After fighting the creepy spider guy, you deserve a little break. A fight with a true sportsman who doesn't think of your pets as a tasty treat is just the ticket. Of course, why he's hanging out in the jungle near a bunch of old troll ruins is beyond me.
This guy has two beast friends and one cool looking magical emerald cat. If you've got a Mechanical, he's a pushover. Otherwise, you should probably make sure most (if not all) of your pets are level 9.
Moonstalker is a cat. Which means he's fast and deadly to critters. He's not that tough against anything else. Put a mechanical or flying pet on him and you're set.
He has one ability to look out for called Prowl. This ability slows him down for a turn and then he hits for extra damage on his next attack. The good news is it's pretty easy to avoid and won't one-shot anything but critters.
Nanners is a big barrel throwing gorilla (think Baby Donkey Kong). He hits pretty hard against most types of pets. And extra hard against critters.
He also has this ability called Barrel Toss that hurts. When he first uses it, it gives him a small damage boost (I think). But when he tosses a full barrel it can hit your pet for half of their health. He tends to do this when your pet or his pet is below half health.
Emeralda is very cool looking but not very tough. She has one beast ability that doesn't hit for much and one magic ability which only hurts flying pets. Put a critter or any other pet that isn't good against beasts on her and you should be fine.
In conclusion: unless you have a critter heavy team, this should be an easy victory.