Asian House Shrew

The Asian house shrew (Suncus murinus) is a large shrew widespread across South and Southeast Asia, often living close to people. It has grey-brown fur, a musky odour, and a long, tapering snout. Active mainly at night, it feeds on insects and other invertebrates and is a familiar household visitor.

The Asian house shrew is primarily nocturnal and crepuscular, though it is frequently active during daylight hours in the dim, sheltered environments it prefers, such as drains, kitchens, and cluttered storage areas. Its activity is characterized by near-constant movement in short, frenetic bursts, as its extremely high metabolic rate demands almost continuous foraging to avoid starvation, which can occur within a few hours of food deprivation. This species has adapted remarkably well to synanthropic living, thriving in dense urban and peri-urban human settlements throughout South and Southeast Asia, often occupying the same buildings as rodents while remaining ecologically separate as a strict insectivore.

Socially, Suncus murinus is solitary and highly aggressive toward conspecifics outside of breeding encounters, with individuals maintaining and defending overlapping home ranges through scent-marking using specialized flank and ventral glands that produce a strong, musky odor—the source of its common nickname “money shrew” or “monk shrew” in various regions due to the smell resembling old coins. Communication includes a range of high-pitched clicks, squeaks, and chittering vocalizations, some of which may extend into the ultrasonic range, used both in aggressive encounters and during a distinctive juvenile behavior called “caravanning,” where young shrews form a chain by grasping the fur at the base of the tail of the sibling or mother ahead of them while moving between nest sites.

Territoriality is pronounced, particularly among adult males, and encounters between unfamiliar individuals often result in vocal threat displays, biting, and chasing. Despite this aggression, home ranges can overlap considerably in resource-rich human habitations, where high insect and refuse availability reduces the need for large foraging territories. This adaptability, tolerance of disturbed environments, and generalist foraging strategy have made the species one of the most successful and widely distributed shrews in the Old World tropics and subtropics.

As an obligate insectivore, the Asian house shrew forages almost continuously, using its highly sensitive whiskers, mobile snout, and keen olfactory senses to locate prey in low-light conditions since its eyesight is poor. Its diet consists primarily of cockroaches, crickets, beetles, ants, termites, spiders, earthworms, and other invertebrates commonly found in human dwellings and refuse areas, but it will also opportunistically consume small vertebrates such as geckos, mice, and even carrion when available. Foraging occurs along fixed runways and edges of walls or drains, exploiting scent trails and tactile cues rather than active visual hunting.

The species exhibits one of the highest mass-specific metabolic rates among mammals, requiring it to consume food equivalent to a substantial proportion of its own body weight daily—often 70–100% or more—to sustain its energy demands. This extreme metabolic need means individuals cannot survive extended fasting periods and must feed multiple times throughout a 24-hour cycle. Water is typically obtained from prey moisture content, though free water is consumed opportunistically when available; there is little evidence of pronounced seasonal dietary shifts given the relatively stable insect abundance in tropical and human-associated habitats it occupies.

Asian house shrews breed year-round in tropical and subtropical climates, especially in stable, resource-rich urban environments, with mating being polygynous or promiscuous and lacking any lasting pair bonds. Males seek out receptive females through olfactory cues and engage in brief, sometimes aggressive courtship interactions before mating. Gestation lasts approximately 30 to 35 days, after which females give birth to litters typically ranging from two to six young, though litters of up to eight have been recorded, in nests built within sheltered crevices, wall cavities, or debris piles.

Maternal care is intensive but relatively brief, with the female nursing and guarding the altricial young until weaning occurs at around 17 to 20 days of age. During this period, the notable “caravanning” behavior emerges, in which pups form a chain behind the mother while relocating between nest sites, an adaptation thought to reduce predation risk and prevent separation. Sexual maturity is reached remarkably quickly, often by 6 to 8 weeks of age, allowing for rapid population turnover and high reproductive output—traits that contribute significantly to the species’ success and abundance in disturbed and urban habitats.

The Asian house shrew faces few significant ecological threats and is classified as Least Concern by the IUCN due to its vast range, high reproductive rate, and remarkable adaptability to human-altered environments. Unlike many small mammals, it benefits from urbanization rather than suffering from habitat loss, thriving in the very drains, buildings, and refuse areas created by human development. Natural predators include owls, snakes, feral cats, and larger carnivorous mammals, though its pungent musk secretions may deter some predators, contributing to relatively low predation pressure in urban settings.

Human-wildlife conflict is generally limited, though the species is sometimes considered a household nuisance due to its odor and presence in domestic spaces, occasionally leading to localized control or extermination efforts, particularly where it is mistaken for a rodent. Climate change poses minimal direct threat given the species’ broad thermal tolerance and synanthropic lifestyle, and no significant conservation initiatives are currently directed toward this species, as its populations remain stable to increasing across its extensive Asian range, from India and Sri Lanka through Southeast Asia to parts of Japan and Guam, aided in part by inadvertent human transport via cargo ships.

• Extreme Metabolism: The Asian house shrew has one of the highest metabolic rates of any mammal, requiring it to eat nearly its own body weight in food daily to avoid starving within hours.
• Musky “Money” Scent: Specialized glands produce a strong musky odor resembling old coins, leading to the colloquial name “money shrew” in several Asian cultures.
• Caravanning Behavior: Juveniles form a “caravan” by biting onto the fur at the base of the tail of the individual ahead, creating a chain formation while moving with their mother.
• Global Hitchhiker: The species has spread far beyond its native range through inadvertent transport aboard ships, establishing populations on islands like Guam and Zanzibar.
• Poor Eyesight, Superb Touch: With very limited vision, this shrew relies heavily on tactile whiskers and scent trails to navigate and hunt in dark, cluttered environments.
• Not a Rodent: Despite frequently being mistaken for a large mouse due to its habitat and size, it belongs to the order Eulipotyphla and is more closely related to moles than to rodents.
• Ancient Urban Companion: Historical records suggest this species has cohabited with humans for centuries, with its presence documented in old Asian ports and trading centers long before modern urbanization.