In a werewolf story I read recently, the protagonist (a werewolf) remarks on her new-found senses. Especially smell: “Urine. So much urine. It never occurred to her how surrounded by piss she was at all times every time she stepped into the woods.” Think on that next time you go tramping.

It similarly occurred to me to be grateful for human hearing, when I learned just how loud bats really are. Bat echolocation calls are typically two to three times higher in frequency than the human ear can hear. Which is a blessing, because the sound pressure of an individual bat is around 100–110 decibels – which is like sticking your head in the speaker box at a rock concert. The cacophony of a group of bats is at the level of an aircraft carrier deck.

But bats are far from the only creatures screaming their lungs out in the forest. Alex Jones may have been worried about the frogs turning gay but, long before they were flaming, the frogs were screaming.

A study reported in the journal Acta Ethologica recorded the use of ultrasound by amphibians for the first time in South America. It also describes the first documented case of the use of ultrasound for defense against predators, in a distress call of ear-piercing intensity to many animals, but inaudible to humans.

So, the bats are getting some of their own medicine back at them, the screeching little bastards.

“Some potential predators of amphibians, such as bats, rodents and small primates, are able to emit and hear sounds at this frequency, which humans can’t. One of our hypotheses is that the distress call is addressed to some of these, but it could also be the case that the broad frequency band is generalist in the sense that it’s supposed to scare as many predators as possible,” said Ubirata Ferreira Souza, first author of the article. The study was part of his master’s research at the State University of Campinas’s Institute of Biology (IB-UNICAMP) in Sao Paulo state, Brazil, with a scholarship from FAPESP […]

While emitting its distress call, this frog makes a series of movements typical of defense against predators. It raises the front of its body, opens its mouth wide and jerks its head backward. It then partially closes its mouth and emits a call that ranges from a frequency band audible to humans (7 kHZ–20 kHz) to an inaudible ultrasound band (20 kHz–44 kHz).

It’s not just in South America that all this screaming and yelling is going on.

There are also recordings of ultrasound calls by three Asian amphibian species, but the frequencies concerned are used for communication between individuals of the same species. In mammals, ultrasound use is common among whales, bats, rodents and small primates. Its use by amphibians for self-defense against predators was unknown until the study by Souza et al.

The research is raising the question of just what the screaming frogs are trying to achieve. For instance, whether the call is intended to scare off a would-be predator or to summon help.

“Could it be the case that the call is meant to attract an owl that will attack a snake that’s about to eat the frog?” Souza wondered.


Who knows, but, between the screaming and the puddles of piss, I for one am rather glad for our relatively restricted human range of senses. After all, if I wanted to be deafened and overwhelmed by the smell of pee, I’d have stayed at all the pubs I used to see bands in, in the ’80s.

Punk rock philosopher. Liberalist contrarian. Grumpy old bastard. I grew up in a generational-Labor-voting family. I kept the faith long after the political left had abandoned it. In the last decade...