Season 4

So many hippos congregate to feed in Zambia's Luangwa Valley that they threaten the survival of other species in the park, so the authorities cull around 200 of them every year. The cull offers veterinary scientist Mark Evans and comparative anatomist Joy Reidenberg the opportunity to dissect one of these magnificent animals.

Mark Evans and Joy Reidenberg head to Australia to dissect its most iconic animal, and find the marsupials' reproductive organs to be most surprising - the male genitalia is back to front, while the female has three vaginas. Simon Watt heads into the Blue Mountains with Charles Darwin's great-great-grandson in search of other creatures, including a bird that decorates its nest with an assortment of blue ornaments and a primitive mammal that lays eggs like a reptile.

The team take on their hardest challenge so far, to dissect an entire ecosystem - the jungle. Deep in the rainforest of Borneo they erect a high-tech dissection laboratory to investigate giant bugs and titan trees, and to reveal why the jungle is home to the most diverse collection of living things on our planet. With a team of all-star biologists, anatomists and tree climbers, they delve into the mysteries of the rainforest: how it fits together and the extraordinary roles the strange creatures that live in it play; how waterfalls flow uphill, life springs from death and parasites hold the key to holding the jungle in balance. Veterinary scientist Mark Evans climbs 60 metres into the canopy to catch the world's largest ants; comparative anatomist Joy Reidenberg heads deep into the forest to catch venomous centipedes and giant moths; and biologist Simon Watt investigates the most sinister organism of them all - an enormous parasitic fig tree.