Maternal nest-site choice in a lizard with temperature-dependent sex determination

Daniel A. Warner*, Richard Shine

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)

Abstract

In oviparous species, mothers can optimize the incubation environments of their offspring by selecting nest sites with conditions conducive to embryonic development. Hence, maternal nest-site selection can enhance egg survival and offspring fitness. However, the challenge to a nesting female is complex because of trade-offs among relevant parameters (e.g. hotter nests may be drier) and seasonal shifts in ambient conditions. Moreover, the influence of nest conditions on offspring sex ratios adds another level of complexity for species with environmental sex determination. To elucidate these issues, we need field data on nesting behaviour that incorporate the multiple influences that operate under natural conditions. We radiotracked gravid jacky dragons, Amphibolurus muricatus, in open forest habitats of southeastern Australia to document the lizards' criteria for nest-site choice. Females selected sites with lower than average canopy cover, resulting in relatively warm nests throughout the prolonged nesting season. Although soil moisture levels decreased over this period and were strongly correlated with mean temperatures, female lizards were able to locate nesting sites that provided consistently moist (and increasingly warm) incubation conditions as the season progressed. Such sites apparently became more difficult to find later in the season, resulting in a higher incidence of test holes prior to nest excavation. Seasonal shifts in diel maximum temperatures also pushed the daily time of digging activity into the evening. Because jacky dragons have temperature-dependent sex determination, the seasonal shift in mean incubation temperatures of natural nests would generate seasonal shifts in offspring sex ratios in a direction likely to enhance maternal fitness.

Original languageEnglish
Pages (from-to)861-870
Number of pages10
JournalAnimal Behaviour
Volume75
Issue number3
DOIs
Publication statusPublished - Mar 2008
Externally publishedYes

Keywords

  • Amphibolurus muricatus
  • jacky dragon
  • maternal effects
  • nest temperature
  • nest-site selection
  • oviposition site

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