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In a battle between mouse and scorpion, you might put your money on the vicious stinger. You’d lose that bet, if the combatants were a grasshopper mouse and bark scorpion. The rodent wins every time that it takes on the arthropod. Sure, the scorpion might get in a jab or two, but the mouse merely licks the injury and then moves in for the kill, immobilizing the scorpion’s curled tail and biting down on its head. 

In other mammals of comparable size, the scorpion’s venom would be fatal. Not only is the grasshopper mouse resistant to the death stab, the toxins actually act as an analgesic, or painkiller, in the rodent, report scientists in .   

To call these mice aggressive would be an understatement. Grasshopper mice, native to the southwestern desert regions of the United States, devour scorpions, other mice, lizards, and insects. They’re known to before killing their quarry.  When threatened or in desperate need of food, they resort to cannibalism. While usually solitary, individuals sometimes , but these relationships are short-lived: One partner usually murders the other. 

Now, biologists can add another remarkable trait: They’re the only mammal known in which scorpion toxins act as a numbing agent.

“The grasshopper mouse has developed the evolutionary equivalent of martial arts to use the scorpions’ greatest strength against them,” said study author and zoologist, Ashlee Rowe, in a .

Researchers don’t know why the venom isn’t lethal to the mouse, but they do know why it doesn’t feel pain when stung. The toxin binds to sodium channels in the mouse’s pain neurons, blocking them from firing a pain signal to the brain. In fact, this reaction produces an overall numbing effect on the animal’s entire pain transmission system. They’re temporarily incapable of feeling any pain at all.  

[video:190736|caption:Grasshopper mouse fights then eats a bark scorpion in this Youtube video]