The Nara Deer Preservation Foundation in Western Japan said 14 deer have died at Nara Park since March, nine of which were found to have consumed plastic.
Nara Park is famous for having more than 1000 deer reside inside its bounds, where visitors can feed the deer special crackers.
Vet Rie Maruko said the deer that died were very skinny and should not have been fed anything other than the senbei snacks.