The Jackdaw plucking fur off a moulting deer the bird gather soft warm nesting material, and the deer gets a free, highly appreciated, grooming that removes itchy, loose winter hair and ticks
These Russian Tortoises (Testudo horsfieldii) were the first animals to go around the Moon! (Along with some fruit fly eggs and plants and such. But the turts were probably the smartest of the bunch.) They went on the Soviet Zond-5 mission.