Echolocating bats use a nearly time-optimal strategy to intercept prey

Area of Science:

• Behavioral Ecology
• Neuroethology
• Biomechanics

Background:

• Many animals, including humans in sports, use a constant bearing (CB) strategy for intercepting predictable moving targets.
• CB is a time-optimal strategy for targets moving predictably, like ballistic objects or sinking food.
• However, many prey animals exhibit erratic, unpredictable movements, questioning the universality of CB.

Purpose of the Study:

• To investigate the prey capture strategies of echolocating bats hunting erratic insects.
• To determine if bats utilize the constant bearing (CB) strategy or an alternative approach.
• To mathematically analyze bat pursuit trajectories and compare them to known interception strategies.

Main Methods:

• High-speed stereo infrared videography was employed to record 3D flight paths of bats chasing insects in a dark lab.
• The complex pursuit trajectories of the big brown bat (Eptesicus fuscus) were quantified using a delay differential equation.
• Mathematical analysis was performed to compare bat strategies with constant bearing (CB).

Main Results:

• Bat pursuit trajectories were analyzed, revealing a strategy distinct from constant bearing (CB).
• Bats were found to employ a constant absolute target direction strategy during pursuit.
• Mathematical modeling demonstrated that this strategy minimizes interception time for unpredictably moving targets.

Conclusions:

• Echolocating bats do not use the constant bearing (CB) strategy for capturing erratic prey.
• Bats adopt a constant absolute target direction strategy, which is time-optimal for unpredictable targets.
• This bat strategy is analogous to guided missile interception and likely evolved under pressure to capture fast, erratic insects.