Chapter 178 Basic Husbandry and Medicine of Pet Reptiles
Boas, pythons, king snakes, rat snakes, and milk snakes are the most common snakes kept as pets. Iguanas, geckoes, monitors, and bearded dragons are frequently encountered pet lizards. Amphisbaenians are small, worm-like reptiles not commonly found in the pet trade. Snakes, lizards, and amphisbaenians are all in the order Squamata. The order Chelonia has approximately 235 species and consists of turtles, tortoises, and terrapins. Of the chelonians, box turtles, red-eared sliders, and a variety of tortoises are kept most commonly as pets. The order Crocodilia has only 21 species, including alligators, crocodiles, caimans, and gharials.
Determine whether an animal is captive bred or wild caught. Captive-born animals have been somewhat genetically selected to tolerate manufactured environments and accept domestic sources of food. In general, they are less likely to be harboring overwhelming numbers of infectious agents (especially parasites) than their wild-caught counterparts. Many wild-caught animals have been collected overseas, then housed in inadequate, overcrowded facilities, and finally shipped to suppliers without having eaten. The ones that survive often are dehydrated, immunosuppressed, and have been exposed to a wide variety of pathogens. Some imported reptiles are injected prophylactically with antibiotics, which, in combination with dehydration, predisposes them to renal failure. Because of the slow metabolic rate of reptiles, many animals survive this abuse for many months before demonstrating obvious clinical signs.
Most reptiles need to maintain their core body temperature well above ambient temperatures for at least part of the day and generally achieve this by absorbing radiant heat. Reptiles can minimize body temperature fluctuations by modifying behavior. Reptiles that become too cool seek elevated areas to bask, lay perpendicular to the sun’s rays, maximize their surface area by expanding their rib cage, and darken the pigment of their skin to increase heat absorption. If no sunlight is available, some reptiles burrow into warm soil or lay on objects previously warmed by the sun.
|Habitat||Temperature Range (°F)|
|Common Species||Temperature Range (°F)|
|Boas and pythons||75–95|
Tropical animals in the wild are exposed to very little variation in environmental temperature and therefore are not tolerant of large fluctuations. This is in contrast to desert animals that endure and require high daytime temperatures with an evening cooldown period. Reptiles from temperate climates can be very tolerant of temperature extremes (within reason) if they are free of disease. These species experience seasons in the wild and require seasonal changes in light cycle, temperature, and water or food availability to stimulate behaviors such as hibernation and breeding.
The upper half of the shell is referred to as the carapace. The bottom half is the plastron. The shell is composed of bone and incorporates the sternum, vertebrae, ribs, and pelvis. Bone is covered by epidermal scales or skin. The shell is metabolically active.
The speculum or spectacle is a clear epithelial covering that lies over the cornea of snakes and some lizards, such as Tokay geckoes. Speculums should be shed with the skin at ecdysis. Abnormal retention of these structures is a common problem in snakes. Topical ophthalmic preparations do not penetrate through the speculum.
Salt glands are located in the nares or on the tongue. The glands excrete excess salt and allow conservation of water. Salt is excreted by burrowing or sneezing. Pet green iguanas often are presented for sneezing small amounts of clear fluid that dries to crystals on the walls of the cage. Do not confuse this normal salt elimination with a respiratory infection.
The hyoid apparatus is very well developed in most reptiles. In snakes, it usually extends to the tenth cervical vertebra, allowing the tongue to be extremely mobile. This enables the snake to breathe directly through its glottis even while swallowing prey. In chameleons, the hyoid apparatus extends the full length of the abdomen to the cloaca. This structure allows their long, well-developed tongues the motility and strength necessary to catch flying insects.
In reptiles, restrain the head only by its dorsolateral surfaces to avoid damage to the hyoid apparatus and subsequent loss of tongue function. Avoid restraint that places pressure on the ventral cervical region.
Snakes possess an open mandibular symphysis and flexible rami that allow them to swallow large, intact prey. These features also make iatrogenic injury to the mandibles common, especially while performing an oral examination.
Never force open a reptile’s mouth. To open the mouth of a snake or lizard, place a plastic credit card or hard rubber spatula at the corner or front of the mouth and use gentle, prolonged pressure combined with a slight wiggling motion. Once the mouth is opened, slide the card or spatula across the jaws (Fig. 178-1). The beak of larger chelonians can bite through many plastics, so a thin, but sturdy metal spatula may be required to open the mouth. Be careful not to crack the beak. Anesthesia may be required to open the mouths of very large reptiles.
Snakes typically have four rows of teeth in their upper jaw. The teeth of snakes and lizards are fragile and curved caudally to aid in pulling food into the mouth. Be careful not to catch materials on teeth. If items such as swabs or gauze become caught, push caudally to disentangle the fibers before pulling out, or the teeth may break. Broken teeth cause oral pain and anorexia until a new tooth emerges.
The esophagus is lined liberally with mucous glands. Although the musculature surrounding the esophagus is extremely strong in snakes to move whole prey caudally, the esophagus itself is thin and tears easily.
When performing stomach intubation in snakes, the esophagus “grabs” the tube. Use liberal amounts of water-soluble lubricating jelly and gentle, constant pressure to pass the tube smoothly. If firm resistance is felt, redirect the tube. Never force a stomach tube because perforation may occur.
In many species of turtles, the esophagus makes a 90 degree turn before entering the stomach. Place medications administered by stomach tube in the distal esophagus. Use small volumes to prevent regurgitation. Also, in chelonians, the pancreatic and bile ducts enter the pylorus instead of the duodenum.
When present, the gallbladder usually is found near the liver in lizards and chelonians but is located caudal to the stomach in snakes. This is an important difference to recognize when performing surgery or diagnostics in this region.
The reptilian pancreas, although sometimes structurally different than in the mammal, is functionally similar. The pancreas usually is located between the ascending and descending portion of the duodenum in chelonians and lizards. In snakes, the pancreas is located caudal to the pylorus in the region of the gallbladder and spleen. In some snakes, the pancreas and spleen are fused.
The cecum is rudimentary in carnivorous reptiles such as snakes, crocodilians, and monitors. The cecum is present in chelonians and herbivorous lizards and functions in post-gastric fermentation in these species.
The cloaca is a common collecting chamber for wastes from the colon and ureters and for the reproductive tract. The cloaca also receives urine from the bladder in species that possess a bladder. It is important to note that unlike mammals, in reptiles, the ureters empty into the cloaca and not the bladder. In males, the hemipenes or phallus everts from the caudal aspect of the cloaca. In some aquatic species, oxygen can be exchanged across the cloaca. Obstruction of the cloaca affects all of the aforementioned systems and is therefore much more detrimental than mere constipation affecting the GI system in mammals.
All reptiles possess a cleft palate (choana) that is necessary for nasal breathing. In contrast to birds, which have a single central cleft, reptiles have paired paramedian clefts. These clefts allow passage of air from the nares into the oral cavity and trachea.
Most reptiles lack a diaphragm, and breathing is accomplished by expansion of the chest wall by intercostal muscles (except turtles), pectoral limb movement (except snakes), and smooth muscle contraction in the lung. Crocodilians also use movement of the liver to create negative pressure. Chelonians use movement of front limbs and visceral organs instead of excursion of the chest wall, which is impossible because of their rigid shell. A minimal amount of oxygen can be extracted from water through the skin in certain species of all reptilian orders. Some aquatic turtles can exchange dissolved oxygen across their pharynx and cloaca while submerged, although these sources only provide maintenance levels of oxygen.
Reptiles (except for crocodilians) have a three-chambered heart with two atria and one common ventricle. Deoxygenated blood from the body empties into the right atrium via the sinus venosus. The left atrium receives oxygenated blood from the lungs. In non-crocodilians, both atria open on the left side of the ventricle. Blood from the right atrium tends to stay on the right side of the ventricle and enter the pulmonary artery. Reptiles have two aortic outflow tracts, the right and the left aortas, which combine caudal to the heart into a common aorta. The left aortic arch comes from the right side of the ventricle, carrying less-oxygenated blood. The right aortic arch comes from the left side of the ventricle, which has richly oxygenated blood. The right aortic arch supplies oxygenated blood to the head region before it combines with the left aortic arch.
Most aquatic reptiles excrete ammonia, urea, and uric acid as nitrogenous waste products. Urea and ammonia require more water for their excretion compared with uric acid excretion. Terrestrial animals excrete mostly uric acid. However, sea turtles excrete almost exclusively ammonia or urea; semi-aquatic turtles excrete 0% ammonia, 40%–50% urea, and 50%–60% uric acid; and desert tortoises excrete more than 90% uric acid.
Reptiles can only produce isosthenuric urine. The reptilian nephron contains no loop of Henle and therefore lacks the ability to concentrate urine. Water can be resorbed from the bladder or cloacal wall. If renal blood flow is diminished below a critical level (as in dehydration), urates precipitate in the nephron, causing irreversible obstruction.
Reptiles possess a renal portal system that allows blood from tissues caudal to the kidneys to be shunted directly to kidneys. A valve exists at the junction of the abdominal and femoral veins. When the valve is closed, blood is shunted through the iliac vein into the kidney. When the valve is open, blood enters the systemic circulation through the abdominal vein. Blood entering the kidney through the renal portal system is supplied to the tubules and does not enter the glomerulus. Therefore, drugs such as penicillins, which are cleared via tubular secretion, can be removed by the renal portal system, but drugs cleared by the glomerulus (e.g., gentamicin) are not affected.
Do not administer drugs that are cleared by tubular secretion in the caudal half of the body. These drugs may be cleared before achieving therapeutic levels or, if the drug is nephrotoxic, may reach the kidneys in concentrations high enough to cause toxicity.
Not all reptiles have a urinary bladder. The bladder is most highly developed in terrestrial chelonians and some lizards. The bladder acts as a reservoir to store urine and conserve water. Isosthenuric urine from the kidneys is diverted from the cloaca to the bladder, where water is reabsorbed. The concentrated urine then is routed back to the cloaca for excretion. In reptiles without a bladder, diluted urine is moved from the cloaca into the large colon for water absorption. Salts also may be reabsorbed.
All reproductive organs, including the phallus in most species, are paired. Chelonians and crocodilians are the exception and have a single phallus. The phallus of adult crocodilians is fibrocartilaginous and is therefore palpable in the cloaca. This is a common sex determination technique used in this order. The male copulatory organs of squamates are paired and are composed of highly vascular fibrocartilaginous and elastic connective tissue called hemipenes. Erection occurs secondary to engorgement with blood and contraction of the propulsor muscle, causing eversion of the organ. Hemipenes may be ossified in some monitors and geckoes; sex determination of these individuals can be performed radiographically. Hemipenes frequently have keratin spicules to aid in maintenance of copulation. Only one hemipene is used at a time and it may prolapse if traumatized or following prolonged use.
Seasonal variation in testicular size exists in most species. This is caused by an increase in the number of interstitial androgen-producing Leydig cells during breeding season. Spermatozoa move through the seminiferous tubules and are stored in the epididymis. During breeding, spermatozoa leave via the vas deferens, cloaca, and then hemipene or phallus. The male copulatory organs of reptiles do not contain a urethra and is not involved in the elimination of nitrogenous wastes. Therefore, amputation does not affect urination but does affect breeding ability in animals with non-paired organs.
The right ovary is located cranial to the left in snakes. Fertilization occurs in the upper portion of the oviduct. Crypt-like pits in the oviduct can store sperm for up to 6 years in some species. Reproduction may be oviparous (egg-layers), ovoviviparous (hold eggs in oviducts until they hatch), or viviparous (live-bearers), depending on the species. The oviduct produces albumin, shell membranes, and the shell. In viviparous species, a placenta-like structure is formed.
Many reptiles indefinitely delay oviposition until the right conditions for egg laying occur. These conditions vary with the species. In aquatic turtles, this may be as simple as providing a moist sand pit of sufficient depth for the turtle to dig a nest. In other cases, a female in a multiple-specimen cage may not lay her eggs unless she is housed singly. Certain environmental clues may be required to trigger hormonal cycles necessary to stimulate egg laying. The absence of the proper environmental triggers often leads to dystocia.
Females have short, abruptly tapering tails; males have longer, thicker tails necessary to accommodate the hemipenes. In very young snakes, a finger can be rolled from the mid-tail region toward the cloaca in an attempt to evert the hemipenes. This technique is only moderately reliable, and there is a risk of injuring a hemipene.
In general, female tortoises and box turtles have a flat plastron with a notched caudal region to allow for the passage of eggs. Most females have short, poorly developed tails. The males have a concave plastron to allow for balancing on the female. Males also have long, well-developed tails to allow for copulation and storage of the phallus. Female box turtles have brown to orange irises, whereas male box turtles have bright red irises.
It is more difficult to differentiate gender in water turtles than in their land counterparts. The females usually have shorter tails than the males. Because the water in the environment bears the male’s weight, male water turtles usually do not have concave plastrons. In the Emydoidea genus, males have very long front claws that they wave in front of females during courtship.
In general, males become more brightly colored during the courtship season. Males have more highly developed dorsal spines, dewlaps, and horns. Male iguanas produce keratinaceous plugs along the insides of their thighs from glands called femoral pores. Their function is unknown, but they are thought to be used for marking territories and to stimulate females by rubbing (scratching) the femoral pores over the female’s hind quarters. Females have smaller versions of these pores. Only males of some gecko species have preanal pores that appear as little black pores located near the vent.
The adrenal glands usually are located just cranial to the kidneys. In the green iguana, the left adrenal gland lies in the mesovarium and must be avoided during ovariectomy. The cortex contains chromaffin cells that produce neuroactive substances. The more centrally located population of cells produce adrenocorticosteroids. The structural architecture of these glands varies tremendously from species to species.
Reptilian ears have no incus, malleus, or cochlea. In snakes and some lizards, the cavity of the middle ear and the tympanic membrane are vestigial. There is no external auditory opening in snakes. In these species, the stapes articulates directly with the quadrate bone. This mechanism picks up low-frequency sound and vibrations. Some snakes can “hear” vibrations transmitted from the body wall overlying the lungs. Crocodilians have a movable ear flap that is located just behind the eye. They are able to open and close this flap to keep water out of their ears.
The eyes of most reptiles (except snakes) are similar to those of mammals with a few exceptions. Bony scleral ossicles support the globe. The iris and ciliary body are composed of striated muscle and do not respond well to mydriatics. The retina contains a darkly pigmented projection called the conus papillarus, similar to the pecten in birds.
Snake eyes are unique among the animal kingdom and are thought to be the result of redevelopment of once rudimentary eyes. The lens accommodates by moving forward and backward. The eyes are covered by a spectacle that is impervious to topical ophthalmic preparations. The retina does not have a conus papillarus but is covered by a thin mat of vessels called the membrana vasculosa.
Cramped quarters induce stress. Snakes need room to stretch out to at least two-thirds of their length. For lizards, provide a minimum of 6 square inches of cage per inch of body size. Tortoises require a minimum of three times their body area. These are minimum areas for solitary animals. To reduce the chance of cagemate aggression, increase the cage size for more than one animal and for breeding. Clients should be counseled about the size their pet will reach as an adult.
Cage wall surfaces should be smooth to prevent abrasions, particularly to the nose. A rough branch or stone can be placed in the cage to aid in shedding. Provide cage “furniture,” such as plastic containers, clay pots, and plastic plants, to provide visual security. Access to these hiding places allows reptiles to relax and prevents cage pacing. Provide additional furniture that provides a varied terrain, without hazards, to stimulate activity.
The ideal cage liner is paper, such as newspaper. It is non-toxic, inexpensive, and disposable. Change cage papers at least once daily or after feeding or defecation for animals that are fed infrequently. Artificial turf is a good alternative to newspaper. Change the turf as soon as it is soiled. It requires 48 hours to completely clean and dry turf, so make plenty of replacement pieces available. Remove loose strings to prevent foreign bodies. Rabbit or guinea pig pellets or recycled paper bedding may be used as cage substrates for herbivorous reptiles if they are replaced at least two times per week, or more often if moist, to prevent fungal and bacterial growth. Large stone gravel and bark chips also can be used but are less desirable because they can be ingested and harbor bacteria, parasites, and moisture. Thoroughly clean and sanitize or replace substrates at least once a month (can be expensive).
Sand is recommended for desert species only. Other species contaminate sand quickly and are prone to GI sand impactions. Even products commercially marketed as “reptile-safe” such as Calcisand may be ingested and can cause intestinal impactions. Some colors may be more attractive to reptiles to ingest than other colors. Dry sand potentiates low environmental humidity, which is ideal for desert species but causes dehydration in non-desert species. If sand is used for burrowing desert species, it must be changed frequently to prevent buildup of wastes.
The environmental humidity should be kept low for most species, because high humidity predisposes animals to disease. Excellent sanitation prevents buildup of wastes, and adequate ventilation allows evaporation of residual moisture, thus keeping the humidity low. Ventilation holes or screening on the top of cages is usually adequate. However, screen lids do not work well for animals that pace in their cage. These animals often rub their noses along the lid, resulting in severe nasal abrasions. Cages used to house animals that produce copious stools, require moisture-laden food, or have high water consumption may need shielded fans to aid in evaporation. On the other hand, some tropical species may require specially designed humidifiers to maintain a supply of fresh, humid air.
Maintain the ambient cage temperature as a gradient incorporating as much of the POT range as possible. One of the easiest methods of accomplishing this is to place a heat source at one end of the enclosure. The heat source should be able to heat the closer end of the cage to the high end of POT and the far end of the cage to the low end of POT. Thermal burns are a common problem. To decrease the possibility of thermal burns if heater malfunctions occur, be certain that the surface temperature at the hottest spot is no hotter than the top range of POT and never higher than 115°F. Heating pads or heating tape designed for use with reptiles are the safest to use. It is safest not to place heating elements within a cage. Instead, place the cage on small blocks to create an airspace (¼ inch to ½ inch) between the outside of the cage floor and heat sources. The air space will even out potential hot spots.
Heat lamps also can be used successfully if care is taken to prevent thermal burns. Radiant heat actually is required by many large herbivorous lizards, such as adult green iguanas. To prevent burns, check the temperature by placing a hand directly under the heat lamp (at the site that the reptile would be basking) for 15 minutes after the lamp has been on for 2 to 3 hours. If it is uncomfortable to leave your hand in one spot, the lamp light is too intense. Also, place a thermometer on the surface to ensure that the POT has not been exceeded. Hot rocks are unreliable and only provide enough heat for small species. Any heat sources placed within the cage need to be shielded to prevent animals from coming in direct contact with them.
Any heating elements that have the potential to attain temperatures greater than 105°F must be shielded. Routinely test the thermostats on heating devices. Malfunctioning thermostats cause animal deaths and fires.
For arboreal animals, caging is similar to that for terrestrial animals but incorporates more vertical space and objects for climbing. Do not place climbing structures over water or food containers to prevent fecal contamination. Willow, bamboo, oak, birch, beech, and most fruit trees provide safe branches.
Never use an under-gravel filter because these may cause anaerobic toxins to accumulate in the gravel. Disturbance of the gravel or an overturn of tank water allows release of these toxins and may kill tank inhabitants. An out-of-tank biologic filter works best. Flush the sand, gravel, or fibers in these systems frequently to remove gross debris. Even these systems often cannot handle both fecal and discarded food loads. Therefore, offer food for limited periods in a separate tank, then return the reptile to its usual enclosure. The feeding tank does not need a filter because the water is changed completely before and after each feeding session and/or group of animals. Disinfect the tank and allow it to dry after feeding to prevent waste buildup and transmission of disease.
All aquatic reptiles except sea snakes and sea turtles need adequate basking space. Most “water” turtles drown because of exhaustion if not allowed to rest out of the water. In group tanks, this is often the cause of unexplained deaths of smaller animals. These losses can be eliminated by adding several basking areas, which allows the smaller reptiles to rest even when dominant individuals are defending their territories. Basking also is needed to allow drying of the skin and shell. An increased incidence of skin disease also is seen in reptiles not allowed to bask under ultraviolet (UV) light.
Maintaining appropriate water temperature is very important. A reliable waterproof heater is essential. Electric shock from non-waterproof heaters kills not only animals in the tank but also human caretakers. In addition, malfunctions resulting in overheating or failure to heat a tank may kill aquatic animals. In small tanks, an aquarium heater with an in-water thermostat works well. Heaters with thermostats above the surface may under- or overheat the water because the thermostat measures the air temperature and not the water temperature.
Take care to ensure tank inhabitants will not burn themselves if they decide to wrap around the heater. This is accomplished most easily by screening the heater. Water temperature in larger enclosures can be maintained by keeping the room temperature at the lower end of the POT range and using infrared lights or heaters at one end to maintain a gradient. Temperature gradients over the basking areas are controlled as in terrestrial cages.
Many herbivorous and insectivorous reptiles require UV light (280-315 nm) to synthesize vitamin D3. This spectrum of light is best provided by unfiltered sunlight (i.e., not passing through glass or plastic). Most plant lights do not provide adequate light in the appropriate spectrum. Vita-lite (Durotest, Fairfield, NJ), ReptiSun (Zoomed, San Luis Obispo, CA) are two products that produce the appropriate wavelengths. The intensity of all these lights is much less than that produced by natural sunlight. These lights produce UV radiation in the appropriate spectrum for only 2 to 4 months. Black lights also may be used, but the potential for damage to human as well as reptile vision has not been evaluated. Provide UV light at a rate of 20 watts/3 to 6 cubic feet. Place a basking area 18 to 24 inches from the source. Shield the light from direct animal contact. Provide UV light 8 to 10 hours a day. Constant UV light overstimulates the pineal gland and destroys normal circadian rhythms, which can lead to anorexia and disease.
Provide 10-14 hours of light and dark daily. Base the proportion of light to dark on seasonal variations in the animal’s natural habitat. Room light or light from an incandescent bulb used for heating left on at night does not provide adequate darkness. Only use infrared or ceramic bulbs if heating lamps must be used for 24 hours. If room lights must be on into the dark part of the cycle, cover the cage.
Reptiles rarely come in contact with their excrement in the wild. In captivity, the goal is to minimize this contact and the chance of spreading disease when contact occurs. The most important part of sanitation is mechanical removal of fecal material, urates, and leftover food. This can be as simple as removing a soiled sheet of paper, or as time consuming as scrubbing stones. Only after gross debris is removed can disinfectants destroy microbes that cannot be killed by cleaning alone. Disinfection is not a substitute for cleaning.
Phenolic cleaners such as Lysol and Pine-Sol can be toxic to reptiles. Bleach (sodium hypochlorite) diluted 1:30 with water is an excellent, safe, and inexpensive disinfectant. It is inactivated by organic matter. Chlorhexidine and Roccal also can be used safely.
Non-sealed and porous surfaces cannot be disinfected thoroughly. Therefore, discard items such as wood, pottery, artificial turf, porous rocks, and bedding if they become too soiled. Do not transfer these items from one group of animals to another. Use great caution in cleaning reptile cages in kitchen sinks or bathtubs as these are likely situations in which salmonella may be transmitted to people.
Plenty of space and visual security is essential when housing more than one animal in an enclosure. Signs of inadequate space are cagemate aggression, disease, high parasite loads, starvation, and cannibalism. Some animals naturally prey on cagemates. These animals should be housed alone or at least with non-prey species.
Do not mix species. Mixing genuses is often disastrous because organisms that are symbiotic or cause only mild diseases in one species may be fatal to another. An example is amebiasis, which causes a mild disease in turtles but may be fatal in snakes and tortoises.
New animals should be quarantined in a separate building for at least 90 days. Many sources recommend 180 days. If the ideal situation is not possible, quarantine animals in separate rooms. Service new animals last and make sure that clothes are not contaminated. Dispose of wastes and wash hands thoroughly. Clean and disinfect food and water dishes at a separate location from the food preparation area. Animals should be tested for parasites and infectious disease before entering the main collection.
Change water at least every 24 hours. Clean water containers with soap and water daily and disinfect weekly. Large, shallow water dishes that allow reptiles to soak and defecate are preferred. Some lizards (e.g., chameleons, anoles) will not drink from bowls and require a drip watering system or mist sprayed on plants or the side of the cage.
Providing a complete and balanced diet is accomplished more readily in carnivorous reptiles compared with herbivorous or omnivorous ones. Most wild carnivorous reptiles eat whole animals (usually rodents or small birds), which are easily supplied in captivity. When they are fed whole prey, few nutritional deficiencies or excesses occur in this group of reptiles. Severe nutritional disease is seen in animals mistakenly fed only animal parts (e.g., all muscle, liver, etc.).
Some carnivores such as king snakes only eat other snakes. Be sure that “feeder” snakes used as prey are free from disease and parasites. If the snake eats thawed, frozen prey, it is recommended to freeze all food snakes for at least 30 days before feeding to prevent transmission of parasites. Good-quality feeder snakes can be difficult to obtain. Some snake eaters accept mice stuffed into a shed snake skin.
Some carnivores eat only amphibians or small reptiles of various genera. Freezing to prevent disease transmission is extremely important in these species as well. Some amphibian eaters can be trained to eat mice by placing a mouse inside a fresh frog skin or smearing a mouse with frog slime. Be careful not to attempt to feed amphibians, which produce toxic skin secretions.
Some snakes and monitors eat mostly eggs. Ideally, these eggs should be fertilized and contain embryos at different stages of development. Reptiles fed only unfertilized hen eggs suffer many nutritional deficiencies.
Some reptiles only eat crustaceans, gastropods, worms, or other specialized diets. Special attention needs to be paid to the natural history of reptiles needing specialized diets. If the suitable prey items cannot be obtained year-round, do not keep the animal in captivity.
Nutritional diseases such as secondary hyperparathyroidism commonly occur when owners feed their crocodiles hamburger or table scraps. Feed only whole-animal diets (e.g., whole fish, rats, chickens, rabbits) to prevent nutritional diseases. Feed crocodilians individually whenever possible to prevent feeding frenzies and subsequent cagemate trauma.
Crickets, mealworms, and inch worms commonly fed to reptiles in captivity are deficient in nutrients. Provide an excellent diet for these insects to replace missing nutrients. To maximize their nutritional worth and provide extra nutrients from the intestinal contents of the insect, raise these insects on a high-calcium medium such as chicken layer mash or commercial cricket diet from a reputable company. Use of dark, leafy greens or orange vegetables as a water source for insects further increases their nutritional value. Before feeding the reptile, dust crickets and mealworms with a vitamin and calcium supplement (daily for reproductively active females and juveniles, 1-3 times per week for others). Large insectivores may accept young, hairless mice (commonly called “pinkies”) or captive reared earthworms as an additional source of nutrients. Feed small, chiten-free insects, such as juvenile crickets, mealworms, or wingless fruit flies to small or neonatal insectivores. Some insectivores require highly specialized diets. Do not feed fireflies to reptiles because they are often toxic.
Adult herbivores, such as green iguanas, should receive 90% to 98% of their calories from plants. Ninety percent of the plant diet should consist of a mixture of dark leafy greens, with 10% mixed vegetables and fruits. Many adult herbivorous tortoises require high-fiber diets, such as high-quality grass hay or fresh grass. Omnivores or young herbivores should receive 70% to 95% of their calories from plants. Most herbivores and all omnivores require the addition of some protein to their diets. Good sources of protein are crushed hard-boiled egg (with shell), prepared reptile diets from reputable companies, trout chow, pinkie mice, alfalfa pellets, or tofu. Dog food or monkey chow should not be fed. These foods contain excessive amounts of vitamin D and may cause metastatic calcification of soft tissues and renal failure when fed extensively. Although some experts believe that feeding any animal protein to herbivores may cause renal disease, we have found that renal disease is related to the quantity rather than the source of protein. To avoid over feeding, be aware that the concentration of nutrients and calories in animal-based food is usually at least an order of magnitude greater than in the same volume of vegetable matter.
Restrain small lizards and crocodilians by using the thumb and forefinger to grasp the caudal mandibular area. Cradle the dorsal body in the palm of the same hand. Control the abdomen, chest, and pelvis with the remaining fingers, thus allowing for respiration (Fig. 178-2).
Grasp medium-sized lizards and crocodilians over the dorsal surface of the head and neck with one hand, and grab the base of the tail and pelvis with the other hand (Fig. 178-3). Wrap the reptile securely in a towel to prevent the back legs from scratching. If necessary, restrain the back legs by taping them to the tail. To capture mildly aggressive animals, use a towel as a blind to hide the restrainer’s hand from view. If an aggressive animal is brought in a sack, use the sack as a blind and grasp the head through the sack. Peel the sack away from the body without losing control of the head. A snare or snake hook can be used to pin the head if the animal is extremely aggressive. Care must be taken to use just enough pressure to prevent escape but not enough to cause trauma. Large lizards and crocodilians can inflict serious bites and often use their powerful tails as whips. Tape the snout of aggressive crocodilians shut with duct tape. The masseter muscles are extremely strong; the digastricus muscle, which opens the jaw, is very weak.
Most non-aggressive snakes may be picked up mid-body and allowed to glide from hand to hand. Some snakes are more secure if allowed to coil around an arm (Fig. 178-4). Most snakes struggle less when handled with minimal restraint. Never let any snake near your face or around your neck!
Never pick a snake up only by its head only because serious damage to the spine may occur. Reptiles only have one occipital condyle, making it relatively easy to luxate the spine from the head. Always support the body.
If an aggressive, non-venomous snake arrives in a bag, grasp the head through the bag. If necessary, gently pin the head of free individuals with a snake hook or snare. Be careful not to injure the snake. Alternatively, grab the snake using a towel as a blind.
Hold chelonians by the dorsal caudal portion of the shell (Fig. 178-5). This placement makes it difficult for the animal to reach around and bite, or to scratch with its rear feet. Be sure to have a firm grip, especially if the turtle is wet. Always hold a chelonian over a table. Dropping a turtle may cause severe life-threatening shell fractures. Handle soft-shelled turtles with rinsed examination gloves, thus preventing damage to the delicate shell. Snapping turtles and some other long-necked turtles can reach the rear of their shells with their beaks. Grasp these turtles by the base of the tail. Hold them with tail in one hand and the front of the carapace just over the head in the other hand. Large snapping turtles are very dangerous to handle and should be left to experts.
Transport non-venomous reptiles of moderate size in a tied cloth sack placed in a styrofoam or dedicated camping cooler containing air holes. Chelonians do not need to be placed in a sack. Coolers can be fitted with space for hot or cold water bottles or chemical packs if extreme temperatures are anticipated. These methods are to be used for transporting animals a short distance only.