Herbert Meier Fig. 15. Although this female Podocnemis vogli retained her eggs for an estimated two months, they are normally shelled. Podocnemis erythrocephala The red-headed river turtle is the smallest and most delicate species of Podocnemis. Even though it can grow to 32 cm in carapace length, it is less massive than its congeners. Its vernacular name refers to the conspicuous red pattern on the head, which is, however, retained into adulthood only by male specimens. Females, on the other hand, begin to change their colouration during their third or fourth year of life, with the once intense red fading into a dirty shade of greyish brown so that it is hardly visible in sexually mature females. Like all other species of Podocnemis, the red-headed river turtle grows fast and reaches sexual maturity at an age of five to seven years. At this point of time, males typically measure about 15 and females up to 20 cm in carapace length. In contrast to the other two species, Podocnemis erythrocephala appears to prefer feeding off the ground, although it will, like the other two, also pick up food floating on the water surface if it has to. It is furthermore notable that it basks less often and responds with much greater sensitivity to disturbances. While both Podocnemis vogli and Podocnemis unifilis are easy to keep in captivity if only they have enough space available, Podocnemis erythrocephala presents itself as extremely difficult with regard to the required water quality. Being an inhabitant of black water rivers with pH values around 4-4.5 and conductivity levels of 10-20 µS/cm (data from Michels pers. comm. 2007), it is hardly possible to adjusted it to a life in “polluted” water. In general, this species is much more difficult to keep in hard, pH-neutral, or even alkaline water than in an acidic and soft environment. Even well-acclimatized turtles respond badly to polluted water in their tank. Smallest scratches and other injuries will then commonly result in necrotic infections of the shell that take a log time to heal. An indication of suboptimum husbandry conditions could be imperfect moults of the shell. This phenomenon could, however, also 14 RADIATA 17 (3), 2008
Experiences with the Keeping of River Turtles of the Family Podocnemididae have to do with the fact that, in their natural habitats, red-headed river turtles often shelter in underwater thickets of tree roots, amongst branches of fallen trees, or, in other places, in dense tufts of grass with partly sharp-edged blades. The contact with these then might have a “sweeping” effect that could be needed to remove the products of shedding. In fact, the animals kept by the author can often be seen actively scratching themselves on submerged branches. Although a besom that was hung into the water for this purpose has been so far ignored, it is possible that such an aid needs to form a patch of a certain size so that it can be used as a place to hide in. Until a better solution will be found, their shells are cared for manually at irregular intervals: the turtles are very carefully scrubbed with a hard brush so that the dead scutes come off. Oviposition takes place between late December and March. Nesting spots may be situated in sandy savannah, but also in loosely vegetated savannah with low brush, or even on sandbanks. At least the savannah nesting spots may be several hundred metres from the water, but it is likely that the eggs are laid when the water level is high and a spot can be chosen near the water’s edge. The greater distance is then merely a function of receding water levels. The numbers of eggs in seven clutches examined were always less than ten (own obs.). Barrio-Amorós & Narbaiza (2008) stated that oviposition would take place in October through November, but own observations suggest that eggs may also be laid in December, January and March, as was evident from fresh tracks and clutches present. A single hatchling was found around the beginning of April. The observation of oviposition in March was extraordinary insofar as there had been unusually heavy and lasting rains during the dry season that saw rivers rise to high water levels. Almost all suitable nesting spots were submerged and the abnormal weather caused a shift in the breeding season. Castaño-Mora et al. (2003) also indicated the nesting season to fall into the months of December and January. Considerations of husbandry and propagation Owing to their substantial adult sizes, the resultant necessary space, and the partly expressed intraspecific incompatibility, all representatives of the family Podocnemididae are suitable for keeping in aquaterraria only with severe limitations. Juveniles grow very rapidly to impressive sizes and will soon need to be kept in a tank of a size that far exceeds the average aquarium of even the dedicated enthusiast. Their metabolism is enormous and calls for either a high-volume filter system or continuous exchanges of their water. A trickle filter, as used to be employed for the large pond mentioned above, proved unable to handle the amount of dirt and had to be replaced with a linear filter with four chambers, ahead of which lies a Zyklon extractor. This system has a volume of altogether 1,200 l. The water is furthermore sterilized by means of a 40 W UV-C burner. The enormous space requirements, added to which is the tropical animals’ need for warmth, renders the captive keeping of these turtles at least very problematic for the private enthusiast. As a result of strict export bans imposed by their native countries, these turtles - fortunately - do no longer feature prominently in the European pet trade. Their keeping is thus reserved to zoological institutions and a few specialist keepers. Captive propagation has been successful only very occasionally in Europe, and passing on offspring in a responsible manner proves everything but easy. Even though turtles of the family Podocnemididae may not be threatened with immediate extinction, an increase of threats must be expected in the long run. It must also be supposed that predatory pressures on the animals gain in momentum, and at least the populations of Podocnemis expansa have already suffered severe damage from being RADIATA 17 (3), 2008 15
