Historical Papers
Dorrian, C., 1994, Captive Management of Carettochelys insculpta, Herpetofauna, 24(1):15-18
The largest specimen collected was in Irian Jaya by John Cann. This animal had a carapace length of 550mm. Cann (1978) thought it is possible that females may reach a carapace length of 600mm (Cann, 1978).
Females lay between 10 and 30 round eggs (39 x40mm) during the dry season, between April and November. A nest observed in the wild produced hatchlings after about 70 days (Georges and Kennet, 1989). Webb, et.al. (1986) found that three clutches artificially incubated showed that the sex of hatchlings was temperature dependent. Eggs incubated at 28°C and 30°C hatched after 101 days, and 69 days respectively. Both clutches produced all male hatchlings whilst the third clutch, incubated at 32°C saw the emergence of all females after 53 days.
CAPTIVE HISTORY
Taronga Zoo currently houses three subadult C. insculpta. Two were donated on 13 December 1989 by Dr Arthur Georges from the University of Canberra. These had hatched in December 1985. A further specimen was acquired from Barry Springs on 23 May 1991. The animal appears to be about five years old. The carapace length of the three individuals are No. 1, 195mm, No. 2, 173mm and No. 3, 125mm.
MATERIALS AND METHODS
A glass aquarium tank, 120 cm long by 46 cm wide by 46 cm deep, was divided in half by means of a clear Perspex sheet with a number of holes drilled into it to allow water circulation. No. 3 was placed in one half and No. 2 in the second half. It would appear visual contact triggers aggressive behaviour. The two had been in the respective compartments of the tank for eight minutes before the smaller animal (No. 3) approached the perspex divide and the larger individual (No. 2) became aware of it, and quickly swam toward No. 3, stopping when it collided with the perspex. No. 2 immediately began biting at No. 3, whose nose was touching the divide. Although no actual contact was made, the fury of the attack startled the smaller animal who pushed backwards from the wall and retreated to the far end of the tank, taking refuge behind a sunken log. Once visual contact was lost the aggressor (No. 2) showed no further interest and returned to the bottom of the tank.
The animals were rotated and always the larger turtle was the aggressor. It was thought that if the turtles were placed into a less confined body of water it may negate this aggressive behaviour, however, this did not prove to be the case.
No. 1 and No. 2 were introduced into a communal display tank housing several species of Chelids, Chelodina expansa (3), Chelodina longicollis (4), Chelodina rugosa (1), Elseya latisternum (1), and Emydura krefftii (3). This tank holds approximately 16,000 litres of water and has a water surface area of about 15 sq.m. Each time the subject animals came into contact the larger (No. 1) immediately gave chase to the other, mouth agape, ready to bite. These pursuit occurred several times over the following six hours and when it became obvious that the larger turtle was not going to tolerate the smaller’s presence, the smaller individual was removed.
A few days later, it was noticed that No. 1 has a bite mark on the top pf its head. Monitoring the enclosure showed the offending animal was Ch. Rugosa. C. insculpta was removed and replaced in turn with each of the remaining two C. insculpta. It was observed that each time visual contact was made, Ch. Rugosa would give chase to C. insculpta, biting at the head and flippers. This aggression was not pursued when C. insculpta outdistanced its adversary.
The Northern Snake-neck, Chelodina rugosa, ranges across river systems of northern Australia and members of it are sympatric with C. insculpta, but it is unknown whether the aggressive attitude shown by this individual (a female) is typical of the species, or of interaction in their natural environment.
DISCUSSION
Although these animals display no aggressive behaviour when handled, or toward turtles of the family Chelidae, the pugnacious attitude shown towards members of their own species prohibits pig-nosed turtles from being displayed as a group. Different combinations were tried, but the larger animals always harassed the smaller, constantly chasing it and trying to bite.
From personal experience it is known that males of some species of Chelidae are known to attack each other if placed in a confined area. However neither individual of C. insculpta show any of the characteristics typical of mature individuals.
Heaphy (pers. comm.) kept four C. insculpta at the University of NSW in 1988. These were housed together in a large pool with sunken drums in which they could take refuge. The largest animal, a female with a carapace length of 390mm behaved aggressively toward the three smaller turtles whenever they emerged from their retreats. The three small animals would shelter peacefully together, but on removal of the large female, the next largest would assume the role of aggressor. When the large female was returned, she would resume dominance and the next largest would rejoin the other two.
Heaphy (1990) estimated that males in the Daly River reach sexual maturity between 14 and 16 years of age at a size of about 300mm (carapace length) and females between 20 and 22 at 330mm. the lengthening tail of the male may be apparent from 10 years onwards. The largest male observed by her in the Daly River between 1986 and 1988, had a carapace length of 372mm and the largest female a carapace length of 413mm.
HOUSING
Each animal is now housed in its own water filled enclosure with the water heated to a constant 26-27°C. These temperatures are closely monitored as it has been noted in the past captive pig-nosed turtles have developed and died from pneumonia (Heaphy pers. comm.)