- And got the T-shirt
The acid test of a boar is being able to extrude the penis. Failing that, if you rub your finger crosswise across the abdomen right at the genitalia, you should be able to feel a penis bone if there's one there.
I've spent so much time looking at and photographing pig butts...LOL
I'll try again in the morning, the concept of having more litters is making me panic but we don't have enough cages to separate them individually until it's sorted out!
I asked our vet but she said she's not the best at sexing them because she doesn't get much practice :-/
- Supporter in 2019
Ditto bpatters' comment about feeling for a somewhat hard, slightly raised area above the penis and trying to extrude (pop out, for lack of a more delicate way to put it) the penis itself. By very gently pushing in and pulling upwards (up towards the guinea pig's tummy) along that ridge above the penis, you can usually get the penis to make an appearance if it's in fact a male.