Cockroaches adjust body and appendages to traverse cluttered large obstacles

Area of Science:

• Biomechanics
• Animal Locomotion
• Robotics

Background:

• Animals transition between locomotor modes to navigate complex terrain, driven by neural control or energy cost minimization.
• Physical interactions with the environment, controlled by the nervous system, can also induce locomotor transitions in 3D cluttered terrain.
• The discoid cockroach transitions from pitch to roll mode on stiff beams to save energy, but must overcome an energy barrier.

Purpose of the Study:

• To investigate how the discoid cockroach actively adjusts its body posture to facilitate transitions between locomotor modes on cluttered terrain.
• To quantify the effect of specific adjustments, such as head and leg movements, on overcoming the energy barrier during pitch-to-roll transitions.

Main Methods:

• Observing and analyzing cockroach movements during pitch-to-roll transitions on cluttered beams.
• Developing a refined potential energy landscape model incorporating additional degrees of freedom for body adjustments.
• Quantifying the reduction in the transition energy barrier due to head flexion and reduced leg sprawl.

Main Results:

• Cockroaches exhibited unique adjustments, including head/abdomen flexion and altered hindleg sprawl, during transitions on beams, unlike on flat ground.
• Head flexion minimally reduced the transition energy barrier (∼10⁻³ mJ).
• Reduced hindleg sprawl significantly lowered the transition energy barrier (∼10⁻² mJ).

Conclusions:

• Active adjustments, particularly reduced leg sprawl, are crucial for discoid cockroaches to overcome energy barriers during locomotor mode transitions in complex terrain.
• Head flexion may serve a sensory feedback role, guiding the transition process.
• These findings highlight the interplay between active motor control and physical environmental interactions in animal locomotion.