Well I would say - leave out a tin of cat food and a tin opener and see if they can figure out how to open it. If they give up and order a takeaway instead, you know you've got two blokes there. But I wouldn't want to be sexist!
In all seriousness, I believe it's pretty hard to tell the difference without taking a peek at the nether regions. Males may be a little bulkier, but I'd imagine the size difference would be marginal, particularly at this time of year when both sexes should be fattened up ready for hibernation.
They really should be thinking about hibernating now, but will come out occasionally if the temperature isn't too low. Let's just hope that all that cat food you're feeding them keeps their weight up for the winter. Hedgehogs are in real trouble at the moment, and need all the help they can get, so I applaud you for buying food for them!
Lucky you having hedgehogs in your garden. I'm sandwiched between two "concrete gardens" with homeowners that don't give a damn about flora or fauna of any kind. It's been years since I've seen a hog round here.
