One Zoo Three

The brothers unveil their biggest and best enclosure yet, a huge new habitat for the Amur tiger sisters Aleena and Siberia. The boys test out the tigers new 80,000-gallon swimming pool and get hands-on as they prepare to move the world's biggest cats. 

Meanwhile, the other animals at the park are treated to a bubble show, Tyler has to clean out the tapir toilet and the boys recall their travels to Kenya to see the world‘s last two remaining northern white rhinos.

It's the zoo's grand reopening and the boys are preparing to open the gates to the public for the first time. 

The night before, they were rudely awoken, and Moto the lion took the opportunity to investigate what the animals get up to during the dead of night. Cam draws the short straw and has to clean out the camel enclosure, while Billy the ocelot is given a pungent treat to play with and the boys recall the extraordinary story of how the zoo was started. 

Meanwhile, the brothers catch up on when they met with rangers on the front line training to intercept and arrest wildlife poachers.

Temperatures rise as the zoo is hit by a heatwave. Many of the animals are well adapted to the sun, but those from cooler climates need extra attention. 

The boys devise a series of ingenious tricks to keep each animal cool, including ice baths, mist showers and giant ice lollies. It's fish flavour for the penguins, lettuce lollies for Marion the tortoise and a huge blood lolly for the big cats. 

Meanwhile, the camels get their yearly comb-down, Tyler has to muck out the stinky Penguin pool and the boys play with an orphaned elephant in Uganda.

The boys welcome some new arrivals to the zoo. Mimo the Pygmy Marmoset emerges from its nest box for the first time and two penguin chicks hatch. 

Meanwhile, it's Tilly the red panda's birthday, and to celebrate, the brothers decide to hold a cake-off. It's a tradition at the zoo that when a new animal in born, all the animals get presents. 

Finally, we catch up with the boys in Rwanda as they meet wildlife heroes fighting to save the planet's largest primates - the mountain gorilla.

It's health check day and the boys give each of the animals a thorough MOT. Tamara the tapir gets a pedicure, Marion the tortoise gets a shell rub and the keepers discover a worrying lump on Luna the reindeer's leg. It's Aaron's turn to clean out the giant anaconda enclosure, and the boys venture to Uganda to ride with the country's first animal ambulance.