From a human perspective, the southern grasshopper mouse is undeniably cute and unthreatening. From the tip of its nose to the end of its tail, it measures just six inches (15 cm) long. Yet to other tiny creatures in the deserts of the southwestern U.S. and northwestern Mexico, it’s a fearsome predator with numerous adaptations that make it particularly tough and deadly.
Only distantly related to common house mice, grasshopper mice will stalk and attack a wide variety of prey on their nocturnal hunting missions. This includes grasshoppers and other insects, centipedes, worms, snakes, small lizards, and even other rodents. Its favorite food, however, is the Arizona bark scorpion—a surprising preference given the scorpion’s lethal venom.
Undeterred, the southern grasshopper mouse attacks these scorpions by biting their heads, though they have also been known to bite off the scorpion’s stinging tail. Unlike most animals (including humans), the southern grasshopper mouse has developed an immunity and isn’t significantly affected by the scorpion's neurotoxin, even after being stung multiple times. When exposed, the mouse can turn off the chemical pathway that would otherwise transmit pain signals, essentially turning the toxin into a painkiller.
The southern grasshopper mouse is also known by another, even more fitting name: the werewolf mouse. Like wolves howling at the moon, the mice are known for their loud, high-pitched nighttime vocalizations, which they emit while standing on their hind legs and pointing their noses in the air. The mice frequently produce these howls right before making a kill and also use them to mark their territory. These calls can be heard by humans from 330 feet (100 m) away.
Tiny but incredibly fierce:
- The southern grasshopper mouse prefers to live alone, in a fiercely guarded territory. Male-female pairs sometimes share a territory, although, perhaps unsurprisingly given the species’ aggressive tendencies, this frequently ends with a lethal dispute.
- In addition to being one of America’s hottest deserts, the Sonoran Desert, which makes up part of the grasshopper mouse’s territory, is also home to more venomous creatures than anywhere else in the United States. Although the desert can reach or exceed summertime highs of 120°F (48.9°C), the grasshopper mouse usually only emerges at night, when temperatures are cooler.
- In 2017, researchers found that grasshopper mouse vocalizations are produced in a similar way to human speech and wolf howls, by using airflow to vibrate vocal tissue. The researchers also discovered that grasshopper mice have a bell-shaped vocal tract, which helps increase vocal intensity.
