It was long believed that animals only played to learn, only mated to reproduce and only took drugs by accident. But sometimes, they just do it for fun! Research has revealed that animals seek for pleasure just like humans do, and that there are many ways in which they enjoy themselves. Did you know that rats loved to play hide-and-seek? That primates played erotic games to ease tensions within their groups? Or that reindeers were quite fond of hallucinogenic mushrooms? Scientists show that this...