Chuckwalla, Western

Western (Common) Chuckwalla

Latin Name Sauromalus ater   OrderReptilia Family: Iguanidae

Named after its color, Latin “ater, atra, atrum” = dark or black. 

Sauromalus obesus has also been used to describe this species, but after a 2004 ruling by IUCN, S. obesus was deemed obsolete and S. ater the proper terminology.  (IUCN) https://www.iucnredlist.org/species/64054/12740491

There are currently five species of chuckwalla, with the Common Chuckwalla (also called the Western Chuckwalla) and San Esteban Island Chuckwalla most commonly held in institutions.   (ZIMS)

Overview

Chuckwalla are commonly used as ambassador animals in zoos.  They are a hardy, generally docile and food-motivated lizard.  As juveniles they may exhibit more active behavior during handling, but calm quickly with consistent handling. With their high food motivation as well as alert and curious demeanor, they are a great candidate for training and have been taught to station and target. Their unique physiological adaptations for their environment give an excellent educational topic in addition to some implications for their care.  A desert species, they need low humidity and high heat/UV access in their habitat. Overall a versatile, excellent species for consideration as an animal ambassador.

Natural History Information

Range and Habitat:

Common chuckwallas can be found throughout the southwestern United States and into northern Mexico.  They are desert, scrubland lizards commonly found in rocky outcroppings or lava flows with low growing plants. They will alternate between basking on large rocks and resting in crevices or shallow holes to thermoregulate.  Male lizards typically have a home range of around a football field (0.57ha), while female lizards have a range of approximately 1/3rd the size (0.17ha). 

Longevity

Chuckwallas have a median lifespan of 15 years in the wild, but regularly will live beyond 25 in human care.  The oldest recorded chuckwalla (in human care) was 65.  

Ecosystem Role:  

Chuckwalla represent an important prey species for many desert dwelling species, including raptors, medium to large carnivores and snakes. Due to their herbivorous, foraging behavior, they also help regulate plant diversity in their habitat. 

Husbandry Information

Housing Requirements

Life Cycle Natural History Relevant Information 

  • Anecdotally, juveniles tend to be more active and need regular, consistent handling to be calm during programming. This species reaches sexual maturity after 2-3 years and becomes more docile in hand.
  • During egg laying, females may need increased depth of dig boxes to accommodate egg laying (6-12 inches) as well as increased calcium supplementation 
  • Activity levels vary seasonally and some facilities will change lighting schedules to match seasonal trends.  Males have been noted to be more active than females during breeding seasons.

Habitat

  • A desert-dweller, they get the majority of the water they need from the food they eat.  A water dish is not necessary (with proper diet and monitoring) and may over-humidify the habitat. If adding a water dish, ensure it is small/shallow so that animals do not accidently get over-hydrated.
  • Chuckwallas wedge themselves into crevices between rocks in the wild and will often attempt to squeeze into small places in its habitat.  Ensure all furniture placed in habitat cannot fall, tip over or otherwise injure the animal. Having tight-fitting hides will also encourage their use.
  • Chuckwallas like to climb. Always check furniture to ensure animals cannot get too close to basking lights.
  • High temperature basking zones and high UV availability is particularly important for this species

Temperature, Humidity, Light Cycles

  • Temperature:  
    • A temperature gradient with many ‘micro-climates’ is important for chuckwalla thermoregulation in a habitat. 
    • Temperature recommendations: 75-95 degrees ambient; 100 to 120 degrees basking; 72-80 overnight
      • A secondary basking zone if habitat size allows
      • Provide heat retaining furniture (ceramic hides, rocks) under basking spots 
    •  Multiple hides in a variety of temperature zones to allow for cooler thermoregulation.  
    • Chuckwallas have been known to stay on heated surfaces and can give themselves burns, so be mindful of any underbelly heat sources and ensure temperatures do not get to dangerous levels.
      https://reptilerapture.net/chuckwalla-caresheet.html
    • Also be aware of temperature zones in habitat and monitor enrichment placement to 1) ensure chuckwallas will have options of hides in various micro-climates and 2) that enrichment does not allow them climbing opportunities around heat sources/bulbs that could result in burns or overheating
  • Humidity:  
    • Chuckwallas are an arid species that thrive in very low humidity (15-50%) 
    • Should occasionally offer a small, humid hide (ex: plastic box with damp sphagnum moss or coconut fiber) option in the habitat or a damp substrate dig area. 
      • Provides humid areas that would be found in natural habitat and are beneficial to long term health, but need to be monitored and not offer if individual is over-hydrated (or if an individual is prone to over-hydration)
    • Open mesh tops to habitats to increase ventilation to decrease humidity. 
    • Chuckwallas can be prone to over-hydration that can lead to medical issues.  Monitoring hydration levels is important for animal health. Hydration levels can be assessed through palpation of their accessory lymph sacs (with vet approval/training)

  • Light:  
    • Chuckwallas are a Ferguson Zone 4 species and need very high levels of both UV and heat for proper health. Some suggestions are:
      • 10-12% UV bulbs or mercury vapor UV bulbs at appropriate distance from the animals (minimum of 18 inches)
      • They also will need a combination of other bulbs (deep heat, CHE, halogen) for light and heat options.
      • ALWAYS check distance from bulbs, temperatures (and UV output if possible) before placing a chuckwalla into a habitat to ensure they do not overheat or present with burns
    • An example of a chuckwalla habitat with proper heat/light availability can be seen here: http://www.reptilesmagazine.com/Reptile-Health/Habitats-Care/Reptile-Lighting-Information/
  • General note:  
    • Nothing is a substitute for true sunlight!   Offering (temperature/humidity/safety-approved) options for basking outside can greatly benefit chuckwallas in human care. 
  • Substrate: 
    • Commonly used:  sand, sand/soil/clay/gravel mixes and woodchips.  
      • Monitor individuals for any potential impaction concerns with pure sand and provide a feeding area that will not allow for excess sand ingestion.
    • Newspaper can also be used, particularly for easy clean-up during quarantine or with sick individuals.

Social Housing/Colony Management

  • 1.1 set ups or ‘harem’ set-ups with multiple females and a single male.
  • Males should only be housed singly or with females as they will engage in territorial disputes.
  • Females have had rare instances of displacement of other females in habitat during breeding season

Other General Housing Requirements or Management information

Diet Requirements

Diet in the Wild 

  • Chuckwallas are herbivorous and browse on a variety of plants.  They will consume leaves, shoots, flowers and fruits of the plants. 
  • They are attracted to bright colors and have increased interest in eating flowers and flowering plants in their native habitats. 
  • Occasionally they will also eat insects.  
    • Mostly behavior seen in juveniles and gravid females.

Diet under human care

  • Chuckwallas require a diet of leafy greens high in calcium
    • Small amounts of vegetables and fruits may be offered
    • Some facilities offer occasional insects like crickets or mealworms
  • Supplementation with a reptile supplement (with or without vitamin D depending on UV availability) is used in many facilities
  • Reid Park Zoo: ½ cup kale, collard or mustard greens and ½ cup mixed greens  (arugula, green leaf lettuce, spinach, radicchio); all chopped small
    • Offers native plants (desert mallow, evening primrose, honeysuckle) and edible flowers (rose petals, hibiscus, marigolds, pansies) as often as are available.
    • Mists greens lightly with water when hydration levels are low
  • Turtle Bay Exploration Park: 14g of greens and 7g of fruit/veggie mix
  • As they are attracted to bright colors, flower petals make a great training reinforcer.  Reid Park has had success with hibiscus flowers in particular. 
  • Many will also readily take their normal greens from their diet as reinforcers as well. The Audubon Nature Institute has had success with this. 

Veterinary Concerns

  • Bladder stones 
    • Surgeries to remove stones have been successful, although individuals with a history of bladder stones should be closely monitored for recurrence 
  • Hydration levels (proper salt regulation)
    • Chuckwalla regulate their fluid levels in their accessory lymph sacs.  These can be palpated to determine proper fluid levels (always check with vet before). They will also excrete salt from their nostrils. Salt deposits can also be monitored as a way of evaluating fluid levels. Food can be misted or dried out depending on needs. 
  • Tail dropping
    • This species can drop their tails if excessively stressed or if there is some outside force (pulled on, caught under furniture). Tails will regrow, but slowly. 
  • Egg retention
    • Females should have access to proper nesting/burrowing areas during breeding season to promote proper egg laying behaviors.  It is also sometimes recommended to be provided with extra calcium during egg laying cycles, but check with your vet.
  • Gut bacteria
    • In human care, some individuals won’t develop proper gut bacteria, or lose diversity of gut flora.  Typical signs of this are inappetance, unexplained weight loss, poor stool formation or lethargy.
  • Gout 
    • Typically seen in older individuals, it can be the result of long-term dehydration. This is anecdotal, with little literature specifically on chuckwallas but a common problem encountered across reptile species.

Enrichment & Training

Enrichment

Behavioral Relevant Information

  • Chuckwallas are an active and curious species who regularly move around their native habitat to thermoregulate and forage. 
  • They are often found in the wild basking on tops of rocks or squeezed into cooler, safer crevasses. 
  • They will climb small shrubs to forage.
  • They dig shallow burrows in rocky, sandy soil.
  • This site provides some good images of their native habitat as well as videos of wild behaviors: http://www.californiaherps.com/lizards/pages/s.ater.html

Environmental Enrichment 

  • At Reid Park Zoo, these are some of the most common enrichment opportunities
    • Changing secondary basking spot
    • Tight hides 
      • Commercially available plastic and ceramic hides may not be tight enough to be used often by chuckwallas. These can be modified for increased use however, if filled with substrates (browse, newspaper, gravel) or have flat rocks underneath (slate or flagstone works well) to simulate natural burrows/crevices.
      • There are also lots of DIY options utilizing carved styrofoam with a grout covering or simply stacking pavers/rocks into narrow hides (but monitor closely for safety)
    • Tunnels (PVC/drain piping or purchased plastic tunnels)
    • Rock stacks
    • Seasonally appropriate humid hide/dig box
    • Climbing opportunities (vines, logs, browse)
    • Novel substrates (gravel of varying sizes, sand, coco dirt, leaves, twigs)

Behavioral Enrichment 

  • At Reid Park these are the most commonly used BE
    • Hammocks (both shade cloth fabric as well as seagrass mat styles are commercially available) 
    • Dig boxes with substrates
    • Novel diet presentation (greens from diet scattered or speared on browse/branches is very interactive)
    • Puzzle or slow feeders 
    • Native greens/flowers (Reid Park follows these desert tortoise native browse recommendations for our chuckwalla as well: https://www.desertmuseum.org/programs/tap_diet.php
    • Logs/climbing opportunities
    • Outdoor basking 
    • Grass clippings/leaf litter 
    • Brightly colored play balls

Schedule 

  • Reid Park Zoo offers daily enrichment opportunities as well as scheduled outdoor basking when seasonally appropriate.

Other Enrichment Resources 

Training

Behaviors Trained

  • Target training – As chuckwallas can also be movement-focused, targeting using a laser pointer (with all necessary safety precautions), is an easy way to begin a behavior
    • A normal target stick can also be easily used, but it is recommended that the ball/target area is a bright color (red or yellow) to attract attention
  • Station training – The Audubon Nature Institute will station their chuckwalla on a cork bark flat for moving in and out of habitat.  He is targeted on, then offered food on cork bark while moving

Reinforcers used & schedule of reinforcement 

  • As they are attracted to bright colors, flower petals make a great training reinforcer.  Reid Park has had success with red hibiscus flowers in particular. 
  • Many will also readily take their normal greens from their diet as reinforcers as well. The Audubon Nature Institute has had success with this. 

Other

Colony or Breeding Management

  • Chuckwallas can be managed in large colonies for breeding. Contact San Esteban Chuckwalla SSP coordinator Kelly Garner at the Santa Barbara Zoo (kgarner@sbzoo.org) or the Arizona-Sonora Desert Museum’s Herpetology curator Howard Byrne (hbyrne@desertmuseum.org) for more information. 

Individual Identification

  • During breeding season, sexually mature males develop white “fringes” along the femoral pores on their back legs. 
  • Chuckwalla color patterns vary based on original sub-populations and can range from full black to gray spotting to vibrant orange on back/tail 
  • Juveniles exhibit striped patterning

Programmatic Information

Messaging Themes

  • Climate change – leading to habitat degradation
    • Chuckwallas are desert-adapted species, but rely on seasonal rains for food and breeding and are very sensitive to temperature fluctuations.  By reducing greenhouse gas emissions and planting more trees, we can help reduce the impacts of climate change. 
  • Conservation of resources – water conservation (also desert adaptations)
    • Chuckwallas are experts at water conservation.  They rarely need to drink, instead getting most of the water they need in the plants they eat.  Their accessory lymph sacs also provide them with ‘canteens’ to help them avoid dehydration in the hot, dry summer months. They also have special glands which filter the salt out of their body, which allows them to reduce the amount of urates they need to produce. 
  • Native species protection 
    • Chuckwalla populations are very localized, if there is a road built, it can establish a barrier to completely separate populations.  Development of their native habitat also has a negative impact on populations. It reduces the amount of available habitat, increases run-off and water drainage changes which can flood habitats at certain times of the year and can also increase pollutants in the habitat.
  • Zoos save species (SSPs)
    • The largest chuckwalla species, the San Esteban chuckwalla, is an endangered species due to being only located on one small island in the Sea of Cortez. Zoos (the Arizona-Sonora Desert Museum and Santa Barbara Zoo) participate in a SSP for the San Esteban chuckwalla.  This ensures a genetic ‘ark’ for this species in case there is a loss in their population in the future. 
  • Proper nature interaction 
    • Chuckwalla (like many lizard species) hold the fat stores in their tail.  If picked up in the wild, they may drop their tails as a distraction from being eaten by a predator. This puts their life in danger as they may not have enough stores to make it through the lean summer/winter months.  Watching animals in the wild is better then attempting to capture them. Chuckwallas also make burrows in rocky areas. Stacking rocks on top of each other, hiking off-trail or other behaviors impacting the physical habitat can have negative repercussions to the chuckwalla.  Practicing leave-no-trace behaviors while experiencing nature can help the species.

Threats and Conservation Status

  • Chuckwalla are considered Least Concern by the ICUN
  • However, due to localization of sub-populations, there can be threats to these small diverse pockets due to habitat degradation, particularly with an increase in farming and grazing practices in their range.
  • The pet trade also poses a threat to these populations as over collection from sub-populations with desired color patterns has been documented to lead to the loss of these populations over time.

Interesting Natural History Information

  • Chuckwallas will go through periods of dormancy at certain points of the year. Brumation is where they will have reduction in body temperature, activity and heart rate in the winter.  Estivation is a period of torpor they enter when the weather is too hot and arid (and food resources are low).
  • Chuckwalla are often found with their nostrils coated in salt.  They have special salt-secreting glands which empty into their nostrils and they sneeze out the salt. 
  • Chuckwallas have territorial displays that look like they’re doing push-ups!  They will bob their upper body to warn off potential treats or attract mates. 
  • Chuckwallas escape predators by going into narrow crevices and inflating their bodies to prevent extraction.

Did you know…

  • Due to their large size, chuckwalla were an important food item for many native tribes in their range.  Some developed specialty tools for puncturing the chuckwalla’s inflated sides to more easily remove them from tight crevices. 
  • Some researchers think the chuckwalla’s blotchy coloration is for cameoflage to mimic bird droppings on rocks

Handling & Presentation Tips

  • Some chuckwallas also have prefered being presented with their head elevated as opposed to on a flat plane, which mimics a lot of their alert/surveillance behaviors in the wild. 
  • Presenting chuckwallas out in the sun can be beneficial for their health, but will also increase their activity levels over time.  It is also important to monitor temperatures to ensure they do not become overheated as they cannot thermoregulate. Offering a display with a shaded hide can mitigate this. 
  • Some stress signs to watch for during handling are:
    • Tail whipping – they will also sometimes do this during pick-ups and can be a sign that they are not properly supported or feel uncomfortable. It is usually readily avoided/mitigated by adjusting handling positions to support all levels of their body. 
    • Push-ups – sometimes if seeing their reflection or other large lizards, they may exhibit territorial displays. 
    • Over-activity – this can be sparked by a number of instances (loud noises, discomfort, overheating), but should be viewed as stress and considered as an end of program if they do not readily calm quickly. 
    • Inflation – if a chuckwalla has inflated their extra skin and is staying inflated while out with the public, it can be a sign of stress that RPZ uses as a firm end to programming
      • Chuckwallas will also ‘pancake’ while in hand, this is generally a relaxed behavior, but can be easily confused with inflating by new handlers
    • Gaping/Open mouth – this is a sign of intense stress/overheating. Chuckwallas should be immediately returned to their crate/habitat.
  • Reid Park Zoo: we will present our chuckwallas in hand for the majority of our programming. When picking up from enclosure, it is important to always monitor to ensure the chuckwalla is aware they are being picked up and not holding tightly onto furniture as their nails can be damaged.
  • Audubon Nature Institute: we targets our chuckwalla onto a cork flat then is able to remove them from habitat into their crate, which eliminates this concern.

Use Guidelines

  • Reid Park Zoo: 
    • As this is a quick, potentially skittish if startled animal, newer handlers are encouraged to start indoors for use.  
    • Reid Park also uses a plexiglass display mounted on a cart to display chuckwalla. We always provide climbing opportunities in the display as well as monitor temperatures closely. 
    • As our chuckwalla lives in a temperature controlled area, we also do not have any seasonal variation in activity levels, but this may change dependant on location/seasonality.

Public Contact and Interaction Guidelines

  • Reid Park Zoo:
    • Allows one or two finger touches with calm, small crowds, but generally avoids touching with this species due to quickness and potential for tail drop. 

Transportation Tips

  • Reid Park Zoo: our chuckwalla has a larger plastic box  (Sterilite 12 gal latch and carry) with locking handles and small holes drilled into the sides and top, we place a layer of newspaper on the bottom.  He is always given some sort of food option (usually part of his greens mix) while in crate.
    • Things to be aware of: holes that cannot have limbs fit through or toes get caught in. 
    • For winter: microwaved sock with rice or cooler depending on temperatures
  • Wildlife Discovery Center at the historic Elawa Farm: We’ve transported desert dwelling herps including chucks to many outreach programs in the dead of winter and they do great if proper precautions are taken.  We use a cooler with some limited ventilation.  Herps are placed in a pillow case and placed on a thick towel on bottom of cooler.  We then place a large 48-72 hour heat pack inside cooler but also have a thermometer and probe that reaches bottom of cooler where animal is sitting so we monitor temps inside the cooler without having to open it. 

Crating Techniques

  • The Audubon Nature Institute will station their chuckwalla on a cork flat prior to crating.

Temperature Guidelines

  • Reid Park Zoo: Outdoor use only between 61-90 degrees
    • They generally can be handled for maximum of one hour
    • If 61-70 degrees must be presented in a sunny spot for only a half hour
    • If 81-90 degrees must be presented in a shady spot for only a half hour

Acquisition Information

  • The San Esteban Island Chuckwalla has an SSP.  The program lead is Kelly Garner at the Santa Barbara Zoo (kgarner@sbzoo.org).  They are also breeding Common Chuckwallas at the Santa Barbara Zoo.
  • The Arizona-Sonora Desert Museum also currently breeds both common and San Esteban Island chuckwallas.  Contact: Howard Byrne, Herpetology curator (hbyrne@desertmuseum.org)
  • Common chuckwalla are also available in the pet trade.  However, be aware of sourcing. Illegal wild collection (particularly for desired sub-population colorations) is very common.

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