Orca mothers keep 5-tonne sons out of trouble

Older, "post-menopausal" orca mothers protect their adult sons from fights, according to new research.

The study examined tooth rake marks on the animals' bodies - inflicted in confrontations with other orcas.

It revealed that, when an adult male's post-menopausal mum is with him, he is much less likely to be harmed.

But, while four or five-tonne males benefit from this maternal protection, female offspring do not receive the same attention.