Prove it. I don't trust your evidence.
Prove which
Deer
http://wildlifecontrol.info/deer/Pages/DeerPopulationFacts.aspx
There is also yellowstone elk
"Our discussion begins in Yellowstone National Park. In the late 1800s, Yellowstones game population its elk, bison, antelope and deer began to disappear. So in 1886, the US Cavalry took over management of the park. And its first order of business was to help bring back the game population.
After a few years of protection and special feeding, the game population started to come back strong. But what the government didnt understand was that it was dealing with a complex ecosystem. You cant just change one thing and think that it wont also lead to cascading changes elsewhere.
The surging elk and deer populations ate a lot more. This caused the plant life to diminish. Aspen trees, for instance, started to disappear, eaten by the numerous elks. This hurt the beaver population, which depended on the aspen tree. The beavers built fewer dams. The beaver dams were important in helping prevent soil erosion by slowing the flow of water from the spring melt. Now the trout population took a hit, because it didnt spawn in the increasingly silted water. And so on and so on
The entire ecosystem started to break down because of mans desire to boost the elk population. It got worse. In the winter of 1919-1920, more than half of the elk population died with most of them starving to death. But the National Park Service chalked it up to predators. So it began killing wolves, mountain lions and coyotes all of which only made the problems worse.
This anecdote from Yellowstones past comes from Michael Mauboussins book, Think Twice. He writes: The population of the game animals began to experience erratic booms and busts. This only encouraged the managers to redouble their efforts, triggering morbid feedback loops.
By the mid-1900s, the Park Service managed to kill off nearly all of the predators. In 1926, it shot the last wolf."
This is actually used today to discribe financial markets as ecologies.