Foxes use the Earth’s magnetic field as a targeting system
Jaroslav Červený has found that when red foxes pounce, they mostly jump in a north-easterly direction. He thinks that they’re using the Earth’s magnetic field to hunt.
In Schenck v. United States (1919), the Supreme Court invented the famous "clear and present danger" test to determine when a state could constitutionally limit an individual's free speech rights under the First Amendment.^[PBS. " Schenck v. U.S. (1919)." PBS. http://www.pbs.org/wnet/supremecourt/capitalism/landmark_schenck.html (accessed July 27, 2014).]
During World War I, British intelligence explored various methods of writing secret messages, including using invisible ink. Captain Sir Mansfield Cumming, the first director of MI6, reportedly discovered that semen could be used as a form of invisible ink that was not easily detected by traditional methods of espionage at the time, such as iodine vapor. However, this method was eventually abandoned because of obvious hygiene concerns and the unpleasant odor as it aged.
https://en.m.wikipedia.org/wiki/Mansfield_Smith-Cumming#:~:text=When%20the%20SSB%20discovered%20that,masturbatory%20habits%20of%20the%20agents.