Drug lord Pablo Escobar died in 1993. But his legacy lives on. For example, more than 40 hippopotamuses roam free in Colombia, stemming from a handful that wandered away from his private zoo. It's the largest population outside Africa.

Natural history filmmaker and author Lucy Cooke mentioned what have been dubbed the “cocaine hippos” on a recent visit to New York City from her home in London. She was in town to talk about her new book The Truth about Animals: Stoned Sloths, Lovelorn Hippos, and Other Tales from the Wild Side of Wildlife.

Cooke rounds up tales of 13 species—her “menagerie of the misunderstood.” Some animals have a bad reputation to this day based on medieval texts, including bestiaries, which “mixed up fact with folklore and a lot of morality,” Cooke remarked.

Our still negative image of hyenas may date back to the salacious conclusions moralists drew from the animals, before more open-minded field researchers realized that the larger individuals were actually females sporting what is called a pseudo penis.

On the other modified forelimb, penguins do that humanlike upright walk and have a tight-knit family structure that led conservative commentators to laud the 2005 documentary March of the Penguins, Cooke said, for its display of “models of Christian family values.” But, she continued, “unfortunately, penguins are birds with little, tiny brains ... and they're programmed to have sex with anything that moves and quite a lot of things that don't move, like dead penguins.”

Moving slightly faster than the dead are sloths. The first Spaniards to see them were not impressed. Cooke quotes the conquistador Oviedo, who wrote that the animal was “the stupidest thing that can be found in the world.” But he was looking at a specimen sprawled on the ground. “Gravity removes its dignity,” Cooke said. When enjoying its evolved arboreal lifestyle, however, the sloth is a genius. It's “an incredibly energy-efficient way to exist,” she added. “All you need to have is strong hands to hook on and hang .... They require [significantly] less muscle than most mammals, so they burn much less energy.”

The endangered pygmy three-toed sloth lives only on a small island off Panama, where it eats leaves “believed to contain alkaloids with a property similar to Valium,” Cooke writes in her sloth chapter. Hence the stoned sloths of her subtitle.

Speaking of drugs, Escobar had kangaroos, zebras, giraffes, rhinos and other exotic living booty, in addition to the starter set of four ornery hippos. “One male ... nicknamed El Viejo—‘the old man’—and three females,” Cooke explained. When Escobar violently bought the farm, most of the animals were sent to zoos and other facilities that could care for them properly.

“Apart from the hippos,” which, she noted, were too massive to be moved. They “couldn't have been happier.” In Africa, they face challenges of drought, competition and predation on their young. “Whereas in Colombia, the hippos have got all the rain all year-round, verdant fields to graze in, no hippos to compete with and no predators. So the population of Pablo's hippos just went boom.”

Rivers in Colombia serve as what Cooke called “hippo superhighways,” making it easy for hormonally active young males kicked out of the group by the jealous El Viejo to quickly find a new home. But the hippo harem lifestyle means that females stay close to home. And so intrepid explorers won't find female companionship, leaving them “sexually frustrated Lotharios,” aka lovelorn.

Possibilities for population-control plans include killing the invaders, which many hippo-liking Colombians are against. After all, hippos are charismatic enough to get Jada Pinkett Smith to voice one in the Madagascar films. But they are actually quite dangerous—being hit by a charging hippo is like getting run down by a 1973 Cadillac Fleetwood doing about 30 mph.

Or “Plan B, which was a radical castration program.” But “hippos have internal testicles.” And they can retract when grabbed by forceps. A castration is thus long, expensive and potentially perilous. Looks like we'll eventually find out how expensive it is to have an ever growing population of hungry, hungry hippos cruising down the rivers of South America. Looking for love.