Bat
Microbats make use of magnetoreception, in that they have a high sensitivity to the Earth's magnetic field, as birds do. Microbats use a polarity-based compass, meaning that they differentiate north from south, unlike birds, which use the strength of the magnetic field to differentiate latitudes, which may be used in long-distance travel. The mechanism is unknown but may involve magnetite particles.
Magnetix
The leading American expert in the area of the effects of swallowed magnets on the human body is radiologist Dr. Alan Oestreich. As early as 2004 he warned the medical community about the dangers of "multiple magnet ingestion", but the case studies never made it into the popular press. A pediatric gastroenterologist, Dr. Marsha Kay of the Cleveland Clinic, is one of the first to write an article for health consumers on steps to take if a child is suspected of swallowing a magnet.