Two by two: London Zoo holds annual count

London zoo held its annual stocktake on Wednesday, cataloguing the 184-year-old zoo's entire collection of mammals, reptiles, inects, fish and birds. The data is used to monitor the success of the zoo's breeding programmes, and can be accessed by other zoos around the world. But with more than 18 thousand animals from hundreds of different species, counting them all is no simple matter. Duration: 01:53