Quantity or quality? Determinants of maternal reproductive success in tropical pythons (Liasis fuscus)

A female's reproductive output (size and number of o¡spring) may say little about her reproductive success; the `quality' of her progeny and the time that they are produced may be more important in this respect. We marked and released 1224 hatchling water pythons (Liasis fuscus) from 116 clutches of laboratory-incubated eggs, in a study site in tropical Australia. Clutches varied widely in the number of eggs, mean o¡spring sizes, the proportion of eggs that hatched, and recapture rates of o¡spring. Clutch size was not signi¢cantly correlated with the number of recaptured hatchlings in either year, nor was mean o¡spring size related to recapture probability. Instead, o¡spring recapture rates varied as a function of the time of hatching. Recapture rates were higher for hatchlings released in a year with high prey availability than in a year with few prey. In addition, recapture rates were higher for earlier-hatching clutches in the year with few prey. The other signi¢cant e¡ect on recapture rates involved o¡spring viability: some clutches had a much higher proportion of surviving o¡spring than did others, and recapture rates were higher from clutches with higher hatching success (i.e. proportion of eggs hatching). Hence, the usual measures of reproductive output (clutch size and o¡spring size) o¡er only a poor index of a female's reproductive success in this system.