Rabbits thump their hind feet mainly as an alarm signal.
A strong strike against the ground creates both sound and vibration.
Why is that useful?
Wild rabbits are prey animals.
If one detects danger, a thump can warn others even when they are not looking in the same direction.
Ground vibration can also travel into burrows.
What can trigger a thump?
A strange animal.
Sudden movement.
An unfamiliar noise.
A new object.
A household appliance.
Domestic rabbits can react to things their humans do not consider remotely threatening.
The rabbit gets a vote on what counts as suspicious.
Does a thump always mean fear?
No.
Rabbits can also thump when frustrated or annoyed.
The rest of the body and the situation matter.
Why are rabbit hind legs so powerful?
Rabbits depend on strong hind limbs for fast acceleration and jumping.
The same muscles make a foot strike loud and forceful.
What should you do if a pet rabbit keeps thumping?
Look for a possible source of stress.
Provide hiding places and reduce sudden disturbances.
A major behavior change combined with reduced eating or abnormal posture deserves attention because rabbits can hide illness well.
This is another good example of animal communication, just like frog calls or dog scent marking.
Most of the time, the rabbit is sending a simple message:
Something has my attention.
Everybody else should probably know about it.
And that’s the short explanation.
Related explanations: Why do frogs croak?, Why do dogs kick the ground after they poop?, and Why do animals have tails?