Is PEX very susceptible to damage from rats/rodents?
Rats are not specifically attracted to PEX, but they do have to "seek out opportunities to" chew on things all the time. Their incisor teeth never stop growing, so if left unchecked they would grow so long that the rats would no longer be able to open their mouths and starve to death. So they are compelled to keep them worn down by biting on things all of the time. In the wild it would be nut shells, eggs, grit from dirt on the food etc. But when they forage on our soft garbage, they have to find anything and everything they can to chew on to keep their teeth worn down. So anything semi-hard but still "chewable" is what they seek out. PEX is just one of many things that fits that bill.