Kate Humble and Ben Fogle return to Longleat Safari Park for another spectacular summer series following the fascinating stories of the exotic animals and the keepers who look after them.This year, the park and the world celebrated when the first southern koala was born at Longleat. Hazel is growing up fast, but koalas are notoriously difficult to look after, and Hazel's development is monitored day and night. One of the precious koalas that arrived at the park five years ago, Wilpena, died, and the first sign of problems was a steady weight loss that pointed to kidney disease. It's for this reason that every weigh-in is a nervous moment. Is the precious new koala's weight heading in the right direction?Over the years, we have trained our speed gun on some of the most impressive animals on the planet. On paper, the fastest two at the park should be the cheetah and the ostrich, but it has not been easy to get them to run flat-out at the park. One species that we have never clocked the top speed of is the hyena. In the wild, they are endurance runners and can run for several kilometres at a pace of approximately 40 miles per hour. Can Kate and keeper Kayleigh get them running?Wildlife cameraman Hamza Yassin spends an hour studying the famous lions at the park, but he gets more than he's hoping for when handsome Harry gets amorous with one of his lionesses. Zoologist Megan McCubbin gives a home makeover to the emperor scorpions, and a tiny zebra mouse has an appointment with the dentist.