She's after crickets! Red and Blue cattledogs (and red-and-blue cattledogs) have a lot of dingo in their ancestry. Dingoes are carnivores who also eat insects and berries, very much like a fox does.
I watched Polly stalk around the yard, staring at the ground with her ears cocked, then she'd freeze, sit back slowly, and POUNCE the cricket. Both front feet would smack the ground and she'd dig like mad, then shove her nose in the hole. I don't know if she's eating the crickets but the instinct is there.