15 Reptiles – an introduction
Reptiles are among some of the more unusual pets seen in veterinary practice (Fig. 15.1). An approach similar to that for other pets may be taken with regard to their clinical history and examination, although species-specifics must be known in order to interpret findings pertinent to husbandry conditions. The metabolic rate is in general slower with these ectothermic animals than with mammals, and hence disease processes tend to be more prolonged with reptiles. Investigative techniques and some basic husbandry requirements for selected species will be outlined in this chapter.
It is impossible to detail husbandry requirements for the huge range of reptile species that may be seen by the veterinary clinician in practice. The reader is referred to other texts for further information. Husbandry advice for some common species is listed below.
Unless housed outdoors with access to sufficient sunlight, most species will require supplemental UV-B light to synthesize vitamin D, which is necessary for calcium metabolism. Carnivorous species can obtain minerals from digestion of bone in their diet.
As reptiles are ectothermic (relying on environmental temperature to control their body temperature), most require supplemental heating in their captivity enclosure. A temperature range should be provided across the enclosure, to allow the animal to select an appropriate temperature. This preferred optimum temperature range (POTR) varies between species. Many heating sources can be thermostatically controlled, but the environmental temperature should still be monitored using a digital maximum–minimum thermometer (strip and dial thermometers may be inaccurate). Heaters should be protected to prevent accidental burns. In species that hibernate, care should also be taken to control and monitor the environmental temperature during this period.
Most reptiles carry potentially zoonotic pathogens, such as Salmonella spp, in their gastrointestinal tract. Although these rarely cause disease in humans, general hygiene precautions should be observed when handling reptiles or cleaning their enclosure, in particular ensuring that transmission does not occur via the faeco-oral route. Enclosures should be spot-cleaned daily, and intermittently disinfection should be carried out and the substrate changed.
Sexing of reptiles depends on the species concerned. In general, adult male tortoises have a longer tail than females; males may also have a concave plastron. Male terrapins may have longer claws on their fore-feet. Some lizards are sexually dimorphic, with males having more prominent pre-femoral pores (such as bearded dragons) or various facial adaptations (such as crests or horns in chameleons, or the dewlap in green iguanas). Few snakes are sexually dimorphic. Where obvious external characteristics do not enable gender identification, probing the hemipenes in situ caudal to the cloaca may be used to sex lizards and snakes. An alternative is coelioscopy or coeliotomy to visualize the internal gonads.
This group is divided into tortoises (terrestrial species), turtles (aquatic marine species) and terrapins (aquatic freshwater species). Owing to space restrictions, smaller species are most commonly kept as pets. Most chelonian species prefer to be solitary, but same-sex individuals may be housed together if accommodation is large enough with several hide areas.
Many species of chelonia (and some other reptiles) will hibernate in the wild for varying periods of time (Box 15.1). In captivity, it is usually advisable to keep this period to a maximum of 12 weeks, otherwise, metabolic reserves will become dangerously low during hibernation and it may be difficult for the tortoise to eat sufficiently during the warmer months in preparation for hibernation. Tortoises should be fasted for 1 month before hibernation to allow the gastrointestinal tract to empty; otherwise continued fermentation may lead to gas build-up and pressure on the lungs, resulting in dyspnoea. During this pre-hibernation time, the tortoise should be bathed to encourage drinking. Water is stored in the urinary bladder for reabsorption during hibernation.
BOX 15.1 Important note
Geochelone species such as the leopard tortoise (Geochelone pardalis) and African spurred tortoise (Geochelone sulcata) do not hibernate. They should be over-wintered, ensuring sufficient environmental temperatures are maintained despite outdoor temperatures dropping.
Traditional hibernaculums include boxes insulated with straw, but these are susceptible to environmental temperature changes. Some animals housed in gardens may dig into soil as their free-ranging counterparts do, but monitoring is nigh on impossible in this situation. Often, owners do not actually know where the tortoise has buried itself, and owners digging in gardens during spring have caused traumatic injuries to hidden pets. A safer alternative is to build an indoor insulated terrarium with thermostatically controlled heating coils underneath protective matting, covered with soil to permit digging. A reasonably constant temperature can be maintained using a refrigerator. It can be helpful to have bowls of water in the fridge to ensure the air does not become excessively dry.
Hibernation is induced below 15°C, and maintained between 2 and 9°C. Temperatures below 0°C will result in pathology such as blindness. The environmental temperature should be measured constantly, for example using a maximum–minimum digital thermometer. Tortoises should be checked daily and weighed weekly during hibernation. If a tortoise urinates during hibernation, it should be awakened and ‘over-wintered’ (i.e. kept awake and maintained in conditions similar to the warmer months). Similarly if a tortoise loses >5–10% of its body weight during hibernation (or >1% in a week), it should be awakened.
Tortoises should begin eating within a couple of days of wakening from hibernation. Bathing in shallow warm water will encourage the tortoise to drink and urinate. Often they will pass a large amount of urates at this stage. If they do not start to eat within a week, tortoises are deemed to have ‘post-hibernation anorexia’, and veterinary investigation and treatment should be instigated.
This species hails from the Mediterranean region, and specimens can grow up to 30 cm in length. Their diet should mostly consist of weeds such as dandelions (both leaves and flowers), plantain, sow thistle and sedum. They will also favour flowers such as hibiscus, nasturtium and honeysuckle. Salad leaves may form a small part of the diet. Mineral supplementation in the form of a proprietary powder is usually added two or three times weekly. Food is placed onto a smooth surface (e.g. a piece of slate) to reduce the risk of ingestion of substrate material and resulting gastrointestinal impaction. Water should be provided in a shallow container (deep enough to submerge their beak to drink), with weekly bathing in shallow warm water to encourage further drinking and excretion of waste products.
Hermann’s tortoises require a large (e.g. 90 × 30 cm for a small juvenile) well-ventilated pen with solid sides, usually made of wood or plastic. A background heat source may be provided with a tubular heater or heat mat (against a wall of the enclosure, not underneath). The environmental temperature should be measured using a digital maximum–minimum thermometer aiming for a daytime range of 20–30°C, dropping by 15°C overnight. A basking area (with a temperature up to 40°C) with a spot bulb should be positioned near the feeding area. UV-B lighting should be provided, either via a strip light or mercury vapour lamp (the latter also produces heat). These should be positioned approximately 30 cm above the tortoise to ensure sufficient UV reaches the animal. UV lights usually require changing every 6–12 months as UV output declines (note that output of visual light remains for considerably longer). In appropriate environments, tortoises may have outdoor access in pens.
Hides should be provided, for example a cardboard box, plant pot, or hollow log. A suitable substrate would be a soil/sand mix, along with an area of large pebbles or stones. Tortoises are usually solitary, except during the breeding season (when sexually active males will pursue females).
These South American species do not hibernate. Their natural habitat is dense humid forests, and this should be emulated in captivity. Despite the need for high humidity, ventilation should not be neglected. It can be useful to provide hide chambers with damp substrate, resulting in focal areas of elevated humidity. The daytime temperature should be 25–27°C. Red-foots grow up to 45 cm in length, and yellow-foots up to 70 cm. Large enclosures (4 × 4 m for a pair) are therefore required.
Red- and yellow-foot tortoises are omnivorous. They will eat ripe fruits (40–70%), flowers and green leaves (20%), as well as a small amount (one meal per week) of animal protein (moist low-fat cat food).
This species is semi-aquatic and can grow up to 20 cm in length. They are found in freshwater in South and Central America. Their enclosure should include an aquatic area for swimming, as well as a land area for basking and resting. Plants (both real and plastic) can provide hide areas. Water filtration is useful to maintain water quality, which should be checked regularly. Water changes and tank disinfection should also be performed regularly. Water temperature should be maintained at 24–26°C (>20°C overnight), usually requiring a water heater. A spot bulb should provide a basking temperature of 32°C. UV-B should be provided as for tortoises.
These animals are omnivorous. Captive diets should be 70–80% animal matter (e.g. low-fat dried cat, dog or trout pellets, bloodworms, earthworms, small fish, and commercial terrapin diets), and 20–30% leafy green vegetables and aquatic plants. Vitamin and mineral supplements are added. They are usually fed in a separate tank to the main enclosure to reduce water soiling.
These hail from the Mediterranean, Asia and North Africa. Some subspecies do not hibernate. As with other Testudo species, the diet is predominantly weeds and flowers. The enclosure and environmental requirements are also similar to those for Hermann’s tortoises.
These large tortoises, growing to over 70 cm in length and weighing up to 20 kg, are from the grasslands of sub-Saharan Africa. The enclosure should reflect the size of the tortoise. Heating should result in a background temperature over 25°C (>22°C overnight), with a basking spot of 40°C. As with other Geochelone species, leopard tortoises do not hibernate, and it is particularly important to consider heating provision over the winter months. UV lighting should be provided.
These originate from sub-Saharan Africa, in arid savannahs and acacia scrublands. They may reach 83 cm in length and 105 kg body weight. Captivity requirements are similar to those for leopard tortoises, with a high-fibre diet and facilities for over-wintering.
Lizards are common pets, with many species frequently seen in veterinary practice. The clinician should be conversant with husbandry requirements for each species in question. Enclosure design, and temperature and humidity requirements will vary between species. In general, supplemental heating and UV-B light is necessary. The substrate for most lizards may be newspaper, artificial turf or other proprietary substrate material. Wood chip substrates are commonly associated with gastrointestinal impactions in lizards, and should be avoided. For insectivores, insects should be fed salad or fruit, and gut-loaded with a proprietary product (high calcium content) for 24 hours prior to being fed to the lizard. Insects, and vegetation for herbivorous species, should be dusted with mineral supplement before being offered to the reptile.
These geckos are common pets, originating from north-west India, south-west Afghanistan, eastern Iran and Pakistan. They can reach up to 25 cm in length. Leopard geckos are usually housed alone, although adults may be paired. Vivaria are usually wooden or fibreglass, with a glass aspect for viewing. A visual barrier at the lizard’s ground level will reduce stress. Ideally, the vivarium should be 0.6 m wide × 1.2 m long × 0.6 m deep. Ventilation should be provided. The cool end should be 25°C, with a hot spot at the other end of 32°C. Although this species is predominantly nocturnal, a low-output UV-B light is usually provided. A shallow water bowl should be provided. It is important to provide hides, and one should contain a damp substrate (e.g. moss or absorbent kitchen paper) to increase humidity and assist ecdysis.
This lizard comes from tropical rainforests in Central and South America, and grows up to 2 m in length. As an arboreal species, their enclosure should be vertically orientated, usually with a base at least 2 × 2 m square and 1.5 m high, with branches for climbing and basking. Background heating is provided, with a lower daytime temperature of 25°C and a basking spot of 40°C. The humidity should be high (80–90%), maintained by regular spraying or misting and placement of the water bowl at the warmer end of the vivarium. A UV-B light should be provided over a basking branch. Iguanas are territorial (particularly uncastrated adult males) and should be housed alone.
Green iguanas are herbivorous, with their diet comprising 90% vegetables (mostly leafy greens) and 10% fruits. They will also eat flowers. Food should be supplemented with a vitamin and mineral powder twice a week. A large container of water will allow the iguana to drink and also to submerge completely.
Although omnivorous, dietary preferences change with age. Juveniles eat a high proportion of invertebrates (such as crickets and locusts). Leafy green vegetables form the main part of the diet in adults. All food should be supplemented with a calcium powder. The water bowl should be large enough for the animal to submerge.
Coccidiosis (usually Isospora amphibolurus) is common in bearded dragons, especially juveniles; other coccidian species may be more common in other reptiles. Along with gastrointestinal disease, the infection may also predispose the bearded dragon to other infections. Transmission is faeco-oral, and may occur via fomites, so good hygiene is required to reduce spread.
This chameleon is also known as the Yemen chameleon, and originates from Yemen and Saudi Arabia. Free-ranging animals are mostly arboreal, and captive specimens should be provided with plenty of climbing and perching facilities. A large vivarium is required for this species, at least 1 m long × 1 m wide × 1.5 m high. Mesh-sided enclosures are preferable, as chameleons may become stressed and attack their reflection in glass. For this reason, chameleons are usually housed alone. Mesh provides visual security and good ventilation. A basking temperature of 35°C should be provided at one end of the enclosure, with a cool temperature of 24°C at the other end. UV-B light should be provided.
An omnivorous species, chameleons should receive approximately 80% insects (such as crickets and locusts) and 20% plants in their diet. Live food should be gut-loaded and all food supplemented with a high-calcium (8%) product. Chameleons drink predominantly from water droplets on plants, usually obtained by regular spraying or by an artificial dripper system. Humidity in the enclosure should be 50–60%.
The most common species in captivity is Physignathus cocincinus (the Chinese, Thai or green water dragon). They may reach 100 cm in length. Like leopard geckos and green iguanas, this species can undergo autotomy (tail shedding) as a defence mechanism. A large vivarium, usually constructed of wood or fibreglass, should be provided (at least 2 m long × 1 m wide × 2 m high). The cool end should be maintained at 29°C, with a basking area of 35°C at the other end. A high humidity (80–90%), hides, branches for climbing, and UV-B lighting should be provided.
Free-ranging water dragons consume insects and small prey; captive animals are predominantly fed on crickets and locusts (gut-loaded and dusted with a calcium supplement). The water container should be deep enough for the lizard to submerge completely.
Snakes make interesting pets. It is vital to design a snake enclosure that is secure, preventing escape. However, snakes are susceptible to respiratory disease and ventilation is important with housing, and should not be compromised while providing secure accommodation. Hides will provide security for the animal. As with lizards, non-ingestable substrates should be used. Snake vivaria should be cleaned and regularly disinfected. Quarantine checks should include assessment for ectoparasites such as mites (Ophionyssus natricis). As snakes obtain most minerals from their diet, UV may not be an absolute requirement; however, a low-output UV-B light is often provided.
As with most snakes, they are carnivorous. Young corn snakes are fed on pinkies (newborn mice without any fur) and fuzzies (mice with some fur), progressing to adult mice and large rats when fully grown. Adults are usually fed once weekly. Food should be thoroughly defrosted and warmed (to approximately 37°C) before feeding. A water bowl should be provided, deep enough to permit submerging.