Care, Husbandry and Diet of the Desert Tortoise
Gopherus (Xerobates) agassizii Cooper
Produced by the ASDM Tortoise Adoption Program
Introduction
Desert tortoises have been kept as pets in Arizona for many decades. It is not surprising that so many people find this endearing desert denizen so appealing. Tortoises are highly personable and often appear to interact with people and other animals around them. Unfortunately, these positive qualities have become yet another threat to its existence, especially near rapidly-growing urban areas.
We generally do not believe that desert tortoises should be kept as pets, if by "pet", one means an animal which is frequently handled. Tortoises fare best when handled or disturbed as little as possible, although much enjoyment and understanding of the nature of the desert tortoise can be gained simply by observation of natural behavior. On the other hand, so many tortoises are presently held in captivity in Arizona that it would be impossible and impractical to strictly prohibit possession of them. Wild desert tortoises have been strictly protected since 1987 due to concerns about the potential for decline of their populations. Tortoises may not be collected from the wild, imported, or exported from Arizona without specific permission from the Arizona Game and Fish Department. Tortoises obtained from a captive source, however, may be kept, with one tortoise per family member allowed under Arizona wildlife regulations.
For these reasons, tortoise adoption programs have been established to help facilitate transfer of surplus or unwanted captives to custodians who are sufficiently informed and committed to provide an appropriate home for them. In Arizona, no one "owns" a desert tortoise, but people may become "custodians" to insure the welfare and longevity of those already in captivity. Because tortoises are so long-lived (80-100 years or more!), the custodial commitment may well last a lifetime. The tortoise may, as likely as not, outlive its custodian!
The Tortoise Adoption Program administered by the Arizona-Sonora Desert Museum was established to aid the welfare of tortoises already in captivity and insure the preservation of wild tortoises. The program is therefore dedicated to the well-being and survival of the desert tortoise throughout its range. However, the program only serves Tucson and its surrounding suburbs. In general, tortoises can be adopted from April 1 through September 30 of each year, subject to availability.
Diet
One of the most important aspects of tortoise care is proper diet; therefore, please follow these guidelines to insure the health and longevity of the animal(s) you care for. The old story of the tortoise and the hare is true but incomplete. Tortoises do move slowly. In fact they live slowly, but they also die slowly. Tortoises will accept many foods that are not good for them and appear healthy for years. In reality, such diets impair organ function and are cumulative, resulting in the eventual death of the animal. Tortoises have evolved by making something out of nothing. They have adapted to withstand food and water deprivation and great fluctuations in climatic conditions.
They cannot tolerate improper diets rich in fruits or animal fats. Please do not make the mistake of viewing a tortoise as if it were a child or typical pet (dog or cat.) They are reptile specialists with specific needs. The desert tortoise is herbivorous, feeding mostly on native grasses, leafy plants and flowers. For feeding a captive tortoise see the recommended tortoise diet in Appendix III.
Caution must be exercised to insure that captive tortoises cannot consume toxic landscape plants such as oleander, chinaberry trees, desert & tree tobacco, and toadstools. Do not feed tortoises lettuce of any kind as it is poor in nutrition. Hamburger or other meat, and dog, cat, or monkey foods do not provide appropriate nutritional balance and should not be offered.
Cactus fruits may be fed in relatively small amounts and only when they are in season. Native grasses and others such as Bermuda grass, dichondra, clover, or alfalfa must be planted inside the enclosure in sufficient quantity to allow daily grazing. When dark greens are offered, they should be clean, fresh, and chopped or grated into pieces small enough for the tortoise to eat. Produce foods should be served on a dish or feeding platform to prevent ingestion of gravel or sand, which can cause gastrointestinal irritation or impaction. A shallow puddle of water for drinking should be provided at least twice a week during the months of activity. A partially buried saucer or shallow trash can lid (plastic or galvanized steel) works well (be sure that the tortoise can climb in and out of it easily.) This water source should be allowed to dry up in between waterings.
Cold Weather Care
In Arizona, desert tortoises should be kept outdoors all year whenever possible. As the weather turns cool in the fall, the tortoise will prepare to hibernate.
The appetite will decrease and it will become less active. It will have a fat reserve built up and should easily survive through the winter's hibernation if it has eaten well during the warm months. A den can be constructed above ground using concrete blocks and 3/4" plywood or half of a metal trash can. See Appendix IV for burrow construction. The structure should be covered by at least 8-12 inches of soil for insulation. Ideally, two dens should be constructed, a winter den with a southern exposure and a summer burrow with an eastern, northern or northeastern exposure (for the open end).
An alternative method of artificial hibernation is to place the tortoise in a cool, dry protected area such as a garage or storeroom. An insulated box such as a styrofoam ice chest packed with shredded paper or straw and covered with several layers of blankets or newspapers generally provides adequate protection. The box should be kept up off the floor and away from drafts and rodent invasion. The temperature should remain around 40-55°F (4.5-13°C) and the humidity range between 30-40%. These parameters can be monitored using an inexpensive thermometer and humidity meter. The tortoise will not achieve metabolic hibernation if the hibernaculum is too warm.
Hibernating tortoises should be kept in the dark, and quietly checked every week or two to see that no health problems are developing. Otherwise, do not expose the tortoise to light or other disturbances. In general, it is best to avoid moving tortoises around during hibernation. However, tortoises hibernated artificially (indoors) have a significant risk of dehydration. Therefore, animals kept indoors through the winter should be offered water, once every 2-3 weeks for juveniles and every 4-6 weeks for adults. Additionally, tortoises hibernated outdoors that choose to hibernate outside of their burrows in places that leave them vulnerable to the elements, should be moved inside the burrow. If they continually leave the burrow, they may not be healthy or there might be a problem with either the placement or construction of the burrow. Please contact the TAP for help in these cases (520-883-3062).
Winter Procedures for Tortoises in Poor Condition
If the tortoise cannot hibernate due to a health problem or inadequate weight, follow these recommendations for indoor care: house the tortoise in an enclosure at least 1 square meter in area. The enclosure should maintain a daytime temperature of between 80-85°F. (27-30°C.). This can be achieved by placing a light above the enclosure and installing a thermometer inside. A 75 or 150 watt infrared flood lamp works well for this purpose. Be sure to calibrate the floor temperature with a thermometer before introducing the tortoise. Different wattages may be tried until the desired temperature is achieved.
Provide food according to the summer feeding schedule and provide fresh water at least three times weekly. Take the tortoise outside whenever the sun is shining and temperatures are around 70°F (18°C.). Frequent exposure to sunlight is beneficial to tortoises in rehabilitation and will usually stimulate their appetite. Shade must always be available. Placing a container in full sunlight can cause the tortoise to overheat and die. Maintain a normal daily photoperiod by turning off the light at sunset. Leaving the light on at night may result in hyperthyroidism, a glandular disorder.
Warm Weather Care
As spring approaches, tortoises become more active. As soon as the tortoise emerges, be sure to provide shallow puddles of lukewarm drinking water. It will gradually resume its warm weather routine of eating, basking and exercise. Tortoises maintained in southern Arizona are usually active by early April (this varies greatly among tortoises) but may remain or become inactive in the hot, dry summer months. Tortoises in the Sonoran Desert are most active during the summer rainy season.
The minimum enclosure size for a single adult desert tortoise should encompass at least 120 square feet. This area is large enough for a single male or up to three females. (Females should be kept in a separate enclosure from males to avoid breeding.) The enclosure can be constructed of concrete block, adobe, or other solid material. Other acceptable materials include 1"x 2" welded wire fencing or 2" poultry netting supported by rebar and sunk at least 8 inches in the ground. Wire fencing for adult tortoises should have 2" wide spacing to prevent tortoise legs and heads from becoming entangled. Enclosures for hatchlings to approximately three years of age require no more than 1" wide spaces to prevent escape. If you are housing sexually-mature females, it is a good idea to install an outer perimeter fence of 1" poultry netting to contain hatchlings which might appear unannounced and escape through the 2" fencing. The wall should be at least 18 inches high. Desert tortoises climb well, so the shelter den or other interior structures should be at least 12 inches away from the perimeter enclosure. Tortoises will readily escape and may travel considerable distances.
Pools or ponds must be fenced off from tortoises. Insecticides, pesticides, paint and paint thinners, fertilizers and other toxic agents should never be used in or near any tortoise enclosure. Dogs may be a problem if they have access to the tortoise. Dogs can chew the tortoise shell and limbs causing serious damage.
In warm weather, it is essential that the tortoise have access to shade. A tortoise may dig a shallow depression (pallet) in the soil, usually beneath a shrub or other low-growing vegetation for shelter from the summer sun. The pallet may become a frequently used shelter site during the warm months. Water is best provided by creating a depression in the soil or using a plastic saucer with water available at least twice weekly. It should be large enough for the animal to crawl into and soak and shallow enough to allow easy exit (tortoises can drown). Tortoises will absorb water through the cloaca (located in the tail) during this process. During the summer the burrow (den) must have afternoon shade and the interior can not exceed 90°F. Otherwise the tortoise may overheat and be subject to brain damage! If one is unsure of how hot a burrow is getting, use a Minimum/Maximum thermometer to record high and low temperatures (which is usually available at a hardware store). (See the checklist in Appendix I for tortoise enclosure guidelines.)
Disease and Injury
Desert tortoises are subject to various diseases. Disease often results from opportunistic pathogens or parasites which take advantage of tortoises weakened by stress, malnutrition, or improper physical environment. Prevention of disease is best accomplished by providing the recommended physical environment, shelter features, and diet. These are the most important responsibilities of the tortoise custodian and cannot be emphasized enough!
If the custodian also keeps tortoises of different species it is critical that the desert tortoise not come in contact with those tortoises or their habitat. Very serious and potentially fatal diseases can be transmitted between species. Regular veterinary checks are recommended.
Although most tortoise pathogens are not transmissible to humans, some, like Salmonella, are. Therefore, children under five years of age and individuals with an impaired immune system should be discouraged from handling tortoises (or any reptiles for that matter.) After handling a tortoise or its fecal pellets a person should wash the hands with an anti-bacterial soap.
Tortoises are susceptible to pneumonia and other respiratory ailments. Symptoms are inactivity, runny nose, labored breathing and loss of appetite. Healthy tortoises do not move the head and forelimbs in and out to facilitate breathing. Chronic nasal discharge or raspy breathing should receive veterinary attention. Respiratory problems are sometimes treated with antibiotics.
Parasites are also common in tortoises. If their presence is suspected, consult a veterinarian immediately. Symptoms are usually listlessness accompanied by weight loss and abdominal stress.
Another common problem is vitamin deficiencies. For example, symptoms of a vitamin A deficiency include swollen eyelids and nasal discharge. This can be prevented by providing the recommended diet. Tortoises are easily overdosed on fat soluble vitamins so these should be avoided unless prescribed by a veterinarian.
Sunken eyes indicate dehydration. Swollen body tissues and pasty or liquid feces indicate malnutrition or infection. Prolonged inactivity or tendency to keep the eyes closed may also be indicative of a health problem, although tortoises are normally inactive during winter hibernation or dry summer aestivation.
Sick tortoises often refuse to eat and become emaciated. A tortoise should be referred to a veterinarian if it seems abnormally light, indicating dehydration or emaciation, or too heavy, which may indicate large bladder stones. The legs and head should appear symmetrical and bones should not appear too prominent.
The condition of the fecal pellets often reflects the health of the tortoise. Normal healthy feces are very fibrous, firm, and brownish-green in color, with plant material readily recognizable. It is normal for tortoises to periodically excrete a gray to whitish, chalky material; however, this should not occur continuously. Feces which are loose, runny, or contain mucous often indicate a health problem requiring veterinary attention.
Fibrous osteodystrophy is typically evidenced by a soft shell, usually caused by malnutrition resulting from lack of a proper calcium to phosphorus ratio, sunlight, or both. This condition can be prevented by feeding only those foods on the recommended diet and by keeping the tortoise outdoors when night temperatures do not go below 45-50°F. (9-10°C.). In cases where tortoises, particularly hatchlings, must be kept indoors for any length of time, it is wise to provide a source of artificial full-spectrum lighting (see Appendix II).
Tortoises sometimes suffer physical injury resulting in cracks or fractures in the shell. Such problems can be treated at home unless the crack is severe. Consult a veterinarian to determine whether professional assistance is necessary. The following procedures are recommended to repair minor cracks:
Cleanse the crack with sterile (boiled and cooled) water. Apply Betadine (Povidone iodine) solution to disinfect the wound, cover it with a sterile gauze pad, and tape the gauze in position with first aid adhesive or surgical tape. Place the tortoise in a box lined with clean rags or paper towels. Place the box in a warm, quiet place indoors and do not disturb except to occasionally offer water (NO FOOD) during the first 24 hours. Within a few days, it is usually safe to offer food and gradually reintroduce the tortoise to its regular enclosure. It will take many months for the shell to heal, so the tortoise should be handled as little as possible during this time. The wound should be checked periodically to monitor infection. Re-tape as necessary until the wound heals. Consult a veterinarian immediately whenever you suspect that your tortoise has contracted a disease or has been injured.
Summary of Disease Symptoms
If your tortoise exhibits any of the following symptoms, please consult a veterinarian (familiar with tortoises): runny nose; labored breathing; sunken eyes or swollen eyelids; loose stools; loss of appetite; listlessness; swollen body tissues; prominent bones (in head or limbs); soft shell; tendency to keep eyes closed; noticeable weight loss or gain (in short period of time.)
Tortoise Reproduction and Arizona Wildlife Laws
Per AZGFD Rule (R12-4-407) it is illegal to breed desert tortoises . Captive desert tortoises may not be imported, or exported outside of Arizona under any circumstances, without authorization by the Arizona Game and Fish Department. It is illegal to collect desert tortoises from the wild. Additionally, it is illegal to release captive tortoises because of the following concerns:
- Introduction of pathogens or parasites to wild populations.
- Displacement of resident wild tortoises.
- Maladaptation of the released tortoise to wild conditions which could lead to death.
Additionally, young tortoises require more intensive care, are subject to predation by a greater number of animals and many die before reaching adulthood. Consequently, it is difficult to find homes for hatchlings. Because it is illegal to breed desert tortoises in Arizona, we will not place pairs of animals or an animal that completes a pair with custodians unless the tortoises are kept in separate enclosures.
Distinguishing the Sexes
The sex of adult tortoises can be determined by several criteria. First examine the plastron (lower shell). The rear portion is concave in mature males. This indentation enables the male to fit the carapace (upper shell) of the female during mating. The plastron is flat in mature females. Immature tortoises of either sex have flat plastra. Therefore age, best determined by size in the absence of an actual life history, is important in determining sex. Tortoises are generally sexually mature when the straight-line carapace measurement reaches between 6-8 inches (which usually occurs between 10 and 20 yrs of age). The rear of the carapace typically flares out in females and is nearly vertically flat in males, and males have proportionally longer tails.
Courtship and Mating
In the wild, male tortoises court females in the spring and summer. The male will nod his head at the female as he approaches, often circling her before attempting to mate. The female will often appear to ignore the male, but usually becomes receptive to his courting attitude. Copulation can be very brief or may continue for hours. Both males and females may mate with several individuals in the course of a year. Fighting between males may occur where one male rams the other. Sometimes one male will be flipped over by the other and will suffer internal damage, and may die, if it doesn't flip itself back over in a fairly short period of time.
Eggs and Incubation
In the wild, eggs are typically laid in July immediately before or after the first summer rains. The female may be capable of laying fertile eggs for up to 4 years from a single mating by retaining viable sperm. In such cases, the number of fertile eggs per clutch will diminish with time. The female digs a nest hole in the soil to lay her eggs. The typical clutch includes from 2 to 14 eggs. The size and age of the female determines clutch size. After depositing the eggs, the female fills in the nest hole. There is some evidence that females may defend the nest site for some time against potential predators, although they do not care for the offspring. Hatching normally occurs between 80 to 120 days after the eggs are laid. The hatchlings crack the eggshell with a temporary protrusion on the upper jaw, called the egg tooth, which is lost soon after hatching. Alternating between periods of activity and rest, the hatchling emerges from the egg and digs its way to the surface. At this time, the hatchling is about the size of a silver dollar. The shell is quite pliable, and some yolk may still be attached to the plastron. The hatchling may take 1-2 days to exit the egg.
Special Care for Adopted Hatchlings
It is highly recommended that hatchlings be kept outside. It is possible to maintain them inside during the first year, but it is not advisable after that.
Indoor Care
Hatchlings can be kept in a plastic shoe or sweater box, or similar container. The container must be clean and protected from invasion of insects, especially ants. Hatchlings easily tip over onto their backs, usually by climbing against the wall or over siblings. One hatchling per box is best to reduce this problem.
Hatchlings should be maintained on a substrate of soil or gravel 1/4 - 1/2 inch in diameter. Sand and fine gravel should be avoided since they may ingest it, causing fecal impaction and gastrointestinal infections. The daytime temperature for hatchlings should range between 80-85°F (27-32°C) with a temperature drop at night to 68-75°F (20-25°C.) A normal day/night light cycle should be maintained. Hatchlings must receive regular solar radiation to insure proper vitamin D synthesis and calcium assimilation. Standard glass filters out the required ultraviolet radiation in the UV-B range, thus placing the hatchling container by a window is ineffective. The minimum requirements seem to be met by artificial full-spectrum lighting (see Appendix II.) Daily exposure to sunlight or a reasonable substitute is essential to optimal health and bone development. Shade and respite from heat is essential to avoid dehydration, heat stress and death. A sleeping shelter box of some type should be provided.
If healthy, hatchlings should be allowed to hibernate during their first winter. An inside hibernation is acceptable if the same methods outlined for adults are followed on a miniature scale. Approximately two or three weeks prior to placing hatchlings in hibernation, feeding must be stopped to allow the digestive tract to empty. During hibernation indoor hatchlings should be soaked in a shallow dish containing approximately 1/4 inch of water for 30 minutes every 2 to 3 weeks. When the hatchlings become active in the spring, they should be removed from hibernation and placed in their enclosure to resume regular feeding.
Outdoor Care
Hatchlings may be maintained in an outside enclosure as described previously. A miniature version of the adult burrow should be prepared for warm weather shelter and cold weather hibernation. Several tortoises can use the same burrow. The enclosure should provide both sun and shade throughout the day. Avoid sand or fine gravel as a substrate for the reasons mentioned above.
Since young tortoises must be protected from predators such as cats, dogs and birds, the enclosure must be covered. The covering must allow sunlight into the enclosure. Wire fencing or poultry netting is appropriate provided the openings in the mesh are of a size that the tortoise will not get its head or legs stuck in it. It should either be too small for the head or limbs to penetrate or large enough to allow the head and limbs to freely enter and exit.
To protect the hatchlings from ants, it is advisable to keep their burrows away from grassy feeding zones which may attract ants because of the availability of extra water.
As the weather becomes cooler in the fall, the appetite of the hatchlings in an outdoor enclosure should naturally decrease. Do not provide any supplemental food after approximately October 1. If a hatchling attempts to hibernate outside the burrow, move it inside the burrow. During hibernation either inside or outside, some mortality can be expected, but survival is usually considerably higher than in the wild.
Diet
The same types of foods offered to adults should be available to young tortoises; however, in different amounts. The diet should contain about twice the protein and half the fiber content of the adult diet until the third year. Course, dry, alfalfa hay should be avoided. It is best to offer mulberry and grape leaves, clover, alfalfa, dichondra, filaree, spurge, rose petals, petunias, verbena, and native plants such as globe mallow. Hatchlings eat frequently and must have food provided to them several times a day. In an outdoor enclosure, several of these plants must be established in the enclosure to allow frequent browsing. If the hatchlings are housed inside, a grazing box is recommended. A plastic sweater or shoe box can be planted with a mixture of alfalfa and clover. After the plants are established, the tortoises should be placed in the box several times a day and allowed to graze. Shade must be available in the container at all times and avoid the hot part of the day in the summer. For inside and outside enclosures, to prevent overgrazing, fourteen days of plant growth is recommended before allowing the tortoises access to the plants. If supplementary foods are offered, remove uneaten portions from the enclosure at the end of the day to avoid attracting insects. Insecticides, pesticides or other toxic chemicals should never be used near the hatchlings, as hatchlings are especially susceptible to these compounds.
Hatchlings require shallow puddles of water for drinking and soaking. As mentioned above, shallow saucers can be used for this but should be allowed to dry in between waterings. The shell of a hatchling is relatively soft but will harden over time if the tortoise has access to an appropriate diet and sunlight (or an acceptable substitute.)
Summary of Hatchling Tortoise Feeding and Management
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The hatchling diet should contain about twice the protein and half the fiber content of the adult diet until the third year. Foods high in cellulose such as coarse, dry alfalfa (hay) should not be offered since they are difficult for hatchlings to digest. By the third year, grasses should be gradually increased. Hatchlings eat frequently and must have food provided to them several times a day. Remove uneaten portions of supplementary foods at the end of the day. If left overnight, it will often attract insects, especially ants, which are a major threat to hatchlings.
The hatchling diet should consist of mulberry and grape leaves, clover, dichondra, alfalfa, filaree, spurge, roses, petunias, verbena, and native plants such as globemallow. Several of these food plants should be established inside the tortoise enclosure to allow frequent browsing. Clover and alfalfa seed should be mixed before planting and at least 14 days of growth allowed before placing the tortoise in the enclosure. This will give the plants time to grow so that they will not be overgrazed.
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Construct a smaller burrow (miniature version of the adult burrow) for hatchlings that allows easy removal of the animals for inspection. Be sure that the animal cannot escape under or through the enclosure barrier and will not become entrapped by the enclosure material.Use soil and/or medium gravel as a substrate (do not use sand.)
The Authors
This document was originally written by James L. Jarchow, D.V.M. and Howard E. Lawler. Dr. Jarchow is the consulting veterinarian for reptiles and amphibians at the Arizona-Sonora Desert Museum. He is an internationally-recognized authority in wildlife veterinary medicine and a specialist in desert tortoise health management who has conducted numerous field and clinical studies of North American tortoises. He can be contacted at (520) 888-8988. Mr. Lawler was Curator of Herpetology and Ichthyology at the Arizona-Sonora Desert Museum from 1981 - 1996. Since its publication in 1994, this document was revised by Craig S. Ivanyi, Collections Manager for Herpetology, and Cynthia Wicker, the Coordinator of the TAP, for the Arizona-Sonora Desert Museum.
This document is dedicated to the memory of Ms. Betty Vance who served as the Coordinator for the TAP for many years. Through her love of tortoises and tireless efforts this program was made possible.