In Australia, David reveals newly-discovered behaviour. On a flooded road by a small river, over 40 huge saltwater crocodiles gather and work together to feast on migrating fish. Just like bears feeding on salmon, they gather together especially for this event and dramatically pick off fish as they leap through the air. This is remarkable behaviour, since these crocodiles are highly territorial and have to suppress their aggression when they are massed together.
This cooperative feeding behaviour has only recently been discovered - saltwater crocodiles are usually highly territorial creatures.
The animals were filmed with the help of infrared cameras because the spectacle took place during the night.
Mullet migrate in spring; they wait for the high-tide so they can swim up-river to breed.
The crocodiles knew when to gather at the river. The BBC crew filmed them picking the mullet off one by one as the fish swam past.
The footage was recorded for BBC One's Life in Cold Blood.