Free: Contests & Raffles.
I think I have a 32gig card in my Gopro 6 or 7. It will record for at least an hour or more at 1080p not sure how much on 4k. Batteries may not last that long if it is cold out.
On my list too. Get 7 black $400. Image stabilization is very good. Waterproof to 33ft. Top quality vids.
I did this, you'll want to look at lens options or you won't hardly be able to see the predator you're shooting at. fish eye makes the predators very small and distantI think I have the old gopro 3-4 and records like 720p As for the duration it depends on the recording quality, if you're recording at 4k that is a massive chunk of memory and will require a HUGE sd card, back the recording quality down and you'll get longer times. Also 4k would require a lot more battery, I was constantly buying batteries and after market batteries trying to extend my sessions but only really got to 30 mintes or so. I was recording snowmobile movies, predator calling and other crap so I had quite a bag of accessories. I think for predator calling a scope mount with proper lens would be good. Although I think I'd skip the go pro and just get a real vid recorder where you can use other memory options and external batteries..not to mention proper lenses and zoom. Models a few years old aren't bad.