From the city of Jena in eastern Germany comes news that – after three years of experimentation – researchers reluctantly have concluded that their objective cannot be achieved. And it's all Mats's fault. Who is Mats and what has he done to blunt the advanceof science? Well, ah, Mats is a sloth – one of the species of medium-sized mammals that are native to Central and South America and are best known for their lack of get up and go. Which is what scientists at the University of Jena's Institute of Systematic Zoology and Evolutionary Biology were trying to overcome. Since sloths live in trees, they had hoped to observe Mats climbing a polein their laboratory and then backing his way down again. But he wouldn't ... despite being offered such inducements as spaghetti and cucumbers. Sloths, you see, mostly eat leaves, digesting them so slowly that the process can take more than a month to complete. Result: an extremely low metabolism and lots of sleeping – as many as 18 hours in every 24. Said a spokesman for the institute: "Mats obviously wanted nothing to do with furthering science." So he has been packed off to a zoo elsewhere in Germany, where he is said to be resting comfortably.