mole-rats
© Kai Robert CasparA cuddle pile of mole-rats in the lab
In the gloom of subterranean tunnels, chonky little mole-rats build their nests, tucked safely away, deep inside the earth. Strangely, one species always carefully builds these nests in the south-eastern part of their den.

Why they do this remains unclear, but even in total darkness, it seems, these burrowing rodents - animals that can barely see in the best of conditions - can still sense direction.

We've long known animals like birds can sense magnetic fields, and recently discovered dogs navigate via them too. But the biological mechanisms behind this sense - and how it might function in mole-rats - are still very much a mystery. We didn't even know where in the body these magnetic detectors, whatever they prove to be, are located.

A recent theory suggests this sensory ability may somehow occur via magnetotactic bacteria living within these species. But so far clues about mole-rats' magnetoreceptors suggest that their mechanism is magnetite-based.

This sense of Earth's magnetic field works independent of light, and is affected by strong magnetic pulses but not radio frequencies, explain researchers from the University of Duisburg-Essen in Germany. They've been studying Ansell's mole-rat (Fukomys anselli) to learn more about how this sensory mystery works.

Ansell's mole-rat is a highly cooperative social species that lives in colonies of around 10 individuals and builds the longest known tunnel of any (non-human) mammal. They may even be friendly with their neighbours, with some colonies linked by joining tunnels.