Mouse

A mouse is a small rodent typically belonging to the genus Mus within the family Muridae, with the house mouse (Mus musculus) being the most widespread and well-known species.^[1] Native to central Asia and the Middle East, it has a compact body measuring 7.5–10 cm (3–4 in) in length, a scaly tail of equal or slightly longer length, prominent rounded ears, a pointed snout with prominent whiskers, small black eyes, and soft fur that is usually grayish-brown above with a paler gray or buff underbelly; adults weigh 12–30 grams.^[2][3] Characterized by high adaptability and opportunistic behavior, house mice are commensal species that thrive in human-modified environments, nesting in walls, attics, or burrows near food sources and reproducing prolifically with females capable of producing 5–10 litters per year, each averaging 5–6 pups after a 19–21 day gestation period.^[4][2][5] In natural settings, they inhabit grasslands, farmlands, and shrublands across Eurasia, North America, and other regions where introduced, foraging nocturnally on seeds, grains, insects, and scavenged materials while evading predators through agility and burrowing.^[6] As both agricultural pests and vectors for diseases such as salmonellosis, house mice cause significant economic damage by contaminating food stores and structures, prompting integrated pest management strategies worldwide.^[2][4] Conversely, their biological traits—rapid reproduction, well-understood genome, and physiological similarities to humans—make them a cornerstone model organism in biomedical research, facilitating studies on genetics, immunology, cancer, and neurology since the early 20th century.^[1][7]

Taxonomy and Classification

True Mice and Relatives

In biological terms, true mice are small rodents classified within the family Muridae, primarily in the subfamily Murinae, which encompasses Old World rats and mice distributed across Europe, Asia, Africa, and introduced elsewhere.^[8] The genus Mus represents the core group of true mice, with the house mouse (Mus musculus) serving as the most studied and widespread species, originally described in 1758 by Carl Linnaeus as a commensal of humans.^[9] These rodents are characterized by their compact bodies, prominent ears, and scaly tails, distinguishing them from larger rats in the same family through smaller overall size and proportionally larger ears relative to body length.^[2] Key species include the house mouse (Mus musculus), with a head-body length of 7.5–10 cm, tail length of 5–10 cm, and adult weight ranging from 12–30 g, featuring a light brownish-gray coat and nearly hairless tail.^[2] The long-tailed field mouse (Apodemus sylvaticus), also in Murinae, has a head-body length of 6–15 cm, tail length of 7–14.5 cm, and weighs 14–25 g in adults, notable for its yellowish-brown fur, large eyes, and long tail often exceeding body length.^[10] In the New World, the deer mouse (Peromyscus maniculatus) exemplifies true mice from the subfamily Sigmodontinae, measuring 11.9–22.2 cm in total length and weighing 10–24 g, with distinctive white underparts, large ears, and a bi-colored tail.^[11] The subfamily Murinae, comprising over 500 species in more than 100 genera, originated in southern Asia during the middle Miocene and includes Old World taxa like Mus and Apodemus, which lack cheek pouches and exhibit diverse body forms from shrew-like to rat-sized.^[8] In contrast, Sigmodontinae represents New World mice and rats, with about 450 species in 90 genera, including Peromyscus, adapted to the Americas and sharing muroid traits like gnawing incisors but differing in evolutionary divergence from Old World lineages.^[12] These subfamilies together highlight the global radiation of murids, with Murinae focused on Eurasian-African forms and Sigmodontinae on Neotropical and Nearctic ones. Historically, Linnaean classification placed the house mouse in the genus Mus under order Rodentia, emphasizing morphological traits like dentition and pelage for grouping.^[9] Post-2000 DNA studies, using mitochondrial and nuclear sequences, have refined this by revealing the genus Mus encompasses at least 38 species across four subgenera—Mus (including M. musculus), Pyromys, Nannomys, and Coelomys—with phylogenetic analyses showing deeper divergences and hybridization events among subspecies like M. m. domesticus and M. m. musculus.^[13] These molecular updates, from genome-wide data, underscore reticulate evolution in Murinae, contrasting earlier morphology-based hierarchies.^[7]

Other Animals Known as Mice

Several animals unrelated or distantly related to true mice (subfamily Murinae) bear the name "mouse" due to superficial similarities in size, body shape, or behavior, stemming from the broad historical application of the Old English term "mūs," which denoted small, rodent-like mammals.^[14] This linguistic tradition has led to misnomers across various taxa, often highlighting convergent evolution in small-bodied mammals adapted to similar niches. Spiny mice of the genus Acomys (family Muridae) are rodents but belong to a distinct lineage from typical house mice, featuring stiff, spine-like hairs on their backs for defense against predators.^[15] These North African and Middle Eastern species, such as the golden spiny mouse (Acomys russatus), with a total length of up to 25 cm, exhibit unique regenerative abilities, unlike the more generalized Murinae.^[15] Their naming reflects the spiny dorsal pelage that sets them apart from smoother-furred true mice, though they share burrowing habits.^[16] Jumping mice of the subfamily Zapodinae (family Zapodidae) are also rodents but form a separate family from Murinae, characterized by elongated hind limbs enabling leaps of up to 3 meters for escaping threats.^[17] Native to North America and parts of Asia, species like the meadow jumping mouse (Zapus hudsonius) weigh 20-35 grams and hibernate seasonally, contrasting with the non-leaping, more sedentary true mice.^[17] The "mouse" moniker arises from their small size and long tails, which aid in balance during jumps, mimicking the agile scampering of Murinae.^[18] Elephant shrews (order Macroscelidea) are not rodents at all but afrotherian mammals more closely related to elephants and aardvarks, despite their mouse-like appearance with slender bodies, large eyes, and long snouts used for probing insects.^[19] Found in African savannas and forests, species such as the round-eared sengi (Macroscelides proboscideus) weigh around 50 grams and bound bipedally, a locomotion distinct from the quadrupedal gait of true mice.^[20] Their naming as "shrews" or mouse-like stems from superficial resemblances to rodents, though they lack gnawing incisors and have insectivorous diets.^[19] Marsupial mice, including species of the genus Antechinus (family Dasyuridae), are Australian marsupials rather than rodents, resembling mice in their small size (10-20 cm) and pointed snouts but featuring pouches in females for underdeveloped young and carnivorous habits focused on insects.^[21] The brown antechinus (Antechinus stuartii), for instance, has bristly fur and bulging eyes, leading to frequent misidentification as rodents, though it lacks placental reproduction.^[22] Known regionally as "marsupial mice" due to these visual parallels and burrowing behaviors, they differ biologically in their semelparous mating strategy, where males often die post-breeding.^[22] In Southeast Asian cultures, chevrotains (family Tragulidae), small even-toed ungulates called "mouse deer," are named for their diminutive, mouse-sized frames (up to 30 cm long) and timid, deer-like evasion tactics, despite being more closely related to pigs and camels than rodents.^[23] The greater Malay mouse-deer (Tragulus napu) inhabits tropical forests and browses on leaves, with cultural significance in Malay folklore as the clever "kancil," a trickster figure symbolizing wit over strength.^[23] This vernacular name highlights their secretive nature and small stature, contrasting with the gnawing, seed-eating habits of true mice.^[24]

Physical Characteristics

Anatomy and Morphology

The house mouse (Mus musculus) exhibits an elongated body form adapted for agility, measuring 65–95 mm in length from nose to base of tail, with a long, scaly tail of 60–105 mm that aids in balance during locomotion and contributes modestly to thermoregulation through vasodilation and heat dissipation.^[25][26][27] The head features prominent, rounded ears and large, dark eyes positioned laterally, while the dentition includes characteristic sharp, ever-growing incisors suited for gnawing.^[25][28] The body is covered in soft fur, typically light brown to dark brown or black dorsally with a white or buff ventral pelage in wild populations, though variations occur; the tail is sparsely haired with annular scales.^[25] The skeletal system includes a lightweight cranium, approximately 60-65 vertebrae (7 cervical, 13 thoracic, 6 lumbar, 4 fused sacral, and 25-31 caudal), a rib cage with 13 pairs of ribs, and appendicular elements adapted for climbing and burrowing, enabling a total body mass of 12–30 g.^[25][29] The muscular system supports this agility with specialized groups, including 17 forelimb muscles like the biceps brachii (maximum force ~0.78 N) and 42 hindlimb muscles such as the rectus femoris (~4.16 N), arranged for efficient force generation across the limbs.^[30] In the wild, individuals typically weigh under 30 g and have an average lifespan of 12–18 months, extending to about 2 years (up to 6 years in some cases) in captivity due to controlled conditions.^[25] Sexual dimorphism is minimal, with males generally slightly larger in body size and mass than females, though external appearances are otherwise similar.^[25][31] Reproductive morphology includes scrotal testes in males, housed in external sacs for thermoregulation of gametes, contrasting with the internal ovaries in females.^[32] Fur variations are pronounced between wild and laboratory strains; wild house mice display agouti-patterned brown coats for camouflage, while lab strains often feature albino white fur due to mutations or selective breeding for other colors like black or spotted patterns.^[25][33] In other wild murine species, such as the wood mouse (Apodemus sylvaticus), similar elongated bodies and tails prevail, but with more reddish-brown fur and distinct white belly markings.

Senses and Adaptations

Mice possess a visual system well-suited to their primarily nocturnal lifestyle, featuring large eyes relative to body size that enhance light capture in dim conditions. Their retinas are dominated by rod photoreceptors, which facilitate scotopic vision for low-light environments, while cone photoreceptors are limited, resulting in dichromatic color perception primarily sensitive to ultraviolet (UV) and green wavelengths. This adaptation supports strong motion detection, crucial for identifying predators or prey in the dark, though overall visual acuity is lower than in diurnal mammals.^[34] Some species exhibit heightened UV sensitivity, allowing detection of UV-reflective cues such as urine marks for navigation and social signaling.^[35] The auditory and olfactory senses of mice are highly developed for communication and environmental interaction. Mice produce and detect ultrasonic vocalizations in the 30–110 kHz range, far beyond human hearing, enabling short-range social signaling during mating, pup isolation, and aggression without alerting predators.^[36] Their olfactory system is supported by approximately 1,000 functional odorant receptor genes, more than in humans, which encode proteins that bind volatile odorants to facilitate precise scent discrimination for foraging, kin recognition, and mate selection.^[37] Tactile and gustatory senses further aid survival in constrained habitats. Whiskers, or vibrissae, serve as specialized mechanosensors innervated by trigeminal neurons, allowing mice to map burrow walls and detect obstacles in complete darkness through rhythmic protraction and retraction movements.^[38] In terms of taste, mice display an innate preference for sweet flavors, which promotes consumption of energy-rich foods, coupled with aversion to bitter compounds that often signal toxicity, mediated by distinct G-protein-coupled receptors on taste bud cells.^[39] Physiological adaptations underscore the high metabolic demands of mice as small, active mammals. Their core body temperature is maintained at 36–38°C, supporting rapid enzymatic reactions and thermoregulation in fluctuating environments. Resting heart rates range from 450–750 beats per minute, enabling quick responses to threats and efficient oxygen delivery during bursts of activity. Fur coloration, often grayish-brown with agouti patterns, provides camouflage against soil and vegetation, reducing visibility to predators like owls and cats in natural habitats.^[40][41][42]

Behavior and Reproduction

Social and Daily Behaviors

House mice (Mus musculus) exhibit primarily nocturnal or crepuscular activity patterns, with peak foraging and exploration occurring during the night or twilight hours to avoid predators.^[43] They construct nests from shredded materials like paper or fabric in sheltered locations and may burrow into the ground when other cover is unavailable, using these structures for rest and protection during inactive periods.^[43] Territorial marking is a key daily behavior, particularly among males, who deposit urine droplets to delineate boundaries and signal dominance, often producing hundreds of such marks per day.^[44] In the wild, house mice typically live in small, kin-based groups known as demes, consisting of one dominant male and several related females, though individuals may be solitary when population densities are low.^[45] In communal breeding among related females, higher oxytocin levels are associated with reduced reproductive skew and increased success in shared pup-rearing.^[46] Social dynamics involve the formation of hierarchies, especially among males, who display aggression through fighting and chasing to establish rank, reducing ongoing conflict within the group.^[47] Juvenile mice engage in play behaviors such as pouncing, wrestling, and chasing, which strengthen social bonds and aid in motor skill development.^[48] Mice express emotions through distinct facial expressions, including nose wrinkling for disgust, ear flattening for fear, and whisker retraction for pleasure, as identified via machine learning analysis of high-speed video footage.^[49] Cognitively, they demonstrate basic learning capabilities in tasks like the Morris water maze, where spatial navigation improves over sessions, with memory retention lasting up to several weeks in probe trials assessing long-term recall.^[50] Communication among mice relies on ultrasonic vocalizations (USVs), high-frequency squeaks above 20 kHz used for social signaling, such as alarm calls or courtship songs, which convey intent and emotional state.^[51] Pheromones in urine and glandular secretions play a central role in social interactions, triggering responses like aggression in males or attraction in mating contexts.^[52] Allogrooming, or mutual fur licking, serves as a form of social bonding and stress relief, often occurring between familiar individuals to reinforce affiliative relationships.^[53]

Reproduction and Life Cycle

Female house mice (Mus musculus) are polyestrous, exhibiting estrous cycles every 4 to 5 days throughout the year without seasonal restrictions.^[54] These cycles consist of four phases—proestrus, estrus, metestrus, and diestrus—with ovulation occurring spontaneously during estrus, typically 10 to 12 hours after the luteinizing hormone surge.^[55] Mating often occurs immediately following ovulation, facilitated by the female's receptivity during estrus, and pregnancy follows successful copulation. Gestation lasts 18 to 21 days, after which females give birth to litters averaging 4 to 12 pups, though averages are typically 6 to 8 in wild populations.^[56] High fecundity allows a single female to produce up to 5 to 10 litters annually under optimal conditions, contributing to rapid population growth.^[57] Newborn mouse pups, known as neonates, are altricial, born blind, deaf, hairless, and unable to thermoregulate effectively.^[58] They rely entirely on maternal milk for nutrition during the neonatal stage (0 to 3 weeks), with eyes opening around 12 to 14 days and ears unfolding shortly after.^[59] Weaning occurs at approximately 3 weeks (21 days), marking the transition to the juvenile stage (3 to 6 weeks), during which pups begin exploring independently and consuming solid food.^[60] Sexual maturity is reached at 6 to 10 weeks of age, enabling juveniles to enter the adult reproductive phase, though full reproductive competence may take slightly longer in males.^[61] The overall life span in the wild is typically 9 to 12 months, limited by predation and environmental factors.^[61] Reproductive success in house mice is influenced by density-dependent factors, such as population crowding, which can delay embryo implantation and extend estrous cycle lengths, thereby reducing litter frequency and overall fecundity.^[62] In high-density conditions, females may exhibit suppressed ovulation or smaller litters to mitigate resource competition.^[63] Maternal care is primarily provided by the female, who nurses pups multiple times daily, retrieves strays to the nest, and aggressively defends the litter against intruders.^[64] Recent research has identified antagonistic neural circuits involving estrogen receptor alpha-expressing neurons in the medial amygdala and bed nucleus of the stria terminalis that control the behavioral switch from infanticide to maternal care during motherhood.^[65] This protection is crucial during the vulnerable neonatal period, but infanticide can occur under high-stress conditions, such as resource scarcity or intrusion by unfamiliar males or non-lactating females, who may kill unrelated pups to redirect maternal resources or eliminate future competitors.^[66] Such behaviors are more prevalent in dense populations, where the risk of infanticide prompts females to increase vigilance and nest relocation.^[67]

Ecology and Diet

Habitats and Distribution

The house mouse (Mus musculus), the most widespread species in the genus Mus, is native to Eurasia and North Africa, with its range extending from the Mediterranean region to central China.^[68] Through human-mediated dispersal over the past approximately 15,000 years, it has become nearly cosmopolitan, establishing populations on every continent except Antarctica, including remote islands.^[69] Three main subspecies account for much of this distribution: M. m. domesticus predominates in Europe, North Africa, and the Americas; M. m. musculus in northern Eurasia; and M. m. castaneus in southern and southeastern Asia.^[68] Other true mice in the genus Mus, such as the African pygmy mouse (Mus minutoides), are more regionally confined to sub-Saharan Africa, inhabiting savannas and grasslands.^[70] Habitat preferences among true mice vary between commensal populations closely associated with human settlements and feral or wild populations in natural environments. Commensal house mice thrive in urban and agricultural settings worldwide, nesting in hidden spaces like walls, attics, and storage areas, while feral groups occupy grasslands, farmlands, forest edges, and scrublands.^[71] In wild settings, house mice construct complex underground burrows with multiple tunnels and chambers for shelter and rearing young, often excavating in soft soil near vegetation cover; these burrows can extend up to several meters in length.^[72] Species like the steppe mouse (Mus spicilegus) prefer open arid steppes in Central Asia, digging shallow burrows to evade predators.^[73] Among other animals known as mice, spiny mice (Acomys spp.) favor rocky deserts and arid scrub in Africa and the Middle East, utilizing rock crevices and shallow burrows for protection.^[16] True mice play key ecological roles as prey for numerous predators, including owls, snakes, foxes, and cats, thereby supporting food webs in their native and introduced ranges. In introduced island ecosystems, house mice can act as invasive predators, impacting native invertebrates, seeds, and seabird populations.^[74] They contribute to seed dispersal by caching uneaten seeds in burrows or surface middens, aiding plant regeneration in grasslands and agricultural edges, though this role is often overshadowed by their impacts as seed predators. Populations can boom rapidly in favorable conditions, such as post-agricultural expansion or mild winters, leading to irruptions that alter local vegetation dynamics through intense foraging pressure.^[69] Adaptations to diverse environments include huddling behavior in house mice to conserve heat during cold exposure, enhancing survival in temperate and sub-Antarctic regions.^[75] In arid habitats, spiny mice exhibit drought resistance via highly concentrated urine and metabolic water conservation from food sources, allowing persistence in water-scarce deserts.^[16]

Feeding Habits and Foraging

Mice of the genus Mus, particularly the house mouse (Mus musculus), exhibit an omnivorous diet that is predominantly granivorous, relying heavily on seeds and grains such as wheat, oats, and wild grasses as primary food sources. This base is supplemented by opportunistic consumption of insects (including larvae and adults), fruits, green vegetation, roots, and tubers, providing essential proteins and nutrients. In urban and commensal settings, house mice readily scavenge human foodstuffs like cereals, bread, and discarded scraps, which can constitute a significant portion of their intake where natural resources are limited.^[25][7][71] Foraging in house mice is typically nocturnal or crepuscular, allowing them to raid food sources under cover of darkness while minimizing predation risk; they travel short distances from nests, often no more than 3-8 meters, and employ caching behaviors to store excess seeds in burrows or hidden locations for later consumption. Nutritional demands vary by life stage, with breeding females requiring elevated protein levels—up to 20-25% of the diet—to support lactation and offspring growth, while general maintenance diets emphasize carbohydrates from grains with moderate fat content around 5-10% derived from seeds. These behaviors are guided by acute olfactory senses, enabling detection of food odors from afar.^[76][25][77] Among mouse relatives, species in the subfamily Perognathinae, known as pocket mice (e.g., Perognathus flavescens), possess external fur-lined cheek pouches that facilitate efficient seed storage and transport during foraging, allowing them to carry multiple loads back to burrows without repeated trips. Contrary to popular depictions, mice lack an innate preference for cheese; experimental studies demonstrate a strong bias toward grains like soft wheat, canary seed, and rice over dairy products, which they may consume only if alternatives are scarce and often find unappealing due to odor.^[78][79][80] As prolific seed consumers, mice play a dual role in ecosystems: they regulate plant populations by predating on seeds and insects, potentially aiding in biodiversity control, but as invasive pests, house mice inflict substantial agricultural damage by consuming and contaminating stored grains and directly destroying crops like wheat during outbreaks, leading to economic losses estimated in billions annually in affected regions.^[25][81][74]

Health, Diseases, and Genetics

Common Diseases and Pathogens

Mice, particularly species like the house mouse (Mus musculus) and deer mouse (Peromyscus maniculatus), serve as reservoirs for several zoonotic diseases that can transmit to humans through direct contact with urine, droppings, saliva, or contaminated environments. Hantavirus, primarily carried by deer mice in North America, causes hantavirus pulmonary syndrome (HPS), a severe respiratory illness with symptoms including fever, muscle aches, and rapid progression to respiratory failure, with a mortality rate of about 38%.^[82] Lyme disease, caused by the bacterium Borrelia burgdorferi, is vectored indirectly through ticks that feed on infected white-footed mice (Peromyscus leucopus), which act as primary reservoirs, facilitating transmission to humans via tick bites leading to symptoms like rash, fever, and joint pain if untreated.^[83] Salmonellosis, resulting from Salmonella bacteria in mouse feces, contaminates food and water, causing gastrointestinal illness in humans with symptoms such as diarrhea, fever, and abdominal cramps, as documented in outbreaks linked to pet rodents.^[84] In addition to zoonoses, mice are susceptible to various internal parasites and common infections that affect their health and can indirectly impact human populations. The dwarf tapeworm (Hymenolepis nana), a prevalent cestode in house mice, infects the intestines and can also transmit to humans via ingestion of contaminated food or water, leading to abdominal pain and nutritional deficiencies in heavy infestations.^[85] Fleas, such as Xenopsylla cheopis, commonly infest mice as ectoparasites and serve as vectors for plague (Yersinia pestis), though less frequently in modern settings; these parasites cause itching and secondary infections in mice while posing zoonotic risks.^[86] Respiratory infections, including those caused by Mycoplasma pulmonis and viruses like Sendai virus, are widespread in dense mouse populations, manifesting as chronic pneumonia and exacerbated by overcrowding in wild or urban settings.^[87] Health profiles differ markedly between wild and captive mice, with urban wild populations exhibiting higher pathogen loads due to environmental stressors and close proximity to humans. Urban house mice often harbor a broader array of bacteria, viruses, and parasites, including Salmonella.^[88] In contrast, laboratory mouse strains are maintained in specific pathogen-free (SPF) facilities with rigorous hygiene protocols, and some colonies receive vaccinations against common pathogens like mouse hepatitis virus to minimize infections and ensure experimental reliability.^[89] Preventing diseases from mice involves integrated rodent control measures to reduce contact and transmission. Effective strategies include sealing entry points in buildings with caulk or metal flashing, trapping and removing rodents humanely, and cleaning contaminated areas with disinfectants while wearing protective gear to avoid aerosolized pathogens like hantavirus.^[90] In mice, clinical symptoms of infections such as respiratory disease or parasitism include lethargy, weight loss, ruffled fur, and hunched posture, signaling the need for population management in both wild and captive contexts.^[91]

Genetics and Evolutionary Biology

The genome of the house mouse (Mus musculus) consists of approximately 2.7 gigabase pairs (Gbp) distributed across 20 pairs of chromosomes, including 19 autosomes and the X and Y sex chromosomes.^[92] This genome was fully sequenced in 2002 by the Mouse Genome Sequencing Consortium, providing a foundational reference for comparative genomics. Recent advances include complete telomere-to-telomere genome assemblies of mouse subspecies in 2025, adding over 200 Mb of sequence and enhancing comparative genomics.^[93] Approximately 80% of protein-coding genes in the human genome have one-to-one orthologs in the mouse genome, reflecting extensive conserved synteny and functional similarity that underscores the mouse's utility as a model organism.^[94] Key developmental genes, such as the Hox cluster, play critical roles in patterning the anterior-posterior axis during embryogenesis; these homeobox genes are expressed in a collinear manner along the chromosome and body axis, ensuring proper segmentation and organ formation.^[95] In laboratory settings, selective breeding has produced numerous inbred mouse strains to minimize genetic variation and facilitate trait studies. The C57BL/6 strain, one of the most widely used, exhibits consistent phenotypes suitable for genetic mapping and is the basis for many reference genomes.^[96] Knockout mice, generated by targeted disruption of specific genes, have been instrumental in elucidating gene functions; for instance, null mutations in aggression-related loci reveal how genetic ablation alters behavioral outcomes.^[97] Behavioral traits like aggression show moderate to high heritability in inbred strains, with quantitative trait loci (QTL) analyses identifying genomic regions that account for inter-strain differences, such as elevated aggression in NZB/B1NJ compared to A/J strains.^[98] These strains enable controlled studies of heritability, where environmental factors interact with polygenic backgrounds to influence traits like territoriality. The evolutionary history of mice traces back to the origin of the Mus genus approximately 10-12 million years ago in Asia, during the late Miocene, when ancestral murids adapted to diverse ecological niches in the expanding grasslands.^[99] The Mus lineage diverged from other murines, such as Rattus, around 10-12 million years ago. Within the genus, major diversification of subgenera occurred around 6-7 million years ago, coinciding with speciation events driven by geographic isolation and climatic shifts in Eurasia.^[99] Within M. musculus, subspecies divergence occurred more recently, around 0.3-0.5 million years ago, with adaptations such as enhanced burrowing behavior linked to genetic variants in sensory and skeletal genes that improved survival in variable habitats.^[100] Recent advances in genetic tools have expanded mouse models for evolutionary and functional studies. Since 2012, CRISPR/Cas9 technology has enabled precise genome editing in mice, allowing rapid generation of knock-in and knock-out models to investigate evolutionary conserved pathways, such as those involved in adaptation to novel environments.^[101] Epigenetic modifications, including DNA methylation patterns, differ significantly between urban and wild mouse populations; for example, urban mice exhibit non-parallel methylation changes at loci associated with stress response and metabolism, reflecting rapid, environment-driven epigenetic adaptation without underlying sequence alterations.^[102] These findings highlight how epigenetic mechanisms contribute to evolutionary flexibility in response to anthropogenic pressures.

Human Interactions

Use in Scientific Research

Laboratory mice have been pivotal in scientific research since the early 20th century, when William E. Castle introduced fancy mice into systematic genetic studies at Harvard's Bussey Institution in 1902, marking the beginning of their use as model organisms for inheritance and variation analysis.^[103] By the 1900s, mice became central to advancements in cancer research, such as early tumor transplantation studies by Clarence C. Little, and in genetics through the development of inbred strains like C57BL/6.^[104] Their role expanded into neuroscience, enabling foundational work on neural circuits and behavior, with institutions like The Jackson Laboratory standardizing strains for reproducible experiments since 1929. In biomedical applications, mice serve as key models for disease through genetic engineering techniques, including knockout and transgenic modifications. For instance, transgenic mice overexpressing human amyloid precursor protein (APP) genes, as in the Tg2576 model developed by Hsiao et al., recapitulate amyloid plaque formation and cognitive deficits observed in Alzheimer's disease, facilitating studies on pathogenesis and potential therapies. Behavioral paradigms like the Morris water maze, introduced by Richard Morris in 1981, assess spatial learning and memory in mice by measuring their ability to navigate to a hidden platform in a pool, revealing hippocampal dysfunction in disease models.^[105] These tools leverage mice's genetic manipulability, such as CRISPR-based knockouts, to study gene functions in vivo, with brief reference to foundational genetic similarities enabling precise targeting.^[106] Mice's advantages as model organisms include a short generation time of approximately 9-10 weeks, allowing rapid breeding and multi-generational studies, alongside their small size and low maintenance costs, which make large-scale experiments feasible.^[106] Their genome shares about 85% homology with humans, supporting homologous recombination for targeted mutations, though ethical frameworks like the 3Rs principle—replacement, reduction, and refinement—guide their use to minimize animal distress, as outlined by Russell and Burch in 1959.^[107] This principle emphasizes alternatives to animal use where possible, fewer animals for reliable data, and improved welfare to reduce suffering.^[107] Recent advances highlight mice's continued relevance, particularly in optogenetics, where light-sensitive proteins like channelrhodopsin-2 enable precise neural control; Boyden et al. demonstrated millisecond-scale activation of mouse neurons in 2005, revolutionizing circuit-level neuroscience. In immunology, humanized mouse models, such as those engrafted with human hematopoietic stem cells into immunodeficient strains like NSG, support functional human immune responses for studying infections and therapies, as advanced by Shultz et al. in 2007. In 2025, researchers developed improved mouse models for studying systemic aging, better mimicking human inflammation and organ deterioration.^[108] These innovations underscore mice's adaptability to cutting-edge techniques while adhering to ethical standards.

As Pets and in Pest Control

Fancy mice, domesticated varieties of the house mouse (Mus musculus), are popular companion animals known for their diverse breeds, including satin mice with their glossy, high-sheen coats and long-haired mice featuring silky, extended fur that requires regular grooming to prevent matting.^[109][110] These breeds, along with others like standard short-haired types, come in various colors and markings, making them appealing to enthusiasts who breed and show them at events organized by groups such as the American Fancy Rat and Mouse Association.^[109] Proper housing for pet mice is essential to accommodate their active and social nature; a minimum enclosure size of 20 inches long by 10 inches wide by 12 inches high—equivalent to at least 10 gallons—is recommended for a single mouse, while larger enclosures (e.g., at least 80 cm x 50 cm x 40 cm floor space for 3-4 mice) are advised for groups to prevent stress and behavioral issues.^[111][112] Enclosures should include wire bars for ventilation, escape-proof lids, and enrichments such as exercise wheels, tunnels, and nesting materials to promote natural foraging and climbing behaviors, with deep bedding like aspen shavings for burrowing.^[113][111] Fancy mice typically live 1 to 3 years in captivity, though lifespan can vary based on genetics and care quality, and they thrive in small same-sex groups—females together and males separately to avoid aggression—due to their highly social instincts that mimic wild colony structures.^{[113][114][115]} Care for pet mice involves a balanced diet primarily consisting of commercial pelleted rodent food formulated with around 16% protein and 18% fiber to meet nutritional needs, supplemented sparingly with fresh vegetables, fruits, and seeds to prevent obesity and dental issues.^[116] Regular veterinary checkups are crucial, as exotic animal specialists can monitor for parasites, respiratory infections, and other conditions; owners should watch for signs like lethargy or weight loss and seek prompt care.^[111][117] Common health problems in older pet mice include tumors, particularly mammary gland tumors in females, which are frequent after one year of age and often malignant, requiring surgical intervention or palliative management from a veterinarian experienced in small mammals.^{[114][118][119]} In contrast to their role as pets, mice are often managed as pests in human environments due to their potential to damage crops, spread diseases, and contaminate food supplies. Common pest control methods include snap traps for quick kills and anticoagulant rodenticides, such as brodifacoum or bromadiolone, which prevent blood clotting over several days and are placed in tamper-resistant bait stations to minimize risks to non-target wildlife.^[120][121] Integrated pest management (IPM) approaches in agriculture and urban settings emphasize prevention through sanitation, sealing entry points, and habitat modification—such as removing food sources and clutter—before resorting to chemical or mechanical controls, reducing overall rodent populations while limiting environmental impact.^[120][122] Mice inflict significant economic damage globally, with rodent pests causing losses exceeding $30 billion annually to agriculture through crop consumption and contamination, particularly in stored grains and field crops like rice and wheat in developing regions (as of 2025).^[123] In urban areas, commensal mice exacerbate costs via structural damage and health-related expenses, contributing to broader invasive rodent impacts estimated in the tens of billions worldwide when including business disruptions.^[74] Regulations on pest control methods have evolved, with bans on inhumane glue traps—adhesive boards that cause prolonged suffering—implemented in regions like England since 2024 under the Glue Traps (England) Regulations, following earlier advocacy and EU animal welfare directives from the 2010s that influenced national policies against indiscriminate trapping.^[124][125]

Consumption and Cultural Roles

In various cultures, particularly in parts of Africa and Asia, mice and other small rodents serve as a traditional food source, often valued for their nutritional content during times of scarcity. Among the Tumbuka people of eastern rural Zambia, field mice known as mbeba are hunted seasonally and roasted as a delicacy, providing a high-protein snack that is deeply embedded in local customs and traditions.^[126] In Malawi, roasted field mice have historically been a seasonal treat, gaining renewed importance as a food savior during economic hardships like the COVID-19 pandemic, when they helped sustain rural communities.^[127] Similarly, in eastern Africa, Ethiopians along the western border consume mice and giant rats, while in west Africa, rodents constitute a significant portion of bushmeat diets, with species like the grasscutter rat being harvested for meat.^[128][129] In Asia, rodent meat enjoys popularity in countries like Vietnam and Cambodia, where wild rats—including field varieties—are sold in markets and even exported, with Cambodia shipping up to 2 tonnes per day during the peak season to Vietnam for consumption.^[130] Beyond human diets, mice are widely used as feed for captive reptiles, birds of prey, and other carnivorous pets, often provided live or frozen to mimic natural prey. Neonatal "pinkie" mice, which lack fur and are easily digestible, are a staple for young snakes and lizards, while larger varieties feed adult reptiles and raptors like hawks.^[131] This practice supports the pet trade and zoos, with specialized breeders ensuring hygienic production to minimize disease risks to predators.^[132] Historically, mice have featured in medicinal practices, particularly in medieval Europe, where they were applied in unconventional remedies. A 14th-century Irish manuscript describes a cure for baldness involving the application of pot-roasted mice aged one year, pulverized into a paste.^[133] Mouse excrement was also used externally to treat cataracts and other eye ailments, reflecting the era's reliance on animal-derived substances in pharmacology.^[134] In modern niche contexts, such as survival training, mice may be included in emergency diets for their caloric value, though this remains rare outside traditional settings.^[130] Mice hold diverse symbolic roles in global culture, often representing cleverness, timidity, or humility in folklore and literature. In Western cartoons, Mickey Mouse, debuting in 1928's Steamboat Willie, embodies playful ingenuity and has become an enduring icon of American pop culture. E.B. White's 1945 children's novel Stuart Little portrays a anthropomorphic mouse as an adventurous everyman, highlighting themes of belonging and resilience. In folklore, mice symbolize quick-witted survival, as seen in tales like Aesop's fables where they outsmart larger foes, or Eastern traditions where they denote diligence, such as in Korean zodiac lore associating the rat (a mouse relative) with wisdom and prosperity.^[135][136] Proverbs further illustrate this duality, with expressions like "quiet as a mouse" emphasizing stealth and caution, derived from ancient observations of their behavior, or the Greek-influenced "the mouse that tasted the pine-pitch," warning against bold starts that end in cowardice.^[137] Conservation concerns arise from the harvesting of mice for food and feed, particularly in bushmeat-dependent regions, where overexploitation can strain local populations. In Africa, the significant role of rodents in bushmeat trade—estimated to supply protein to millions—raises sustainability issues, as unregulated hunting contributes to declines in species like cane rats amid habitat pressures.^[129] In Asia, commercial rodent farming mitigates wild overharvesting, but wild collection persists, prompting calls for regulated practices to prevent ecological imbalances.^[130]