That's an excellent and very practical question! As someone who's watched squirrels perform acrobatics around public bins, I can tell you this is a real concern for city planners. The short answer is: modern urban bins are specifically designed to resist rodent damage, but complete "proofing" is an ongoing challenge.
Most quality municipal bins now use thick, hardened plastics or powder-coated steel in vulnerable areas—particularly around lids, hinges, and potential entry points. Squirrels have incredibly strong teeth that never stop growing, so they will chew on almost anything. Manufacturers combat this by using materials like metal reinforcement strips around openings and adding bitter-tasting chemical additives to the polymers during production. These non-toxic additives make the plastic taste awful to rodents.
Smart design plays a huge role too. You'll notice many newer models have smooth, rounded edges with no convenient corners for teeth to grip. Critical mechanisms are often housed internally behind metal plates. Some cities even use bins with weighted or magnetic lids that are simply too heavy or tricky for small animals to pry open.
That said, determined squirrels can sometimes find a weak spot, especially if a bin is already damaged or poorly maintained. Regular inspection and prompt repair of any cracks or holes are crucial. The goal isn't always 100% imperviousness—which can be cost-prohibitive—but rather creating a bin so frustrating and unrewarding that the animals move on to easier targets.
So, while your local trash bin might show some scratch marks, chances are its core integrity is holding strong thanks to these engineered defenses. It's a quiet but important battle for urban cleanliness!