 We have a story of endurance now from the animal kingdom. Two lions have been filmed making what looks to have been a record-breaking one and a half kilometre swim across and along a crocodile-infested channel in Uganda. Their feat says a lot about their determination to get out of the way of humans and also to mate. As Craig Packer explains, he is founder of the Lion Centre at the University of Minnesota in the US and he's been analysing what happened.