- Ensure the patient is hydrated and warm enough to handle nutritional support.
- Lizards utilize a range of dietary strategies although many species are insectivores or omnivores.
- Determine if an anorectic lizard is brumating. Brumation is a normal period of fasting associated with metabolic slow down.
- Many gravid females also eat less or go off feed entirely.
- Routine weighing is recommended for fasting reptiles. Prolonged or multiple fasts in less than ideal conditions or brumation of a sick or thin reptile can lead to starvation and debilitation.
- Over the first 2-4 days, feed debilitated patients 40-75% of calculated energy requirements. Gradually increase the calories fed.
Most reptiles will not waste away if they skip a meal or two. A more common mistake is to feed the hospitalized lizard too quickly before the animal is hydrated and warm (Fig 1). Reptiles are ectothermic or poikilothermic therefore body temperature relies on the environment rather than internal metabolism. To minimize stress, provide patients with an appropriate temperature gradient and take measures to meet other environmental requirements, which can vary widely. For instance a species native to an arid environment, such as the bearded dragon (Pogona vitticeps) requires a much lower relative humidity when compared to a tropical species such as the crested gecko (Rhacodactylus spp). Crested geckos do well in moderate humidity provided by live plants, a shallow water bowl and daily misting (Table 1). (See Hospitalizing Non-Traditional Pets for more specific advice.)
|Table 1. A comparison of husbandry requirements for the bearded dragon and crested gecko|
|Bearded dragon||Crested gecko|
|Preferred optimum temperature zone||80-88 °F (27-31°C)||72-80°F (22-27°C)|
|Basking light||92-95°F (33-35°C)|
|Nighttime low||60-70°F (16-21°C)||mid-60s°F (18°C)|
Dehydration is a common finding in sick reptiles. Dehydrated lizards may display sunken eyes and dry loose skin fold. Maintenance fluid replacement has been estimated at 20-40 ml/kg/day for lizards.
Most lizards are insectivores or omnivores, however a wide range of dietary strategies are employed (Table 2), and as in other taxa, dietary strategies in lizards do not always fall into easy categories:
- Spiny-tailed lizard (Uromastyx spp.) are herbivore-granivore-insectivores that should be offered greens, a variety of seeds, such as peas, lentils, and bird seed, as well as the occasional invertebrate.
- Small monitors and tegus may eat some fruit even though they are predominately carnivorous.
- The Savannah monitor (Varanus exanthematicus) is a carnivore-insectivore.
- Chuckwallas (Sauromalus spp.) are herbivore-insectivores.
- Although chameleons are insectivorous, the veiled chameleon (Chamaeleo calyptratus) can also consume small amounts of leaves, greens, or fruit.
- Crested geckos and day geckos (Phelsuma spp.) are insectivore-nectarivores. Captive specimens are fed insects and fruit baby food.
|Table 2. Dietary strategies practiced in lizards.|
|Dietary strategy||Gastrointestinal tract||Primary sources of dietary energy||Examples||Prey or natural food items|
|Carnivore (vertebrates)||Relatively short and simple gut||Fat, protein||Large monitors (Varanidae)||
See Self-feeding for more details.
|Insectivore (invertebrates)||Enzymes that digest chitin have been found within the gut, pancreas and liver of insectivorous reptiles (Micha 1973, Marsh 2001).||Fat, protein||
See Self-feeding for more details.
|Herbivore||The distal gut is relatively large for bacterial fermentation of fiber.||Fermented fiber and soluble carbohydrate||
See Self-feeding for more details.
|Omnivore||Fat, protein, and soluble carbohydrate.||
See Self-feeding for more details.
Recognizing true anorexia
Fasting may be expected in lizards during certain times of the year. Many gravid females eat less or go off feed entirely due to the large number of eggs filling the coelom (Gregory 1999). Some species also fast for weeks or months as an adaptation to excess heat or cold, drought, or lack of food. This dormancy in reptiles is called brumation as opposed to true hibernation. Fasting may be observed in captive animals, such as bearded dragons, even when kept warm with adequate food and water.
True brumation is associated with very little weight loss since the metabolic rate slows dramatically and the lizard consumes much less energy. Routine weighing is recommended for fasting reptiles. Prolonged or multiple fasts in less than ideal conditions or brumation of a sick or thin reptile can lead to starvation and debilitation.
To determine if nutritional support is indicated in your lizard patient, obtain a detailed history and look for evidence of clinical disease. The first questions to ask when evaluating an anorectic lizard are: Does this species normally brumate in the wild? And Is this individual gravid? Even if your patient is brumating or gravid, it can still encounter health problems so next determine if there has been significant weight loss. The slower metabolism of the reptile means that body weight may not be the most sensitive clinical parameter. Evaluate body condition by assessing the degree of muscle and fat over bony protuberances. The vertebral processes, ribs, and pelvic girdle should not be readily palpable.
Laboratory diagnosis of starvation can be difficult in the reptile. Blood glucose and electrolytes decrease inconsistently. Low plasma albumin may also suggest malnutrition. Survey radiographs may be used to rule out gastrointestinal obstruction or impaction. Use ultrasound to confirm the presence of intracoelomic fat bodies.
Once the need for nutritional support has been confirmed, determine how to best deliver food to your patient. Encourage self-feeding (see below) whenever possible, however limit insects to critically ill reptiles. Chitin in the insect’s exoskeleton is a source of nonprotein nitrogen which can be deleterious to water balance and renal function in the critical patient (Donoghue 2006).
Critically ill reptiles may be syringe or tube fed Emeraid critical care formula. When tube feeding, select a relatively wide bore tube such as a red rubber catheter or a stainless steel feeding needle. Use a speculum to hold the mouth open and take care not to injure the teeth. Rubber spatulas, some bird speculums, or padded hemostats can all serve as mouth specula. Go to Nutritional Support in Reptiles for demonstrations of syringe/tube feeding lizards.
To syringe or tube feed a lizard:
- First weigh the patient on a gram scale.
- Provide fluids and electrolytes as needed.
- Calculate caloric requirements. Daily energy needs are estimated as SMR = 32 (BW0.75)for reptiles kept at 86°F (30°C) where SMR is basal metabolic rate in kcalories per day and BW is in kilograms (Table 3). Variations in metabolism have been documented between seasons, gender age diet, and habitat.
Table 3. Estimated daily maintenance caloric requirements (1XSMR) in reptiles based on 32 (BW0.75)* Body weight (grams) Daily caloric requirements (kcal/day) 5 0.60 10 1.01 25 2.01 50 3.38 75 4.59 100 5.69 150 7.71 200 9.57 300 12.97 400 16.10 500 19.03 600 21.82 700 24.49 800 27.07 900 29.57 1000 32.00 2000 53.82 3000 72.94 4000 90.51 5000 107.00 10,000 179.95 15,000 243.90 20,000 302.64 25,000 357.77 30,000 410.20 * BW stands for body weight in kilograms; based on values at 86°F (30°C) (Donoghue 2006)
- For the first 2-4 days, feed debilitated patients 40%-75% of daily energy requirements to avoid digestive and metabolic upset. Overfeeding a starved critically ill patient can lead to life-threatening decreases in potassium and phosphorus. Rapid administration of calories, particularly carbohydrates, predisposes patients to this “refeeding syndrome”. Gradually increase calories fed to 100% of calculated energy requirements.
- When feeding, also keep mechanical limitations in mind. The stomach capacity of most adult lizards ranges from 2%-5% body weight. Therefore the stomach of a 100 gram lizard should theoretically be able to hold somewhere between 2-5 ml of formula.
- Monitor patients for stool production
- Gradually taper off assisted feeding whenever possible.
To stimulate voluntary feeding of the hospitalized lizard, house the patient in an environment appropriate for the species with a basking light and an appropriate temperature gradient.
Offer hospitalized carnivorous lizards warm meat baby food or warm, pre-killed whole prey. Feeding rates vary with species, age, size, and condition. Depending on these factors, those eating vertebrate prey are fed from 3-times weekly to once monthly. Reptiles eating invertebrate prey may be fed several times daily to about twice weekly.
Although short-term feeding of frozen foods is economical and convenient, offer herbivorous lizards fresh produce whenever possible. Wash all fruits and vegetables, and then chop into bite-size portions. Allow salad mixtures to reach room temperature for 30-60 minutes before feeding. Flat plates are preferable to bowls for many species, however the lizard can easily walk through its meal so take care to minimize or prevent fecal contamination.
- The bulk of the green iguana (Iguana iguana) diet should consist of raw, chopped, dark, leafy greens (i.e. mustard greens, collard greens, turnip greens, dandelion greens, escarole, endive, water cress). Mix leafy greens with other vegetables such as legumes, carrot tops, okra, bell pepper, mushrooms, zucchini, mild peppers, and pumpkin.
- Small amounts of brightly colored produce such as strawberry, tomato, melon, banana (with peel), yellow squash, and sweet potato can attract attention and stimulate the appetite.
- Well-washed, chemical-free leaves and blossoms such as clover, dandelion, grape leaves, Hibiscus, kudzu, Nasturtium, Pothos, and rose are consumed by green iguanas and Uromastyx spp.
The bearded dragon is a popular omnivorous lizard. The diet of the adult bearded dragon should include:
- Crickets and other insects
- Dark, leafy greens such as collard greens, kale, romaine, dandelion, turnip greens, mustard greens, beet greens, bok choy, Swiss chard, spinach, chicory, and escarole.
- Mix greens with other vegetables such as squash, zucchini, sweet potato, broccoli, peas, carrot, beans, okra, bean sprouts, or frozen mixed vegetables
- Flower blossoms like hibiscus make great treats.
- Commercial diets are sold for bearded dragons. The completeness, balance, efficacy and safety of these products have not been confirmed by independent evaluations or trials.
Insect eaters are often fed mealworms purchased at the local pet store or grown in a mealworm “farm”. Earthworms may be obtained from a local bait shop.
As a general rule, invertebrate prey should be no longer than the width of the lizard’s head or preferably insect prey should be 75% of head width.
Invertebrates are typically fed alive because their movement stimulates feeding behavior. Allow insect prey to roam freely through the habitat or place them in a bowl or cup. Place insects intended for chameleons directly in front of the animal or within a smooth-sided bowl suspended in the branches. Be sure to count the number of insects before placing them in the cage so the amount eaten may be determined. Never place more insects in the cage than may be eaten at one time. Feed adult lizards once daily; feed juveniles two to three times a day. Insect prey should be removed if uneaten after 6-8 hours as they can nibble on lizard toes, eyes, or other body parts.
Food items to avoid
Avoid feeding in large quantities:
- Broccoli, kale, bok choy, radish as they contain goiterogenic or iodine-binding substances.
- Spinach, beets, celery stalks, and carrots are high in oxalates.
The following food items are considered toxic based on anecdotal evidence:
- Avocadoes (although iguanas have been observed eating in the wild)
- Fireflies (toxicity documented in bearded dragons)
- Eastern tent caterpillar
- Invertebrates in contact with pesticides or herbicides
During a short-term hospital stay, vitamin-mineral supplementation may not be absolutely necessary. Long-term feeding requires supplementation for good health, however supplement with care to minimize the risk of under- or over-supplementation.
- Young, growing lizards should receive vitamins once or twice weekly and calcium once daily.
- Donoghue has recommended the vitamin supplement contain 100 parts vitamin A to 10 parts vitamin D3 to 1 part vitamin E.
- The rate of dusting should decrease as the animal grows. Food intended for mature adults is generally dusted with calcium once or twice weekly, and with a multivitamin every 2-4 weeks.
- Invertebrates are dusted with supplement by placing prey in a container and shaking. Alternatively, add food items to a bowl with supplement.
Unless the lizard has neurologic deficits or is extremely weak, make water available at all times. Many but not all lizards will drink from bowls. Also provide a large, shallow, sturdy container that allows easy entry and exit for soaking. Soaking enhances water uptake, stimulates defecation, and aids shedding.
Arboreal species like Old World chameleons, geckos, and anoles only lap droplets from leaves. Provide chameleons with a water drip system. Dropper systems are commercially available. Makeshift systems may be created with intravenous tubing, or a plastic container of water set on top of the cage with a pinhole in the bottom. Most tropical species should have access to water misted onto plants once or twice daily.
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