Nimzy,
I light them, I didnt 1 year and my litters were later and they were spread over more days few here few there, never again without lights, buy lighting they all implant together so a mink bred March 1,10,11 and another mink that didnt bred till March 25 and only 1 time could whelp the same day.

Lots of people will also light there males 2 weeks prior to breeding to get them more ready, we dont we have lots of natural light in our sheds so haven't and havent had issues with the males, but we do give them some enrichment to get.them more active like a golf ball, toy, plastic chain across multiple pens so they can play with the pen next to them

Yes, I train mine for pest control. We don't have very many tree squirrels, so squirrels in the attic aren't our normal calls, but we've done a couple. Most of the time we are getting rats or ground squirrels out from under sheds, porches, or chicken coops, or catching problem muskrats who are digging up the shore.