Yes, silverfish, this is my experience too so you are probably right. Greys here seem to do 'roadwork' as part of their training too which I don't think happens at all in the USA. I just wondered if this did account for the difference as they do seem to be more delicate over there. However, in my experience ours seem to get less skin damage to other parts of their bodies too, which made me wonder if there is some genetic difference.