Intrinsic factors are relatively more important than habitat features in modulating risk perception in a tropical lizard
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Anti-predator responses in animals are dynamic and depend on multiple factors. However, most of our understanding about animal escape responses comes from studies which examine only a small set of factors at a time and are done over a short period of animal life spans. This limits our understanding of the dynamic nature of animal escape behaviour and the relative importance of individual factors in determining their escape behaviour. We used a repeated-measures study design to assess the anti-predator response of a wild population of a sexually dimorphic tropical lizard, Psammophilus dorsalis. We followed marked individuals throughout their breeding lifespan, repeatedly assayed their escape response and measured representative intrinsic and extrinsic factors that could modulate their escape response. Our findings suggest that intrinsic factors, such as sex and body size, influenced escape response relatively more than extrinsic factors did, such as distance to refuge and perch height. Although individual variables influenced escape behaviour, in a direction mostly consistent with predictions from optimal escape theory, the interaction between factors led to novel insights into how animals dynamically evaluate multiple and changing costs throughout their lifetime to evade predation.
Fleeing from a potential predator is crucial to animals and depends on different factors, as there are various costs to escaping. Although several studies in the past have evaluated the role of various factors in determining escape response, the relative importance of factors and how it changes across the lifetime of individuals are not clear. By assessing individuals repeatedly over a substantial part of their lifespan, we could gain insight into how escape response changes as associated factors, intrinsic or extrinsic, change for an individual over time. This approach provided us a more robust and accurate representation of the dynamic nature of escape decisions. We also demonstrate that when multiple factors are considered simultaneously, their relative importance in determining timing of escape can considerably differ from theoretical predictions.
KeywordsAnti-predator response Flight initiation distance Optimal escape theory Perch Psammophilus dorsalis State-dependence
This manuscript results from part of thesis work that was submitted in partial fulfilment for a BS-MS Degree at IISER Pune. We thank P. Somnath for his impeccable field assistance; Pratik Gupte and Ambika for assistance in tagging lizards early in the summer; Rishi Valley School and NCF for providing field logistics; Maria Thaker and Raghav Rajan for their advice regarding methods and presentation; peers at CES and IISER Pune for their encouragement and support throughout the course of this project; and E.D. Brodie III, R.M. Cox, all members of the Brodie-Cox lab, S. Zeeshan Ali, the handling editor and two anonymous reviewers, whose comments greatly helped improve earlier versions of this manuscript.
We thank the varied funding agencies that provided financial assistance throughout the project. This project was made possible by funding and scholarship provided through Scholarship for Higher Education (SHE-INSPIRE) to RB and Funding for Improvement of Science and technology (FIST) grant to CES provided by the Department of Science and Technology (DST) and DBT-IISc Partnership Programme.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This species is not covered under the Schedules of the Indian Wildlife Protection Act; thus, specific permits from government were not required. All experimental protocols on field including the capture and handling of animals were approved by the Institutional Animal Ethics Committee constituted by the Indian Institute of Science (CAF/Ethics/390/2014).
Data and R code generated and analysed during this study are available from the corresponding author upon request.
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