http://www.eecs.harvard.edu/~yaz/en/squirrel_fishing.html

Squirrel Fishing
A new approach to rodent performance evaluation

Nikolas Gloy and Yasuhiro Endo
Division of Engineering and Applied Sciences
Harvard University

Note:
We simply tie peanuts to the end of the string (using slipknot). No hook was
used and no squirrel was harmed during this "research."