There was a question that one of our customers asked about when squirrels eat lead. I would defer to an expert like Bob Thomas at Loyola who wrote the article on this located on our home page at the Read The Literature tab. However, I do believe they tend to eat it more in the fall and spring vs the summer, at least here in Florida.
Regardless, they do a lot of damage that causes leaks. Critter Quitters will protect the vent, stop the leak if you got one, and will let you keep squirrels from eating it further while adding a good look to the roof.