The grasshopper mouse, a member of the genus Onychomys, stands out among its rodent relatives for its carnivorous diet. While most mice subsist primarily on seeds and plant matter, the grasshopper mouse functions as a true predator, with animal matter making up the majority of its food intake. This small mammal, native to the arid and semi-arid regions of North America, has adapted both morphologically and behaviorally to a hunting lifestyle.
Primary Prey: Arthropods and Invertebrates
The primary component of the grasshopper mouse’s diet is a wide array of arthropods and other invertebrates. This prey provides the consistent protein and moisture necessary for survival in its often dry, desert habitat. Common items include insects such as grasshoppers, beetles, crickets, and various insect larvae.
Spiders, centipedes, and other terrestrial invertebrates are also regularly consumed. Arthropods constitute between 75% and 100% of the diet, depending on the season and specific species of mouse. The high moisture content of this live prey helps the mouse meet its hydration needs where standing water is scarce. Unlike many other desert rodents that rely on metabolic water from seeds, the grasshopper mouse obtains water directly from its prey.
Specialized Predation and Hunting Techniques
The grasshopper mouse is an active hunter, employing a predatory style that involves stalking and pouncing on its victims, often likened to that of a cat. This aggressive behavior allows it to take down prey sometimes larger than itself. The mouse uses its forepaws to seize and manipulate fast-moving prey before delivering a fatal bite, typically to the head or neck.
A signature behavior is the “wolf-like howl” it performs after a kill, a vocalization used to mark its territory and warn rivals. This predation includes dangerous prey, most notably scorpions. The southern grasshopper mouse (Onychomys torridus) is known for consuming the highly venomous Arizona bark scorpion (Centruroides sculpturatus).
The mouse survives this encounter because it has evolved a resistance to the scorpion’s neurotoxin. The venom’s components, which normally trigger intense pain signals, are blocked by the mouse’s sensory neurons, rendering the mouse numb to the pain. The mouse often disarms the scorpion by quickly biting off its stinger or immobilizing the tail before consuming the rest of the body.
Beyond arthropods, the grasshopper mouse preys on small vertebrates, including lizards, snakes, and other rodents such as pocket mice and voles. This aggressive nature extends even to its own species, as cannibalism occurs when food resources are low.
Seasonal Shifts and Non-Animal Consumption
While animal matter forms the bulk of its diet, the grasshopper mouse is not strictly carnivorous and will adjust its consumption based on resource availability. When insects and other prey are scarce, such as in the colder winter months, the mouse supplements its diet with plant material.
This consumption includes seeds, grasses, and other green vegetation. The proportion of plant-based food can increase to nearly a quarter of its intake when animal prey is less abundant. Although the high water content of its prey usually provides sufficient hydration, the mouse will readily consume water or moisture-rich plants when they are available.