Tree collars wrap tree trunks in an exhibit to prevent animals from climbing out.
At the cheetah exhibit at the ABQ Biopark I saw a successful attempt to conceal an especially large tree collar.
Usually tree collars are made of sheet metal, which is just painted black, green or some generic camouflage color. This can work if the collar is high up and out of view.
But here the collar is in plain sight and it's huge. Someone took the time to paint the metal in a way that mimics the color and pattern of the tree bark, making it disappear. Or, if not disappear, making it less noticeable and less distracting. It worked very well. It looked even better in real life than here in the photos.
Below a photo from the years when I lived in Ohio. Our neighbor tried to keep the squirrels out of the trees with sheet metal tree collars while we put squirrel feeders up in ours. A good example of how ugly and distracting the metal can be.