Ultimately, private citizens may have to be enlisted in the war on so-called water horses. At least, that’s the hope of Allen Ward, president of the Idaho Hunting Alliance. “Now that you can’t shoot a grizzly in this country, you’ve got people craving the chance to take down big, dangerous game,” he says. “Well, we’ve got aggressive four-ton animals in our own backyards. What could be better than that? And I hear the meat’s okay.”

Ward’s idea, however, doesn’t sit well with animal advocates, who argue that hippos are highly intelligent animals that form close social bonds within family units. The San Francisco-based Citizens for Animal Respect and Ethics (CARE) is among the groups touting a $5 billion plan to capture the animals, secure them in large slings beneath the bellies of Apache helicopters, and fly them back to Africa.

“It will be a true tragedy if even a single hippo is slain,” declares Edward Bernard, executive director of CARE. “The only humane approach is repatriation.”

Some environmentalists even wonder whether we should move the hippos at all. “These creatures are filling an ecological niche that has been vacant for ten thousand years,” says Elena Sanchez, conservative biologist with the Pleistocene Rewilding Association. Sanchez points out that North America used to be packed with megafauna, from mammoths to ground sloths. “The hippopotamus could restore much-needed balance to our streams and grasslands,” she argues.

While the management debate rages on, landowners like Larry Sanders continue to bear the invasion’s brunt. After our encounter at the irrigation ditch, we walk back up to his house, picking our way around fly-speckled mounds of hippo dung and through swaths of trampled hay. As we pass through the electrified hippo-proof fence that Sanders has installed around his yard, he turns to look back at the ditch. There stands his nemesis, now hauled out onto dry land, its moist maroon flanks sparkling and its giant head lowered to graze, as though mocking us.

Sanders makes a move toward his gun, but we’re too far away for a shot, and he throws his hands up in surrender. The gate in the electric fence swings shut with a clang and the hippo turns in our direction, not startled by the sudden noise but curious. Strands of duckweed hang from its snout. Its thick lips are curved in what looks suspiciously like a smile.

Ben Goldfarb is an editorial intern at High Country News. He tweets @BenGoldfarb13.