Believe it or not, a monster just arrived in these woods.
Don't believe me?
Just listen to what the animals in the monster's forest are saying:
This is a raccoon. She heard the monster.
There used to be wolves and bears here, but they left when humans showed up. She remembers what those big predators sounded like, though, and she'd recognize big-predator-noises anywhere.
Sure, she hasn't seen the monster yet, but she's pretty sure it's around somewhere. Ever since the scary noises returned to the forest, she's been way too scared to go down and fish for crabs in the river.
This is a crab. He heard the monster too.
He thinks it sounds scary, but if having the monster around means the raccoons are all too scared to eat him and his friends, that's OK with him!
Without the raccoons around, there are more crabs than ever. It's like a giant crab-party. All the snails they can eat. Even so, the crab knows the monster must be really terrible to frighten away the raccoons...
This is a snail. She's not scared of the monster, but she knows it's there.
After all, she's way too small for it to eat. She's definitely not happy that the monster scared away the raccoons though, because without them around to eat the crabs, the crabs are eating all of her friends. :(
But wait — do you hear that?! Is it the monster???
OH MY GOODNESS! IT'S HERE!
IT'S THE MONST—
—wait, what? OK, OK, I'll level with you. There wasn't really a monster.
I know, I'm sorry. It'll all be made clear soon. And yes, that's a loudspeaker.
This roller coaster of emotion was a dramatic re-enactment of a science experiment recently conducted in British Columbia.
The point of the study was to show how predators like dogs, wolves, or bears can affect the behavior of animals in a given ecosystem.
To see how local animals reacted to the threat of a predator — even one they couldn't see — scientists put a speaker playing predator noises in the forest.
The study found that raccoons, for example, reacted to the perceived threat by being less inclined to go down to the river to catch crabs. This meant that the crab populations in the river increased. This was, in turn, bad news for the snails, which crabs like to eat.
The simple act of introducing the threat of a new species into an ecosystem caused a cascade of changes. In fact, that's what it's called: a trophic cascade.
And removing a species can change things just as much. As wolves disappeared, white-tailed deer have been eating their way through American forests, changing which plants live and which plants get gobbled into oblivion.
This is why predators and prey are such an important part of an ecosystem — you need both to keep things in harmony.
Forests and other ecosystems are always part of a giant, highly connected balancing act. Adding or removing players can affect not just that animal or plant's immediate neighbors, but it can ripple out to everyone that lives there.
That's why it was worth tricking a few hapless raccoons.