- [Narrator] The team discovers something astounding: a male panda under a tree and a second male, a challenger, in the bamboo.
Above them in the tree, a third panda.
It's a female, probably the only one in the area.
So she's there one chance.
Guarding her as the dominant male at the base of the tree.
Nothing like this has ever been seen before.
(panda bears growling) The rival backs away.
Female pandas are only fertile for a couple of days.
So every male battles to be in the right place at the right time.
After an hour, she starts to come down.
The male has to be careful.
Females will attack and can injure males if they don't want to mate.
(panda bears squealing) The couple of fight for only a second, he retreats and she makes her escape.
She's not ready.
Both males will follow her until she comes into estrus.
Calls between the male rivals become more frequent.
A showdown seems inevitable.
(panda bear roaring) The challenger is to the left.
He's younger and takes the high ground.
An advantage in a fight.
The old dominant male backs down.
But then he rallies and comes back in.
It's a psychological battle as much as one of strength.
This stressful buildup has taken weeks.
A week later, the female is found in a tree with no sign of either male, the female panda peers down.
The younger male and no sign of his elder.
Youth has won out.
He sniffs, licks the ground and drools.
She's coming to estrus and is finally ready.
(panda bear squealing) Then, in what they may have imagined as a discreet corner, they mate.
The roaring, scent marking, fighting and being held hostage may actually trigger her ovulation.
It's similar in other bear species and it explains why pandas have such problems breeding in captivity.
Wild animals lead complicated lives.