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A café in Brooklyn has become an unexpected center of diplomacy for two of nature's most adversarial animals: cats and rats.

In partnership with the Brooklyn Bridge Animal Welfare Coalition, the Brooklyn Cat Café in New York City typically houses about 20 cats that are up for adoption. Visitors can stop by for treats and to interact with the animals, some of which may end up finding new homes.

In one case, though, a kitten housed at the café was diagnosed with feline leukemia and had to be isolated from other cats to prevent the disease from spreading. Feline leukemia is one of the most common infectious diseases seen in cats. An estimated two to three percent of cats in the U.S. have the virus, which is contained in bodily fluids and is spread by close contact, like mating or bite wounds. After being diagnosed with the condition, cats live for only about two and a half years.

The situation prompted the café owners to seek out a different kind of companion animal for the black kitten, named Ebony. That's how they came to adopt a white rat from a nearby rescue center, which they named Ivory. Rats cannot contract the feline leukemia virus, making Ivory an ideal companion for the small kitten.

Ebony died after five months, but the café owners believe her life was "immeasurably enriched" by having a companion. After two years Ivory died (rat lifespans average around two years), and the café decided to continue bringing in companion rats from a nearby animal rescue center, starting with a pair named Remy and Emile.

According to the café's website, rats are unafraid of kittens because they're relatively similar in size. The kittens often chase and pounce on the rats' tails, which the café says is OK as long as the kittens are gentle.

Domestic cats evolved to be solitary hunters, and kittens learn hunting behaviors from their mothers. When separated early from their mothers or the rest of their litter, some kittens can show too much or too little aggression, according the Humane Society. And when they become adults, their potential relationship with rats gets more complicated.

Katie Lisnik is the director of cat protection at the Humane Society International. She notes that regardless of anecdotal stories about interspecies relationships, cats still act on instinct, and rats are their natural prey.

"Even though bonds are formed, rats can move in a certain way that triggers the cat's [hunting] response," she says.

Sarah Gibbens, the reporter, is an associate digital producer at National Geographic