Voles are small rodents, often mistaken for mice, that are common inhabitants of grasslands, meadows, and areas with dense ground cover. These mammals, belonging to the genus Microtus, are generally perceived as purely herbivorous creatures because of the significant damage they cause to garden plants, tree roots, and lawns. However, their feeding habits are more complex and flexible. This raises the question of whether they consume non-plant matter, such as worms, and requires looking beyond their primary food sources to understand their need for specific nutrients.
Vole Consumption of Earthworms
The direct answer is that voles will consume earthworms opportunistically, though they are not a primary or preferred food. Voles are often confused with moles, which are true insectivores whose diet consists primarily of earthworms and insect larvae. Unlike moles, voles do not actively hunt earthworms as a staple food source.
Voles create extensive burrow and tunnel systems just beneath the surface, often seeking plant roots and tubers. While tunneling, they occasionally encounter soil invertebrates, including smaller earthworms, snails, and various insects. These animal items are consumed as occasional supplements rather than a targeted food source, especially when easily accessible. This consumption falls under their broader category of opportunistic feeding.
The Predominance of Herbaceous Diet
The bulk of a vole’s caloric intake comes from plant material, establishing them as herbivores. Their diet is highly varied and includes grasses, forbs (broad-leafed herbs), and seeds. Voles are non-ruminant herbivores and possess a specialized digestive system adapted for processing large quantities of fibrous vegetation.
A large cecum houses symbiotic microorganisms that help break down cellulose in plant cell walls. This structure, along with the practice of coprophagy—re-ingesting specialized feces—allows the vole to maximize nutrient extraction from low-quality forage. Their dental structure is also adapted for grinding, with high-crowned molars that continuously grow to compensate for the wear caused by tough, abrasive plant matter.
In autumn, voles often hoard seeds, bulbs, and rhizomes in underground chambers to sustain them through the colder months. When green vegetation is scarce, their diet shifts to consuming the inner bark and roots of trees and shrubs. This behavior, known as girdling, is a survival strategy to access nutrients stored in woody plants.
Opportunistic Omnivory and Protein Sources
While their diet is predominantly plant-based, voles are better classified as opportunistic omnivores, supplementing their diet with animal matter when necessary. This shift is often driven by a need for protein and other essential nutrients that are difficult to obtain in sufficient concentration from grass alone. Voles actively select plant species with higher protein content and lower levels of digestion-inhibiting compounds.
When high-quality plant food is unavailable, or during periods of high physiological demand, animal protein becomes an important dietary component. Reproduction, for instance, requires a significantly higher protein intake. To meet this demand, voles will consume a variety of animal items, including insects, snails, and even small amounts of carrion.
The consumption of grubs and insect larvae, often found while tunneling for roots, provides a concentrated source of protein and fat. This flexibility allows voles to survive and reproduce even when their primary herbaceous food sources are limited or of poor nutritional quality. Their diet is a flexible one, shifting from a dominant herbivorous base to an omnivorous one driven by seasonal availability and metabolic needs.