Grapevines and leaves are not toxic. However, before you use them in your new glider's cage, you need to know: Did you grow the grapevine and dry it yourself? If not, what's the source? If it was bought at a craft shop or department store, then it
may have been treated with a preservative. There's a good chance he'll instinctively chew on the vine; even if he doesn't, anything on the surface could transfer to his paws. Since gliders groom and eat using their front paws as hands, you want to avoid anything that's not all-natural and non-toxic. But if it is, I bet he'll enjoy playing on it!