Muridae

The Muridae, commonly known as murids or Old World rats and mice, form the largest family of rodents and the most speciose family of mammals, encompassing approximately 876 species across 156 genera and 18 subfamilies.^[1] These small to medium-sized mammals are defined by key anatomical features, including a "keyhole"-shaped infraorbital foramen in the skull, a broad zygomatic plate, and sciurognathous (squirrel-like) lower jaws with prominent gnawing incisors adapted for constant growth and wear.^[2] Native to diverse habitats worldwide except Antarctica and many oceanic islands, murids exhibit remarkable ecological versatility, occupying terrestrial, semiaquatic, arboreal, fossorial, and even desert environments from tropical forests to tundra.^[2] Murids play pivotal roles in ecosystems as both predators and prey, with diets ranging from omnivorous foraging on seeds, fruits, and insects to specialized consumption of earthworms, fungi, or aquatic invertebrates in certain species.^[2] Their reproductive strategies are highly variable but generally prolific, featuring short gestation periods, large litters (often 4–12 young), and sexual maturity reached within months, enabling rapid population growth that contributes to their global success.^[2] Behaviorally, they employ a mix of solitary and social structures, communicate via tactile, chemical, and auditory signals, and demonstrate high motility for foraging and evasion.^[2] Economically and medically, murids have profound impacts on humans; species like the house mouse (Mus musculus) and brown rat (Rattus norvegicus) are commensal pests that damage agriculture, spread diseases such as plague and leptospirosis, and serve as reservoirs for zoonotic pathogens, while others are valued in biomedical research for genetic studies and as models for human physiology.^[2] Conservation challenges include habitat loss and invasive introductions, affecting endemic species in regions like Australia and islands, though many remain abundant due to adaptability.^[1] The family's evolutionary radiation, originating in the Early Miocene and diversifying through the Miocene, underscores its dominance in rodent biodiversity, with ongoing taxonomic revisions revealing cryptic species through molecular analyses.^[3]

Taxonomy

Definition and Etymology

The Muridae, commonly known as murids, represent the largest family of rodents and mammals overall, encompassing approximately 876 species across 156 genera. These rodents are predominantly Old World rats and mice, including familiar taxa such as the house mouse (Mus musculus) and the black rat (Rattus rattus), which have played significant roles in human history due to their commensal associations with settlements.^[4] The family's diversity underscores its evolutionary success, with species adapted to a wide array of ecological niches, though detailed classifications of subfamilies and genera are addressed elsewhere in taxonomic treatments.^[5] Muridae is classified within the order Rodentia and the superfamily Muroidea, forming one of the two primary families in this superfamily alongside Cricetidae. While both families share similarities as myomorph rodents—characterized by elongated snouts and continuously growing incisors—Muridae is distinguished phylogenetically by its predominantly Old World origins and lack of cheek pouches in most members, in contrast to many Cricetidae species like hamsters that possess them. This separation reflects deeper evolutionary divergences within Muroidea, supported by molecular and fossil evidence.^[6][7] The taxonomic name Muridae was formally established by the German zoologist Johann Karl Wilhelm Illiger in 1811, based on the type genus Mus. Its etymology derives from the Latin word mus (genitive muris), meaning "mouse," a direct reference to the core members of the family, which include all true mice. This nomenclature highlights the historical focus on murine forms, with the genitive form muris emphasizing the familial grouping around mouse-like rodents that often inhabit human structures, such as walls and homes.^[8][9]

Subfamilies and Genera

The family Muridae is classified into six main subfamilies based on a combination of morphological traits and molecular phylogenetic analyses: Murinae (true mice and rats), Deomyinae (African spiny mice and link rats), Gerbillinae (gerbils and jirds), Leimacomyinae (African brush-furred mice), Lophiomyinae (maned rat), and Otomyinae (African rock mice and whistling rats). This classification, as outlined in authoritative taxonomic references, reflects the family's diversity across approximately 156 genera and 876 species, with a strong emphasis on Old World distributions.^[1] Recent taxonomic revisions, driven by molecular phylogenetics, have solidified this six-subfamily structure while resolving prior uncertainties, such as elevating Deomyinae from a tribe within Murinae based on mitochondrial and nuclear DNA analyses.^[14] Debates persist regarding groups like Dendromurinae, traditionally allied with Muridae but now often excluded due to evidence of non-monophyly and reassignment to Nesomyidae from morphological and genetic data.^[15] These updates highlight the role of integrative approaches in clarifying the family's hierarchical diversity.

Physical Characteristics

Morphology and Size

Members of the family Muridae display considerable variation in body size, ranging from small species such as the African pygmy mouse (Mus minutoides), with a head-body length of approximately 5–7 cm and weight of 3–12 g, to larger forms like the Gambian pouched rat (Cricetomys gambianus), which can attain head-body lengths up to 40 cm and weights exceeding 1.4 kg.^[16] Tail lengths in murids often equal or exceed head-body length, serving functions in balance during quadrupedal locomotion and in thermoregulation through vasodilation and heat dissipation, as observed in species like the house mouse (Mus musculus).^[17][18] Morphologically, murids are characterized by a quadrupedal body plan with an elongated snout that facilitates olfaction and foraging, though specific sensory adaptations are detailed elsewhere. Many species possess relatively large eyes and ears, contributing to their overall head structure, while fur varies from soft and dense pelage in terrestrial mice to stiff, spiny coats in genera such as Acomys and Maxomys, where spines provide protection or aid in movement through vegetation.^[19][20] Limb morphology shows adaptations suited to diverse lifestyles; arboreal species like the harvest mouse (Micromys minutus) have elongated digits and flexible ankles for climbing, whereas fossorial forms such as mole rats exhibit robust forelimbs with strong claws for burrowing.^[21][22] Sexual dimorphism is evident in many murid species, particularly in body size, where males are typically larger than females, as seen in the Norway rat (Rattus norvegicus) and yellow-necked mouse (Apodemus flavicollis), potentially linked to intrasexual competition. Pelage coloration often exhibits dimorphism as well, with variations that enhance camouflage against local substrates, such as cryptic browns and grays in desert-dwelling gerbils (Gerbillinae) that match sandy environments.^[23][24]

Dentition and Sensory Adaptations

Members of the Muridae family exhibit a characteristic rodent dentition adapted for gnawing and grinding, with a dental formula of 1.0.0.3 / 1.0.0.3, consisting of one incisor, no canines or premolars, and three molars per quadrant, totaling 16 teeth.^[25] The incisors are hypsodont (high-crowned) and elodont (continuously growing without anatomical roots), enabling persistent gnawing on hard materials to maintain their chisel-like shape through wear against the opposing incisor.^[7] In contrast, the molars are typically brachydont (low-crowned) with well-defined roots and are anelodont (non-continuously growing), facilitating efficient grinding of plant and other food matter once erupted.^[7] Variations in molar structure within Muridae reflect dietary specializations, particularly between herbivorous and omnivorous species. Some herbivorous murids exhibit hypsodont molars that continue to grow throughout life, providing durability against abrasive vegetation.^[26] Omnivorous species, like many in the Murinae subfamily (e.g., rats and mice), retain simpler brachydont molars with enamel patterns that vary in complexity; for instance, lophodont (ridged) enamel in some taxa enhances grinding efficiency for mixed diets. These enamel configurations, including prismatic arrangements, allow for specialized occlusion and wear resistance tailored to ecological niches. Sensory adaptations in Muridae emphasize olfaction, tactile sensitivity, and audition over vision, supporting survival in diverse, often nocturnal environments. Acute olfaction is facilitated by large nasal cavities and expansive olfactory epithelia, which house numerous sensory neurons for detecting pheromones, food, and predators; nocturnal species allocate proportionally more brain volume to olfactory bulbs compared to diurnal counterparts.^[27] Sensitive vibrissae (whiskers), innervated by the trigeminal nerve, serve as mechanoreceptors for navigation and object localization in low-light conditions, with their arrangement forming a somatotopic map in the brainstem.^[28] Hearing extends into ultrasonic frequencies up to approximately 100 kHz, enabling detection of predator sounds and conspecific vocalizations beyond human auditory range.^[29] Vision is typically dichromatic, relying on short-wavelength (UV-sensitive) and middle-wavelength cones, which limits color discrimination but enhances sensitivity to ultraviolet light for foraging cues.^[30]

Evolutionary History

Origins and Fossil Record

The origins of the Muridae family trace back to Asia during the early Miocene, approximately 23 to 16 million years ago, within the superfamily Muroidea. The earliest definitive fossils of murids have been recovered from middle Miocene deposits in the Siwalik Hills of northern Pakistan, dating to around 14 million years ago, including the genus Antemus from the Chinji Formation, which represents one of the oldest known members of the family. These finds indicate an initial diversification in tropical southern Asia, where environmental conditions favored the evolution of small, adaptable rodents from hamster-like ancestors.^[31][32] Fossil evidence from China further supports an Asian cradle for Muridae, with early Miocene (about 20 million years ago) muroid forms such as Tachyoryctoides from the Lanzhou Basin in Gansu Province exhibiting primitive traits transitional to true murids. These specimens, including isolated teeth and jaw fragments, highlight the region's role in the family's initial radiation, though identification as stem murids underscores the transitional nature of these proto-murids. The overall fossil record remains sparse, attributable to the diminutive body size of early murids (typically under 100 grams), which reduced the likelihood of fossilization in fluvial and terrestrial sediments.^[33] By the late Miocene, murids had begun to diversify and disperse, as evidenced by genera like Huerzelerimys from European sites such as the Vallès-Penedès Basin in Spain and Baccinello in Italy, dated to around 10 to 7 million years ago.^[34] This presence signals early migration from Asia into Eurasia via continental connections. Subsequent spreads occurred to Africa during the late Miocene (~11 million years ago) through land bridges across the Arabian Peninsula, and to Australia in the early Pliocene via island-hopping across Wallacea, with fossil murines appearing in Australian deposits by approximately 5 million years ago.^[35][36] In contrast, the Americas saw limited pre-human colonization, with native murid fossils virtually absent until recent introductions by humans disrupted natural barriers.

Phylogenetic Relationships

Muridae forms a monophyletic clade within the superfamily Muroidea, consistently supported by analyses of both mitochondrial and nuclear DNA sequences, positioning it as the sister group to Cricetidae.^[37] This relationship is robust across multiple studies utilizing genes such as IRBP, cytochrome b, and GHR, resolving the major lineages of muroid rodents into distinct clades where Muridae encompasses the Old World rats, mice, and allies.^[38] The monophyly of Muridae is further corroborated by supermatrix phylogenies incorporating thousands of loci, affirming its divergence from other muroid families like Nesomyidae and Spalacidae. Recent Bayesian tip-dated analyses (as of 2024) estimate the crown age of Muridae at approximately 21.9 million years ago.^[39][37] Internally, Muridae exhibits a basal dichotomy separating the diverse Eurasian subfamily Murinae from a clade of predominantly African subfamilies, including Deomynae, Gerbillinae, and Leimacomyinae. Gerbillinae, comprising gerbils and jirds, represents an early-branching lineage adapted to arid environments, with phylogenetic analyses placing it alongside other African groups in a polytomy resolved by nuclear markers.^[6] Within Murinae, the phylogeny reveals multiple radiations, with African lineages such as Praomyini and Arvicanthini arising from repeated Eurasian colonizations, forming polyphyletic assemblages across the subfamily.^[14] Key molecular clock studies, calibrated against fossil constraints, estimate the crown radiation of Murinae at approximately 11-12 million years ago during the late Miocene, coinciding with climatic shifts that facilitated diversification in Eurasia and Africa.^[14] These analyses, employing relaxed Bayesian models on concatenated mitochondrial and nuclear datasets, indicate initial African colonizations around 11 million years ago, with subsequent bursts post-7-9 million years ago. A 2024 study refines the Murinae divergence to ~15 million years ago.^[14][37] Debates persist regarding polyphyly in genera like Rattus, where molecular phylogenies demonstrate paraphyly with respect to other Murinae tribes, necessitating taxonomic revisions based on multi-locus data from Southeast Asian and Oceanic species.^[40]

Distribution and Ecology

Geographic Distribution

The family Muridae is native to the Old World, encompassing Eurasia, Africa, and Australasia, but occurs naturally nowhere in South America or Antarctica.^[22][41] Several species within the family, such as the black rat (Rattus rattus), have been introduced worldwide through human-mediated transport, establishing populations on oceanic islands, in North America, and across South America.^[42][43] Species richness for Muridae reaches its peak in Southeast Asia, a biodiversity hotspot supporting over 150 species across diverse genera, while sub-Saharan Africa also harbors substantial diversity with dozens of native species in subfamilies like Murinae and Deomyinae.^[44][43] Notable endemism characterizes isolated regions such as Madagascar, where unique lineages have evolved, and the deserts of Australia, home to specialized hydromyine rodents comprising around 59 native species.^[45][46] The geographic expansion of Muridae traces back to post-Miocene dispersal events originating in Asia, with subsequent human-assisted introductions dating back thousands of years, beginning in antiquity, further promoting their near-cosmopolitan presence today.^[6][47]

Habitats and Environmental Adaptations

The family Muridae exhibits remarkable habitat diversity, occupying a wide array of ecosystems across Africa, Eurasia, Australasia, and introduced regions elsewhere, ranging from arid deserts and grasslands to moist tropical forests and montane zones. In tropical rainforests of Southeast Asia and New Guinea, arboreal species such as those in the genera Lenomys and Bullimus, often referred to as tree rats, thrive in the canopy, utilizing elongated limbs and prehensile tails for climbing and navigating branches. Conversely, in arid environments like the deserts of North Africa and the Middle East, burrowing species in the subfamily Gerbillinae, including gerbils such as Meriones unguiculatus, construct extensive underground tunnel systems to escape extreme daytime heat and conserve moisture. Temperate woodlands and savannas support ground-dwelling forms like Rattus species, while semiaquatic members, such as Hydromys chrysogaster in Australian wetlands, inhabit riparian zones with adaptations for swimming.^[2][48][22] Physiological adaptations enable murids to cope with water scarcity in desert habitats, where species like Mongolian gerbils (Meriones unguiculatus) possess kidneys with elongated loops of Henle and enhanced expression of aquaporins, allowing production of highly concentrated urine up to approximately 20 times hypertonic to plasma (osmolality ~6000 mOsm/L), thereby minimizing water loss during dehydration.^[49] These renal modifications, combined with behavioral strategies like nocturnal foraging, facilitate survival in environments with limited free water, relying instead on metabolic water from seeds. In contrast, arboreal murids in humid forests, such as the Sulawesi giant squirrel-like rats (Hyomys), feature velvety fur that repels moisture and specialized vibrissae for detecting prey in low-light canopy conditions, enhancing sensory acuity in dense vegetation.^[50][51][52] Energy conservation through torpor is a key adaptation in some temperate and subtropical murids facing seasonal resource fluctuations. For instance, the African fat mouse (Steatomys pratensis) employs daily torpor, reducing its metabolic rate and body temperature by up to 20°C during periods of food scarcity or high ambient temperatures, which helps mitigate energy demands in variable savanna habitats. Saltatorial locomotion has evolved in desert-dwelling species like the spinifex hopping mouse (Notomys alexis), where elongated hindlimbs and elastic tendons enable bipedal jumps of up to 2.5 meters, optimizing energy-efficient travel across open, sparse vegetation while evading predators.^[53][54] Nocturnal activity patterns predominate in many murid species across hot climates, allowing avoidance of diurnal heat stress; for example, the Arabian spiny mouse (Acomys russatus) restricts locomotion to cooler night hours, synchronizing with circadian rhythms to maintain thermoregulation in rocky desert terrains. In high-altitude environments, such as the Himalayas where species like the Himalayan field rat (Rattus nitidus) occur up to 4,000 meters, adaptations include elevated hematocrit levels to enhance oxygen-carrying capacity in hypoxic conditions, as observed in related Ethiopian murids like Arvicanthis abyssinicus. Thickened pelage provides insulation against cold, aiding thermoregulation in montane zones with diurnal temperature swings exceeding 30°C.^[55][56] Habitat fragmentation poses significant threats to murid populations, particularly for habitat specialists, as reduced patch connectivity increases isolation and elevates extinction risk; studies on fragmented landscapes show that generalist species like Rattus rattus persist better than arboreal endemics, whose small home ranges limit dispersal across barriers. This vulnerability is exacerbated in montane and forest habitats, where deforestation disrupts ecological niches essential for these adaptations.^[57][58]

Diet and Foraging Behavior

Members of the Muridae family display a broad dietary spectrum, with most species being primarily granivorous or omnivorous, feeding on seeds, fruits, nuts, insects, and green vegetation.^[59] This opportunistic consumption allows adaptation to diverse environments, where seeds from grasses and shrubs form a staple, supplemented by invertebrates during periods of scarcity.^[60] For instance, species like the sandy inland mouse (Pseudomys hermannsburgensis) rely heavily on seeds (up to 92% of diet) but shift to higher invertebrate intake in arid bust periods.^[60] Their dentition facilitates processing this varied intake, from hard seeds to softer plant matter.^[59] Specialized diets occur within the family, including mycophagous habits in bamboo rats of the genus Rhizomys, which incorporate fungi alongside vegetation, rhizomes, and occasional insects. Other specialists, such as grasshopper mice (Onychomys spp.), exhibit carnivorous tendencies, with diets comprising approximately 90% animal matter, including insects, scorpions, and even small vertebrates, while plant material remains minimal.^[61] Aquatic specialists like Hydromys chrysogaster consume fish, crustaceans, and plants, reflecting subfamily-specific adaptations.^[48] Foraging behaviors in Muridae are typically nocturnal, enabling raids on crops and natural food sources under cover of darkness to minimize predation risk.^[62] Many employ opportunistic caching strategies, storing seeds in burrows or scatter-hoards for later consumption, as seen in field mice (Apodemus speciosus), which hoard up to 70% of available acorns rapidly.^[63] This behavior supports survival in seasonal or unpredictable habitats but can lead to significant agricultural damage, with Muridae species causing direct gnawing on wheat stems, leaves, and grains throughout crop growth phases.^[62] Nutritional adaptations include hindgut fermentation in the cecum, where microbial activity breaks down fibrous plant material into short-chain fatty acids, enhancing energy extraction from low-quality diets.^[64] This process is crucial for granivorous and herbivorous species, allowing efficient nutrient absorption from seeds and vegetation. Dietary flexibility and caching influence population dynamics, as access to high-energy foods like seeds during booms supports rapid reproduction, while shifts to invertebrates sustain numbers during resource busts.^[60]

Reproduction and Life History

Members of the Muridae family display high reproductive output adapted to their typically small body size and r-selected life strategy, featuring polyestrous cycles that enable multiple breeding events annually. Gestation periods generally span 20 to 30 days across species, with litter sizes ranging from 3 to 12 young, reflecting variations in resource availability and habitat. For instance, in the house mouse (Mus musculus), gestation lasts approximately 19 to 21 days, and females can produce up to 10 litters per year under favorable conditions, underscoring the family's rapid reproductive turnover.^[65] Offspring in Muridae are altricial, emerging blind, hairless, and helpless, necessitating nest-based care for survival during early development. Parental investment is typically minimal, centered on lactation and basic nest defense for 2 to 3 weeks until weaning, though this can vary with species-specific traits. In the wild, average lifespan ranges from 1 to 3 years, constrained by predation, disease, and resource scarcity, whereas captive individuals often reach up to 5 years due to reduced stressors and consistent nutrition.^[66][67][68] Reproductive patterns are modulated by environmental cues, including seasonal breeding in temperate regions where activity intensifies during warmer months to align with peak food resources. Density-dependent mechanisms further regulate fecundity, as elevated population densities induce stress that delays ovulation or reduces litter success, helping maintain population stability.^[69][70]

Behavior and Social Structure

Locomotion and Communication

Members of the Muridae family exhibit diverse locomotion strategies adapted to their varied habitats, ranging from terrestrial to arboreal and aquatic environments. In arid and open habitats, gerbils (subfamily Gerbillinae) employ bipedal hopping as a primary mode of locomotion, utilizing elongated hindlimbs and a stiffened tail for stability during saltatory movement, which allows efficient travel over sandy substrates at speeds up to about 1.1 m/s.^[71] Arboreal species, such as certain rats in the genus Rattus or Old World tree rats like Thallomys paedulcus, rely on climbing, employing flexible forelimbs, grasping feet, and long tails that serve as counterbalances to navigate branches and vines, with tail lengths often exceeding body length to enhance maneuverability on discontinuous supports.^[72] Semi-aquatic forms, including the Australian water rat Hydromys chrysogaster, utilize paddling with webbed hindfeet for propulsion during swimming, achieving speeds of approximately 0.3 m/s while keeping the body buoyant at the water surface, though the tail primarily aids in steering rather than direct thrust.^[73] Across these taxa, the tail plays a crucial role in balance and propulsion; for instance, in jumping and climbing, it provides angular momentum to prevent falls, while in swimming, it contributes to directional control. Communication in Muridae is multifaceted, incorporating acoustic, chemical, and seismic signals to convey information about alarm, mating, and territory. Ultrasonic vocalizations, typically in the 20–100 kHz range, are prevalent, with rats (Rattus norvegicus) producing 22-kHz flat calls during aversive events like predator encounters to signal alarm and elicit freezing responses in conspecifics, and 50-kHz frequency-modulated calls (e.g., upsweeps and downsweeps) during mating or affiliative interactions to attract partners and indicate positive affect. Mice (Mus musculus) emit complex frequency-modulated syllables, including U-shaped and complex forms, primarily by males during courtship to facilitate mate recognition and approach. Scent marking via specialized glands, such as preputial and sebaceous glands in males, deposits volatile compounds that signal dominance and reproductive status; for example, dominant male house mice produce androgen-dependent marks that deter subordinates and influence female mate choice for up to 48 hours. Substrate drumming, observed in gerbils like Meriones unguiculatus, involves rapid hindfoot thumping to generate seismic vibrations, serving as an alarm signal to warn of predators or intruders and communicate territorial boundaries over short distances. Muridae lack echolocation, relying instead on other sensory modalities for orientation in low-light conditions, as ultrasonic emissions in this family function for social communication rather than echo-based navigation. Whisker-assisted navigation, or thigmotaxis, is prominent in burrow-dwelling species; vibrissae on the mystacial pad detect tactile cues from tunnel walls, enabling precise movement in dark subterranean environments without visual input, as seen in the African giant pouched rat (Cricetomys gambianus), where long, robust whiskers facilitate backward and forward traversal of complex burrows. This sensory integration complements olfactory and auditory cues, allowing efficient foraging and escape in confined spaces.

Social Organization and Predation Avoidance

Social organization within the Muridae family exhibits considerable variation across species, reflecting adaptations to diverse ecological pressures. Many rat species, such as those in the genus Rattus, tend to be solitary or form loose aggregations, with individuals maintaining personal space except during mating seasons.^[43] In contrast, numerous mouse species, including the house mouse (Mus musculus), are colonial and live in groups where dominance hierarchies emerge, often established through agonistic interactions like fighting and chasing among males.^[74] These hierarchies determine access to resources and mates, with dominant individuals suppressing subordinates via pheromonal cues and physical displays.^[75] Territoriality is prevalent in many murids, enforced through scent-marking with sebaceous glands, particularly by males who delineate boundaries to deter intruders and reduce competition.^[43] Infanticide occurs in some species, such as Mus musculus and the Norway rat (Rattus norvegicus), where unrelated males may kill offspring to bring females into estrus, thereby enhancing their own reproductive success.^[76] Predation avoidance strategies in Muridae are multifaceted, combining behavioral, morphological, and life-history traits to mitigate risks from diverse predators like birds of prey, snakes, and carnivores. Burrowing networks serve as primary refuges, with species like the four-striped grass mouse (Rhabdomys pumilio) constructing complex underground systems that provide escape routes and protection during vulnerable periods.^[43] Vigilance behaviors are enhanced in social species, where group members alternate scanning for threats, allowing individuals to forage more efficiently while reducing per capita risk; for instance, exposure to predator odors prompts heightened alertness in murids such as spiny mice (Acomys spp.).^[77] Morphological defenses include spiny fur in genera like Acomys, which deters grasping by predators, and neutral pelage for camouflage in open habitats.^[78] As r-selected strategists, many murids compensate for high predation through elevated reproductive rates, producing large litters (e.g., 4–12 young per Mus musculus litter) with short gestation periods to ensure population persistence despite frequent losses.^[43] Communication via scents and vocalizations briefly aids these collective defenses by alerting kin to dangers.^[43]

Human Interactions

Cultural Significance and Literature

In ancient Egypt, mummified mice of the house mouse species (Mus musculus), a member of the Muridae family, have been unearthed in sites like the Sacred Falcon Necropolis at Quesna, suggesting occasional incidental or votive inclusion in rituals associated with the god Horus, despite rodents' predominant status as pests without strong divine ties.^[79] In medieval and early modern European folklore, rats were frequently linked to witchcraft as familiars—demonic entities in animal guise that witches allegedly used to perpetrate harm, as evidenced in 16th-century English trial accounts and pamphlets depicting rats alongside other creatures like cats and toads.^[80] Across cultures, murids occupy diverse symbolic roles. In Hindu mythology, the mouse (or rat) called Mushika serves as the sacred vahana, or mount, of Lord Ganesha, embodying humility, adaptability, and the triumph over ego and uncontrolled desires, thereby elevating the rodent to a revered status as a divine companion.^[81] Western traditions, by contrast, have long cast rats and mice as emblems of cunning infestation and moral corruption, reinforcing their pestilent reputation in folklore and societal narratives. Literary works have perpetuated these dualities. Rats symbolize plague and existential threat in Albert Camus's The Plague (1947), where swarms of staggering, dying rats emerge in the Algerian town of Oran as harbingers of epidemic horror, mirroring broader themes of human indifference and resilience against catastrophe.^[82] The Pied Piper of Hamelin legend, rooted in 13th-century German folklore, depicts rats as insidious invaders that a cunning piper lures to drown in the River Weser with his enchanted music, only for the rodents' role to underscore themes of betrayal and retribution when the piper turns on the deceitful townspeople.^[83] Mice fare more positively in Aesop's fables, such as "The Lion and the Mouse," where a timid mouse gnaws through a net to free a trapped lion, imparting the moral that kindness from the weak can repay the strong and that no act of mercy is wasted.^[84] Modern media has often reframed murids with empathy and humor. In Pixar's Ratatouille (2007), the rat protagonist Remy pursues culinary mastery in a Parisian kitchen, subverting stereotypes of rats as vermin to explore ambition, prejudice, and the sensory artistry of food across species barriers.^[85] Likewise, the film Stuart Little (1999), adapted from E.B. White's novel, portrays a mouse adopted by a human family, using his outsider status to delve into themes of identity, family bonds, and societal acceptance of difference.^[86]

Economic Impact and Conservation Concerns

Muridae species, particularly commensal rats and mice, exert considerable negative economic pressure as agricultural and structural pests. Globally, rodent damage to crops—through direct consumption, contamination, and spoilage—results in reported annual costs of at least US$3.6 billion (1930–2020 total), with estimates reaching up to US$163 billion annually, affecting staple grains like rice and wheat in regions such as Asia and Africa where yield reductions can reach 20-30% in severe outbreaks.^[87][88] These pests also cause structural destruction by gnawing on electrical wiring, insulation, and building materials, leading to fire hazards and repair costs estimated in the billions for urban and industrial settings. Conversely, murids provide economic benefits in scientific research; mice and rats from this family account for approximately 95% of laboratory animals used worldwide, enabling breakthroughs in genetics, pharmacology, and disease modeling that underpin the biomedical industry.^[88][89] Beyond economic costs, murids pose significant public health risks as vectors for zoonotic diseases. Species like the black rat (Rattus rattus) and brown rat (Rattus norvegicus) transmit bubonic plague via fleas infected with Yersinia pestis, historically causing pandemics and still leading to thousands of cases annually in endemic areas. They also spread leptospirosis through urine-contaminated water and soil, resulting in severe infections that affect kidneys and liver, with global incidence exceeding 1 million cases per year. Other diseases include hantavirus and rat-bite fever, often contracted via direct contact or contaminated food. To mitigate these threats, integrated pest management relies heavily on rodenticides such as anticoagulants, though their application must balance efficacy with risks to non-target wildlife.^[90][91][92] Conservation concerns for Muridae are mixed, with the vast majority of the family's approximately 870 species classified as Least Concern by the IUCN due to their resilience and broad distributions.^[93] However, habitat destruction from logging, agriculture, and urbanization threatens over 100 species, rendering them Vulnerable, Endangered, or Critically Endangered; for instance, the alpine woolly rat (Mallomys gunung) in New Guinea's montane forests is Endangered, primarily due to ongoing deforestation and logging in protected areas like Lorentz National Park. Invasive murid populations, such as introduced rats on oceanic islands, exacerbate biodiversity loss by preying on native fauna and competing for resources, contributing to the extinction or decline of over 100 island-endemic species worldwide. Efforts to address these issues include habitat protection and eradication programs for invasives, though challenges persist in remote regions.^{[94][95][96][97][98]}