The simple fact is larger groups have a larger more detectable foot print than a smaller group.
First, just the noise levels and the vibrations on the ground that 50 people cause versus 1.
Then there the pollution, waste products, and smells. A large group disrupts a large portion of the forest as it goes through and is far more noticeable.
Cooking fire for 1 vs 50 is going to be way more massive, and the scent and smoke will travel everywhere. A single adventure might limit themselves to precooked food they can eat without starting a fire.
Everything is larger, bathrooms for 50 is going to generate tons of waste and probably emit a large amount of smell. Way easier for an animal(s) to track.
They will form a large camp which will be super easy to spot from a distance.
Our own body oils will ruby over everything we touch and brush up against,break branches, and etc, forming an easy path for animals to follow.
So your creatures are variable sensitive to sound,smell,and vibration depending on the group size you want to be attacked. Also it doesn't hurt if the animals are larger so they have a bigger appetite thus there hunger will be better satisfied by eating a group of 50 adventures vs 1 which isn't even a snack.
The biggest problem here is that more adventures will be better equipped to handle larger more vicious enemies. A party of 50 can have 20 machine gun operators, and 5 missile launchers.
I am thinking like in the movie "tremors" with the large hazardous earth worms that are sensitive to just the things we are looking for here. While its underground its pretty much safe from machine gun and missile attack. Otherwise we would just drop bombs on them from 2000 feet up where they can't reach us. Even if some of your animals can fly they can't keep up to a plane at 500+ mph.