The genus Pyxis includes the spider tortoises (Pyxis arachnoides arachnoides, Pyxis arachnoides brygooi and Pyxis arachnoides oblonga) and the flat-ta
The genus Pyxis includes the spider tortoises (Pyxis arachnoides arachnoides, Pyxis arachnoides brygooi and Pyxis arachnoides oblonga) and the flat-tailed tortoise (Pyxis planicauda). They are unique in appearance and habits, as well as their small size. With adults being in the 6-inch range, Pyxis fall into the group of the world’s smallest tortoises. Given their variety in color/patterning, they are certainly among the most beautiful, as well.
Spider tortoises range in size depending on subspecies.
The Spider Tortoise's Limited Range
Native to the island of Madagascar, spider tortoises inhabit a strip of dry, deciduous forest along the southwestern coastline. Pyxis a. brygooi occupies the most northern portion of this range, between Morombe and the Manombo River. Pyxis a. arachnoides is found further south, as far as the Menarandra River, and P. a. oblonga is found further south, on the southern tip of the island. Pyxis planicauda has the smallest range in the region of Menabe between the Morondava and Tsiribihina rivers. A second, small subpopulation also occurs north of the Tsiribihina River.
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In the northernmost portion of their range, spider tortoises are found in dry, tropical Mikea Forest habitat. In the south, they are seen near xerophytic spiny vegetation where there is a low level of rainfall. Their habitat consists of sandy areas with spiny vegetation close to the coast.
As with P. planicauda, spider tortoises are more active during the wet months. They forage for a variety of foods, including fallen fruits, leaves and flowers. Examples of these tortoises feeding on cow dung containing insect larvae have also been reported.
Spider Tortoises Are Diminutive And Long-Lived
Spider tortoises range in size depending on subspecies. Both P. a. brygooi and P. a. oblonga reach similar sizes, with adult females measuring 6 inches and males slightly smaller. Pyxis a. arachnoides reach a larger average size, with large females reaching up to 8 inches in length.
Reproductive age for spider tortoises is thought to be around 10 to 12 years. Single-egg clutches are laid, and multiple clutches may be laid during a breeding season. The life span for a spider tortoise is estimated to be up to 70 years.70 years
Spider Tortoise Shell Patterns
As implied by their name, the spider tortoises possess a web pattern on their shells that ranges from white/tan to yellow on a darker background. Tremendous variation can exist from one individual to another, even among the same subspecies. Flat-tailed tortoises are not generally as vibrantly colored/patterned; however, individuals with complex and beautiful patterns are also seen.
Distinguishing between the various P. arachnoides subspecies can be difficult, especially when trying to identify hatchlings and young tortoises, when the plastral hinge is not fully developed. In adults, P. a. arachnoides is notable for a plastron without markings. The plastral hinge is well developed and anterior plastral lobe will close completely to touch the carapace.
Similar to P. a. arachnoides, the plastron in P. a. brygooi is also unmarked. However, the plastral hinge is not developed and the anterior plastral lobe is essentially immobile. In P. a. oblonga, the plastron will have a variable degree of black markings on the scutes. The plastral hinge is well-developed, allowing the anterior lobe to close completely to touch the carapace. The plastron of P. planicauda will be variably marked and these tortoises have no plastral hinge.
Spider Tortoise Captive Care
The captive care of all of the Pyxis tortoises, in my experience, is similar. Here, I will emphasize the indoor husbandry methods I have used and found to be very successful. Outdoor enclosures, which seek to replicate wild conditions that Pyxis tortoises are accustomed to, can be utilized with success, as well, particularly in areas where climate fluctuations are not extreme. However, challenges regarding outdoor husbandry have been encountered and this point will be elaborated upon later.
Given their diminutive size, adult tortoises can be maintained in smaller enclosures, depending on the number of animals kept. A single adult pair can be housed in a sweater box or similar enclosure measuring 2 feet long by 3 feet wide and roughly 12 inches in height, which will allow enough substrate depth for burrowing without increasing the risk of escape. Pyxis like to burrow, depending on the season, so a fairly deep substrate (6 to 8 inches) is necessary. A mixture of cypress mulch/topsoil provides an excellent burrowing mix, as well as an ideal egg-laying medium. Other types of mulch, including eucalyptus, can be equally successful.
For a group of 10 to 12 adults, an enclosure measuring 4 feet long by 6 feet wide is adequate.
While male-male combat has been described, I have not seen significant aggression between males in any of my Pyxis groups, during breeding season or otherwise, and I maintain several males per enclosure year-round. Providing adequate hiding places is important. I use clay pot halves, but cork bark or log hollows can also be used. Silk plants provide additional hiding areas. Although I rarely see tortoises drink or soak, I do include a shallow water basin in my enclosures.
For lighting and heat, I provide ultraviolet incandescent bulbs and UV fluorescent lighting over enclosures. A basking site at one end of the enclosure is maintained in the mid-upper 80s Fahrenheit and the cooler side is typically in the mid to upper 70s to allow the tortoises to thermoregulate.
Spider Tortoise Nutrition Requirements
As with all captive tortoises, a varied diet is essential for Pyxis health, especially if you’re hoping to breed them. The bulk of the diet I provide consists of chopped greens: romaine, green/red leaf lettuce, chickory, escarole and dandelion. Strawberries, banana, zucchini, carrot and white mushrooms are finely chopped/diced to the consistency of a paste and mixed with the greens. I offer this every other day during the period when tortoises are active. Well-acclimated Pyxis will run to food and feed voraciously. Captive-bred tortoises are even more aggressive at feeding time. During their winter slow-down (see following section), food can be offered much less frequently — even once a week — as tortoises are barely interested in food at this time.
Brumate to Breed
Brumation is essential to Pyxis tortoise health and breeding success. Efforts to force tortoises to remain active and feeding year-round have not resulted in healthy nor reproductive tortoises. They should undergo a period of inactivity when temperatures in their enclosures are lowered.
In my collection, this period coincides with winter and lasts roughly three to four months. During this time, their enclosures are cooled at night to the mid 60s, and returned to between the high 70s and 80 degrees during the day. If left alone, the tortoises will remain in their burrows and show essentially no interest in food during this time. I do still offer a small amount of food one to two times a week, really for my own benefit, as I will have to pull the tortoises from their burrows and place them directly in front of the food for them to take a few bites before they return to their burrows.
During this time, I soak the tortoises and weigh them every few weeks, so as to identify potential health problems. During a typical winter slow-down, adult tortoises will generally lose no more than 5 to 10 grams in weight.
Upon emerging from brumation, breeding activity will be most brisk. In the wild, this would correspond with the onset of the rainy season. This can be accomplished in captivity by a variety of methods, including sprayers, misting systems, etc. Within six to eight weeks of the onset of breeding activity, females will nest and lay a single egg. On a very rare occasion, two-egg clutches will occur. Females can lay several clutches in a season, with intervals of three to four weeks between nesting.
Spider Tortoise Egg Incubation
In the past, Pyxis egg incubation was challenging. Traditional regimens that are successful with other captive tortoises call for a constant incubation temperature. This will rarely be successful with Pyxis eggs. Efforts to solve the riddle regarding Pyxis eggs have revealed that a period of diapause is essential to development and hatching. Diapause refers in the strictest sense to a delay or suspension of development. It corresponds to adverse environmental conditions that eggs would be exposed to in the wild when development would be unfavorable. When and for how long a period of diapause should be provided for Pyxis eggs can be debated. In my collection, when eggs are laid, they are initially incubated at warm temperatures (around 84 degrees) for six to eight weeks. The eggs are then gradually cooled over one to two weeks to 60 to 65 degrees. They remain cool for six to eight weeks, after which they are warmed gradually to 84 degrees once again. If fertile, hatchlings can be expected to emerge from their eggs 10 to 12 weeks after being warmed.
Spider Tortoise Hatchling Care
For hatchlings and young tortoises, I utilize husbandry techniques very similar to those for the adults. Rubbermaid sweater boxes or like-sized containers are suitable. I typically use only cypress mulch as a substrate, 1 to 2 inches in depth. Clay pot halves and silk plants will provide good hiding places. A shallow water basin, deep enough to cover their limbs, is provided with similar usage patterns to adult animals.
It is essential to provide adequate humidity without creating a soaking-wet enclosure. This can be accomplished by having dampened sphagnum moss in hides, as well as piled in one corner of the enclosure. This is where young animals will typically be found buried.
I soak young tortoises once a week, at which time I weigh them to track their growth. Lighting, again with UV incandescent/fluorescent bulbs, is provided to achieve a hotspot with a temperature range in the mid to upper 80s. Again, having a cooler side of the enclosure in the upper 70s will allow tortoises to thermoregulate and prevent them from overheating.
As with the adults, I provide hatchlings with multivitamin/calcium supplementation, sprinkled over their food, one to two times a week. Immature animals will brumate just as adults do. In my facility, I do not allow young tortoises to cool as significantly as the adults. In my experience, they will remain relatively more active. However, to suggest that a cooled Pyxis tortoise is “active” is an oxymoron. These are not very active tortoises. When warm, during the summer months, they move around quite a bit, especially around feeding time. They still will burrow a fair bit though, even when “active.” These are definitely not leopard tortoises or sulcatas in regard to activity levels.
Spider Tortoise Health Watch
Addressing Pyxis tortoise health concerns is a complex issue. When initially imported in the late 1990s, wild-caught Pyxis suffered from myriad health problems, similar to any animal new to herpetoculture. De-parasitization regimens taken from experience with other wild-caught tortoises were employed and were successful in some cases. Founder groups were established and reproductive efforts were successful in both private collections as well as zoos. Captive-bred spider tortoise babies, in particular, were fairly common in the pet trade as recently as a few years ago. Captive-bred flat-tailed tortoises were rarer and have remained so.
Unfortunately, the initial success experienced with Pyxis tortoises was fleeting. Very substantial die-offs, specifically with founder adult animals, have occurred both in private hands and specialized institutions. A pattern of exposure to external stress has been seen prior to many of the die-offs, specifically in animals maintained outdoors. Significant losses have been observed after adverse weather events. Very comprehensive veterinary examination has not revealed a definite pathogen in the vast majority of cases. Intranuclear coccidiosis has been identified as a potential cause of the deaths. However, as this organism can be identified in outwardly “healthy” tortoises, it is unclear whether coccidiosis is the true cause of the deaths or just a bystander.
Spider Tortoise Conservation Concerns
The current state of Pyxis tortoises both in the wild as well as in captivity is dire. Captive-bred babies are now only rarely available in the pet trade. Efforts to concentrate the remaining founder adult animals in the hands of those who have been successful maintaining them is underway in an attempt to reestablish this group in captivity and provide genetically diverse offspring. Captive-bred offspring should not suffer from the same health issues that the wild-caught adults do. However, what is certain is that even captive-bred animals should be considered delicate and captive-husbandry methods should be geared to avoid exposure to external stress, including exposure to other species, etc.
Unfortunately, the state of Pyxis tortoises in the wild is even more threatened. In the most recent (2010) IUCN Red List of Threatened Species, Pyxis tortoises are designated Critically Endangered, the category one step before Extinct in the Wild. Threats to Pyxis are multifactorial.
Recent studies suggest that the current Pyxis range is much more limited and fragmented than previously thought. Deforestation for charcoal production, mining, highway development and livestock grazing has had the most significant impact on Pyxis populations. Invasive plant species affecting local fauna and hunting for food by locals, especially as populations of radiated tortoises have been decimated, has also contributed to decreased numbers of tortoises in the wild. Finally, collection for the international pet trade was, and still remains, a significant threat.
As a result of these pressures, P. a. brygooi is now absent across 50 percent of its former range. If current trends continue, conservative models predict the species’ extinction in 60 to 80 years. More aggressive estimates suggest that wild extinction could occur much more quickly, within 20 to 30 years.
Efforts are being made in Madagascar to protect habitat vital to the survival of its endemic tortoises. The Turtle Survival Alliance has established the Village des Tortues at Ifaty, a facility which provides naturalistic environments for Pyxis tortoises as well as the larger radiated tortoise. Needless to say, as the threats to Madagascan tortoises are multifactorial, efforts to ensure their survival must also be multifactorial.
Finally, the role of the hobbyist must be considered in regard to the fate of Pyxis tortoises. As previously mentioned, collection to supply the international pet trade has had a significant impact on Pyxis numbers in the wild. While exportation is no longer permitted legally, it is likely that adults are still making their way into the pet trade by a variety of means. Given the very slow reproductive rate in the wild, it will be difficult, if not impossible, for wild populations to recover if current stresses are not addressed.
For animals already in the hands of hobbyists, every effort should be made to concentrate these animals in successful breeding groups. As previously mentioned, wild-caught animals are very sensitive in captivity and the maintenance should be left to individuals or specialized institutions with a proven track record of success. Captive-bred animals can be kept by less-experienced keepers, as they should not be as sensitive. However, once again, any and all animals should be given the opportunity to contribute to the ultimate survival of the species, whether that be through participation in breeding cooperatives, studbook programs, etc.
Will Ahrens, M.D., is a surgical pathologist in Charlotte, N.C. He has concentrated on the husbandry of African and Asian tortoises for appoximately 20 years. The author would like to thank Michael Ogle, Assistant Curator of Herpetology at the Knoxville Zoo, for providing the wild habitat information and photos.