How do you get someone chasing ''ghopers''

Ohayo Konnichiwa!

Question: I cant get my people to chase gophers - i have tried dropping them onto the gophers when they pop out of the holes but this doesnt work!

Answer: If you have kids 1 of them will run out in the yard and it will say somthing like "running in the lawn" and you will see them put their arm in the hole. 

You cant make them do it, it happens automatically.