I've been looking up info on foxes. Red foxes have phase variation, i.e., not all red foxes are red. Some can be black or silver or have a cross-type pattern. Foxes also have very good night vision but have a poor eye for detail. This might be pretty important to have in mind for particular plot twists.
Also, I've been making notes on geographic terrain for the setting. However, since most of the story is planned to take place in the city, I'm not sure how much of that I'll end up using.
