Shrews are small mammals often mistaken for mice due to their diminutive size. However, they are not rodents, but belong to a distinct group more closely related to moles and hedgehogs. Characterized by an elongated, pointed snout and tiny eyes, shrews are primarily insectivores. Their diet largely consists of insects and other invertebrates, highlighting their role as active predators.
Main Food Sources
A shrew’s diet primarily consists of diverse invertebrates. They commonly consume insects such as beetles, crickets, grasshoppers, and moth and butterfly larvae. Ants, wasps, earthworms, slugs, snails, spiders, millipedes, and centipedes are also key components of their diet.
While invertebrates are their main sustenance, some larger shrew species also prey on small vertebrates. These include mice, voles, salamanders, and frogs. Some, like the northern short-tailed shrew, use venomous saliva to immobilize larger prey. This demonstrates their predatory capabilities.
Shrews are opportunistic feeders, sometimes consuming non-animal matter when preferred food sources are scarce. This can include plant residues like stems, leaves, fruits, seeds, nuts, and fungi. However, animal protein forms the majority of their diet.
Hunting and Foraging Strategies
Shrews employ active foraging strategies, constantly moving and diligently searching for prey. With poor vision, they rely heavily on a keen sense of smell and highly developed hearing to detect food, even hidden beneath the surface.
They probe leaf litter or loose soil with their snouts, using sensitive whiskers to detect vibrations. Their rapid movements allow them to quickly investigate potential food sources. Shrews utilize natural tunnels and dense ground cover to hunt for subterranean and surface-dwelling invertebrates. Some species, like the American water shrew, forage in aquatic environments, capturing aquatic insects and minnows.
Some shrews use a primitive form of echolocation for spatial orientation, not for actively pinpointing food. Their hunting is generally a solitary activity, reflecting their territorial nature. When a shrew locates prey, it acts swiftly, often biting the head of insects before consuming the rest.
Dietary Habits and High Metabolism
Shrews have an exceptionally high metabolic rate, one of the highest among mammals relative to their body size. This rapid metabolism requires a continuous intake of food to sustain energy and maintain body temperature. They quickly burn through energy reserves, making them vulnerable to starvation if they go without food for even a few hours.
To meet these energy requirements, shrews consume a remarkable amount of food daily. Many species eat their own body weight in food each day, with some consuming up to two or even three times their body weight. This constant need means they feed frequently, often every two to four hours.
Their feeding habits are highly opportunistic; they eat whatever suitable prey is available to avoid rapid energy depletion. During colder months or food scarcity, some shrews can undergo morphological changes, such as shrinking their body size, to reduce energy demands and enhance survival. This adaptation is crucial because shrews do not hibernate, as they cannot store sufficient fat reserves.