Most of the time, the life of a male Emei moustache toad (Leptobrachium boringii) is a tranquil affair. But for a few weeks of the year, the urge to mate transforms these rare toads into muscled-up, weaponised fighters. Their weapon of choice? A spiky moustache.

Take a look at this photo of a male toad taken just as breeding season is wrapping up for the year.

Spiny -moustache -toad 2_2015_07_10
Image: © 2013 Hudson, Fu

Now, look at the difference when mating is at a frenzy. What's that growing on your upper lip, Emei moustache toad?

Spiny -moustache -toad _2015_07_10
Image: © 2013 Hudson, Fu

That impressive set of spikes sprouts forth in preparation for an annual gathering of lustful male toads that determines who gets lucky. And the transformation doesn't end there: the toads' forearms also pack on power, making them look bulkier.

"Each male can grow between 10-16 sharp, conical black spines, which re-grow if broken during this time. The spines are 3-5mm in length, and are oriented away from the snout," writes a team of researchers who observed dozens of the amphibians over the course of two breeding seasons in Sichuan, China. Their findings are published in the journal PLOS ONE.

When breeding season kicks off, around February or March, male toads emerge from their usual forest hangouts and gather in rivers and streams, croaking out sexy songs to lure females their way. And then things get combative.

Over the course of two or three weeks, fighters repeatedly butt heads in watery duels, wrestling and driving their face-spikes (also known as nuptial spines) into the flesh of rivals. At stake is dominion over the best nesting sites and the precious egg cargo they hold.

It all looks something like this:

But after all the violent duelling is done, victors conduct themselves in a gentlemanly fashion befitting a mustachioed amphibian. When taking over nests, conquering toads will spare the eggs of their rivals, although there are probably good reasons for their benevolence: having more eggs around might up dial up a male's allure, for example.

And the toads don't shun daddy duty either. While the females return to the forest when their eggs are laid, the males stay behind to care for the clutch until the tadpoles emerge. 

H/t: io9