The Endangered Forsten’s Tortoise



Put an attractive, relatively large animal on a small island and allow export, and the invariable result is a decline in the animal’s population. Found only on the Indonesian islands of Sulawesi and Halmahera, the Forsten’s tortoise (Indotestudo forstenii) is categorized as Endangered by the World Conservation Union. The species has undergone an estimated population decline of 70 percent within the last three generations mostly due to local consumption and export for the pet trade.

 

 

Sometimes Caramel but Always Crepuscular

Adult Forsten’s tortoises are typically about 10 inches long and 51⁄2 pounds. Large scales cover the anterior parts of the tortoise’s front legs, but its hind legs lack this protection. Females tend to be wider and more rounded than males, and males’ tails are larger and longer than females’. A small keratinous hook tips the end of the tail. Males also have slightly concave plastrons; females’ plastrons are completely flat.

Tremendous color variability occurs in this species. The shell’s base color is generally caramel-colored to dark yellowish-brown with blotches of black on each scute, but some tortoises appear totally caramel-colored and others nearly completely black. The unarmored skin is gray to yellow, and the head is yellow-tan except in breeding season. Both sexes take on a pinkish color around the nostrils and eyes at this time.

Although Indotestudo forstenii is primarily a damp-forest species, it is found in areas with a large climatic range, indicating a tolerance of arid conditions. A crepuscular tortoise, it becomes active in the twilight hours before dawn or just after sunset. Its large eyes are well-adapted to low-light levels. The tortoise has an omnivorous diet in the wild consisting of fruits, leafy greens, worms, slugs and carrion.

Two distinct populations of I. forstenii appear to be on Sulawesi, but they are not discernible by mitochondrial DNA. However, there are distinct, observable differences. Northern populations are larger and lack a nuchal scute. Southern populations are smaller, and many possess a nuchal. Although the absence of a nuchal scute has been heralded as an identifier for I. forstenii, many specimens possess a well-defined nuchal. Forsten’s tortoises lacking nuchal scutes are heavier and longer than those with them, but regardless of the presence of a nuchal, a Forsten’s tortoise is still a Forsten’s.

 

Kept Indoors and Out

Indoor accommodations for small- or medium-sized Forsten’s tortoises can best be accomplished by what I term “small-scale stall management.” The habitat consists of a turtle table. This is essentially an open-topped box large enough to offer a temperature gradient, allow maximum ventilation and still prevent escape. A reasonable sized table for a hatchling is 2 feet by 2 feet. For an adult Forsten’s tortoise the indoor enclosure should be at least 4 feet by 4 feet, and for an adult pair I suggest a table measuring 4 feet by 6 feet. Holes can be cut in the bottom of the table, and containers for food, water and eventually nesting material can be sunk flush with the surface to allow easy access.

The habitat’s water area should be large enough to allow I. forstenii to soak but shallow enough to prevent drowning. Photographic developing trays can be placed into holes cut into the table’s surface to provide excellent water areas for adult tortoises.

Due to humidity retention characteristics, cypress mulch or a mixture of sphagnum moss and cypress mulch is the indoor substrate of choice for this species. Droppings should be removed on a daily basis, and the entire substrate should be replaced every month or so.

A 100-watt incandescent lamp should be positioned over one corner of the turtle table. Position the fixture to provide a basking spot of about 90 degrees Fahrenheit. A full-spectrum fluorescent light to provide UVB should also be used. A UVB source is necessary for vitamin D3 syntheses, which is needed in calcium metabolism. Advances in herpetoculture have brought mercury vapor lamps, which provide both UVB and heat, to the market, and these lamps fulfill both requirements.

A hide box located in the corner opposite the basking spot also is necessary because it allows the tortoise a cool, dim retreat, which will be well-utilized during the day. If desired, this hide box can be built to hold a removable dampened sponge in the top. This provides higher humidity in the retreat, which more closely simulates a moist woodland refuge.

Once nighttime temperatures stay above 60 degrees, Forsten’s tortoises are best moved outdoors. They appear to be cold-tolerant and are active on days exceeding 70 degrees. They do not appreciate bright lighting and tend to hide at midday. Consider allowing their pens to become overgrown, supplying the shady areas they seem to require.

Forsten’s tortoises also appreciate a shallow pond in their habitat. If using a pond or bog area, be certain to allow for ease of egress because they frequently soak in warm weather. Overall, this species does best in naturally humid climates outdoors. For tortoisekeepers in areas not naturally humid, timers and a misting system can be utilized to artificially create this kind of environment.

 

Medical Care Eminent

Newly imported I. forstenii invariably need medical care. This species is often exposed to a number of exotic (to it) pathogens in the shipping process particularly during warehousing for export. It is often the case that though these tortoises might look like they are doing well for several months, if left untreated they crash and often die from various brewing ailments. This problem is inherent in a number of Asian wild-caught species.

One extremely common problem encountered in this species is erosive lesions in the roof of the mouth. These lesions are believed to be herpes-based. Whenever an animal is purchased, a thorough oral examination should be performed to check for these lesions. Checking for any foreign bodies, as well as pneumonia and upper respiratory tract disease, which often results from these lesions, is also wise. If your tortoise has these lesions, be extremely careful about allowing the animal to live outside on grass. There have been reports of animals lost because foreign bodies lodged in these lesions and caused subsequent problems, such as pneumonia. A frequent check of the oral cavity ensures the lesions are not spreading or impacted.

If you intend to add an animal to an existing group, do so with extreme caution. Medical ability to delineate which animals are carriers of disease is lacking, so a long quarantine is necessary. This makes it extremely important to reproduce this species and raise the offspring in relative isolation in order to establish clean groups.


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Turtle and Tortoise Species


Opportunistic Omnivores

Indotestudo forstenii is omnivorous, consuming both animal and plant material. Captives can be fed a minimal amount of biologically appropriate raw foods, dog food or whole-prey items twice a month. Do not feed meat as a part of the tortoise’s daily diet. Occasional earthworms and other insects are much appreciated. Forsten’s tortoises also forage for insects in their outdoor habitats. Wild-caught animals actively seek out yellow foods, such as corn and squash. Use this color preference to switch the animals over to a captive diet.

Additional calcium supplementation is highly recommended. For proper growth and egg production, powdered calcium can be sprinkled on all foods once a week. Use calcium supplemented with vitamin D3 if the tortoise is being maintained indoors. If it is outdoors, calcium without D3 is recommended. Providing a cuttlefish bone, which the tortoises can gnaw for its calcium content as well as for proper beak growth, also is a good idea.

 

Breeding Forsten’s

Male I. forstenii engage in aggressive courtship behavior, which can result in injury to the female if a large enough habitat is not provided. Male aggression towards other males can also be rather damaging, so it is best to keep only one male per enclosure. Some large females also can be highly aggressive, and they can cow smaller males. During courtship, males engage in ramming behavior and vigorously bite a female’s head, neck and front legs. Males loudly vocalize while mating and emit a harsh, raspy sound while exhaling.

 

juvenile Forsten's tortoise

Photo by Riou108/Wikipedia

Juvenile Forsten's tortoise.

Preparing to nest, a female Forsten’s tortoise becomes restless, often attempting to escape the enclosure. While constantly striding about the habitat, she stops and sniffs the earth from time to time as she selects a spot. Generally, the spot chosen is damp and free of vegetation. Once she has found a suitable site, she digs a flask-shaped nest about 51⁄2 to 71⁄2 inches deep with her back legs. If the soil is too hard and dry, she wets the spot by emptying her bladder. She then proceeds to lay a clutch of one to four eggs in the excavated nest, replaces the soil with her back legs and flattens the spot with her plastron. Forsten’s tortoises can hide their nesting sites extremely well.

Nesting occurs in the early spring in captivity, and the species can produce up to three clutches per year in optimal conditions. To date, only minimal captive breeding of this species has occurred in the United States outside of a few private collections and isolated successes at zoos.

Breeders with the most success in incubating Forsten’s tortoise eggs use two methods. Ben Forrest uses moist vermiculite, about 80 percent relative humidity and temperatures ranging from 78 to 86 degrees. These incubation conditions are inside a small Styrofoam box with ventilation holes, and the eggs are about one-third to half-buried. Eggs and substrate are misted one to two times a week as needed to maintain the warm, moist environment.

Another Florida breeder places the eggs in moist 1-1 to 1-3⁄4 vermiculite to water by weight substrate and then places the container in a reptile room where the daily temperature varies between 78 and 88 degrees. Interestingly, both breeders use nearly the same conditions, but they’re reached by differing methods.

Incubation typically takes between 130 and 165 days at these temperatures. Like the adults, Forsten’s tortoise hatchlings have a tremendous variability in color and markings.

Endangered and difficult to captive breed, the Forsten’s tortoise still presents many questions. However, tortoise care is ongoing, and hopefully, with time tortoisekeepers will learn the answers to some of these questions before it is too late.  

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