Hi Catherine
It would be a good idea to get the little one checked out as Stef said. If it was with Mum and you don’t know why she died, the baby could have a problem too. It would be unlikely to show it, so possibly still eat, until it got really ill. That’s the way hogs are.
You can get the contact details of your local hedgehog carer/rescue/rehabilitator from BHPS 01584 890801 You can explain the whole thing to them in more detail and they can advise you about the best course of action.
Good luck.
