active during the day often requires placing several stations for basking, eating, and drinking that are all out of the view of dominant animals from the same species and any human observers. Overcrowding must be avoided to reduce stress and competition for food, water, basking sites, and mates. Aggressive species may have to be separated during feeding to prevent injury to cage mates. Fighting can be reduced significantly by housing only compatible species together.

The floor of the enclosure should be covered with a material that is disposable, inexpensive, nontoxic, and nonabrasive. The best ground coverings, or substrates, are those that provide the least amount of area for microbial growth and help make cage cleaning easy. Newspaper, sand, peat moss, potting soil, wood shavings, cypress mulch, corncob bedding, walnut bedding, gravel, alfalfa pellets, and artificial turf have all been used successfully for snakes. Cedar shavings should be avoided as the strong odors and vapors may cause breathing problems as well as potential neurologic problems. Snakes less than 18 inches (45 centimeters) long should not be fed while on “loose” substrates such as shavings, corncob or walnut bedding, or small gravel because these substrates accumulate around the mouth (possibly causing inflammation of the mouth) and may be swallowed (possibly causing a blockage in the intestine). One solution is to remove the snake from its normal cage and feed it in a separate cage on newspaper. This results in conditioned behavior that is thought by some to decrease feeding frenzy activity in large snakes when approached in their normal, nonfeeding cage.

Ease of cleaning is a good reason to choose a less complicated substrate. In order to minimize parasites, bacteria, and other organisms that cause disease, it is essential to be able to clean thoroughly and frequently. Newspaper is the substrate of choice for sick reptiles because it is inexpensive, easy to clean, and allows regurgitated material or droppings to be easily observed.

The humidity level necessary for a particular reptile also determines substrate choice. Cypress mulch can hold moisture and is resistant to mold. In contrast, corncob bedding is readily available but is expensive and subject to severe molding if wet. Mixtures of sand, peat moss, and soil hold moisture and allow burrowing. Sand or soil can also be used for a drier substrate. Smaller environments within an enclosure can provide increased humidity without creating high humidity levels in the entire cage.

Sand, potting soil, and leaf litters are adequate substrates for many species of lizards, turtles, and tortoises. Alfalfa pellets (common rabbit pellets) are also useful bedding for turtles and tortoises. The pellets are inexpensive and easy to clean—and they are nutritious if eaten!

Aquatic turtles and crocodilians can be maintained on a combination of sand, gravel, and cement substrates if basking areas are provided. Gravel should be large enough so that it cannot be eaten.


Most reptiles are ectotherms (often called “cold-blooded” animals), because they maintain their body temperatures by moving to different places in their environments. In their natural habitat, they are quite good at keeping their body temperature within a relatively narrow range compared with the outside temperature. To control daily changes in body temperature, many reptiles seek out cool or warm areas. For example, a reptile might bask on a rock that has been warmed by the sun to raise its body temperature.

The cage or enclosure used to house reptiles should provide a range of temperatures (within the preferred temperature range for each species) from one end of the enclosure to the other to keep the occupants healthy. A range of temperatures also helps with digestion, keeps their immune systems healthy, and increases the effectiveness of certain drugs. Tropical species generally prefer temperatures of 80 to 100°F (27 to 38°C) and temperate species, 68 to 95°F (20 to 35°C). Semiaquatic turtles prefer a slightly lower range. The temperature in the enclosure must be carefully monitored; temperatures that exceed the upper limits by only 10°F (5°C) may prove deadly for some species of reptiles.

Most reptiles prefer basking sources of heat, perhaps because these are the most similar to their normal environment. Basking lights are preferred for turtles, tortoises, and lizards; this can be an incandescent bulb, infrared device, mercury vapor lamp, or a ceramic bulb heater. Heat lamps should be used with extreme caution, as overheating is common. These sources should all be protected from direct contact with reptiles and placed more than 18 inches (45 centimeters) from the ground covering. Smaller enclosures with limited ventilation should have a reptile thermostat with a probe attached to the heat source, and all cages should have a thermometer. It is a good idea to place thermometers in both the directly heated and unheated regions of the enclosure. Undertank heaters are also useful heat sources for lizards and snakes; when used with a basking light, they can provide heat at night as well as during the day. However, undertank heaters should cover no more than 30% of the available cage space and should be designed specifically for this use.

Two more recent products for heating reptile enclosures are mercury vapor bulbs and infrared heaters. Mercury vapor lamps are very good basking lights and also provide some ultraviolet (UV) light—the type of rays found in natural sunlight—that is necessary for reptile health (see Providing a Home for a Reptile : Lighting Requirements). Infrared panels are produced in many sizes and can easily be attached to the roof of the cage so as to radiate heat downward. Infrared heaters are unique because they heat objects in their path without overheating the enclosure. As with any basking light or heater, you should always check the temperature on top of the ground covering. If the heated surface is too warm for maintaining comfortable contact, it is too warm for the reptile as well. “Hot rocks” are not recommended because the heat they provide is not consistent and may cause burns.

Reptiles become inactive at lower temperatures. This is a normal seasonal event for many nontropical species, and it promotes the best conditions for reproduction and longterm physical well-being. However, hibernation should never be attempted with an ill reptile because its immune system is not as strong during seasonal changes and lower temperatures. Tropical species may decrease their level of activity due to minor temperature changes, but they should not be hibernated. Temperature extremes and fast changes of temperature should be avoided. You should ask your veterinarian or the person from whom you obtained the reptile about the proper temperature range and seasonal hibernation requirements for your pet.

Lighting Requirements

Feeding behavior, activity, and to a lesser extent, reproduction in reptiles are improved with full-spectrum light, which has qualities similar to natural sunlight and includes ultraviolet (UV) rays. Fluorescent bulbs that produce UVB wavelengths in the range of 290 to 320 nanometers are the most appropriate for reptile enclosures. Mercury vapor lamps are the only nonfluorescent bulbs available that can also provide ultraviolet light.

Providing the proper ultraviolet spectrum is essential in order to maintain healthy reptilian skin. While exposure to unfiltered sunlight is the best form of UV light available, sunlight filtered through most glass or plastic contains almost no ultra-violet rays. Ultraviolet-producing bulbs should be placed near resting or basking areas so that the reptile can obtain adequate ultraviolet exposure. Typical ultraviolet-producing lights should be within 18 inches of resting or basking areas, while mercury vapor lamps can be several feet away. The practice of using a black light in combination with full spectrum bulbs may promote reproductive activity in lizards, but does not significantly increase UVB exposure. Even the best full‑spectrum bulbs available are a poor substitute for natural sunlight. A species-appropriate supplement that contains vitamin D3 may be necessary (see Providing a Home for a Reptile : Nutrient Requirements).

The daily cycle of light and darkness, called the photoperiod, affects the behavior and physical functions of all animals. Photoperiod requirements for reptiles are based on daily and yearly activity cycles. For reptiles that come from areas with seasonal temperature changes, the photoperiod provides cues to ensure that reproduction occurs within the best environmental conditions. For tropical species, variations in the photoperiod are less important. Changes in photoperiod from about 10 hours of daylight for winter months to about 14 hours of daylight for summer months are common for many tropical and subtropical areas. Temperate areas experience changes in photoperiod ranging from about 8 hours of daylight during the winter to about 16 hours during the summer.

Water and Humidity

Semiaquatic reptiles, those that naturally live and grow near and in water, must be able to submerge themselves completely in water. Feeding, reproduction, and social interaction occur under water in many species. Filtering and aerating the water helps lower the level of toxic organic wastes and disease-causing organisms. For salt-water species, the salinity (level of salt) in the water should be carefully monitored. Water pH for some species of aquatic turtles may need to be adjusted to match their natural habitat.


Reptile Housing Requirements


Tropical species

80 to 100°F (27 to 38°C)

Temperate species

68 to 95°F (27 to 38°C)

Semiaquatic turtles

Slightly lower range


All species

Varies by species; in general anything below 35% or above 70% may cause problems


Subtropical and tropical species

10 hours (winter) to 14 hours (summer)

Temperate species

8 hours (winter) to 16 hours (summer)


All species

UV and UVB: 290 to 320 nanometers

Basking light: 50 to 75 watts at least 18 inches from basking area

Requirements for water intake are linked to the availability of water in the reptile’s natural habitat. Aquatic and semiaquatic reptiles need more water, while species from drier environments tend to conserve water. It is very important that water be available at all times to avoid dehydration. Loss of water through the skin occurs in many species when deprived of soaking areas; likewise, absorbing water through the skin has also been documented. Many species drink readily from pools or bowls, but a number of small lizards (such as anoles and true chameleons) drink by lapping water droplets that accumulate through condensation. Misting the environment or creating a drip system provides options for water intake. Be sure to ask your veterinarian or local pet store the best way to ensure that your reptile is getting enough water.

The humidity should mimic that of the natural environment of the reptile. Excessively low humidity (less than 35%) can result in dry skin and abnormal skin shedding, especially in species that are not used to a dry environment. Excessively high humidity (greater than 70%) can result in skin infections. (See table: Reptile Housing Requirements.)


Cleanliness is essential for successful longterm maintenance of reptiles. Cages should be kept free of any urine or animal droppings, and uneaten food should be removed and disposed of daily. Internal parasites are one of the most common health problems seen in reptiles in captivity; these parasites often need only one host—the reptile—and the offspring of the parasite can re-infect the same host. Therefore animal droppings should be removed in a timely manner. Tools used for scooping wastes should be disinfected before use in each cage to reduce the possibility of spreading the disease from cage to cage. Owners should check with their veterinarian regarding the most appropriate disinfectant or sanitizer to use for disinfecting their reptile’s environment and the frequency and concentration that is safest for their pet.

All substrates should be completely replaced at least every 3 months. Likewise, aquatic and terrestrial environments should be disassembled and disinfected at least every 3 months. Water dishes should be thoroughly cleaned at least once every 2 weeks. Although turtles appear to tolerate chlorine in treated water reasonably well, its effects are not known. While chlorine may result in temporary irritation of eyes in aquatic turtles not used to chlorine, it appears to be beneficial in controlling infection-causing bacteria and viruses in the water.


The nutritional requirements of reptiles are still being investigated. Most recommendations are based on experience and observation. The required levels of protein, carbohydrates, and fat in the diet are thought to be similar to those of mammals.

Feeding behavior and digestion are related to the environmental temperature. Because reptiles have a lower metabolism than mammals and other “warm-blooded” animals, they feed less frequently. Humidity, light, food type, and the presence of other animals also affect feeding behavior. In turtles and some plant-eating lizards, the color of the food contributes to food acceptance; red and yellow are often preferred colors. Some reptiles become accustomed to certain foods and are unwilling to accept alternatives. Providing a variety of foods at each feeding, especially to younger reptiles, may lessen this problem.

Quality is important when feeding whole-animal foods. Goldfish, mealworms, crickets, wax moth larvae, mice, or rats intended for use as reptile food should be fed a complete and balanced diet so that they provide adequate nutrients. Herbivores (animals that eat plants) and omnivores (animals that eat meat and plants) also require balanced rations. Vegetarian diets are often lacking in calories, protein, and calcium. Insects and grubs lack calcium, and supplementation is required.

The practice of gut loading is a common technique that involves providing insects with a nutritious mixture of cereals and vegetables immediately before being fed to the reptile—thus loading their gut with nutrients. Another common practice is the use of powdered vitamin/mineral supplements. Crickets brought home from a pet store and never fed have little nutritional value. Placing them in a bag with vitamin and mineral powders and shaking the bag will coat the insects with the powder. Although some of the powder will fall off, the newer microfine powders adhere remarkably well. Adding calcium and calcium-rich foods to the diet of crickets and wax moth larvae is another way to provide more calcium.

Nutrient Requirements

The protein content of a reptile diet has traditionally been recommended to be about 18 to 20% for meat-eaters and 11 to 12% for plant-eaters. Inadequate protein levels result in weight loss, muscle wasting, increased chances of infections, failure to reproduce, and slower healing after injury. An infection that will not go away after treatment can be the result of inadequate nutrition. Many newer commercial diets offer protein levels up to 28 to 32%, which may prompt rapid growth but can have severe longterm consequences such as hyperuricemia (see below). Consequently, lower protein levels are currently recommended, because reptiles excrete uric acid.

Excess protein levels occur in meat-eating lizards when excessive meat products are fed rather than whole animals. Feeding large amounts of high-protein cat foods has been shown to cause increased levels of protein and vitamin D3. Many nutritionists recommend not feeding cat foods to reptiles. Dog food, especially low-fat varieties, can be used sparingly as part of a complete and balanced diet in both meat-eaters and plant-eaters. The overuse of high-protein diets prepared for meat-eaters has been shown to cause disease in tortoises and iguanas. Feeding excess protein can result in a condition called hyper-uricemia, in which uric acid is deposited in internal organs. This may lead to gout of the affected organs, which can be fatal.

Most protein deficiencies are seen in plant-eating species on “salad-type” diets or in individual reptiles with no appetite. Diets for plant-eaters may be supplemented with alfalfa sprouts, bean sprouts, soybeans or meal, invertebrates (such as insects or worms), or soft-moist or low-fat dog food (used sparingly). Reptiles that refuse to eat may require force-feeding, a change in their environment, or enough variety in the diet to identify a preferred food item.

Fiber is required for the normal functioning of the digestive tract. In large land tortoises and other plant-eating species, adding roughage (such as hay) to the diet may eliminate chronic, smelly diarrhea.

Specific fatty acid requirements have not been determined for reptiles, but 0.2% linoleic acid (found in natural oils) in the diet is recommended. Atherosclerosis, a condition in which fatty material is deposited along the walls of arteries and then thickens, hardens, and eventually blocks the arteries, has been reported; restriction of cholesterol may be an important longterm dietary consideration in captive reptiles.

Mineral deficiencies are seen frequently in captive reptiles, especially turtles, tortoises, and lizards. Vitamin and mineral deficiencies are rare in snakes that are fed nutrient-rich whole prey. A vitamin/-mineral supplement should be added to the diet of every captive reptile; many products designed for use in reptiles are available in pet stores. There is a delicate balance of calcium, phosphorus, and vitamin D3 that is necessary to maintain good health in reptiles. If the balance is upset, hormonal disorders or bone diseases can occur.

Calcium imbalance is the most common mineral imbalance in reptile nutrition. Feeding a pure meat diet not only provides excessive protein but also is extremely poor in calcium and rich in phosphorus. Including whole prey or a low-fat, low-protein dog food in the diet can help reduce excess protein. Calcium should be supplemented with products developed for reptiles.

The exoskeleton of insects does not contain calcium. Therefore, reptiles that feed primarily on insects must obtain dietary calcium from insects “gut loaded” and powdered with calcium supplements. Plant-eating reptiles should be encouraged to eat items rich in calcium, including cabbage, kale, okra, sprouts, collard greens, and bok choy. These foods typically are also rich in vitamin A. A calcium supplement developed for reptiles should be routinely given to plant-eaters.

Vitamin D is also required for proper calcium metabolism and balance. Animals housed outside with access to natural, unfiltered sunlight usually have adequate levels of vitamin D3. Access to ultraviolet light is strongly encouraged in reptiles that are not exposed to unfiltered sunlight (see Providing a Home for a Reptile : Lighting Requirements). Reptiles that are fed whole mammals (such as mice) as prey generally consume adequate levels of preformed vitamin D3. The food items of reptiles that eat mostly insects should be fortified by gut loading and powdering. Plant-eating reptiles that have limited exposure to ultraviolet light should receive supplemental vitamin D3. Most reptile supplements that contain calcium also contain adequate amounts of vitamin D3. Care should be used when providing supplements, however, because excessive levels of vitamin D3 in the diet can lead to excessive absorption and use of calcium.

Inappropriate levels of calcium, phosphorus, or vitamin D can result in an imbalance in the hormone that regulates calcium, phosphorus, and magnesium levels within the blood and bone. If these levels are not corrected, the bones may become weak and spongy and begin to bow outward as they are pulled upon by the muscles. This condition is most often seen in the jaw bones. Self-feeding becomes difficult and then impossible as the jaw bones become too soft. Force-feeding by tube is needed in extreme cases. Osteomalacia (softening of the bones), kidney stones, cloacal calculi (accumulated mineral deposits, similar to kidney stones), and rickets (which also leads to softening and weakening of the bones) are also possible results of a diet deficient in calcium or vitamin D3. Broken bones, bone deformities, and soft or deformed shells in turtles may occur. Deadly signs may include seizures in which the muscles stay contracted.

Treatment consists of correcting the balance of these minerals and giving vitamin D3, if necessary, either by exposure to an appropriate ultraviolet light source or by an injection given by a veterinarian. A dietary history of your reptile would be useful in helping the veterinarian evaluate any deficiencies and determine possible courses of treatment. If a calcium supplement is to be provided in the initial stages of treatment, it should not contain phosphorus. An excellent calcium source is calcium glubionate, given on the recommendation of a veterinarian. Other sources of dietary calcium include crushed cuttlebone, crushed oyster shells, crushed or pulverized calcium lactate, or commercially available products. In severe cases, a veterinarian can give a calcium injection before giving extra calcium by mouth.

Feeding of certain green foods that contain goiter-causing compounds, such as bok choy, broccoli, Brussels sprouts, cabbage, and soy, may cause an iodine deficiency. Signs of deficiency include a lack of normal energy and activity and an abnormal swelling (goiter) at the base of the neck where it meets the chest. The imbalance is corrected by supplementing with a balanced vitamin-mineral mixture containing iodine, or iodized salt (0.5% of the diet).

Vitamin A deficiency is common in captive, plant-eating turtles. Box turtles, particularly in the US, appear most at risk usually due to improper diets that do not contain enough vitamin A. Signs of vitamin A deficiency include swollen eyelids, chronic respiratory disease, and kidney disease. Sometimes a thickened, sticky discharge from the eyes, in addition to swollen eyelids, is seen. The eyes may eventually remain closed, impairing the ability of the turtle to find food. Treatment consists of short daily soaks to allow the turtle to drink and wash its eyes, application of an antibiotic ointment to the eyes, and vitamin A injections given by a veterinarian. For less severe cases, vitamin A can be supplied by adding a drop of cod liver oil to the reptile’s food twice a week. Commercial vitamin products are also available for reptiles. Dietary levels of vitamin A should be increased for up to 6 weeks before hibernation in turtles and tortoises. However, caution should be used when supplementing, as too much vitamin A can cause severe thickening and irritation of the skin as well as incomplete and inadequate shedding of the skin.

Vitamin B1 deficiency can result from diets containing fish with high thiaminase levels. Giving extra vitamin B1 is required in such cases. Weight loss even though the reptile is eating enough food is a common sign, but neurologic problems (such as paralysis and lack of coordination or balance) can also occur. Goldfish have low thiaminase activity, while smelt have extremely high levels. Frozen fish have increased thiaminase levels. Deficiencies of the water-soluble vitamins often involve more than one vitamin and require treatment with a multivitamin preparation.

Deficiencies of other vitamins and minerals sometimes occur in reptiles and can be diagnosed and treated by your veterinarian.


Aggression during mating and feeding is common in some semiaquatic turtles, some skinks and iguanas, and many other lizards and snakes. Injuries to cage mates can be severe and are best avoided by separating animals at feeding and reducing the number of animals allowed in a breeding group. When separated individuals are placed together for breeding, they should be carefully monitored. If reptiles are to be kept together, it is vital that the enclosure is large enough to accommodate a perch and/or hiding area for each reptile. Food and water is best placed in multiple locations to prevent dominant animals from intimidating the others.

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