Hi Andria, according to the ferret vets I know around 50% of ferrets have adverse reactions to being left in their oestrus cycle. Most young ferrets seem to cope with being left in their first season but a friend of mine lost one of a pair of yearling jills last year after telling me "my other jill was ok last year so I'm not giving them hormone jabs this year". Some bloodlines seem stronger than others but I get all my jills hormone jabbed every year these days. Chris. Wessex Ferret Club=20 www.wessexferretclub.co.uk [Posted in FML issue 5196]