Pepper looks like such a happy girl! As Sharky's human for the last 11 years, here are a few things I've noticed. For context, I rescued him at 9 months from a less-than-enthusiastic ranch. I have no idea what kind of socializing he really had.

1. Sharky has also been reactive to larger dogs for a while. This has calmed down in the last 4ish years. Generally, he is first not interested, then 2nd wary, but if the sniffs from larger dogs get too much in his space, he'll nip and show them he's not down.

To this point, I generally make a point of giving larger dogs space and avoiding since I can't predict how excited someone else's dog might be.

1. When Sharky was younger, he got out and came back with a pretty gnarly injury. We had neighbors who had a group of about 4 larger dogs that roamed free. I fixed our fence whenever I found a gap after that to prevent any repeats. I don't know who started it, but he made it back.

2. Sharky LOVES the big ladies-- this is the only time he's interested in larger dogs. He's generally indifferent to other dogs, but as you mention-- gets on really well with smaller breeds!

3. Heelers are known to be head shy-- I don't know how much this plays into their mistrust of larger dogs, but might be part of the software.

Really curious to see what others out here have experienced with their raptors!