Seems that rats in a British wildlife exhibit were scampering out whenever the keepers watered the plants in order to bathe themselves with the water coming off the leaves. So they're now installing a little sprinkler area for the rats. No more "dirty rats"!
Outside of wildlife exhibits, though, rats are persona non grata (or is that animalia non grata?). An article a while back described a South Norfolk roundabout rat problem.
Evidently the local (human) population had a habit of dumping trash there. Rats, not being stupid creatures, took up residence and began munching away at the free food. The local council and police are pleading with people to stop dumping their trash on the roundabout. Now we'll see if the humans can adapt their habits as well as the rats. :)