Energy versus risk: costs of reproduction in free-ranging pythons in tropical Australia

Thomas Madsen, Richard Shine

Research output: Contribution to journalArticlepeer-review

59 Citations (Scopus)


Data from a 12-year field study have allowed us to quantify 'costs of reproduction' in a natural population of water pythons (Liasis fuscus) in tropical Australia. Both sexes of pythons cease feeding during the reproductive season. For males, this involves fasting for a 6 week period. Adult males lose weight rapidly over this period (approximately 17% of their body mass) but regain condition in the following months, and do not experience reduced survival. In contrast, reproductive adult females cease feeding for 3 months, lose an average of 44% of their body mass over this period, and experience increased mortality. A causal link between reproductive output and reduced female survival is supported by (i) a decrease in survival rates at female maturation; (ii) a correlation between survival rates and frequency of reproduction, in a comparison among different size classes of adult pythons; and (iii) a lowered survival rate for females that allocated more energy to reproduction. Hence, both sexes experience substantial energy costs of reproduction, but a relatively higher energy cost translates into a survival cost only in females. Such non-linearities in the relationship between energy costs and survival costs may be widespread, and challenge the value of simple energy-based measures of 'reproductive effort'.

Original languageEnglish
Pages (from-to)670-675
Number of pages6
JournalAustral Ecology
Issue number6
Publication statusPublished - Dec 2000
Externally publishedYes


  • Feeding
  • Growth
  • Liasis fuscus
  • Life-history
  • Reproductive effort
  • Reptile
  • Snake
  • Survival


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