We believe the earth is a magnet for sure, but have you think about all creatures are magnetized as well. Biologists have found tiny particles of the magnetic mineral greigite (a type of iron sulphide) in ants, bees, and termites.
Magnetizing a strong neodymium magnet
If we use magnetic viewer firm, you will see how nature magnetized cockroach, and I guess this is the reason why cockroach will lose direction around magnet, especially strong neodymium magnet.
MIT scientist find magneto-sensing abilities of American cockroaches, which quickly become magnetized when placed in a magnetic field, just like us magnetize a magnetic materials, with reconciling inside magnetic domain of magnetic materials.
There is a interesting experiments are straightforward. Kong at Nanyang Technological University in Singapore and co placed a series of living and dead cockroaches in a magnetic field of 1.5 kilo Gauss even with air gap; that’s about 100 times stronger than a fridge magnet. The team left the creatures in the field for 20 minutes and then measured how strongly they had become magnetized and how long it took for this magnetization to decay.
The results make for interesting reading. we could easily measure the magnetic field associated with all the cockroaches, alive or dead, as soon as they came out of the external field. The field associated with living cockroaches then decayed in about 50 minutes. By contrast, it took almost 50 hours for the field to decay in dead cockroaches.