We clean out the nest boxes each year, when we are expecting the hedgehogs to come out of hibernation. We keep an eye on them during the year and if we suspect they are getting a bit grotty inside we will give them a clean during the summer, but when a hedgehog is in residence it is difficult, and we don't like to disturb them, so the cleaning only takes place during a change of tenant in normal circumstances.
We cleaned all the nest boxes in the autumn, when all the hedgies had hibernated, but we leave plenty of nest material in case we have one looking for accommodation during the winter. We also give them a clean in the spring, since they could have suffered over the winter. When we clean the old bedding out, we normally leave the boxes empty for a few days, to let them "air" with the roof off during the day if the weather is good. We cleaned 9b out today, since we are expecting lodgers soon - we wonder if Alfie has made it through the winter, and if so if he will move back into 9b, his home for the whole of last season.
It reminded us of Alfie's arrival last year - on the 6th April, almost a month later that the first hedgies arrived this year.
We mistimed the clean out last year. When Alfie arrived, 9b was completely empty, except for the remote sensing thermometer. The poor chap looked rather bewildered, as if he couldn't believe there was no bedding. He even lays down for a ten minute nap - but goes out.
The next day we put the bedding in - and when Alfie returned the next night he moved in, and stayed every night until he left the garden to go into hibernation in September.
Let's hope Alfie returns this year. We got very fond of the little chap (he wasn't so little by the autumn!)