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Ontogenetic shifts in the nesting behaviour of female crocodiles

  • Cameron J. Baker
  • Craig E. Franklin
  • Hamish A. Campbell
  • Terri R. Irwin
  • Ross G. DwyerEmail author
Behavioral ecology – original research


Body size and age are crucial factors influencing reproductive capacity and success. As females grow, their reproductive investment and success often increase due to improved overall physiological condition and experience gained through successive reproductive events. While much of this work has been conducted on birds and mammals, surprisingly little is known on how body size affects nesting decisions in other long-lived vertebrates. We monitored the movements and nesting behaviour of 57 wild female estuarine crocodiles Crocodylus porosus over a 10-year period (and across consecutive nesting seasons) using externally mounted satellite tags, implanted acoustic transmitters and a network of submerged acoustic receivers. Applying Hidden Markov models to the telemetry-derived location data revealed that female nesting behaviours could be split into three distinct states: (i) ranging movements within home ranges and at nesting sites; (ii) migrations to and from nesting sites; (iii) and nesting/nest guarding. We found that during migration events, larger females migrated further and remained away from dry season territories for longer periods than smaller individuals. Furthermore, not only were migratory movements stimulated by increases in rainfall, larger females migrated to nest sites at lower rainfall thresholds than smaller females. We provide some of the first evidence of body size influencing nesting decisions in an ectothermic vertebrate, with shifts likely resulting from an increased willingness to invest in nest protection among larger and more experienced females.


Estuarine crocodile Hidden Markov modelling Nest-site selection Parental investment Telemetry 



This study was supported by the Australian Research Council linkage scheme with Australia Zoo and CSIRO as industry partners. We thank Australia Zoo staff for their aid in the capture and tagging process and Gordon C. Grigg for his reviews of the manuscript. All procedures were carried out with approval from The University of Queensland Animal Ethics Committee (SIB/302/08/ARC, SBS/204/11/ARC/AUST ZOO (NF), SBS/215/14/AUST ZOO/ARC) and Queensland Environment Protection Agency Permits (WISP00993703, WISP05268508, WISP13189313).

Author contribution statement

CB, RD, HC and CF conceived the ideas and designed methodology; All authors collected the data; CB and RD led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.


Funder: Australian Research Council-Linkage Grant, grant number: LP140100222.

Supplementary material

442_2019_4382_MOESM1_ESM.pdf (305 kb)
Supplementary material 1 (PDF 304 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.The School of Biological SciencesThe University of QueenslandBrisbaneAustralia
  2. 2.School of the EnvironmentCharles Darwin UniversityDarwinAustralia
  3. 3.Australia ZooBeerwahAustralia

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