When Pet Battles first came out, there was some speculation on how pets spawned in the wild. Do they spawn in as battle pets, or do they generate first a normal critters and then "transform" into battle pets? Regardless of which one is the case, does killing critters help/speed up wild pet spawning?
While hunting for a specific colored, rare quality maggot in Howling Fjord, I stumbled across a possible answer to how wild pets are generated.
There are three clusters of maggots in Howling Fjord. These groups of maggots spawn in as critters. However, after clearing out one cluster of wild maggot pets and after some time, a different group of maggots would DESPAWN, and a new group of wild pets would spawn (same spot). These new maggots were 100% battle ready, green paw print and all.
I can't be certain, but I think the same number of pre-existing maggot critters respawned in as maggot wild pets. So if there were 5 wandering around, after they despawn, 5 battle-able versions would spawn in.
The transition is immediate and very subtle, so I had to sit and watch it happen at least 3 times before I could believe my eyes.
I don't know if this applies to all pets, or just groups of companions, but it's pretty interesting to think about. Any existing critter doesn't exactly turn into a battle-able pet on the spot, but it can despawn and a battle-able pet could spawn in and take its place.
So taking this into consideration, killing critters could potentially help speed up wild pet spawning. Not just because it clears up a "slot" for another critter and/or wild pet, but because it opens up the possibility for a battle-able version of that critter to spawn in its place. This could be based on RNG or perhaps specific spawning script is written for certain critters.
I have no way to confirm this 100%, and I've only experienced the despawn/respawn situation in Howling Fjord. But this is something that's worth keeping in mind when hunting for wild pets.