In order to track the paths of wild animals, researchers cover them in non-toxic fluorescent powder that glows under ultraviolet light. Seen here is a deer mouse, Peromyscus maniculatus, covered in this powder; when the mouse moves, it will leave a powder trail detectable by UV light and measurable by researchers.
<a href="//commons.wikimedia.org/w/index.php?title=User:Midwesternmouse&amp;action=edit&amp;redlink=1" class="new" title="User:Midwesternmouse (page does not exist)">Midwesternmouse</a>
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<span class="int-own-work" lang="en">Own work</span>