The wallaby has no effective immune system upon birth and uses antimicrobial peptides to battle diseases. W. Warby

Crop circles: Are they made by alien UFOs landing in corn fields, or are they made by something more sinister, like drug-fueled marsupials running amok on farm land? In Australia, it appears to be the latter.

Australian wallabies have been eating poppy seeds, then hoping around fields while "as high as a kite," according to Lara Giddings, the Attorney General for the island state of Tasmania.

The animals get so stoned that they begin running around in circular patterns.

"Then they crash," Giddings said. "We see crop circles in the poppy industry from wallabies that are high."

Apparently, this isn't uncommon for animals on opium.The same phenomenon has happened in sheep, who begin to walk in circle-formations after munching on poppy plants.

The crop circles have become so serious that they were debated at a parliamentary hearing on the security of poppy crops in Tasmania.

Farmers grow poppies for medicine, particularly painkillers, and Australia produces about 50 percent of the world's legally-grown opium. Opium is derived from the resin of the poppy flower, which can also be refined to make morphine and heroin.

Apparently this isn't a new development, and wallabies have been the cause of crop circles in Australian fields for years.

"They would just come and eat some poppies and they would go away. They'd come back again and they would do their circle work in the paddock," retired farmer Lyndley Chopping told the Australia Broadcasting Company.

A wallaby is a small pouched mammal, related to the kangaroo. They are smaller and often chubbier than the mighty kangaroo, and share much of the same habitat as they inter-species cousin.

Luckily, it appears that the wallabies know when enough opium is enough.

"They seem to know when they've had enough," added Chopping. "They'll still be around and they would leave them alone. It's hard to work out. Didn't seem to be any real pattern to their behaviour."