Which of the following is NOT a structural adaptation? camouflage
mimicry
spikes on a hedgehog
a squirrel climbing up a tree

Camoflauge.

Explaination:

Camouflage is when a species changes to resemble its surroundings to protect itself.

Structural adaptations are physical features of an organism such as spikes on a hedgehog.

Since camoflauge is not a physical feature, it is therefore not a structural adaptation.

Hope this helps!