What will squirrels not walk on?

Squirrels are agile climbers that can walk on most surfaces, but there are certain textures and materials they dislike or find difficult to navigate, which can be used to deter them. Squirrels do not like walking on very slippery surfaces like smooth metal sheeting, polished aluminum flashing, or greased poles, because they cannot get grip with their claws, which is why pole baffles made of metal are effective for bird feeders. They avoid walking on sticky surfaces like fresh adhesive or very sticky tape, though this should not be used in a way that harms them. They dislike walking on unstable, wobbly surfaces that move under their weight, such as loose netting or spinning baffles that throw them off balance. They are hesitant to walk on very hot surfaces in summer or surfaces coated with strong irritants like cayenne pepper, though pepper alone is not a reliable barrier. They also avoid walking on surfaces with sharp or prickly textures like hardware cloth with sharp edges or thorny branches placed as barriers, but they can often jump over them. Contrary to myths, squirrels will walk on most natural surfaces including wood, shingles, vinyl, and even upside down on wires. So while slippery metal baffles and spinning feeders are effective, there is no magic surface that squirrels absolutely will not walk on if highly motivated by food, and combining barriers with feeder placement is more effective.