There are lots of wildlife in big cities as long as there are some relatively quiet ecological tunnels left there (usually around the rivers). I'd expect it to

There are lots of wildlife in big cities as long as there are some relatively quiet ecological tunnels left there (usually around the rivers). I'd expect it to take weeks, maybe even days with good weather and some luck, to get animals like deers or boars to roam freely across the whole city (they already do at night in some places) if humans had suddenly disappeared. However, unlike those from some of the currently viral reports, these animals are already there - they're just pretty good at hiding from humans, so most people don't even realize it.