Coupla years ago on a bike trip thru Missouri and Arkansas, we saw tons of armadillos on the road, both dead and alive. I too never realized they were so far north. While crossing Bull Shoals on the ferry, I had a chance to talk to the local DNR official for the area about them. He told me that altho they are native to the area, they have huge fluctuations in population because of weather. Because their main food supply is grubs , in years when the winter gets cold enough to freeze the ground, they die off in droves, and it may take many years for their numbers to come back, mainly because the breeding animals must migrate north again(and they don't move very fast). After a few years of mild winters, their population explodes because of lack of predation and plentiful food. Blame it on global warming.