Something eating my tractor seat

[Paddlefoot]

i parked my tractor down one of my 4 wheeler trails and also my side by side when I left my farm for a couple of days. When I retrieved the tractor is had all these same size holes in the back test All of the depressions appear to be the same size. No problem with the side by Side. Have you any idea what varmint could have attacked the plastic trastic seat And why?

 

[Wildlife]

You might also consider birds pecking seat or squirrels.