Carrying eggs uphill: are costs of reproduction stronger on steeper slopes?

Anthony L. Gilbert*, Richard Shine, Daniel A. Warner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
23 Downloads (Pure)


Locomotor impairment during pregnancy is a well-documented cost of reproduction, but most empirical studies have not incorporated ecological complexity, such as locomotion on sloping inclines rather than horizontal surfaces. Biomechanical factors suggest that carrying a heavy burden - including shifts in the body's centre of mass - may impair locomotor ability even more when an animal is running uphill. If so, then measuring costs of reproduction on horizontal racetracks may underestimate these costs in nature for arboreal species. To evaluate this prediction, we measured the pregnancy-induced reduction in speed for jacky dragons (Amphibolurus muricatus) at inclines ranging from 0 to 45°. Both pregnancy and steeper slopes reduced lizard performance, but pregnancy did not exacerbate the locomotor decrement on steeper racetracks. An ability to maintain mobility on steep slopes during pregnancy may be a target of selection in arboreal taxa. To understand the evolutionary context of locomotion-based costs of reproduction, we also need studies on the relationship between organismal performance and ecologically relevant measures such as predation risk.

Original languageEnglish
Article number20230025
Pages (from-to)1-5
Number of pages5
JournalBiology Letters
Issue number5
Early online date10 May 2023
Publication statusPublished - May 2023


  • Agamidae
  • habitat selection
  • life history
  • locomotor performance
  • oviparous
  • sprint speed


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