A National Geographic video of a “home-wrecking penguin” went viral this weekend, with many amazed at the violence that ensues when penguin love goes astray. Anthropomorphism aside, the video shows the “husband” penguin returning to a nest to find his lady with a different male penguin. Two bloody fights transpire, and the female penguin chooses the other guy in the end. It’s a rough day for the cuck and a sobering moment for people who thought penguins were just silly tuxedoed birds that always mated for life.

The species in this video are Magellanic penguins, which are typically socially monogamous birds. An average of 72 percent of these penguins mate with the same bird every year.

“But pair bonds may be broken for a variety of reasons including mistimed arrival at the breeding site, mate death, breeding failure and availability of higher quality mates,” Michael Polito, an assistant professor of oceanography and coastal sciences at Louisiana State University, tells Inverse. “That said, it is not uncommon for socially monogamous birds to not be strictly monogamous in their mating.”

Polito also raises a point that has been lost in the media’s narrative, which posits that the “husband” returned to find his “wife” cheating.

“While it was portrayed as a resident male coming back to the nest to find an intruder, it may also be the opposite case,” says Polito. “This could equally be a video of an intruder male coming to an occupied nest attempting to displace a resident male, and the resident male fighting off this intruder and maintains his female mate.”

While “nest intruding” behavior hasn’t been studied in Magellanic penguins, it has been evidence among a very closely related species called Humboldt penguins. A team of researchers discovered in 1999 that, of the penguins they observed, around 20 percent of male and 30 percent of female Humboldt penguins nested with a bird that was not their mate. Sabrina Taylor, also an associate professor at Louisiana State University, explains in her paper “Aggressive Nest Intrusions By Male Humboldt Penguins” that sometimes intruder male penguins would attempt to steal nests and mates. This typically happened when penguins entered the nests usually occupied by breeding pairs — in one of the observed fights, the battle lasted over two hours.

This destruction of penguin love is another example of why they aren’t just bumbling birds — remember that Adélie female penguins sometimes choose enough to trade sex for stones to build nests. It may seem like a soap opera to us, but it always comes down to the survival of the fittest.

Photos via National Geographic/Giphy (1, 2)