2. Episode 2

Inseparable penguins Rud and Spike have been a couple for 15 years. But Rud's arthritic hip could be affecting his quality of life. The tigers move house, and a tarantula risks his life to reproduce.

3. Episode 3

The giraffe family have a new arrival. Frog keeper Pip creates a love den to try to get endangered frogs in the mood to lay eggs. And the aardvarks wreak havoc by night.

4. Episode 4

A potentially deadly virus hits the elephant house. Will Chester's female zebras be interested in new stallion Mac? Plus: the bizarre world of the naked mole rat.

5. Episode 5

Boris the chimp takes a moorhen chick hostage. French crocodile François turns his snout up at British food. The keepers try to spark romance between turtles Raja and Aris. Plus: young penguins.

6. Episode 6

Female rhino Kitani is introduced to her new mate, Magadi. But rhino mating is a risky business. There's a surprise birth in the orangutan house. Plus: fruit bats, macaques and young jaguars.