Lions are strangely social, the only wild cats to live in family groups. Lion expert and BBC Big Cat Diary presenter Jonathan Scott investigates the reason why with the help of the most famous lion pride in the world - the Marsh Pride of the Masai Mara in east Africa.Jonathan's intimate knowledge of this massive pride and their various subgroups helps him explore the possible reasons for the lion's social lifestyle. While there are some apparent benefits to living in prides, from cooperative hunting to raising cubs, none appear to be a reason enough to evolve social living. Now, after 30 years of intensive study, the Serengeti Lion Project, lead by Professor Craig Packer, may have finally found the answer and it could have direct consequences for the survival of the lion as a species.