simple fix, cut off the rest of the part they chewed, very carefully so as to not nick the blank,(it doesnt have to be perfect, just the big chunks) then order a rear grip from anglers workshop, longer than the damaged area, cut to correct length, ream out the new handle with a rat tailed file so it slides on snugly,(the rod tapers is opposite of the way the handle is usually put on, but epoxy will fill the void) coat the area with epoxy, slide the new part on, clean the excess off and set handle down and let dry.. good as new. lots of videos on you tube to help out