I have a moustache and I’m not afraid to use it (Image: ChinaFotoPress/Getty)

Video: Horny frogs fight with their moustaches

Species: Leptobrachium boringii

Habitat: New York’s Williamsburg, London’s Hackney and San Francisco’s Mission district. Also slow-flowing streams in isolated mountainous regions of south-west China

It’s the start of the breeding season, and a male toad is poised for success. He has commandeered an excellent rock in the middle of the stream, an ideal nesting site that will surely attract plenty of females. Life is good.


Not for long. Another male approaches – big and muscly, a real brawler – and he wants the rock. What’s more, he has a moustache and he’s not afraid to use it.

Among humans, a resplendent moustache isn’t necessarily a sign of a high-quality male – regardless of what the hipsters of Hackney, Williamsburg and San Francisco’s Mission district want you to think. But for Emei moustache toads, a top-quality moustache is an essential, and violent, weapon.

Spiky characters

With a few exceptions, most amphibians are relatively gentle souls. “Combat is normally wrestling or posturing,” says Cameron Hudson of the University of Guelph in Ontario, Canada.

But not for Emei moustache toads. Males are bigger than females, a clue to their violent nature. Among amphibians it’s normally the other way around; males only outgrow females in species where males fight. In a dozen or so of these species, males grow spines on their upper lips, giving Emei moustache toads their name.

During the breeding season, each male grows 10 to 16 spines. “They are as sharp as a pencil lead,” says Hudson, adding that the frogs “do try to stab you a bit when you pick them up”.

The toads spend most of the year in forests, but in February and March they head to streams to breed. The males arrive first and claim rocks in the fast-flowing water. They spend several weeks swimming around their chosen rock, with hardly any food, grunting underwater to attract females.

Puncture wounds

To find out how the breeding season plays out, Hudson and his colleague Jinzhong Fu monitored moustache toads living on a 300-metre stretch of river near Mount Emei in Sichuan, China, over two breeding seasons. They captured and tagged 77 toads, then checked which frog was in control of the nest sites every day.

Hudson saw seven fights between males, and managed to film five. He estimates that there must have been at least 14 fights on this one stretch of river, as many males lost their nest sites to others.

The males fought underwater, headbutting each other in the belly to drive their spines into the other toad’s flesh (see video). “I’ve never seen any of them kill each other,” says Hudson. “But they get a lot of puncture wounds.”

Females visited the males at nest sites and laid their eggs on a submerged part of the rock for the males to fertilise. Job over, the females promptly headed back to the forest. Their partners stayed behind to care for the eggs: these toads are caring daddies as well as brawlers.

Caring daddies

When Hudson examined the genes of males and the eggs they were protecting, he found that many males took care of eggs that weren’t theirs. They probably drove out a previous male, and took over his eggs as well as his nest site. “I’m not sure if they care for the other eggs, but they don’t harm them,” he says.

It’s not clear why conquering males refrain from destroying their vanquished rivals’ eggs. Having the extra eggs might mean their own are more likely to survive if a predator attacks the nest. Alternatively, females might prefer males that already have eggs, believing them to be high-quality.

It’s also not clear what makes for a successful male. The spines don’t vary in length much, so size may not be a factor. Hudson says the size and strength of the males may be key, as stronger males could drive their spines further into their competitors’ bellies.

All this frantic activity comes to a fairly abrupt end. The last females leave in early March, and the males stop fighting. Their spines fall out. Once the broods hatch, the males head back to the woods and leave the tadpoles to fend for themselves.

Journal reference: PLoS One, doi.org/m42