Recreational drug usage in the wild: stoned reindeer and junkie monkeys
You don’t need an IQ much larger than your shoe size to realize that humanity is forever questing for an alternative reality. Apart from the behemoth industries peddling legalized drugs (alcohol, tobacco and caffeine), the extraordinary profitability of heroin, cocaine, marijuana, methamphetamine and the rapidly growing number of synthetics now constitute the single largest income stream of criminal and terrorist organizations worldwide.
Human drug usage began at the dawn of civilization and we may have sought out the first mind-altering substances by watching the behavior of animals which indulged (goats in particular).
Indeed, this fascinating article by Andrew Haynes details the use of naturally-occurring (as well as man-made) psychoactive substances in the animal kingdom.