As captive reptiles are entirely dependent on the environment in which their owners place them, the root cause of many reptile clinical conditions is inappropriate housing, often caused by owner ignorance. As such, the veterinary nurse must have a sound understanding of the basic housing and husbandry needs of the more commonly kept species. Ascertaining the geographical origin of an individual species is essential in order to create as near a natural environment as possible. Texts should therefore be consulted for individual species’ requirements prior to purchasing and setting up a vivarium.
Choice of vivarium and positioning
The design and construction material of a vivarium varies greatly. The essentials of a good vivarium for captive reptiles, apart from obviously being appropriately sized and escape proof, are that it should allow for easy heating, lighting and ventilation. Commonly used materials include Perspex, fiberglass and reinforced glass. Wooden vivariums do exist and are good at retaining heat, however these should be covered with a water-resistant finish to prevent them harbouring bacteria.
Good ventilation is essential whatever type of construction material is chosen to prevent condensation and growth of pathogens. In order to provide an adequate through-flow of air, there should be ventilation panels at both the top and bottom of an enclosure (Gosden, 2004).
For species that are more arboreal (tree climbing) in nature, such as the green iguana, the emphasis should be on vertical height, allowing for the provision of branches and perches, rather than horizontal space. However, for terrestrial species, such as members of the tortoise family, the emphasis should be on more horizontal space which allows for the provision of rocks and low-lying branches.
The location of the vivarium is an important consideration which is frequently overlooked as a source of stress in captive reptiles. Most commonly kept species originate from wild habitats that other than bird vocalization or insect noise are relatively quiet. The reptile living in a vivarium positioned next to the television or speakers will endure vibrations that are completely different to those which it would experience in the wild.
Heating
Heating is essential, and requires an understanding of reptile biology. All reptiles are poikilothermic, meaning they are unable to generate metabolic heat and have a body temperature that varies with the temperature of their surroundings. The preferred body temperature (PBT) of a reptile varies with species, age, activity and season and is the temperature at which metabolism is optimal. The preferred optimum temperature zone (POTZ) is the thermal range of the reptile’s natural habitat in which it functions optimally and has a maximum immune response (O’Malley 2008). The thermal range requirements of a reptile will depend on whether it comes from a temperate, subtropical or tropical climate. The majority of commonly kept species come from the tropics where it is warm all year round. Diurnal temperatures for tropical reptiles range from 26–37°C while temperate reptiles need a range of 24–29°C (O’Malley 2008). In order to provide the optimum POTZ for a reptile, a source of heat will need to be provided. The type of heating method chosen should ideally be selected depending on whether the reptile is a heliotherm or thigmotherm. In the wild, heliothermic species derive radiant heat from basking in the sun’s rays; for this reason heat lamps are the preferred heating method. Thigmotherms include the more nocturnal and crepuscular species that gain heat via conduction from basking on warm objects; heat pads are therefore more suitable in this case.
Heat pads are one of the lowest powered heating methods for reptiles and so are only really suitable used alone for species from more temperate regions, such as corn snakes. In many cases it is appropriate to provide heat by means of both a heat pad, which creates a continuous background heat source, and a heat lamp, which acts as a focal hot spot (Girling, 2003). Heat input should be arranged to provide a temperature gradient in the vivarium so its occupants can choose their own preferred temperature at any time (Figure 1). This can be achieved by placing all the heating devices at one end of the vivarium, therefore providing a distinct warm end and cool end.
For arboreal species, gradients can be established that work vertically rather than horizontally by providing vines or branches that enable the reptile to climb. The heat pad should occupy no more than 30% of the vivarium (O’Malley, 2008) and it is essential that there is no direct contact between the reptile and the heat pad. For this reason, the heat pad should be placed under the vivarium or attached to the side. A focal hot spot in the form of a ceramic or infra-red bulb should also be provided as a basking area; it is essential that this is fitted with a wire guard (Figure 2) to prevent thermal burns which unfortunately are a common and serious occurrence when bulbs are not covered.
A thermostat is an essential part of a vivarium setup as it regulates the output of the heat source in order to keep temperatures within a set range. A thermometer should be positioned at both ends of the thermal gradient to provide accurate measurements of the extremes. An overtly small enclosure will create a fairly linear environment (hot end, cold end) which differs greatly from the mosaic of temperatures a reptile would experience in the wild (Wright, 2008).
Ultraviolet light
Ultraviolet (UV) light is extremely important for diurnal species of reptile who often originate from parts of the world where the intensity of the sun’s ultraviolet rays is high. These ultraviolet rays (particularly the A waveband UVA) stimulate a number of functions in the reptile, including appetite, mating behaviours and general wellbeing. The B waveband (UVB) of the ultraviolet spectrum is extremely important as it encourages the production of vitamin D3 from precursors in the reptile’s skin. Vitamin D3 is intimately involved in the metabolism of calcium and bone growth. A lack of UVB leads to a deficiency of vitamin D3 and subsequent nutritional osteodystrophy (metabolic bone disease) which may prove fatal. UVC is not considered important in reptile husbandry (Shingleton and Cottingham, 2011).
Some reptiles, including the more nocturnal and crepuscular species, are not as susceptible as diurnal species to ultraviolet deprivation, as they are thought to gain sufficient preformed vitamin D3 in their diets (Girling, 2003). Much of the D3 requirement of such species is obtained via their diet of small vertebrate prey, which is rich in vitamin D3.
Recent studies however, have confirmed, through UV meter readings taken in the wild at the mouth of the burrow of nocturnal species, that UV penetrates in moderate levels into the burrow itself. This confirms that nocturnal species are actually exposed to some UV rays. Many nocturnal species also catch the very last few minutes of dusk (Tokay Gecko, for example).
‘If there is any way at all, no matter how small that a wild reptile would or could have exposure to natural sunlight in the wild, then the provision of UV can only be of benefit in captivity, if provided in the correct way and for the correct period of time’ (Courtney-Smith, 2012). Ultraviolet light is, therefore, increasingly considered to be beneficial for all species of reptile (Tedder, 2010).
There are a variety of lighting options available with full-spectrum strip lighting a popular choice for small to medium-sized enclosures. A full-spectrum light is one that mimics the rays produced by the sun and includes UV light (Shingleton and Cottingham, 2011). It is essential to select a good quality, reptile-specific, full-spectrum UV light. UV lights should be provided on the inside of the vivarium as glass and Perspex filter out the UV rays if the light is positioned on the outside. UV output decays with distance from the source and at a distance of approximately 2 feet (60 cm) is almost negligible (Gosden, 2004); for this reason light sources are ideally sited a distance of 30 cm from the reptile’s basking area. Ultraviolet output also decays with age with many bulbs having a shelf life of only 6–9 months; it is essential therefore that bulbs are replaced regularly in accordance with the manufacturer’s instructions. It is advised by Shingleton and Cottingham (2011) that for satisfactory vitamin D3 synthesis, reptiles require access to UVB for 10–14 hours per day. Adequate basking temperatures, and cooler areas elsewhere, will encourage this.
Humidity
The relative humidity of a vivarium is measured as a percentage, 100% being air fully saturated with water vapour. As reptiles come from a variety of climates, their tolerance of moisture in their environment will vary. Species from dry desert regions require humidity levels of as little as 25% whereas rain forest dwelling species can require up to as much as 90% humidity. Providing the correct humidity for individual species is important as too dry an environment may lead to dysecdysis (difficulty shedding) and too moist conditions may lead to skin blister disease (Girling, 2003) or shell rot in tortoises. In order to measure the humidity within a vivarium, a hygrometer is essential (Figure 3).
There is often the perception that ventilation must be decreased in order to increase humidity. Consequently, such action can result in stagnant air and an increase in pathogens, which may lead to disease. It is therefore better to maintain ventilation and regulate humidity by providing a greater water surface area within the enclosure. Humidity levels can be increased via a variety of methods including mist spraying (commonly performed using a spray bottle containing warm water, two or three times daily. Sophisticated misting devices are also available.), water features, shallow water dishes or humidity chambers in focal parts of the vivarium (O’Malley, 2008). A water bowl placed towards the warm end of the thermal gradient will increase atmospheric humidity, whereas a water bowl placed towards the cooler end will keep humidity levels to a minimum.
Substrate
The substrate is the medium that sits in the bottom of the vivarium to absorb urine and faeces. There are a variety of substrate options available, some more aesthetically pleasing than others. The choice however should be determined based on the individual species’ geographical location; for example, desert dwelling species should be kept on sand, whereas terrestrial or burrowing species will appreciate coarse bark chips or wood chips. Whichever substrate is chosen, however, it must be non toxic, easy to clean and not able to cause an impaction if ingested.
Cage furnishings and environmental enrichment
Cage furniture should be selected according to the animal’s needs (Figure 4), and should not include any rough edges or projections that can injure the animal. Arboreal species such as the iguana and chameleon enjoy exploring vertical space (Figure 5). They should therefore be provided with branches and foliage that are vertical or angled along with horizontal perches placed at various heights. Most terrestrial species require a bit of variety in their environment, such as rocks, logs or low-lying branches, along with opportunities to hide. Almost all species of reptile are secretive and welcome places to hide, placed at multiple points allowing the reptile to thermoregulate as appropriate.
Conclusion
Providing a correct environment which acts to reproduce the main elements of the reptile’s natural habitat is essential for its health and wellbeing in captivity. Failure to do so will result in stress and ill health with potentially fatal consequences. Research of a chosen species is therefore essential prior to purchasing and setting up an enclosure. It is essential that captive reptiles are provided with all the elements they require in order to thrive not just survive.