The best way to check whether a nest box is being used is to place a small screwed up piece of paper in the entrance during the day. When the hedgehog emerges the paper will be pushed out and you will know something has left the nest box.
You can help them to put on weight by either giving them a complete hedgehog food like Spike's Dinner or they can have mashed up, meat based dog or cat food mixed with a little cereal (Weetabix, bran or wholemeal bread) to give it some bulk. They can also have meat based cat biscuits, as these are good for the teeth. They will need a dish of water too, especially if dry biscuits are given.
When feeding hedgehogs you could make a feeding station - eg use either a
plastic mushroom box or child’s toy box or similar and cut a 13cm x 13cm (5”x5”)
hole in one of the short sides. Place this over the food, like a tunnel, and the hedgehog can get through the hole to the food but it keeps the cats out. A brick on top should stop the box being pushed aside. Another brick or large stone placed 13cm (5”) from the entrance should stop a cat lying down and hooking the food out with its paw! Another suggestion is to use a paving slab on some bricks (placed on their sides), leave a 5" gap between 2 of the bricks for an entrance. Always make sure there is a little food left in the mornings - if not, you are not feeding them enough.
When feeding in the winter a lot of food could be wasted. It may be best to offer dry food and provide plenty of water. As a trial, before winter sets in, provide one of the dishes of dry food with a saucer placed over it to protect the food. See whether your hedgehogs realise that by pushing the saucer off they will get at the food. This can be useful in the winter to protect/preserve the food and perhaps keep the water from freezing. By protecting the food in this way you should stop smaller creatures eg mice from getting at the uneaten food.
If you find a sick or injured hedgehog contact the BritishHedgehog Preservation Society they can give general advice and perhaps details of a local hedgehog rehabilitator you can contact. Their phone number is 01584 890801. For information about helping hedgehogs at this time of year visit the BHPS website.