The wolves were reintroduced into the Yellowstone National Park in the United States in 1995.
1 The Deers
The number of deers increased (because nobody hunted them). That was a problem for us because the vegetation was disappearing. After the wolves arriving (although few) the effects were really visible. They're also changed the deers compartment.
1.1 The Threes
After the deers' changed comportment the threes size was quintupled in less than six years.
1.1.1 The Birds
After the threes' quintupled size the number of songbirds and migratory birds started to increase greatly.
1.1.2 The Beavers
After the threes' quintupled size the beavers too were coming because they like to eat the threes. They also helped the ecosystem because they built niches for other species and dums that provides the habitat for otters, muskrats, ducks, fishes, reptiles and amphibious.
2 The Coyotes
The wolves killed them therefore the number of rabbits and rats increased.
3 Eagles, Crows and Bears.
They increased by eating the wolves' carrions.
4 The Rivers
They began to meander less. There was less erosion. The channel narrowed. More pools formed, more riffle sections.