W/O seeing the yard, it's hard to tell from here what you might have. Moles usually have a few enter and exit holes but not anything you can, say, 'fall into'. (Maybe sightly sprain your ankle if you hit it the wrong way, sight-unseen.) Grubs are Japanese Beetle Larva. Lots of critters and especially crows like them. Moles in our area are most active from Spring to Fall (in S-eastern PA.) I don't know if they hybernate.
If you need help, ask your neighbors all around. Or, take a few pictures (close-up and on an angle) and take them to a Nursery or a Home Center. If you want to know what Grub-X is, it's in the Nursery and the Home Center. You can search the WEB for 'grubs' for more info to see if that's your problem.