Is it a Harry or a Harriet?
It would be so much easier if boy hogs were blue and girl hogs were pink.....
Playing the Peeping Tom
Most hogs aren't going to let you turn them on their back to get a good look at what's under there. It's their vulnerable area so they curl to protect it. Babies are more amenable which is just as well as it takes a while to work out what they are even with a very good view. Adults will be more difficult, so this is where you get let into my trade secret... Pyrex!
Find yourself a good sized glass casserole. No, we are not going to microwave the hog, we are going to put it in the dish which, being Pyrex, is clear glass. When the hog relaxes out, we lift up the dish and sneak a peek underneath.
What bits go where?
In male hedgehogs the penile sheath is located about halfway up the tummy and looks like a large belly-button.
In females the sex organ is directly adjacent to the anus. Females will also have a row of nipples along each side within the tummy fur. These are often hard to see but show as small pink spots if you have the chance to look carefully.
In babies, it can be difficult to tell sexes apart due to the small size. Little boy's bits start off in the same place as little girl's bits and slowly move towards the chin as they grow. Beyond the baby stage, the rule of thumb is that if you look and can't tell for certain, it's probably a female. If you're desperate to name the little scrap then choose something that can be modified genderwise. Somewhere around this area is a very large, very masculine hog going by the name of Rosie. Yes, well, we all make mistakes.
A Picture Paints a Thousand Words
The picture below is courtesy of the wonderful Wildlife Information site and if you want more in depth information on Hedgehog biology, I suggest you take a visit to that page.
For the eyesight challenged such as myself, the female is on the left and the male on the right