Full Idea
There are amusing buildings, but not amusing rocks and cliffs. If I were to propose a candidate for the formal object of amusement, then the human would be my choice, ...or at least emphasise its centrality.
Gist of Idea
The central object of amusement is the human
Source
Roger Scruton (Laughter [1982], §9)
Book Reference
Scruton,Roger: 'The Aesthetic Understanding' [Methuen 1983], p.163
A Reaction
Sounds good. Animal behaviour only seems to amuse if it evokes something human. Plants would have to look a bit human to be funny.