I don't know what the big attraction to lead is, but squirrels seem to love destroying plumbing vent caps. Specifically, they chew holes in the lead portion of two-piece frost-resistant plumbing vent caps. Once the cap is damaged, water can leak into the attic between the plumbing vent and the cap. The photos below show a few examples.
The wrong way to repair the cap is to goop it up with tar. This is ineffective and temporary.
Another wrong way to deal with a damaged gap is to use caulk.
Another wrong way to deal with this is to install some kind of goofy cap.
The proper and simple way to deal with a damaged cap is to replace it. Most caps are loose enough to just slide right off without any tools. Check out the 15 second video below for a quick demonstration.
Replacement caps can be ordered online from F.J. Moore, which is a company located in Cannon Falls, MN. If you want to go crazy with your repair so the cap never gets destroyed again, check out this permanent solution by Kuhl's Contracting.
Author: Reuben Saltzman, Structure Tech Home Inspections