Police have condemned the “unacceptable and dangerous behaviour” of youths at a York nature reserve.
They have been screaming at the cattle who graze on Hob Moor.
And some of the young people have ridden off-road motorbikes to chase the cows.
A North Yorkshire Police spokesperson said: “Livestock worrying is a crime and causes devastating damage, upset and financial loss to farming communities.
“We are calling on all parents and carers to make their children aware of the safety, emotional and financial implications this can have.
“This anti-social behaviour is unacceptable and causes the cattle to be alarmed, which in turn could put those responsible or others in danger of being seriously hurt.”
They said that cattle can be seriously injured in their panicked attempts to escape. Fences can be damaged too.
And it can be “traumatic” for farmers who have to deal with the aftermath, and take a financial hit.
Police ask anyone with information in relation to people chasing livestock, to report it to them via their website or by calling 101.
Information can also be passed to Crimestoppers anonymously on 0800 555 111 or via an online report.