I can nearly reach it...

I'm assuming he can smell some rodent and is trying to get at it. I'm not aware of him ever catching anything like this, but he's really motivated to hunt for things in the grass at the hippodrome. As long as he doesn't dig, I let him pounce, and sniff. If there are any holes I don't want him making them any bigger in case the create a trip hazard for the horses.