User blog comment:Argulor/Characters ages/@comment-1859920-20130723033113

I personally did not notice that discrepancy, and I think it's pretty neat that you found it. I'm almost tempted to look into it myself. Anywho, an explanation I thought of, was that a sparrow's season("year") could be much shorter than that of a mouse. A new born sparrow could possibly age approx. 13x faster than a young mouse. Besides, typically, as far as size goes, a new-born animal ages physically, faster than an animal that has already reached a size that is close to it's adult size.