Are all holes made by kiwis?

No. But many believe that all holes, that are not made by anything else, are made by kiwis. Some even hypothesize that the supermassive black hole, at the centre of the galaxy, could have been made by a cosmic kiwi at some point.

Comic transcript

Panel 1:
G and H are walking in the forest.
Panel 2:
They find a big hole.
Panel 3:
The hole was made by a giant kiwi.