I have placed solar-powered lights on some of my fence posts. Unfortunately, squirrels run along the fence and knock the tops off the lights, causing the battery to fall to the ground (where my dogs view it as a toy). Is there an exterior tape I can use that will keep the tops attached until such time as I need to replace batteries? Thank you.

Might try a criss-cross of monofiliment fishing line, to secure the tops to the posts? With screw eyes into the wood, if the posts are not metal.