Captive Management and Husbandry of Green Iguana (Iguana iguana)

Soham Mukherjee1 , Akanksha Mukherjee2 , Ushma Patel3 and Rina Dev4
Life Science Education Trust
Agrahara Village Main Road
Bengaluru – 560064 (Karnataka)

 

Abstract

Trade in non-native species has burgeoned due most in part to availability, achievable costs, and often hardy nature of the species. The green iguanas have become a popular exotic pet in India. Many private keepers acquire juveniles but often, when the individuals attain maturity, become larger and more difficult to manage, end up donating them to zoos or other agencies. Since iguana- keeping is a new trend in India, a lacuna in the knowledge and nuances of its captive care and husbandry contributes to poor care and welfare in both private collections and zoos. We present this article as a preliminary guide to good practices.

Keywords: Captive management; captivity; green iguana; husbandry; Iguana iguana

 

Introduction
Green iguana is a large, arboreal lizard native to South and Central America. Due to its extensive distribution, large population and invasive range expansion, it is classified as Least Concern in the IUCN Red List. Additionally, the species has healthy populations in a number of protected sites spread across many range countries (Bock et al., 2018). They typically weigh between 4.5 and 8 kg, averaging 7 kg, but have been reported to weigh up to 18 kg (Dowling, 2008). They reach a length of 1.6 to 2m (snout to tail tip), with their tail accounting for over two-thirds of their body length. Hatchlings are between 17 and 25 cm in length. Juveniles are a vibrant green colour with striped tails, but mature to a dull green, brown or even orange. The dewlap is more noticeable in mature males. A dorsal crest along the spine extends from the middle of the neck to the base of the tail. There are black bands from the base to the tip of the tail.

 

Iguana Housing
Green iguanas are arboreal by nature (Stein et al., 2014) and so they would rather perch on a horizontal branch than cling to the vertical cage wall. Green iguanas should be provided with a variety of horizontal branches of varying widths so they can bask on the branch that is most suitable at the time (Fig. 1A). Sub-adult and adult prefer to be elevated above the ground; therefore, the enclosure must contain a sufficient number of branches above head height for the iguanas to peer down on passing humans. Based on our observations, juveniles spend some time on the ground. Although young iguanas can be kept together, as they get older, males may become more aggressive and territorial, making it necessary to separate them. Females might also develop territoriality as they mature. Juveniles must be provisioned plenty of hiding places, such as logs and dense foliage, as iguanas use visual displays to frighten one another (Fig 1B). If they are unable to escape, it may become a stress inducing factor. If iguanas are kept indoors, the enclosure should be sufficiently large to allow them to exhibit their range of natural behaviours. If an iguana’s enclosure is too small, it will become distressed. Wire-mesh of 10-12 gauge with half inch squares is preferable for the enclosure. This will keep large rodents out and secure the lizards inside from any free ranging predators. Larger gauge (thinner) wire-mesh is not suitable for housing larger green iguanas as it can cause injury when they rub their noses and toes. Iguanas often tend to be persistent and look for a weak spot in the side and attempt to escape. They can spend an extended period in one spot, eventually breaking the wire, which is when they could injure themselves. The enclosure should not have any small gaps that could be used by baby iguanas to hide, as they can be difficult to retrieve. Iguanas must never be handled by pulling on their tails while retrieving from small crevices, as their tails can break off. Smaller mesh size is also not advised as their nails get stuck and can break off when they try to suddenly flee from a threat. When adding natural plants, it must be ascertained that they are not toxic to the iguana. If the plants are edible and care must be taken that the iguana does not destroy the plant by eating away too many leaves. A pair of iguanas should have a floor space that is 4.5mt (l) x 4.5 mt (b) (this is approximately 2.5 times the length of the largest specimen). Floor area must be increased by 20% for each additional individual. The enclosure should have a minimum height of 2.5 mts. The enclosure must be large enough to create a temperature gradient that the iguana can use to control body temperature. The enclosure must be spacious enough to accommodate the iguana’s natural behaviours. A temporary holding enclosure should have a minimum floor space ~3 mts (l) x ~3 mts (b) (1.5 times the length of the longest specimen) for two iguanas. They must be given a platform to rest on. Water and food should be readily available. When keeping iguanas outdoors, the enclosure must face the direction of sunlight, as this allows the iguana to bask in the sun and absorb vital UV (Fig 1C). Outdoor enclosures for Iguanas must be semi-open to protect them from wind and rain while allowing them access to sunlight to bask. In regions that experience cold winters, the enclosure a heat lamp must be added to the enclosure to ensure the iguana receives sufficient heat. Iguanas lick their surroundings with their tongues. This behaviour enables them to collect and analyse data about their surroundings. Due to this behaviour, substrates such as wood shavings, mulch, sand, or powder are not recommended. Anything that adheres to the tongue is consumed, including chemicals that are indigestible and would cause impaction. Outdoor enclosures should have soil mixed with some leaf litter, while temporary cages should have items such as newspaper printed with non-toxic ink, paper towels, and scraps of indoor/outdoor carpet, peat moss, or moss.

 

1. Corresponding author. E-mail: [email protected]
2. NAJA India, Ahmedabad
3. Vet Beyond Basics, Nagpur
4. Dr. Rina Dev’s Animal and Bird Clinic, Mumbai

 

A strong branch placed high in the enclosure and surrounded by leaves or other branches can provide enough bedding material for the iguana throughout the night. Additionally, the iguanas may favour an appropriately sized wooden hide-box (Fig 1D). Although the hide-box may be shared by the pair, it is preferable to offer one for each animal, particularly during mating season, when breeding males become aggressive. A nest box should be created for females by turning a container on its side and filling it with dirt or sand.

 

Enclosure furnishing

Green iguanas are arboreal species and require a variety of vertical and horizontal branches to climb and bask on. The branches must be as broad as the iguana and tightly secured. Flat wooden ledges should be provided at different levels (Fig. 2A). Flatbottomed rocks help in wearing down toenails, which otherwise will need to be clipped in captivity. A pool must be placed in the cage so the iguana can submerge itself if threatened (Fig. 2B). Sufficient sand or dirt must be available for the females to lay their eggs during breeding season (Fig. 2C). If the iguanas are to be kept indoors and space is a constraint, a large box or garbage bin that has been flipped over and filled with the proper nesting material may be added. There must be an abundance of green flora and vines for baby iguanas to hide in (Fig. 2D). Plants that are native to the iguana’s habitat, like as hibiscus, can be used in the enclosure.

 

Sexing and Housing in pairs

Males have significantly bigger ventral femoral pores than females, with all pores having a whitish keratin plug evident in them (Kaplan, 2006) and begin to develop hemipenal bulges at 14-16 months at the ventral base of the tail (Anderson, 1997) (Fig. 3). Females retain pinpoint holes with the exception of the first 3-5 pores right proximal to the vent, which may be slightly expanded (Kaplan, 2006). Males also get significantly larger as compared to females. These distinctions are more subtle in juveniles.

 

Male iguanas should never be kept together in the same enclosure. Males are territorial and may become violent against each other. If two males come into contact, they will cause significant damage to each other or fight to the death. Even a constant visual contact with the other iguana will cause stress leading to health issues. A male iguana that is in close proximity of another male may focus on his rivalry instead of eating, drinking and staying healthy. Female iguanas can be housed together if they are of the same species and size as they rarely fight over territory or food like males do, but they need appropriately sized enclosure to feel safe. To lessen the male’s mating violence, it is advised by several vets and iguana specialists to house two females and one male (Valley, 2022).

 

Temperature and Humidity

In our experience, green iguanas can tolerate temperatures reach up to 45°C during peak summer, provided they have appropriate protection in form of shade, air cooler and regular misting. They may be kept outside in non-peak winters without heating if they have access to unfiltered sunlight to bask and warm themselves as temperature rises in the day. In peak winter (below 20°C) however, they require a heat lamp and UV lamp during day time or may if the temperature drops below 10°C, they may have to be taken indoors. When housing iguanas indoors, the temperature needs are unchanged and the enclosure should be kept at 25-30 degrees Celsius. Heating should be provisioned in one corner to create a temperature gradient and allow the iguanas to choose their preferred position. Young iguanas demand a more humid environment and thus humidity levels of 70-80% must be maintained (Kaplan, 2006). Sub adult and adult iguanas can be maintained at around 50% humidity with provisions to mist spray the animals and the enclosure at least twice a day. Fibre sheets can be used on sides of enclosure to trap humidity, without restricting the sunlight for basking. Rigid plastic sheets filter out around 95% of UV (Tetreault and Anuzet, 2015) and in our experience, we discovered full UV blockage when filtered through a fibre sheet and tested with a Solarmeter 6.5 UV Index Meter.

 

Lighting, Heating and UV

All living species require light and heating, for physiological and psychological well-being. The sun dictates at least a portion of the daily agenda for reptiles. Sunlight allows for thermoregulation and offers the vital Vitamin D. Circadian rhythms are determined by light and heat and they determine when to eat and sleep. Without a healthy circadian rhythm, the animal will be stressed, and their body will react poorly. It is thus essential to pick the lights that are appropriate for daytime and night-time use, as well as those that provides the ultraviolet A and B wavelengths required for proper calcium metabolization and D3 initiation. Iguanas, like all other terrestrial vertebrates, have a distinct light period (day, also called photophase) and a dark period (night, also called scotophase). The two daily periods are collectively referred as the “photoperiod”. The day light period is equivalent in length to the night dark period in the tropics, as both lasting for 12 hours. As tropical lizards, daily photoperiod should follow a 12:12 photophase: scotophase cycle. Inappropriate photoperiod will have a detrimental effect on the iguana’s stress levels, immunological and endocrine functions, digestion, growth, development, breeding season and behaviour etc. (Kaplan, 2006). Reptiles (and some amphibians) require both UVB and UVA light. The ultraviolet spectrum is divided into three components: UVA, UVB and UVC. Natural sunlight contains all three of these forms of light. UVA light aids in the regulation of behaviours like as feeding, diurnal mobility and mating. UVB light promotes Vitamin D3 production, which aids in calcium absorption. They have evolved physical traits and habits that optimise their exposure to sunlight for Vitamin D3 production and other benefits (Baines et al., 2017). Iguanas absorb oral Vitamin D3 , but at a rate that is insufficient to maintain circulating levels of 25-hydroxy Vitamin D3 and 1,25-dihydroxy Vitamin D3 , which is necessary to avoid metabolic bone disease (Allen et al., 1999). If captive iguanas lack access to direct sunlight for more than five hours on most days of the year, heat and UV must be supplemented for captive iguanas. Green iguanas have between 2.9-7.4 UV Index requirements (UV irradiance) in the basking spots (Baines et al., 2016). UV lamps have a chart explaining placement distance for the appropriate UV irradiance. UV lighting and heating should always be coordinated, allow for a thermal gradient such that the entire animal’s body would fit into the optimal upper temperature zone. For species that actively bask, this entails generating a basking area with sufficient UV, visible and infrared radiation to cover the animal’s complete body (Baines et al., 2017). Lamps with broad, flood-style beams or numerous lamps over the basking zone will be required. Daytime basking temperature should be maintained at 35°C, if using heat lamp, with sufficient options to retreat to cooler areas within the enclosure. Ceramic heat bulbs can be used to retain heat at night in extremely cold conditions. They do not emit visible light (which can make it difficult to tell if they are turned on or not). They are particularly advantageous in smaller enclosures, as the bouncing wavelengths eventually warm the enclosure, allowing for the establishment of a horizontal and vertical thermal gradients. They are only useful in large enclosures for heating the basking area. They can also be utilised as an extra heat source in outdoor enclosures in the basking area. The amount of heat produced from either source should always be monitored to prevent under or over-heating, both of which can be harmful.

 

Diet in the Wild

Green iguanas are generally herbivorous (Iverson, 1998; Rand et al., 1990; Troyer, 1984); while they may occasionally consume fragments of carrion (Loftin & Tyson, 1965) or insects (Hirth, 1963), it is not preferred. They prefer green leafy plants (Boyer, 1991), fruits and flowers (van Marken Lichtenbelt, 1993). The digestive system of the green iguana, like that of other primarily herbivorous lizards, is designed to metabolise a high-fibre herbivorous diet and they obtain a significant portion (but not all) of their water requirements from the foods they eat (Iverson, 1998). In the wild, they feed on the leaves, fruits and flowers of a few selected trees also vines and bushes. Frequent feeding bursts occur between late morning and early afternoon. A study indicated that although the majority of forage species were plentiful, effort was in consuming fewer common species and seasonally available items. Although a large variety of species were consumed, stomach contents often contained just one or two species, leading to the hypothesis that dietary diversity occurs over a period of days rather than daily (Rand et al., 1990).

 

Captivity Diet

Iguanas are frequently fed a salad-type diet consisting of leafy greens, different vegetables and fruits. The primary disadvantage of a salad-type diet is that animals can self-select food items, which may not be nutritionally balanced. This also occurs when diets are supplied in excess and a significant portion of the food is not consumed, or when big groups of animals are fed together and the dominant individual have the right of choice from a vast volume of food presented. There is scant evidence that captive animals that are supplied with a variety of food items make nutritionally good choices, even more so when some of the items are highly appetising (Fidgett et al., 2013). To avoid such, self-select feed consumption, an effective strategy can be implemented to ensure a more nutritionally inclusive diet. Basic green iguana diet should always be more leafy greens (80%) and less vegetables (20%). Flowers can be given occasionally as part of foodbased enrichment, but fruits should be given rarely and as treats.

 

In India the availability of edible feed items varies vastly from what is available in US, EU and other developed countries. There is also a lack of iguana specific nutritional profiling of available foods. Iguana diet should be divided into three categories:

1. Staple (to be given every day) 80%: Alfalfa leaves, Amaranthus (pigweed) leaves, Mustard greens, etc. 20%: French beans, butter beans, spring beans, long beans, cluster beans, snow peas and snap peas.
2. Occasional (to be given twice in a week mixed with staple diet) 20% of total diet: Basil, peppermint, carrot, pumpkin, broccoli, beetroot, capsicum, thorn-less cactus pads, hibiscus flowers and leaves, mulberry leaves, melons.
3. Rarely (to be given not more than once a week mixed with staple diet). 10% of total diet: Banana, apple, grapes, papaya, figs, etc.
Enrichment food or treats can be given at any time but in a small quantity. Iguanas do not chew their food, so food must be cut/chopped/grated to appropriate size. Seeds and pits of the fruits must be removed before processing. After processing, the items should be mixed in a large container until all the ingredients are well-distributed. Mixing helps to discourage the iguana from picking out favourite items and leaving the rest. On days when fruits/treats are given, the food composition should be 70% leafy greens/veggies, 20% veggies and 10% fruits/treats. When there is seasonal lack of availability of leafy vegetables, commercially available frozen mixed vegetables can be used after thawing. Green iguanas need access to clean water everyday (Anderson, 1997). Iguanas probably feed daily in the wild (Boyer, 1991). In captivity, they should be fed enough to keep them growing and gaining weight, but not so much that they become obese. If non-adult iguana consumes everything offered and still appears hungry, they should be fed more. Since most baby iguanas grow swiftly, one should be able to see noticeable growth monthly. Hatchlings and juveniles should be fed daily until they are 18 months years of age, at which point they can be fed every other day like adults. If you have a colony enclosure of mixed age iguanas, you may need to feed daily till all reach around 18 months of age (Table 1). Adult iguanas can be fed daily if the feed proportions are kept low enough to avoid obesity. Multivitamin and calcium supplements should be given routinely after consulting with an experienced veterinarian.

Mukherjee et al.
Table 1: Reference growth and age class chart
Age Snout to Total Age
Vent Body Class
Length Length
1 day 5 cm 15-20 cm Hatchling
3 months 10 cm 30 cm Juvenile
6 months 15 cm 46 cm Juvenile
1 year 20 cm 60 cm Juvenile
18 months 25 cm 76 cm Sub-adult
2 years 30 cm 92 cm Sub-adult
3 years 40 cm 114 cm Adult
4 years 46 cm 137 cm Adult
5 years 50 cm 152 cm Adult
6 years 56 cm 168 cm Large adult
7 years 61 cm 183 cm Large adult

 

Hygiene

Green iguana cages should be spot cleaned daily, which involves removing the water bowls and food dishes, and cleaning them with detergent and warm water. Once a week, the food bowls should be disinfected and sterilised to prevent the spread of disease. The cage must be thoroughly cleaned by wiping down all walls, furnishings and removing any damaged or dirty substrate at least once a week. Cleaning solutions must be appropriately diluted prior to use.

 

Handling and Transport

If the green iguanas are kept outside without overnight heat, early morning is the best for capture as they absorb heat from the sun and become more active, decreasing chances of capture as the day heats up. If the iguanas are held overnight with a heat source, they will be difficult to capture as they will have enough energy to out manoeuvre the keepers. Catching bags (Fig) should be made of rigid material and positioned inside out to prevent the iguana from getting its claws, head, or tail stuck and causing damage. Green iguanas instinctively cling to whatever they are currently sitting on when they see you reach for them. It is thus critical that they are picked up cautiously and delicately. Yanking from its perch should be avoided without first relaxing the hold of each foot. This decreases the risk of yanking off claws or injuring the iguana. The iguana should be approached from the side so that it can see the handler approaching and doesn’t get started. One hand should be used to loosen the grip on the front feet, while the other should be used to loosen the grip on the back feet. Once your iguana’s grasp has been loosened, one hand can be slid beneath the front shoulders and the other hand beneath the back legs and the iguana should be raised from its perch. The length of its tail should be taken into consideration and appropriate care is to be taken to not bend or wrap it around anything when the animal is moved. The dangers of capturing and restraint of iguanas include bites from their peg-like teeth, scratches from their sharp claws and being whipped by their long tail. The crate must be well ventilated, with small enough vents to prevent the animal from escaping. The mesh covering the ventilation holes must be attached to the inside surface of the outer container wall. The shipping containers must not be exposed to extremely hot or cold temperatures, as the animals have low tolerance for temperature variations. The container must be labelled and marked appropriately with the consignee’s name, address and telephone number. Labels should not obstruct ventilation openings. The container must be labelled ‘Live Animal’ and ‘This Way Up’ on all four sides, with Reptiles specified on the ‘Live Animal’ label. Because reptiles are highly temperature sensitive, they must be relocated quickly from areas of extreme heat and cold to a temperature of no less than 7 degrees celsius and no more than 29oC. The setting should be draft-free, shaded from direct sunshine, and free of physical tremors and noise. To release the iguana from the box, the box may be set up in the enclosure to which it is being released, the end or lid of the box should be unscrewed and the animal may be carefully picked up and placed on a branch. If the iguana was transported in a bag, place one hand firmly at the base of its head and the other inside the bag, holding the base of the iguana’s head. Release the outside hand and carefully remove the bag and place the iguana on a log or branch. If the iguana is not tame, the animal should simply be released on the ground.

 

Health Monitoring

Green iguanas require sufficient sunlight to bask, absorb the sun’s UV rays or artificial heat and UV, and digest food effectively. Daily non-invasive visual health check-ups are critical for detecting problems early. The caretaker team should check to see if all limbs are moving freely and are injury-free, if the eyes and nose are clear and free of discharge, if all food from the previous feed has been consumed, if the colour of the faeces is normal, if it is malodorous, if there is any discharge from the cloaca, if there is weight loss or abnormal joint swelling and if its demeanour is normal or unusual. Other things to notice include respiration, is it in labour (in breeding season in females), is it having difficulty urinating or defecating.

 

References

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Received on: 05.11.2021
Accepted on: 17.12.2021