Chapter 9 Tortoises and turtles
Chelonia, such as tortoises and their semi-aquatic relatives, terrapins (or turtles) are becoming very popular as pets, especially in Europe where there is a long history of keeping the Mediterranean Testudo species as house and garden pets. Although CITES II listed, this trade is being fuelled by the increasing availability of captive-bred specimens, especially from Eastern Europe.
|The Mediterranean Testudo species including the southern European Herman’s tortoise (T. hermanni), members of the north African spur-thighed complex (T. graeca) and the Horsfield’s tortoise (T. horsfeldi)||These are small to moderately large species; most can be safely hibernated but see Hibernation for more details. Diet should primarily be leafy greens with added calcium supplementation. No animal protein should be given||Metabolic bone disease (MBD), chelonian herpes virus (CHV), ascarids|
|African spur-thighed tortoise Geochelone sulcata||This species from sub-Saharan Africa is a potential monster that can weigh up to 50–80 kg. They require tropical heat with relatively low humidity. Diet as for Testudo spp||Metabolic bone disease (MBD), chelonian herpes virus|
|The leopard tortoise (G. pardalis)||Another sub-Saharan African species. Requires tropical temperatures and a Testudo-like diet||Metabolic bone disease (MBD)|
|Red-footed tortoises (G. carbonaria)||Tropical South America. They need tropical temperatures, high humidity (70%) and a diet with more fruit that Testudo spp with a small amount of animal protein||Metabolic bone disease (MBD)|
|Red-eared slider (Trachemys picta elegans)||Less common in the European pet trade following several scares over Salmonella and concerns over alien releases. It is semi-aquatic and requires a dry, warm haul-out area on which to bask. They are carnivorous as hatchlings and feed on commercially available insect larvae, e.g. bloodworms; graduating up to sea foods such as prawns, fish, mussels and cockles plus calcium supplement. Commercial pelleted foods are available||Metabolic bone disease (MBD), hypovitaminosis A|
|Box turtles (Terrapene spp).||Omnivorous, requiring slugs, snails, earthworms, waxworms, mealworms, fruit, green leafed vegetables and mushrooms||Metabolic bone disease (MBD), tympanic scale abscesses|
As with lizards, the long-term welfare of captive chelonia is intimately dependant upon their environment and they must be provided with appropriate temperatures, full spectrum diet and correct nutrition including a calcium supplement (see Lizards for more detail). This especially applies to hatchlings of the Testudo spp, where a vivarium is mandatory despite the relative hardiness of the adults.
Light in the spectrum of 290–315 nm (ultraviolet-B, UVB) is required for endogenous vitamin D3 production; ultraviolet-A (UVA) spectrum (320–400 nm) has been shown to have a beneficial influence upon normal behaviour.
Endogenous vitamin D3 production in reptiles is a many-step process that involves not only exposure to UVB, but also thermal isomerization and modification in the liver and kidneys. Therefore, correct environmental temperatures and healthy organs are required for normal vitamin D3 synthesis.
Dietary supplementation with vitamin D3 alone is not sufficient for chelonia. In addition dietary calcium supplementation is essential for all captive chelonia. The commercially available leafy greens and vegetables usually offered to tortoises are inherently low in calcium but high in phosphates. Evidence suggests that in the wild tortoise select high calcium foods. A Ca:P ratio of 3.5:1 is recommended.
Most terrestrial chelonia can be safely handled without fear of being bitten, but take care with larger terrapins, or potentially dangerous species such as snapping turtles. These should be held at the rear of the carapace, and in the case of snappers, at the base of the tail.
Start the examination at the head, as this is likely to be withdrawn into the shell precluding further examination. Grasp the head behind the back of the skull and draw it out to its fullest extent. With most tortoises the mouth can now be opened and examined using the tip of a finger as a gag. With terrapins and similar a gag must be used. The rest of the body can then be examined systematically. Useful auscultation of the lung fields can sometimes be achieved by placing a damp towel over the carapace on to which the stethoscope is placed.
For Herman’s tortoise (T. hermanii) and the spur-thigh complex (T. graeca), an indication of health can be gained by the following (Peter Heathcote, pers. comm.). This is achieved by the following actions:
As a general rule, males have longer tails, a slit-like opening to the cloaca and a degree of concavity to the plastron, although this varies from species to species (Fig. 9.2). Chelonia have temperature-dependant sex determination and it is likely that variations in temperature at thermally-sensitive stages of embryonic development may produce a range of such secondary sexual characteristics, meaning that in some cases sexing is not an exact science.
Optimum site for collection in most chelonia is the jugular vein or brachial vein. Collection from the dorsal coccygeal vein and the subcarapacial jugular anastomosis are readily contaminated with lymph.
Large terrestrial chelonia often appear to have difficulty with transparent barriers and may spend a considerable amount of time attempting to walk through, over or under glass vivarium sides and doors. Blanking off these sides with tape or paint may reduce this behaviour.
With semi-aquatic chelonia such as terrapins, for general care they should be provided with a dry haul-out area which has an overhanging heat source to allow thorough drying of the carapace and sufficient water such that the terrapin can rest with its hind feet on the bottom and its nostrils above the surface. A weak terrapin is at risk of drowning. In some cases a terrapin may need to be ‘dry-docked’ for a period of time. Where possible, this can entail only short periods in a deeper bath. This can be combined with feeding as healthy terrapins will often prefer to feed submerged. Alternatively, serious attention to and monitoring of its fluid status should be undertaking if access to water is felt inappropriate (see Fluid Therapy below).
The assessment of dehydration in chelonia can be difficult visually. An obvious sign in chelonia is sunken eyes, so it is better to monitor PCV. This varies with species, but should be around 26–32 L/L.
The structure of chelonian skin of the legs, tail, neck and head is as in other reptiles. However, the chelonian shell is unique – in most species there are 54 epidermal scales covering 59 dermal bony plates. The epidermal and dermal seams rarely overlap, possibly giving increased strength to the shell structure. These epidermal scales are often referred to as scutes or shields. Even here, the skin still has epidermal and dermal components.
In some species such as the spur-thighed tortoise (Testudo graeca) there is hinge between the abdominal and femoral scutes of the plastron, while in others, e.g. the Russian tortoise (T. horsfieldii), there is not. Box turtles, e.g. the Eastern box Terrapene carolina, also have a hinged plastron that enables them to withdraw both the head and all four limbs within the shell, protecting them with the trapdoor-like plastron.
The glottis is located at the base of the muscular, fleshy tongue relatively caudal in the oropharynx. The trachea has complete cartilaginous rings. It bifurcates into two bronchi a relatively short distance along the neck and each of the two bronchi enter a lung dorsally. The lungs occupy dorsal section of shell and are adhered to the overlying dermal bones of the carapace. The lungs are paired and sac-like with the gas exchanging alveoli situated at the periphery of these organs. The lack of a functional diaphragm allows inflammatory exudates to accumulate in the dependant portions of the lungs.