Radiata2010(4)e

Ewald Roddewig When the

Ewald Roddewig When the baby sawbacks are ready to be removed from their incubator, I first place them into small cricket boxes with ventilation holes that are filled to a level of about 5 mm with water. These boxes are then closed with a lid and placed in a spot that is no too brightly illuminated and offers a temperature of 28°C. The water used originates from the tanks of the adults, which serves the purpose of exposing the juveniles to the bacterial fauna present there so that they can pick it up to the benefit of their own intestinal flora (Schulz pers. comm.). Possibly still existing remains of the yolk sac will now be resorbed within the next 24-48 hours, and the baby turtles start feeding. They are now transferred to small nursery tanks with water about 10 cm deep. These tanks are outfitted with a small pyramid made from natural rock onto which they can climb and exit the water, a few aquatic plants, and a small cork island. Their water is kept at a temperature of 28-30 °C by means of an aquarium heater. The baby turtles are excellent swimmers right from the start. They are fed with mosquito larvae, daphnia, small earthworms, Gammarus and flies, for example. It is remarkable what and how much food they can take in. Food is offered twice every day at amounts that can be consumed without leftovers. After just ten days, the juveniles will eat everything the adults also eat, only that it sometimes needs to be cut up to fit into the mouth. A few days later, the babies are transferred to a larger nursery tank. It only takes a short while for them to adapt to even deeper water. At three weeks of age, the skilled swimmers then move into a fully decorated aquaterrarium of 250 l in volume where the water level is 60 cm. This is also the point of time when they can be passed on to interested and qualified keepers of aquatic chelonians. Hatching weights range from 9 to 12 g, at which time the 35-40 mm dorsal shell is still almost circular in outline. The navel slit will have become invisible after a few weeks, which is also when the initially soft and flexible shell has hardened and rigidified substantially. Breeding female 2 (larger specimen) Date of oviposition Number of eggs Number of hatchlings Breeding female 1 (smaller specimen) Date of oviposition Number of eggs Number of hatchlings 29.03.2009 6 0 09.04.2009 3 3 14.04.2009 4 0 23.04.2009 3 3 29.04.2009 4 2 13.05.2009 5 4 30.05.2009 4 0 17.03.2010 5 1 03.04.2010 3 1 03.04.2010 6 5 22.04.2010 3 3 22.04.2010 5 4 06.05.2010 3 3 18.05.2010 5 4 27.05.2010 4 3 11.06.2010 5 2 17.06.2010 3 3 17.07.2010 3 3 Tab. 4: Clutch data from the years 2009 and 2010. The larger female almost always produced five eggs per clutch, whereas the smaller one would typically lay three at a time. Eggs that failed to hatch were either infertile, or their embryos perished during incubation. In the beginning, I made the mistake of incubating the eggs in conditions that were too moist, which had a negative impact on the hatching rate. 16 RADIATA 19 (4), 2010

Black-knobbed Sawback, Graptemys nigrinoda nigrinoda Cagle, 1954 Hibernation The Graptemys nigrinoda nigrinoda in my care hibernate in the unchanged conditions of their aquaterraria in my turtle cellar. Water temperatures are reduced to 20-22 °C by mid-October, with nightly decreases by another 4 °C at maximum. This is also the point of time when feeding them ceases. Around the beginning of November, the water level is reduced to about shell height. Filters and heating are switched off, and the heating thermostat for the room is set to zero. The lights remain on for six hours every day for a week. The windows are left open to reduce temperatures even further and will range around 10-12 °C two weeks later. The animals will by then have become very lethargic. Temperatures will then typically decrease to about 4 °C. The thermostat-controlled room heater will safeguard the cellar against freezing, though. Some turtles spend this period in the water, while others will position themselves thus that some part of the body is on land, and yet others leave the water completely and will lie on a rock, for example. These positions are not static, though, and changed every now and then. The tanks and turtles are checked every five days with the aid of a weak torchlight until mid-February. Mid-February is the time when the room heater is reactivated so that the environment warms up slowly. Lighting is once more provided for six hours every day. The spotlights are now of particular importance as they provide opportunities for basking. The water levels are gradually raised a few days later. The filters and integrated heaters are switched back on simultaneously. About ten to twelve days later, room and water temperatures have been restored to around 20 °C. The turtles will by then have regained their appetite and are offered, for example, Gammarus or earthworms as first food. Their active period of the year begins between early and mid-March. Diseases Aside from damage to the keratinized top layer of the shell of the smaller female, the cause of which has remained an enigma to me, I do not have to report on any other injuries or health problems. The mentioned injuries to the shell healed without medical assistance. Co-inhabitants The aquaterraria also house guppies and suckermouth catfish during the active part of the year. The guppies feed on small remains of food left behind by the turtles and so prolong the operational life of the filters. As long as the fish are fit, they can easily avoid the turtles, and if not, they turn into a complementary, quite natural source of food. For their part, the catfishes keep rocks, roots and the glass panes clean. The fish are not fed in addition. Summary Graptemys nigrinoda nigrinoda is a very pretty and interesting aquatic turtle from North America that grows only to a relatively small adult size. It is a terrarium animal that can be recommended to both the experienced turtle enthusiast and the educated beginner. Prices are still reasonable. Its wild populations are threatened by overbuilding of their natural habitats. Keeping in human care may therefore contribute to conserving the total population. As far I am concerned, I would be pleased to see the circle of Graptemys keepers grow over the next years. Promotion to the end is what forms a large part of my work. References Bull, J. J., R. C. Vogt & C. J. McCoy (1982): Sex determining temperatures in turtles: A geographic Comparison. – Evolution, Rochester, 36 (2): 326-332. Cagle, F. R. (1954): Two new species of the genus Graptemys. – Tulane Stud. Zool., Belle Chasse, 1 (11): 167-186. RADIATA 19 (4), 2010 17