How to choose a male gorilla to keep females happy
4 August 2010 Last updated at 02:17 BST
London Zoo is introducing a new male to its group of gorillas.
They have been without a troop leader since the last male died in March, but keepers say the introduction of Kesho - from Dublin Zoo - is a tricky operation.
A new baby is expected in a couple of months, but there is a risk that the new male could kill the baby.
David Field, director of the Zoological Society of London, explains why a they need a new male to join the group.