A zookeeper weighs Humboldt penguins during the London Zoo annual weigh-in event on August 24, 2016. Home to more than 700 different species, ZSL London Zoo staff regularly record the heights and weights of all the creatures at the zoo as a key way of monitoring the residents’ overall well-being. This important information is shared with zoos around the world to help zoologists compare details on thousands of endangered species. (JUSTIN TALLIS/AFP/Getty Images) Oh my, look how they've grown.Penguins, squirrel...