My group is currently on a roadtrip through the NAN/UCAS (the US in 2071) from Seattle to Boston, driving a ton of chocolate for the Irish mob. They are pretty much all street kids and none of them have spent any significant time outside Seattle. So they are not sure what to expect, but they have heard stories of the trouble outsiders have in the Native American Nations and about awakened (magical) animals and plants.
In real life, one of my players is an old hand at Shadowrun and he has been verbosely paranoid about all the bad things that can happen when you mess with Nature in the NAN. Normally, dark hints would have been my job as the GM, but all I had to do was let him talk.
The group decided to make camp at the side of the road somewhere and hunted down a porcupine (plus its three babies) for dinner. Three of the characters were busy in the woods and two were left in the camp, making a porcupine BBQ. The sight attracted two ravens - they were big birds and they just sat there, watching. The characters start to get nervous and throw them some meat, in the hope that they will go away.
That cunning plan failed, you will be surprised to hear. More ravens appeared, just sitting there, behind the characters. Who grabbed the big porcupine and ran to their truck, locking themselves in, waiting for enforcements. The ravens were left to enjoy their meal more or less in peace and to crap all over the campsite. Oh, and they stole the cookset.
I had originally planned to confront them with Stormcrows, the awakened raven species. These are even more intelligent and can influence the weather. But I quickly realised that this would have been a total waste, my players were absolutely freaking out about a couple of ravens. Alfred Hitchcock would have been proud. It was a lesson in keeping things simple for me and in relying on the fact that characters, given the opportunity, will get themselves into trouble. That's no reason to get lazy with the session planning, but it doesn't always need to be the big monster.