Restricted to our own suite of five senses, it is sometimes hard to imagine what the world is like for creatures that detect phenomena beyond our own capabilities. How many birds and insects negotiate the world by sensing the magnetic field that bathes our planet is a complete mystery to us. However, it is becoming apparent that there are two ways in which animals can detect magnetic fields: through ferromagnetic iron particles embedded in tissue or through pairs of molecules with unpaired electrons (known as radical pairs)that are associated with a light sensitive photoreceptor. Knowing that weak radio waves can jam an animal's radical pair magnetic sense, Martin Vácha and his colleagues from Masaryk University, Czech Republic,decided to see whether they could also `deafen' American cockroaches' magnetic senses with radio waves to find out which magnetic mechanism they may be using(p. 3473).
Filming cockroaches in a magnetic field as they rotated the field back and forth by 60 deg., Vácha, Tereza Puzová and Markéta Kvícalová monitored the insects' activity levels after the magnetic field rotated and found that the cockroaches turned around more during, and after, the field moved. But when the team tried `jamming' the insect's magnetic sense with radio waves, the cockroaches did not rotate in response to the magnetic field's movement. The team was able to `deafen' the cockroaches' magnetic sense with radio waves, suggesting that the insects use a radical pair mechanism to detect magnetic fields.