The Imperial Household Agency announced Thursday that Emperor Akihito's research paper on tanuki, or raccoon dogs living on the Imperial Palace grounds has been published in a research report by the National Museum of Nature and Science.

The report, co-authored with agency officials, was the Emperor's second research paper on tanuki, the agency said.

According to the agency, roughly a dozen or more tanuki are believed to be inhabiting the palace ground. The Emperor collected their droppings every Sunday afternoon between January 2009 and December 2013 and examined plant seeds contained in them through a microscope.

Based on the examinations, the paper concludes that the tanuki mainly feed on eight plants, including muku trees, in different seasons, which indicates that the palace grounds offer a food supply stable enough to support several tanuki.

The museum published the Emperor's first research paper on tanuki in 2008.