Hi Lily of the Valley
The general concensus is that if you see hogs out in the open during the day, especially if they are lying in the sun looking as if they are sunbathing, that they are likely to need help. They may not always have parasites but may be dehydrated, etc. Although if they are weakened for some other reason, they are then more likely to have problems with internal parasites.
One of the problems is that hogs, as with wild animals in general, would not want to give away that they are unwell, so may not appear unwell until they really can’t help it – by which time they are sometimes beyond help. I’m really sorry to hear about the poor hog with the strimmer injury. I know how distressing it is to find a hog in that state – well done for getting help for the poor hog. But hogs with such severe injuries are likely to appear in a worse condition than a hog which might be unwell for other reasons.
Visiting in late evenings whilst it is still daylight during high summer, when it doesn’t get dark until late isn’t so worrying. Also when female hogs have youngsters in the nest they will sometimes come out during the day, presumably to get a rest from the youngsters and also if it is very hot. In those situations they would move purposefully and may settle for a nap in a shady place such as under a bush. The hoglets may venture out of the nest if it was hot or they were thirsty, or mother hog had been gone for a while, but I would expect them to remain amongst vegetation,if possible. But if something had happened to Mother hog they would likely venture out, too and may be squawking and may need help. See further information from ‘Found a sick or injured hedgehog’ – link given below.
In the summer male hogs may also spend the day outdoors, i.e. under shrubs or amongst undergrowth (where they would likely to be naturally if they didn’t have access to a hog house) and it’s not impossible to see them moving from one place to another, for instance if they’ve been disturbed, but I would expect them to remain pretty much under cover if they could and not be out in the open. I would also expect them to be moving purposefully.
If you see a hog which is in the open and looking lethargic, wobbly, moving slowly or still and especially if it has flies in the vicinity, that would be very worrying and indicate the hog needs help.
If in doubt and if you are at all worried about any hogs, and especially bearing in mind that it may be difficult to tell whether they are unwell or or not you can always contact a hog rescuer/rehabilitator and take their advice. With hogs it’s always better to be safe than sorry. Anyone can get contact details of their nearest carers by ringing BHPS on 01584 890801 (also shown at the bottom of this page) if they don’t know one already.
There is some further information about ‘Are Hedgehogs meant to be out in the daylight?’ from BHPS in their FAQs, here: https://www.britishhedgehogs.org.uk/faq/
To try to reduce the risk of dehydration, it’s really important to leave water available for the hogs all day, every day – including during winter when there may be some hogs still around. Wide but shallow plant saucers are ideal for this and they can be positioned around the garden.
Sorry this has rambled on a bit, but things aren’t always as straightforward as first appears.