The Moth with Two Maps

The giant bogong moth has a brain one-tenth the size of a grain of rice. And eyes the diameter of a human hair. Yet it can navigate by sensing the magnetic field of Earth. Or by gazing at the stars, reading a mental map that it was somehow born with. Each spring in Australia, they leave the lowlands by the millions, and fly at night over terrain they’ve never seen before, following their internal compass, and that inherited star map. They’re the only insects we know of that can navigate this way. And they’re all headed to the same place: the cool highlands of the Snowy Mountains, where they sleep away the summer heat in caves. Historically, they’ve been a keystone species here, with a disproportionately large effect on the ecosystem. Other animal populations have relied on their annual arrival for food. Aboriginal tribes used to gather in the mountains to harvest and roast moths. But the bogong has declined precipitously over the last decade. Rising temperatures and drought have reduced their food sources. Pesticides have reduced their numbers. Light pollution from towns and farms has reduced their ability to navigate. Conservation groups are trying to save the moth, but with so many stressors on their population, that’s hard to do. Let’s hope they’re successful, because the bogong moth is another overlooked example of the wonders of nature, its interconnectedness, and its vulnerability.