To answer the question about the group coming. The first sow to respond is generally the "lead Sow" They are not always the biggest as Brian states, they are always the most aggressive. In some some cases there are 2 sows that share this position, they are usually sisters or mother and daughter. While this is hard to prove in the wild without DNA testing, that is what I've observed in penned feral hogs. They share the maternal responsibilities.
One very cool thing I've filmed while tinkering with new toys. I spotted 2 sows with very young piglets in an open field mid day. I called to them, The lead sow responded immediately. Since this was a test I had no intention of shooting either of them right away. So I let the lead sow come on in, which she did aggressively. The second sow took both litters of pigs with her to safety and then came to the calling. Both sows came in saw me in plain clothing and winded me numerous times and still responded to the call 7 times total on video. For contractual reasons I can't share the video yet, but it is coming eventually. very cool to watch.
Now after watching Brian's videos in the first video the hogs that wouldn't cross the fence. I've discovered hogs don't like to "jump through hoops" meaning if there are too many obstacles hogs will give up. It looked to me like that fence had extra wires, tight maybe, possibly looking for an easy trail. Also hogs have territorial boundaries in some cases. It is very unusual to see 2 separate matriarchal groups join together many variables to consider. They did respond very well to begin with, pretty cool! DANG FENCE, Good ethics my friend.
the second video where it appears that hogs are looking for other hogs. They are catching scent of something they don't like hence the heads up. Prime example of the wind playing tricks, this happens a lot near variations in the landscape or drifting thermals. I've learned more about this in the since August than I have in nearly 40 years of hunting thanks to a very cool wind detector. When hogs are looking visually for other hogs they lower their heads nearly to the ground as if looking for bait and bob up and down like a deer that has spotted something she doesn't like. If you watch my videos you will see both instances. Boars responding to my Boar Specific sounds head bob a lot!
Brian in instances like the 3rd video when hogs seem oblivious to calling keep changing the sounds and volume. If they don't respond right away you have an advantage over me, you are a patient man, Turn the sound off and stay quiet for a few minutes, then play a new sound quietly at first and increase in volume, repeat until your run out of things to throw at them. In most cases when they have been called the night before, nothing helps. But you have nothing to lose by throwing the whole bag of tricks at them.
Good videos and good teaching tools.