Any gym-going female human knows just how much men like to show off their muscles. But it turns out that it’s not just male humans who think that flexing their biceps at ladies is an effective strategy to win them over—kangaroos do it, too. According to new research published in the Biological Journal of the Linnean Society, male kangaroos strike poses that show off their arms.

Much like human males, male kangaroos use their arms to wrestle away rival mates. So the researchers thought they would look to see whether male kangaroos with bigger biceps seemed to be selected for. They were. Ellen Adamcewicz at The Conversation spoke with Rod Wells, a kangaroo expert, who said that the bulging biceps might mean an “additional advantage from either females finding big forelimbs sexy or alternatively the males which win the right to access the females are then strong enough to overpower any unwilling female.” In other words, kangaroos appear to show off those fighting muscles to females, who are wooed by them.

People who are familiar with kangaroos might not be that surprised, as the animal has been a symbol of strength for a while. The Royal Australian Air Force used a boxing kangaroo starting in 1891. For a while, kangaroos would fight men in boxing rings. And, in fact, a male kangaroo biceps are a lot more impressive than you might think.

There is little research on whether the bicep flexing of human males works on human females.

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