Outside the range of our senses, the animals around us chirrup, shimmer and moanby Cal Flyn / June 8, 2019 / Leave a comment
A couple of weeks ago, I spent a magical, sundazzled evening as a moth whisperer. It was easy: I went down to the woods alone at golden hour, and drew from my bag a rubber bung about the size of a pencil eraser. I placed this mysterious object atop a broad, mossy stump. Then I waited.
This bung was, I’d been promised, a pheromone lure. Soaked in chemicals selected to mimic those of female emperor moths, the lure was supposed to attract the large, dramatic males from the undergrowth and into my net. A charming concept, but one I couldn’t quite bring myself to believe in. Anyone who’s spent time “spotting” wildlife knows that it rarely shows up when we’re looking for it.
I lay back in the grass, let dappled light dance across my face and waited. After 15 minutes I was feeling silly—glad I’d not brought an audience—and was about to pocket the lure and go home when the moths came racing out of the heather. First one, then two more, and then a fourth, each fluttering and frantic, limbs awhirr, with a dark eye on each wing and a pair of fabulously baroque combed antennae. I caught one, and soon it was walking across my hands quite fearlessly, wings shivering in the breeze. It felt like sorcery.
The pheromone signalling got me thinking about the invisible, inaudible messages that are being broadcast around us at all times. What stations are being played on channels that we simply can’t tune into? What signs are left hanging that we haven’t the capacity to read?
When I went moth-hunting a few months ago with the lepidopterist Reuben Singleton, he brought a sensor that allowed him to detect different species of bats as they flew overhead from their distinctive pattern of ultrasonic chirruping. A common pipistrelle, for example, echolocates by emitting sounds between 45,000Hz and 70,000Hz. Humans only hear from around 20Hz to 20,000Hz. (This reduces steadily through our lifetime; it’s easy to check your range online—at 32, my hearing kicks in somewhere around 60Hz and falls off by 15,000Hz.) By slowing recordings down, we hear the bats as a series of wet slaps and clicks, all extremely loud—around the same volume as a fire alarm—yet undetected by us. And then there’s mice: did you know that they sing? High, fluting songs that glissade into the uppermost registers. Beautiful songs, that we just can’t hear.
Other animals use infrasonic sounds (that is, frequencies below our audible range). For years it was unknown how elephants could find others in the vast expanses of savannah, until it was found they were emitting very loud (85-95 decibles—about as loud as a motorbike) rumbles of as low as 14Hz. Whales and other cetaceans are disturbed by the infrasonic din created by shipping. Japanese scientists have demonstrated how humpback whale communication falls silent as ferries pass, their conversations drowned out.
And even our eyes, which we trust implicitly, are of limited use. Birds have an extra set of violet-sensitive cones in their retinas—rendering us comparatively colour-blind. Male and female starlings, which look virtually identical to us, appear very different when photographed using UV-sensitive cameras. Female blue tits have been found to select their mates based on the appearance of their crown patches, which (unbeknown to us) shimmer with ultraviolet light.
Flowers too speak in this unseen visual medium: dandelions, ragwort and tormentil all appear to humans as a flat yolk-yellow. But to bees and other insects they look quite different, with a “bull’s-eye”-like rim of colour surrounding a darker centre highlighting where nectar is to be found. Some flowers even dampen the UV-reflecting qualities of fertilised organs, so as to attract pollinators in a targeted fashion.
All such notices are being displayed under our noses all the time. Our senses engage with only a very narrow band of existence—and when we brush up against what we don’t have the capacity to perceive, it can feel like magic. And in a way, it is.