Visual versus visual-inertial guidance in hawks pursuing terrestrial targets

• Published in: bioRxiv
• Main Authors: Kempton, James A, Brighton, Caroline H, France, Lydia A, Marco Klein Heerenbrink, Miñano, Sofía, Shelton, James, Taylor, Graham K
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 24.12.2022
• Subjects: Birds of prey; Visual thresholds
• DOI: 10.1101/2022.12.24.521635

The flight behaviour of predatory birds is well modelled by a guidance law called proportional navigation, which commands steering in proportion to the angular rate of the line-of-sight from predator to prey. The line-of-sight rate is defined with respect to an inertial frame of reference, so proportional navigation is necessarily implemented using visual-inertial sensor fusion. In Harris' hawks, pursuit of terrestrial targets is even better modelled by assuming that visual-inertial information on the line-of-sight rate is combined with visual information on the deviation angle between the attacker's velocity and the line-of-sight. Here we ask whether a new variant of this mixed guidance law can model Harris' hawk pursuit behaviour successfully using visual information alone. We use high-speed motion capture to record n=228 attack flights from N=4 Harris' hawks, and confirm that proportional navigation and mixed guidance using visual-inertial information both model the trajectory data well. Moreover, the mixed guidance law still models the data closely if visual-inertial information on the line-of-sight rate is replaced with purely visual information on the apparent motion of the target relative to the background. Whilst the original form of the mixed guidance law provides the best model of the data, all three models can model the behavioural data phenomenologically, whilst making different predictions on the physiological pathways involved.Competing Interest StatementThe authors have declared no competing interest.Footnotes* https://doi.org/10.6084/m9.figshare.21769982