Testing the Impact of Prey Presentation Method on the Feeding Kinematics of Terrestrial and Aquatic Ambystomatidae

In animal behavior, standardizing experimental protocols ensures a rigorous interpretation of the results. However, when working with multisource data, homogeneous standardization is often difficult to attain. This is the case for many studies on feeding kinematics where experimental protocols are carried out using similar but not identical methods. In particular, the impact of the way in which prey is presented remains poorly tested and understood. The aim of this study is to assess whether prey position and the way prey is presented have an impact on the kinematics of prey capture. To do so, we compared the feeding kinematics during the capture of prey presented on the substrate versus prey suspended from tweezers using closely related species of aquatic and terrestrial salamanders. Our results show that changes in prey presentation method directly impact suction feeding kinematics but not terrestrial feeding. In the case of suction feeding, when the prey is suspended by tweezers, mouth opening movements are wider and take more time, the maximum speed and acceleration of mouth opening are higher, and head angle is larger. These changes in kinematics are interpreted as behavioral responses to hydrodynamic changes caused by the different prey presentation methods. This differential sensitivity to prey presentation method between aquatic and terrestrial feeding also highlights differences in the underlying control mechanism: while terrestrial feeding appears to rely on feedback mechanisms, aquatic feeding appears to rely mostly on feedforward mechanisms. As a result, the importance of accounting for prey presentation method is likely context-dependent, being more relevant when studying feeding systems that rely on feedforward control. Finally, when comparing aquatic and terrestrial feeding, the differences in feeding strategies due to the medium itself outweigh the effects of the prey presentation method.