Radiata2010(4)e

Ewald Roddewig

Ewald Roddewig illumination units. The aquaterraria of the females are each outfitted with a 160 W HQI flooder (Power Sun), whereas the tank of the males sports a 100 W flooder of the same make. These UV-heat emitters are mounted thus that they hang, beyond the reach of the turtles, some 30 cm above the cork island. This ensures that the basking spot is warmed to temperatures of about 45 °C right under the flooder. The turtles should be able to dry completely during basking as this eliminates the risk of fungal and algal infections in particular. Light and warmth are furthermore conducive to shedding the uppermost layers of the scutes, which is necessary for an unimpeded growth. My observations showed that growing sawbacks shed older carapace scutes several times during their annual period of activity, i.e., up to five times, depending on their growth rate. Once they have become sexually mature, the uppermost layers will then only be shed once in summer. To enable the turtles to synthesize vitamin D 3 properly, they are exposed to UV-B radiation by means of a permanently fixed lamp (comp. Kober & Geissel 2006). The HQI flooders provide light for about half a day, whereas the remaining daylight hours are created with fluorescent tubes. It would surely be possible to have the UV-flooders running all day long, but in the face of ever-increasing electricity tariffs, this is a question of operating costs. Experience has demonstrated that the turtles learn to use the shortened periods for basking right then – which does not therefore subtract from proper husbandry conditions. Keeping the sun- and light-hungry sawbacks without a UV-flooder and no opportunity for regular basking is, in my eyes, impossible, however. Fig. 10. Parts of the lighting equipment can be seen above the tanks; the cupboard-like substructures accommodate the filters. Fig. 11. Detailed view of a terrestrial section; it offers a localized hotspot under a spotlight during the day, and a vertically buried heating pad warms it around the clock. 10 RADIATA 19 (4), 2010

Black-knobbed Sawback, Graptemys nigrinoda nigrinoda Cagle, 1954 The (cupboard-like) substructure of each tank houses the filters. I only use one type of filter, the Eheim Thermofilter Professional 2224. It permits to set the desired water temperature by means of a controller so that a heating rod (with its inherent risk of breaking) in the tank becomes unnecessary and the amount of visible technology is reduced to a minimum. Its integrated heating unit is controlled with a timer so that it is activated only between 6.00 and 18.00 h. This management results in the water cooling by 2-4 °C at night, similar to the situation in nature. Using one Eheim 2224 per 250 l of water or part thereof ensures that the entire water volume of a tank is turned over and filtered at least once per hour. In total, 28 filters are employed for my 15 aquaterraria. A spare filter is always at hand for the case of a breakdown. The suction pipe of each filter is mounted thus that the basket at its tip is pressed slightly against a tile. This prevents the sawbacks from separating the basket from the suction pipe and accidents with inquisitive specimens that might stick the head into the pipe, then be unable to extricate it against the suction power, and possibly drown as a result. The feeder pipe of the filter releases the water right back into the tank and so creates a distinct current. The filter chambers are filled with ceramic tubes, which in turn are covered with a coarse filter sponge. I would advise against using finer filter material for the keeping of aquatic chelonians, as it would certainly clog rapidly with the waste produced by these animals and substantially reduce the filtering capacity of the filter. The filters are cleaned as necessary and never at the same time when water is exchanged. It is important that a healthy population of bacteria is maintained in the filter so that it can perform in a manner similar to a miniature biological water purification plant. The terrestrial section a.k.a. oviposition site consists of a rectangular plastic container. It measures 55 × 35 × 30 cm and is affixed to the above-mentioned superstructure so that it is sunk into the water for some 70%. This ensures that its filling of sand is warmed a little by the surrounding water. One side of the terrestrial section is further heated by a 50 W spotlight that is switched on for about three hours over midday and so creates a localized hotspot. Moreover, a heating pad (6 W) is buried in an upright position in the sand and runs around the clock. As a result, the terrestrial section offers zones with various temperatures, enabling the females to choose from a range. The sand is always kept moist enough to clot and will not collapse when a nest pit is excavated. To enable the females to access the oviposition site, a sheet of cork has been mounted to form a ramp between the water and the terrestrial section. Breeding I firmly believe that a species-specific, varying and high-quality diet is essential for successful breeding. Graptemys nigrinoda nigrinoda takes only very small amounts of plant matter (Ernst & Lovich 2009). This needs to be taken into consideration when turtle jelly is mixed or complied with by offering pellets rich in algae. The turtles will occasionally also bite off pieces from aquatic plants. In the wild, the sawbacks have available a wide variety of food items, depending on the season and exact habitat. This natural diversity is impossible to emulate all the time in captivity, and it is for this reason that I include types of food (always low in fat) that do not occur in the turtles’ natural environment. By this, I ensure the required variety. The females are fed on a daily basis – sometimes they receive a lot of food, but not too often, again in an attempt to recreate the situation in the wild. My observations indicate that it is particularly important to feed the egg-producing females in an optimal manner right to shortly before they begin to hibernate in order to build a proper foundation for the RADIATA 19 (4), 2010 11