I don't remember hearing about a potto before, so I looked them up -
Found inside the jungles of Africa, Pottos may appear like some sort of smaller, arboreal bear relative, but they are really primates. They may be nocturnal and feed on tree sap, fruit and little creatures. Due to their sluggish movements, pottos are vulnerable to numerous predators, and have an incredibly different protective method; they’ve got enlarged neural spines on its vertebrae, which protrude from your neck and shoulders. These spines have pointy tips and seem to become employed as some form of unlikely weapon, using the primate “neck-butting” its enemies and maybe, just producing alone challenging to swallow. The spines may also function as some variety of shield, safeguarding the potto’s neck from the killing bite delivered by some predators, generally aimed at the neck or back on the head.
(seem to be a few words missing..)
http://www.top10source.com/10-mammals-that-have-the-best-defense.html