I use the soft foam grip stuff. You can
buy it cheaply in metre lengths for butterfly bars, which is typically enough for 4-5 USS recumbent grips' worth. It slides on and off easily (even over bar-end shifters) with liberal application of isopropyl alcohol as a lubricant (which doesn't seem to affect the foam, and evaporates in about an hour leaving no residue). As such, I consider grips to be a wear item, and don't get overly hung up about them getting damaged. Which isn't uncommon as they're the widest point of my bike, and tend to get caught on things when carrying through doorways and on/off trains etc, as well as naturally abraded by the grippy surface on some mitts.
Soft foam's not in the slightest bit fox-proof (though I can testify that the foam is at least cow-resistant, once you've rinsed off the slobber), but at least it's cheap and easy to replace. I suspect handlebar grips of all kinds are naturally of interest to animals as they smell of sweat and (I assume - I haven't actually tried chewing one) taste salty.
Perhaps Charlotte's innovative condom technique could be of use here...?
