wixipixi comments on Four years after the Fukushima nuclear disaster, one man is still living in the exclusion zone in order to feed the animals left behind when their owners fled.: Most people left and were only allowed to bring a small bag (think about the size of one of the small-ish Jansport book bags) and pets were disallowed. There may have even been a weight limit on how much you could bring. The buses did not allow pets. The evacuation shelters did not allow pets. You may find a few pictures of one or two people with a tiny dog in a shelter, but these are exceptions. These shelters were tiny. People basically had enough room to lay out a futon (if you are unfamiliar with them, they are roughly the size of a twin mattress) and that was it. THAT was the amount of space they had to live in, with hundreds of other people doing the same thing in the same room. Everything they needed had to fit within those confines, and anything that may be a burden was banned from the centers.
To put it more directly: People were forced to leave their pets behind.