The reproductive biology and mating system of diamond pythons, Morelia spilota (Serpentes: Boidae)

Observations of 18 radio-tracked snakes in the field, combined with dissection of museum specimens, provided data on reproductive biology of eastern Australian diamond pythons (Morelia spilota). Both sexes mature at about 150 cm snout-vent length (SVL). Pelvic spurs are longer and thicker in males than in females and are used by males to manipulate the female's tail prior to copulation. Reproductive activities occurred in spring (late September to early November), when testes were at their maximal size. Two to six males aggregated around a single female. Male combat was not observed, and more than one male was seen to copulate with the same female, in the presence of other males. Mating aggregations lasted from 4-6 wk. Females oviposited in late December or early January inside "nests" of leaf litter and coiled around the eggs to incubate them. 

Clutch size of diamond pythons varied between 9 and 54 eggs per clutch, and was positively correlated with maternal SVL. During reproduction, females lost approximately 44% of their initial body weight, about two-thirds of which was attributed to oviposition and the other one-third to metabolic costs and reduced feeding opportunities associated with incubation. Probably because of this high metabolic cost and the low energy intake associated with "ambush" foraging, females did not breed every year.