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Reproduction
In the Macleay River the male and female of the Emydura species common to this area were often noticed swimming together. Several such pairs were marked in September, and one pair was still together in November. It is therefore assumed that the courtship period may extend for at least two months. Pairing has been noted at different times of the year in this same locality and is therefore not restricted to one season. In most instances the smaller male tortoise swam about 30cm behind the female.

In one study of courting pairs, it was observed that after following the female for some time the male positioned himself in front of her and while attempting to swim backwards gently stroked her face with his front claws and pushed his nose into her neck in a manner surprisingly suggestive of human behaviour. The two tortoises acted in this manner for about thirty minutes when the male noted the observer's presence and left the female to swim to within a metre of the of his face mask and stare inquisitively until air bubbles blown in its direction sent both male and female hurrying for cover.

Another interesting study was taken of two New Guinea Snake-neck Tortoises in an outdoor pool 2m square. The male swam slowly from behind the female and clasped her carapace from above with all four feet. Once penetration had been effected he relaxed his grip and began to rise slowly until he assumed an almost vertical position. This stance was retained while they swam slowly around the pool. The pair parted and resumed the same position three times. It is possible that this vertical positioning is necessary for long-neck tortoises because of the relatively short tale of the male. The short-neck tortoises, with longer tails, would perhaps find this unnecessary.

Although little has been recorded of the nesting behaviour of Australian tortoises, the incubation periods of the eggs of several common species from south-eastern Australia are well documented. At Patho on the Murray River, Goode and Russell have noted most of the nesting habits of the Macquarie River Tortoise (Emydura Macquaria), the Broad-shell Tortoise and the Common Snake-neck Tortoise. The Oblong Tortoise from the south-west has also been studied. Artificial incubation of the eggs of many other species has been recorded, but it is the field observations which are of primary importance.

Artificially incubated Broad-shell Tortoises
(Chelodina Expansa).

Comparative egg sizes from Australian tortoises -
clockwise from bottom: Emydura sp.Mackleay R.;
Emydura Macquaria; Emydura Kreffti; Elseya Dentata;
Chelodina Oblonga; middle - Chelodina Expansa.

Variations ranging from 130 days to almost two years have been recorded for incubation of long-neck tortoises and from three to six months for most short-necks. The duration of incubation depends on climatic conditions and the composition of the earth in which the eggs are deposited. Rain is relied on to some extent by tortoises in areas where hard soil would otherwise render the nesting process difficult if not impossible. An alternative method of overcoming this problem has been recorded from the Murray River, where a female Common Snake-neck Tortoise, while digging in hard earth, made several trips to the water to drink during a period of one and a half hours. When she returned, she released the liquid through the cloaca to soften the ground.

An Oblong Tortoise (Chelodina Oblonga) using its
long neck to help achieve greater depth when
digging a nest

A nest is excavated to a depth of about 15cm in river sand, soil or clay. Different species appear to select different areas. The Broad-shell Tortoise often makes a hard earthen plug to seal the nest. The plug is made by releasing fluid via the cloaca into the last 8cm of top filling of the nest. This practice is a somewhat feeble attempt to keep predators from the eggs, and often turns the nest into tomb for the young if rain, which is needed to soften the exit, is long overdue.

In 1970 during a dry season at Platho, Jim Russell opened seven Broad-shell Tortoise nests; only one contained live young. The others were either infertile, had at some stage been attacked by parasites beneath the ground or the hatchlings had died awaiting rain. One nest which had been observed being made was opened by Russell almost tow years later and was found to contain live young - the eggs had been deposited an incredible 644 days earlier!

Female tortoises attempt to deposit their eggs above the high water level. At times they will travel 500m or climb steep banks 100m high to accomplish this end. Yet the farther the nest is from the water, the less likely is the hatchlings' survival, for they are exposed to a longer and more hazardous trek to the water.

Towards the end of one laying season, a careless mistake at home flooded an outdoor pond and 7.5cm of water covered the entire enclosure. Although the water level was soon returned to normal, and surrounding land areas restored, eighty percent of the expected eggs were deposited in the water. It is probable that the tortoises subsequently regarded the entire enclosure as liable to flood and decided that any nest building would be futile.

If a female tortoise is disturbed before or during the excavation of the nest she will quickly return to the water, but once she has committed herself to lay it is impossible to move closer and watch. It was in this manner that one observation was made of a Common Snake-neck Tortoise nesting in a outdoor enclosure. The hole was dug in sandy soil with the rear feet and the female then positioned her hindquarters into it. As eggs appeared, they were eased to one side of the excavation with the hind feet so that the following egg would not drop on to them. Once the laying was completed the female began to cover the eggs, pushing the soil back into position and padding it down with the rear feet. After levelling the soil out, she lifted her body high, to the full extent of her front legs, then dropped, hitting the ground firmly with the plastron. This was repeated several times.

A Common Snake-neck Tortoise (Chelodina Longicollis)
filling in after laying eggs

The most unusual aspect of the laying was that she was quite aware of the observer's presence; after she had attempted to disguise the nest by raking her claws over the surface, she walked one metre away and repeated the last stages of nesting, possibly to distract the observer's attention from the original site. Other nesting females, unaware of the observer's presence, returned immediately to the water once they had completed the nesting procedure.