Scientists have been left rather intrigued after a group of penguins in an aquarium were found to be mating with other partners, rather than staying monogamous.

Most penguins are thought to be monogamous, staying with one partner for their entire life and mating each season. Others like Emperor Penguins are serially monogamous, staying with one partner just for one mating season.

However, staff at Loveland Living Planet Aquarium in Utah became suspicious of the behavior of two Gentoo penguin couples – Roto and Copper, and Coco and Gossamer.

They had assumed the animals were raising their own chicks. But to check, they partnered with researchers from Utah Valley University for the first-ever study to test the paternity of Gentoo penguins, now published in the journal ZooBiology.

They tested the DNA of 19 penguins housed at the aquarium and found that two of Coco’s children were actually fathered by Roto in a classic Jerry Springer penguin case of secrets, lies, and questionable paternity.

"The staff that watches over the penguins noticed that some of the penguins were displaying behavior that suggested they might not be 100 percent faithful to their mates," study lead Eric Domyan told Deseret News.

"What we found is that of the eight offspring tested, two of them had a biological father that was not their social father."

According to the New York Times, the discovery did not come as too much of a surprise. Domyam noted that it was “rare to find monogamy in any species where there’s 100 percent fidelity to one’s mate.” Still, the findings could be a bit troublesome.

These Gentoo penguins will be part of a program to pair the most genetically diverse of them together to ensure a healthy population. But for this to work the researchers need to avoid any sort of inbreeding. And if the penguins aren’t as faithful as thought, that could make things complicated.

“The results of this research highlight the importance of genetic tests to validate pedigrees used in SSPs [Species Survival Plans], to provide more accurate data for the support of species conservation,” the researchers wrote in their paper. Basically, aquarium staff can't trust those innocent-looking critters through observation alone.

So, it looks like penguins might not always be the faithful partners we thought they were, but that doesn’t mean they’re any less adorable. Just, you know, they’re a little bit sneaky too.