Adult Sonoran Desert Tortoise

Why have a pet Sonoran desert tortoise?

The Sonoran desert tortoise is a threatened species throughout its range which includes both the Sonoran desert and the Mojave desert.  Phoenix and Tucson are part of the Sonoran desert.  Unfortunately, many new housing developments occur right in the middle of desert tortoise habitat.  In many cases, desert tortoises that are simply wandering about their lifelong home are found by well-meaning citizens and turned in to wildlife rehabilitation centers as “lost pets”.  There are probably even more desert tortoises that are truly “lost pets”, ones that may have meandered through an open gate into a neighborhood alley or been lifted out of a backyard by someone who had second thoughts about bringing home their new pet.  Wildlife officials are unable to return these “lost pets” to the wild even if they knew exactly where a desert tortoise once lived.  For one thing, there is no sure way to know that a desert tortoise that spent time in human care was not exposed to a disease that could prove deadly if it got into a wild population of desert tortoises.  Also, a number of desert tortoises test positive for a disease called mycoplasma; it is controversial about whether or not these infected tortoises should be released back into the wild so most of them end up in permanent holding situations.   Additionally, wild tortoises live their whole lives in particular areas, knowing where the best places are to escape summer heat and winter cold, where to find tender growing plants, and where there are potential competitors and mates.  Once a desert tortoise is out of its territory, its former neighbors and competitors are likely to move in and take over the choicest spots.  Simply put, a desert tortoise that has been in captivity a while is likely to have new tenants living in its wild home; adding another tortoise to the mix spells doom for one or the other.

There are literally thousands of non-releasable desert tortoises living as pets in Arizona.  Adopting a desert tortoise is relatively simple.  Arizona Game and Fish Department often have groups of unreleasable desert tortoises that are up for adoption by responsible citizens of Arizona.  Many people who have desert tortoises end up with babies, often as unplanned events, and it is relatively easy to get into a network of tortoise people and find babies that need homes.

A word of caution: under no circumstances should anyone ask for money or barter for goods in exchange for a desert tortoise.  There should not be a “donation fee”, as is sometimes seen on the internet ads such as Craiglist.  Desert tortoises may be given as gift as long as proper state wildlife guidelines are followed, but they are strictly prohibited from commercial transactions.  If anyone tries to sell you a desert tortoise, you should advise them this is illegal (and report them to Operation Game Thief, 1-800-352-0700).

There are many Sonoran desert tortoises that need homes.  Fortunately, the desert tortoise adapts well to life as an outdoor pet provided you are willing to make some adaptations to your backyard.  For those of you who make the commitment to care for a desert tortoise, you’ll find yourself richly rewarded by a friendly undemanding companion.

What are the legal requirements for getting and keeping a Sonoran desert tortoise?

To know the current regulations, go online at www.azgfd.com or call a local Arizona Game and Fish Department office and ask for the latest regulations on amphibians and reptiles.  Collecting a Sonoran desert tortoise from the wild is illegal because they have no “open season”. As of 2006, Sonoran desert tortoises are considered restricted live wildlife (R12-4-406) and anyone keeping one as a pet is required to possess a special license (R12-4-409).  If a desert tortoise was a pet prior January 1,1988, it may be possessed, propagated, transported, traded, and given away (R12-4-407).  Possession limit is one tortoise per person in a household.

Breeding desert tortoises presents a legal problem for some people.  By Arizona wildlife regulation, babies tortoises must be given away by 24 months of age unless you have received specific permission to keep them longer.

What do I need to keep a Sonoran desert tortoise?

We strongly believe that Sonoran desert tortoises do best when maintained in appropriate outdoor enclosures within their natural range.  In the major metropolitan areas of Phoenix and Tucson, thousands of desert tortoises are backyard companions that stay outside year-round.

You need sufficient outdoor space to keep desert tortoises.  It is important that this space has shade to protect them from the blazing summer sun and bright sunny areas during the cooler months.  Shade can be provided by native plants like palo verde trees, desert willow, jojoba bushes, desert sage, brittle bushes, and prickly pear.  Exotic plants like citrus trees are great shade providers but since they do not drop their leaves as the seasons change they may block too much sun during the winter.  Desert tortoises need an insulated retreat in which they can hibernate when the temperatures are too cold for activity.  Ideally, a desert tortoise yard should be large enough to accommodate two separate artificial burrows, a summer one that opens with a northern to eastern exposure and a winter one that opens to a southern exposure.  The artificial burrow openings need to be elevated or otherwise protected so that heavy winter or summer rains do not flood the burrow.  If you cannot provide a good winter den in your yard, your desert tortoise will have to hibernate in an artificial hibernaculum.

The enclosure should be rich with grasses, spurges, and other suitable plants for grazing.  Bermuda, rye, and fescue grass may be planted to provide grasses throughout the year.  Some species of grass native to North America are available through online seed catalogs. Wild weeds are often readily consumed although some may be toxic.  Desert tortoises love the ripe fruit of prickly pear cactuses and will often munch on the growing pads of spineless prickly pear cactuses, such as the common ornamental species Opuntia ficus-indica.  Other suitable browse plants are hibiscus bushes (leaves and flowers are readily eaten) and mulberry trees (leaves and berries).  With an appropriate lushly planted enclosure, supplemental feeding with produce is minimized.  Nonetheless, a mix of romaine lettuce, green or red leaf lettuce, escarole, kale, collard greens, mustard greens, turnip greens, spinach, broccoli, and other dark green leafy vegetables may be offered to insure that a tortoise has enough food.  Smaller tortoises may need daily salads while adults generally do well on two or three salads a week, in addition to their daily grazing.  Over-feeding produce, or offering produce that is high in simple sugars and moisture, such as bananas and apples, may lead to diarrhea.  Sprinkling calcium, such as calcium carbonate, calcium lactate, or calcium citrate, onto the salad will help balance out the mineral content of the food.  If a tortoise has access to dirt, it seems to not need trace minerals added to the produce.  Occasionally supplementation with a reputable multivitamin may be beneficial.  (Be sure the vitamin is fresh—most powdered vitamins lose their potency within 6 months of breaking open the seal, and they lose it more quickly if exposed to humidity and temperatures above 78°F for any length of time.

As a general rule a male Sonoran desert tortoise needs more space than a female.  While females are tolerant of each other, males will typically not tolerate other males in their enclosure.  We do not recommend that you house two male tortoises together since it is likely that the least dominant one will end up injured, flipped on his back in the hot sun, or chronically stressed and susceptible to disease.

An outdoor enclosure of at least 10 feet by 12 feet will comfortably house a single adult male tortoise and one or two adult female tortoises.  A larger enclosure provides more variety in terrain for the tortoises to explore.  Sculpt the landscape so there are plenty of visual barriers that allow the tortoises to stay out of each other’s sight lines if they so desire.  You may wish to keep only female desert tortoises or only a lone male tortoise to avoid breeding.  Before you set up a group of desert tortoises that have the capacity to produce babies, please have a plan on how to legally place the offspring! 

A cinderblock wall at least two feet high is an excellent perimeter fence for a desert tortoise enclosure.  The footing needs to be at least 12 inches deep so that the tortoise can not tunnel beneath the wall.  If the fence is solid, the tortoise will not try to escape.  However, if a tortoise can see through the fence, it will focus on those gaps and struggle to leave.  This can result in injuries so we do not recommend wire, hardware cloth, chain link, or woven wooden fences.  Sonoran desert tortoise are quite good climbers and in the wild often live high on steep slopes of canyons and foothills.  A slight overhang along the top of the enclosure wall, especially at the top of any corners, will prevent Houdini-like escapes.   

Standing water may lead to the spread of diseases such as Hexamita and other protozoan parasites.  We believe that temporary water, such as a pan that is filled a few times a week and left dry on other days, is the best way to provide water for adult desert tortoises.  A weekly early morning sprinkling of the yard will also offer your desert tortoise an opportunity to drink.  A timer can be set up to periodically irrigate different sections of the enclosure and provide different drinking spots.  Remember, tortoises are often up and moving by dawn during the summer months so you should provide fresh water early in the day during the hottest weather.

Artificial burrows can be constructed quite easily.  We believe it is important to build burrows with easy access to the interior so that hibernating tortoises may be periodically monitored.  A summer burrow provides a retreat from the hottest daytime temperatures.  Facing the burrow so that it opens in a northerly to easterly direction is best.  With an eastern exposure, the tortoise will be awoken by early morning sun and commence activity early, retiring midmorning to avoid the scorching afternoon rays.  It is helpful to lightly mist burrows during hot weather so that they also serve as an area of higher humidity than their surroundings. A winter burrow provides stable temperatures during the coldest days of winter, keeping the tortoise well above freezing throughout hibernation.  Facing south is important so that the winter burrow gets plenty of sun on the bright warmer days of fall, winter, and spring. 

If there is any doubt that there is good drainage in an area during the summer monsoons or the winter rains, you should build a mound of dirt up to 12 inches high where you want to locate the burrow. The structure may be a cinderblock square with a plywood roof covered with a thick layer of insulating dirt. Bales of straw can be arranged in a similar manner, but generally need to be replaced every year. Large garbage cans half-buried in the ground are used successfully by some.

Some Sonoran desert tortoises will excavate their own burrows rather than use the artificial burrows that have been provided.  This should be discouraged because it can be difficult to monitor the health of a tortoise in a natural burrow.

The outdoor enclosure for hatchlings and tortoises under 4 inches long:  Basically, the enclosures for hatchling and juvenile tortoises are the same as the enclosures for adults only with the artificial burrows tailored to their smaller sizes.  The artificial burrows should be misted more often to maintain the higher humidity that young desert tortoises need.  Water should be available daily and a soaking in warm water every week will insure that the small desert tortoise stays well hydrated.  Mesh netting may be placed over the top of the tortoise enclosure to prevent wandering cats and other predators from harassing the babies.

Since small desert tortoises can quickly succumb to ant bites, it is important to thoroughly scour the enclosure every 3 or 4 days for developing ant mounds and to eliminate those when found.  A teaspoon of Amdro™ sprinkled around the entrance of the ant hill will usually eliminate the ants quickly.  A wire barrier can be placed over the baited ant hill to prevent the baby tortoises from consuming the Amdro™. 

A final concern is security against people who may wish to have a tortoise of their own.  Children often learn of a “tortoise house” and will hop fences to meet the tortoises while you are away.  Unfortunately, many tortoises are stolen from yards even in the best neighborhoods.  Some sort of permanent identification is recommended to aid in recovery of a lost or stolen tortoise.  Your address or phone number may be may be adhered to the shell with epoxy or a microchip transponder (125 MHz frequency) may be implanted beneath the skin.  Having current photos of your tortoise is suggested so that you may blanket the neighborhood with flyers if your tortoise goes missing.

May I keep Sonoran desert tortoises inside my house?

We strongly believe that outdoor enclosures are the key to good health for Sonoran desert tortoises when kept within their natural range.  However, if you are able to convert a room in your house to a Sonoran desert tortoise habitat, complete with appropriate substrate, temperatures, lighting, and grazing opportunities, as well as cycling it for hibernation just like it would experience in an outdoor enclosure, you might have some success keeping an adult tortoise healthy and happy long-term.

We sometimes recommend that a Sonoran desert tortoise is kept inside to aid its recovery from an injury or illness.  Sometimes this is to keep wounds or surgical sites clean and prevent “fly strike”, an infestation of maggots around a break in the skin.  At other times it is because we have diagnosed a desert tortoise with an debilitating illness and we know that the tortoise must fully recover and rebuild its strength before it can endure the rigors of its outdoor home, particularly the stress of hibernation or the excess heat of the summer.  With few exceptions, ill tortoises need to be kept warm, active and feeding throughout the winter so that they regain their health and replenish fat and muscle that have been lost during their illness.  Most tortoises that are “kept up” one winter to fully recover are able to hibernate without any problems the next year.

In order to keep a larger Sonoran desert tortoise awake when it should normally be slumbering away the winter, you must provide a large enclosure for it.  We recognize that most people cannot turn a 10 by 12 foot bedroom into a tortoise hospital room, but they may have space for a smaller enclosure.  An adult tortoise will often do well in a temporary home such as a 6 foot by 2 foot wide cattle trough while smaller tortoises may be housed in a 4 foot by 2 foot cattle trough.  Round enclosures provide more area to roam than the “elliptical” troughs, but are often difficult to maneuver through hallways and fit into small rooms.  Hatchlings may live quite comfortably in a 20 gallon long aquarium, or an enclosure 24 to 30 inches long and 12 to 18 inches wide.

Different tortoise keepers swear by different substrates.  We believe good old Arizona dirt is an excellent substrate for desert tortoises but may make the level of dust in your house unbearable.  The dirt has to be collected from an area that is not contaminated with pesticides, herbicides, motor oil, or other toxic substances, and is not contaminated with parasites or diseases from other tortoises.  Cypress mulch works well for most situations where dirt is not practical. Rabbit pellets, either compressed timothy hay or alfalfa hay, are often used with small tortoises.  Care must be taken to spot clean it daily and to completely change the substance out at least once a month to avoid mold growth on these pellets. Tortoises will do well on paper towels or newspapers for short periods of time as may be recommended following a surgery or other illness.

A mistake many people make is to assume a tortoise from the desert doesn’t need water.  In fact, Sonoran desert tortoises in the wild seek out burrows that have a higher humidity than the surrounding ground surface.  When kept indoors, a simple “humidity box” consists of a small enclosed plastic container, like a Rubbermaid™ sweater box, filled with damp sphagnum moss and a small door cut in the side.  The tortoise can shuttle back and forth between moist and dry areas as needed.  The moss needs to be changed regularly and needs to be kept slightly moist rather than sopping wet.  A good judge of moistness is to try and squeeze water out of the damp moss.  If you can only get a drop or two, the moss is the right amount of moist.  While adult tortoises may do perfectly well without a humidity box during their time indoors, young growing tortoises may suffer from a shell deformity known as pyramiding if they do not have access to higher humidity on a daily basis.

A shallow water pan should be available about three times a week.  As with the outdoor tortoises, standing water that has been dirtied by the tortoise seems to promote certain intestinal parasites.  In our experience, tap water is an adequate source of potable water, but some keepers prefer to use filtered or bottled water.  Reverse-osmosis or distilled water should not be used as it is completely lacking in minerals.

You cannot replicate all the qualities of natural sunlight with light bulbs.  Nevertheless, tortoises may be successfully kept under artificial lighting long-term.  Ultraviolet-B must be provided by one of the bulbs to aid in calcium metabolism and other important physiological processes.  There are many different brands of bulbs that claim to provide this, but most of our experiences have been with Reptisun and Powersun bulbs.  These should be on for 8-12 hours a day.  Bright white light is needed to offset the bluish light provided by the ultraviolet-producing bulbs.  This white light allows truer colors—that it, the colors appear more like they do under the sun—which is important to stimulate feeding behavior and other activities in many tortoises.  The bright white light should be on 8 hrs a day during the winter and 14 hrs a day during the peak of the summer. A third light source should provide warm basking areas, where the temperatures reach 95°F during the middle of the day.  Generally a combination of fluorescent bulbs, incandescent bulbs, and a mercury vapor lamp may be needed to provide the quality of light needed to keep Sonoran desert tortoises healthy indoors for extended periods.  The photoperiod should gradually change throughout the year although tortoises that are being intentionally “kept awake” through hibernation should stay on a 12 hr on, 12 hr off photoperiod.

It is important to have cool and warm areas throughout the enclosure so a tortoise can regulate its body temperature.  The background temperature during the day should be 85-88°F with a night time drop to around 75-80°F.  If a tortoise is ill, the temperature should never drop below 82-85°F at night.  An incandescent basking light should provide an area where the temperature is 95-100°F during the day. While incandescent spot lights are great sources of heat during the day, and red-tinted bulbs can be used for night-time heat sources, in most instances radiant heat panels provide more even heating throughout an enclosed space.  The radiant heaters emit no visible light, unlike red bulbs, and do not interrupt a tortoise’s slumber.  It is important to have a thermostat hooked up to the heater to make sure than the cage cannot get too hot.  Some keepers like to have alarms that report when temperatures are above or below the targeted temperature ranges.  There are inexpensive laser-guided handheld thermometers readily available that allows rapid spot-checking of the temperatures in different areas of the enclosure.  We recommend anyone with a pet tortoise have one because it allows you to know the temperature variation throughout the enclosure.  You can even place the laser dot onto the carapace of the tortoise to see check how warm it is.  Do not place the laser dot near the head since it can cause permanent damage and blindness if it strikes an eye.

What should I feed my desert tortoise?

There are many prepared diets available for tortoises.  Most are bad for desert tortoises but there are a few acceptable ones.  Feel free to talk to us about our current recommendations.  (We probably carry them in our office!)

With an appropriate lushly planted enclosure, rich in grasses and small "weeds" such as spurges, there is little need to offer supplemental food such as produce.  Nonetheless, a salad mix is often appreciated by outdoor tortoises and insures that the tortoises are getting enough to eat.  The basic salad mix for Sonoran desert tortoises maintained in outdoor well-planted enclosures includes a variety of greens: romaine lettuce, green or red leaf lettuce, escarole, kale, collard greens, mustard greens, turnip greens, spinach, broccoli, and other dark green leafy vegetables.  We recommend mixing the produce mix with Oxbow Hay's Salad Style Grass Hay Blend to increase the fiber content.  Many desert tortoises like to eat Zoo Med's Grassland Forest Diet, generally after it has been soaked in water for 10-15 minutes, and this also is helpful to maintain sufficient fiber in the diet.  Smaller desert tortoises typically need daily salads while adults generally do well on three salads a week, in addition to their daily grazing.  Indoor tortoises may receive a similar mix, but add some fresh plant material such as fresh grass cuttings, tiny weeds, hibiscus or mulberry leaves, and cactus pads or prickly pear fruits.  Over-feeding produce, or offering produce that is high in simple sugars and moisture, such as bananas and apples, may lead to diarrhea.

Sprinkling a small amount of calcium, such as calcium carbonate, calcium lactate, or calcium citrate, onto the salad will help balance out the mineral content of the food.  One TUMS Ultra Antacid provides 1000 mg calcium carbonate in each tablet and 1 and 1/4 tablets is sufficient calcium to supplement about 8 cups of produce.  A regular strength TUMS provides 200 mg calcium carbonate and may be ground into a powder and mixed with about 2/3 cup of produce.  This calcium supplement is most important for young growing tortoises to prevent “soft shell” (nutritional secondary hyperparathyroidism).  If a healthy adult tortoise has access to dirt, it seems to not need trace minerals added to the produce.  Otherwise, Miner All™ is a good supplement to add to salads once a week.  Supplementation with a reputable multivitamin once a week may be beneficial, particularly to baby tortoises.  (Be sure the vitamin is fresh—most powdered vitamins lose their potency within 6 months of breaking open the seal, and they lose it more quickly if exposed to humidity and temperatures above 78°F for any length of time.

Hibernation

Before you hibernate your tortoise, it is important to have us examine it to make sure it is healthy enough to endure this stressful activity!

Hibernation is part of the natural cycle a Sonoran desert tortoise experiences in the wild.  As the day length shortens and cooler weather begins in the fall, desert tortoises stop feeding and seek out shelters (hibernacula) to protect them from the harshest winter chill.  Since a desert tortoise is unable to generate its own body heat, when the temperature around them falls, their metabolism slows.  Feeding stops during hibernation because the tortoise is no longer using the same amount of energy as it does during warm weather.  A tortoise will often emerge from its burrow on sunny winter days to bask briefly, and may even drink water if it is available, only to retire deep in its shelter if sky turns overcast and the temperature falls.

A tortoise has to be healthy, well-nourished, and well hydrated to survive the rigors of hibernation.  It also must choose a burrow or other shelter that stay above freezing.  If a tortoise lacks sufficient body fat to last through hibernation, it may die during this time or may emerge in the spring so debilitated it is unable to regain its health.  If the hibernaculum gets too cold, the tortoise will freeze to death.  In some cases, the tortoise will survive brief exposure to freezing temperatures but become blind or develop coordination problems.  This spells death for a wild tortoise but captive tortoises can be cared for with these conditions.

Hibernation cues the desert tortoise’s reproductive urges.  Captive female tortoises that are kept indoors may not produce eggs that year and male tortoises may show no inclination to court and mate.  It also appears that hibernation is important to maintain a tortoise’s overall health for captive tortoises that are kept from hibernating over several years tend to have shorter life spans than ones that do hibernate regularly.

Captive tortoises may hibernate either in an appropriate outdoor hibernaculum, such as a properly constructed artificial burrow, or in insulated boxes kept in a cool room of the house where the temperature stays between 40 and 60°F.  If the temperature is much above 60F, the tortoise may be active and use up its energy stores too quickly.  If the temperature is much colder, the tortoise may develop health problems.

Before a tortoise is hibernated, it is important to have a health exam by a knowledgeable reptile veterinarian.  At a minimum, the tortoise should be weighed and its body condition assessed.  A fecal parasite exam and other labwork such as a urinalysis, complete blood cell count, and blood chemistries, may detect underlying dangerous conditions.  A radiograph will pick up otherwise undetectable bladder stones which can compromise the tortoise’s ability to hibernate.  It is best to do the pre-hibernation exam at least 4 to 6 weeks before the tortoise will hibernate, usually in late August or early September.  This allows time to correct simple health problems or to make arrangements for indoor care for tortoises with major medical issues.  Likewise, a post-hibernation exam is recommended to determine if the tortoise has developed any problems that may require veterinary care.

Breeding:

Breeding of Sonoran desert tortoises is somewhat discouraged by Arizona Game and Fish Department.  This is to prevent commercialization of the species, which is considered to be a threat to wild populations.  The threat is twofold: unscrupulous dealers may collect wild tortoises and sell them as “captive bred” animals, quickly depopulating some of the last remaining good tortoise habitat; also, more and more people will impulsively acquire tortoises, get tired of them and try to release them back into the wild, thus possibly introducing new diseases that could wipe out wild tortoise populations.  It seems that this particular cat may be out of the bag since so many people already are accidentally or intentionally breeding their tortoises.  Furthermore, other threats to the tortoise are ongoing--it is relatively easy to get permission to “accidentally harvest” tortoises by developing land for human use.  Although there are efforts to trap and remove the tortoises alive, many end up in research facilities rather than relocated to a new wild space.  Thus the wild populations may continue to decline as they have less and less space available. 

Before you breed desert tortoises, make sure you have good responsible owners lined up that are able to care for any that may hatch!

If you have a healthy male and female adult Sonoran desert tortoise in an appropriate outdoor enclosure, breeding will almost certainly happen every spring once they have both emerged from hibernation.  The courtship and actual mating may be quite lengthy affairs that may go on for hours.

Illnesses:

We strongly believe that early intervention is the key to success with health issues.  If you have a Sonoran desert tortoise as a pet, you must be committed to relieving its suffering when illness befalls it.  If you make an appointment with a good reptile veterinarian as soon as you notice anything wrong, your tortoise has a better chance of getting well than if you let a problem go on long enough to become debilitating.

If you'd like to explore more about desert tortoise care, please see the following website maintained by the Arizona Sonoran Desert Museum, http://www.desertmuseum.org/programs/tap.php

References

The best single compilation at this time is The Sonorant Desert Tortoise: natural history, biology, and conservation edited by Thomas R. Van Devender (©2002, ISBN 0-8165-2191-3).  Although highly technical, this is the book for those of you who want to know a lot more about the Sonoran desert tortoise.

Copyright 2008
Kevin Wright and Jay Johnson
Arizona Exotic Animal Hospital, LLC
744 N Center Street
Mesa, AZ 85203
info@azeah.com