Having put some considerable time into my foxing since Jan 1st (90 so far), and listened to the experiences of others, it seems that this year is somewhat unusual where Charlie is concerned. Whereas we'd normally expect to see a new set of cubs at the beginning of summer, we now have two almost distinct sets out there. One lot is too big to be called 'cubs' - I refer to them as sub-adults, while the others are a little small for what you'd expect at this time of year.
On top of this, I saw almost no fox activity during April and May, despite being out almost every evening with both thermal imaging and NV kit. Every now and then I'd see a fox way off in the distance running between two lots of cover - but none of the usual territorial patrolling, ad hoc hunting, and so on.
I've given the matter some thought, and have come up with a hypothesis - namely, that the dominant vixens mated as per usual in November. Given their two month gestation period, this would produce cubs in Jan/Feb. Since the other vixens in the social group are kept infertile by the behaviour of the dominant female - usually by a form of bullying, she is able to determine whether they are allowed to breed or not. This decision appears to be made based on food availability. As we had an unseasonally warm period in February, there was a lot of food about - for a start, there were rabbits everywhere. I think this meant that an unusual number of subservient foxes bred too. That would explain the two distinct cub sizes we've been seeing.
I also think the reason why there were so few foxes around in April and May is that the dogs had cached large amounts of food during the early warm period. Because pretty well all the adult vixens had cubs (of one size or another) they were out of sight, and the dogs had little time for wandering around, so spent most of what they had running to and from their buried food stashes.
At least that's what seems to have happened around here - what do the site's other foxers think?