More nibbly

Carnegie medal winner Emily Gravett employed rats to nibble and pee on the paper she used to paint the pictures for Little Mouse's Big Book of Fears (the story is by Charlotte Higgins at the Guardian):

Over the six-month period in which she was creating the book, Gravett would leave plain pieces of cartridge paper painted with yoghurt in the rats' cage. After a few days, when it came to cleaning it out, she would retrieve a chewed up, peed-on sheet. She then scanned the paper and used the resultant image, mostly overlaying it on to a more textured sheet of paper to create the look she wanted.

Usually, the pee would have dried. Once or twice, it hadn't, leaving Gravett with the "disgusting" task of wiping her scanner clean of rat urine.

Button, she said, was the artistic rat, being "more nibbly" - for which, perhaps, read greedy, because he was also "hugely obese". And they were both marvellous pets, confirmed the author - "just like very small dogs".