Abstract
The inverse optimality approach can allow us to learn about an animal's environment by assuming their behaviour is optimal. This approach has been applied to animals diving underwater for food to produce the index of patch quality (IPQ), which aims to provide a proxy for prey abundance or quality in a foraging patch based on the animal's diving behaviour. The IPQ has been used in several empirical studies but has never been evaluated theoretically. Here, we discuss the strengths and weaknesses of the IPQ approach from a theoretical angle and review the empirical evidence supporting its use. We highlight several potential issues, in particular with the gain function—the function describing the energetic gain of an animal during a dive—used to calculate the IPQ. We investigate an alternative gain function which is appropriate in some cases, provide a new model based on this function, and discuss differences between the IPQ model and ours. We also find that there is little supporting empirical evidence justifying the general use of the IPQ and suggest future empirical validation methods which could help strengthen the case for the IPQ. Our findings have implications for the field of diving ecology and habitat assessment.
Highlights
Air-breathing animals that hunt for food underwater and return to the surface for air are referred to as divers
We provide a critical evaluation of the index of patch quality (IPQ), including specific issues with the IPQ model, with its empirical validation, and surrounding the use of the inverse optimality principle in this context of diving animals
Alongside potential issues with the IPQ models we have raised so far, a separate reservation relates to the use of inverse optimality in this context of diving animals
Summary
Air-breathing animals that hunt for food underwater and return to the surface for air are referred to as divers. The approach uses the environmental parameters to predict behaviour. Mori et al [1] reverse this direction of analysis; starting from the assumption that behaviour is optimal, they find the value of an environmental foraging parameter that predicts such behaviour. This is an example of inverse (or reverse) optimality [2,3,4,5]. We provide a critical evaluation of the IPQ, including specific issues with the IPQ model, with its empirical validation, and surrounding the use of the inverse optimality principle in this context of diving animals
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