Breeding of the Emydura species
Jan Matiaska and Scott Thomson
In general, Emydura males mature at 5-6 years of age while females mature at 9-12 years of age. In captivity, the maturity of both genders is reached sooner (males at 4-5 years and females at 5-7 years) due to a high in protein diet. We do not recommend speeding up the species’ maturity attainment as this will most probably result in specimens having health problems and shorter life span. The ages of maturity attainment above apply to the whole Emydura genus but some variation is expected among all the currently recognized species.
Mating
The following
paragraph describes the mating behaviour of Emydura macquarii macquarii.
Bopping his head, a male approaches a female while the female reciprocates.
The male swims round and touches the female’s cloaca with his snout.
This is followed by the male trying to align his barbells with those of
the female. Then the male strokes the females’ barbells, neck and
snout with his claws on the forelimbs. When the female is ready, the male
mounts on the female from behind. To maintain the copulation position, the
male uses his claws on all four limbs which are strongly fixed to the female’s
carapace.
According to Banks (1987), this mating sequence has also been confirmed
for Emydura macquarii krefftii. A very similar and possible same
mating behaviour can be expected of the other two E. macquarii
subspecies: E. macquarii nigra and E. macquarii emmotti.
I have observed identical sequence within Emydura subglobosa subglobosa[1].
[1] My (Jan Matiaska) E. subglobosa subglobosa male is so vital that he practices the above described mating behaviour towards a totally different genus (Carettochelys insculpta).
Nesting
There are two main reproductive patterns that are identified within the Emydura genus and the Australian Chelidae as a whole. The species from the temperate zone, Emydura macquarii macquarii (Chessman 1978), Emydura macquarii krefftii (Georges 1983), Emydura macquarii nigra and Emydura macquarii emmotti, tend to nest in spring (August to November)[2] and hatch in summer (December to February)*. Of course, there are variations depending on a particular latitude as well as altitude. Generally, the further south you go, the later the nesting and hatching occurs. The nesting behaviour may begin as early as August in warmer areas (Georges 1982) and as late as November in colder areas (Vestjens 1969). The Emydura species from the temperate zone (the four subspecies of Emydura macquarii) are known to have multiple clutches (Ledger 1981). Even though the number of eggs mainly depends on the size of the female, the clutch size may also vary because of such factors as the temperature and amount of rainfall which take place prior to the nesting.
[2] Applies to the Southern hemisphere
The Emydura genus is oviparous, just like all other living turtles. Females lay eggs in nests dug in either sand or soil near water. Lighter soil is preferred by E. macquarii macquarii and possibly by other Emydura species as well. Generally all Emydura eggs are white in colour and ellipsoidal in shape.
Nesting behaviour of Emydura macquarii macquarii as described by Goode (1965)
“The cavity is dug with the hind limbs and enlarged through a slow process of inserting one leg and then the other into the whole. Dirt is extracted with a cupped foot, while the alternate limb bears the animal’s weight. Once the flask-shaped nest chamber is complete the eggs are laid. After each egg is deposited, the hind leg is inserted into the whole to arrange it in position. When laying is completed, the nest cavity is covered. The hind legs are extended until almost at right angles to the spine, the feet are orientated in a backward direction and brought together through an arc, carrying with them the soil from the excavated cavity. This action is repeated until the nest cavity is filled. The turtle then raises itself on all four legs and then drops its shell hard on the ground to compact the soil in the filled nest.” (Goode 1965).
The species
from the tropical zone, both Emydura subglobosa subspecies, Emydura
victoriae and Emydura tanybaraga, go through a more complex
nesting behaviour which greatly depends on the timing of the wet and dry
seasons, onset of terrestrial rains, water level, and possibly other factors.
As these cannot be precisely predicted, the reproductive patterns of the
tropical zone Emydura species (and other chelids) are very flexible.
Tables
Table 1: Mean size and weight of Emydura eggs
Egg Length (mm) |
Egg Breadth (mm) |
Egg Weight (g) |
Source |
|||
|
Mean ± SD |
N |
Mean ± SD |
N |
Mean ± SD |
N |
|
34.06 ± 3.06 |
127 |
19.96 ± 1.65 |
127 |
8.66 ± 2.29 | 489 |
Legler & Georges |
Table 2: Mean size and weight of Emydura hatchlings
[All hatchlings were measured and weighed between 3 and 14 days of age]
Species |
Length (mm) |
Weight (g) |
Source |
||
| Mean ± SD |
N |
Mean ± SD |
N |
||
Emydura victoriae |
32.6 ± 0.7 |
15 |
5.1 ± 0.3 |
15 |
Legler
& Georges |
Emydura
tanybaraga |
32.7
± 1.7 |
22 |
5.6
± 0.6 |
35 |
Legler
& Georges |
Emydura
macquarii macquarii |
30.1
± 0.6 |
10 |
5.4
± 0.6 |
7 |
Legler
& Georges |
Emydura
macquarii krefftii |
29.8
± 2.4 |
66 |
4.1
± 0.7 |
60 |
Legler
& Georges |
Table 3: Incubation data [N = number of clutches]
|
Incubation temperature (°C) |
Mean ± SD (days) |
N |
| 30°C |
46.6 ± 4.4 |
54 |
28°C |
51.8 ± 0.9 |
6 |
25°C |
72.8
± 1.6 |
9 |
Breeding in captivity
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