The Natural History of Model Organisms: The Norway rat, from an obnoxious pest to a laboratory pet
- Article
- Figures and data
- Abstract
- Introduction
- Natural history
- Ecology
- Characteristics of the wild Norway rat
- Early history of research with the laboratory rat
- Comparison with other animal models
- Variety of strains and stocks
- Changes occurring in the process of laboratorization of Rattus norvegicus
- Impact of domestication on research and research results
- Attempts to recreate new laboratory rat populations from wild colonies
- Conclusion
- Data availability
- References
- Decision letter
- Author response
- Article and author information
- Metrics
Abstract
The laboratory rat was the first mammal domesticated for research purposes. It is descended from wild Norway rats, Rattus norvegicus, which despite their name likely originated in Asia. Exceptionally adaptable, these rodents now inhabit almost all environments on Earth, especially near human settlements where they are often seen as pests. The laboratory rat thrives in captivity, and its domestication has produced many inbred and outbred lines that are used for different purposes, including medical trials and behavioral studies. Differences between wild Norway rats and their laboratory counterparts were first noted in the early 20th century and led some researchers to later question its value as a model organism. While these views are probably unjustified, the advanced domestication of the laboratory rat does suggest that resuming studies of wild rats could benefit the wider research community.
Introduction
The Norway rat, Rattus norvegicus, is known by many names such as the brown rat, common rat, sewer rat, Hanover rat, Norwegian rat, city rat, water rat and wharf rat. Living in close proximity to humans, wild Norway rats are often considered pests (Khlyap et al., 2012). They are well known for invading and damaging property, spoiling food supplies and spreading diseases (Kosoy et al., 2015). Their seemingly unrestricted capacity to reproduce, their ferocious appetite (which can result in cannibalism) and their remarkable ability to survive in adverse and often unsanitary conditions only seem to worsen their reputation among many in the general public. For all of these reasons and more, rats are the targets of intensive pest control strategies.
In spite of their bad reputation in the wild, the laboratory rat is perhaps the archetypal model organism. Widely used in fields such as neuroscience, physiology and toxicology, ‘lab rats’ account for 13.9% of all animals used in research in Europe (European commission, 2012), second only to mice which account for 60.9%. First domesticated from wild Norway rats over 170 years ago (Richter, 1959), today laboratory rats owe their popularity as a model organism largely due to their widespread availability, low breeding costs, short reproductive cycle and ability to thrive in captive environments.
Laboratory rats differ from Norway rats in the wild, just like many other model organisms (Alfred and Baldwin, 2015). In the mid-20th century, these differences led some researchers to suggest that the laboratory rat had become a degenerated form of its wild cousins and lost its value as a study model (Beach, 1950; Lockard, 1968). While these views are probably unjustified, researchers working with laboratory rats should remain aware of its advanced domestication. While few modern laboratories study wild R. norvegicus colonies, a better appreciation of the rat’s natural history would expand its value as a model organism. Resuming studies of wild rats would give the opportunity to not only ‘refresh’ genetic lines and create new highly specialized strains, but also document the many changes that have taken place in wild populations since most laboratory lines were first obtained.
Natural history
Rattus norvegicus is one of over 60 species in the mammalian genus Rattus (Musser and Carlton, 2005), which can be divided into seven systematic groups (Box 1). The deepest divergence within the genus occurred 3.5 million years ago and separates a lineage of rats that are endemic to New Guinea from the other groups (Robins et al., 2008). Rats belong to the Muridae family in the Rodentia order. This family also includes mice (genus Mus), and rats and mice are thought to have diverged about 40 million years ago (Adkins et al., 2001).
Box 1.
Systematics of the genus Rattus.
According to Musser and Carlton (2005), the species belonging to the genus Rattus may be divided into seven groups:
the "norvegicus" species group, including R. norvegicus and a few related species
the "exulans" species group comprising only Rattus exulans (the Polynesian rat)
the "rattus" group comprising Rattus rattus (black rat or roof rat), Rattus tanezumi (Tanezumi rat) and a large number of closely related species
the native Australian group, including Rattus fuscipes (bush rat)
the native New Guinean group including Rattus leucopus (Cape Cork rat) and Rattus praetor (large New Guinea spiny rat)
the native Sulawesian group, including Rattus xanthurus (yellow-tailed rat)
an uncertain "group" containing unaffiliated species whose phylogenetic history has not yet been established
Despite its name, the Norway rat most likely originated in Asia. It diverged from its sibling species the Himalayan field rat (Rattus nitidus) around 620–644 thousand years ago (Teng et al., 2017), and some of the oldest remains of R. norvegicus have been discovered in the Chinese province of Sichuan-Guizhou (Musser and Carlton, 2005). The Norway rat got its name as it was believed to have immigrated to England from Norway aboard ships in the 18th century. However, the species originally arrived in European countries from Asia via Russia, superseding the older black rat Rattus rattus. Numerous remains of the species have been discovered at archaeological sites dated to the 14th century (for instance, in Tarquinia, Italy), suggesting that small populations of these rats had actually inhabited Europe earlier than previously thought (Clark et al., 1989). The Norway rat reached North America between 1750 and 1775 (Nowak, 1999). Some places in northeast and central Asia were not inhabited by the Norway rat until the last decades of the 20th century (Khlyap and Warshavsky, 2010).
Ecology
Rats live in almost all terrestrial environments except deserts, tundra and polar ice. They adapt easily to new conditions thanks to their physical resilience, omnivorous diet and flexible behavior. Like the black rat, the Norway rat often lives in the immediate vicinity of humans, including in cities (Aplin et al., 2011), and can pose a serious threat to human health because it may carry various pathogens and parasites (Box 2). Wild Norway rats often inhabit storage facilities, basements, deserted buildings and landfill sites where human-generated waste is deposited (Sacchi et al., 2008). In cities, its habitats are distributed irregularly, and each rat’s home range is relatively restricted compared to rats in less urban settings. City rats prefer areas with rich vegetation, banks of water reservoirs, old buildings and sewer systems (Ayyad et al., 2018; Traweger et al., 2006; van Adrichem et al., 2013). They dig burrows and build extensive systems of tunnels and passages in riverbanks and open spaces, where they live and breed (Barnett, 2005). Like most mammals, rats are characterized by female philopatry and male dispersal (Gardner-Santana et al., 2009). Rats choose their habitats based on the availability of shelter, food and water (Orgain and Schein, 1953).
Box 2.
Disease and pest control.
Wild Norway rats are commonly perceived as dirty animals, inhabiting sewage systems and feeding on garbage. While the reality is that rats are fastidiously clean animals that groom themselves several times a day, they are nonetheless vectors of numerous diseases. Bacterial infections can spread from rats to humans via multiple routes, including rat bites or contact with the animal’s urine (Himsworth et al., 2013). Other bacteria are transmitted from rats to humans by fleas (Civen and Ngo, 2008). These include bacteria in the genus Yersinia which cause bubonic plague. Yersinia bacteria are present in wild rat populations inhabiting cities in Africa, southeast Asia, and South America (Boey et al., 2019). However, contrary to popular belief, it was the black rat and not the Norway rat that was most likely responsible for the pandemic outbreak of bubonic plague that occurred in the 14th century. Rats are also an important source of antimicrobial resistant bacteria which may infect humans and other animals (Gakuya et al., 2001), and they are the primary reservoir of a hantavirus known as Seoul virus, which causes a hemorrhagic fever with renal syndrome in humans (Jonsson et al., 2010).
Due to the disease risk they represent (and the material damage they can cause), humans have strived to eliminate rats from their settlements for centuries. Today the most commonly used pest control methods include traps, rodenticides, biological control, reproductive inhibition and ultrasonic devices (Tobin and Fall, 2004). Older toxic compounds – such as sodium fluoroacetate, strychnine and zinc phosphide – are still used but have limited efficacy for large populations and long-term campaigns. Rats quickly develop strong aversion to the taste of substances which have caused illness (Riley and Tuck, 1985). The use of these chemicals is also far from ideal because they pose an intoxication risk to other animals including protected species, pets and humans.
The most important improvement in pest control technology was the development of anticoagulant rodenticides in the 1940s, with a second generation developed in the 1970s. These agents decrease blood clotting and their delayed effect means that rats consume a lethal dose before they show any symptoms of poisoning. With time, however, large populations of rats have acquired genetic resistance to these kinds of rodenticides (Meerburg et al., 2014), and third-generation anticoagulant rodenticides are currently under study (e.g., Damin-Pernik et al., 2017). Recently, integrated pest management strategies (focusing on long-term prevention or suppression of pest problems with minimum impact on human health and the wider environment) have been implemented to tackle rat infestations (Flint et al., 2003).
Characteristics of the wild Norway rat
Reproduction
Wild rats reach sexual maturity at about 11 weeks, remain pregnant for 21–24 days, and give birth to litters of about 7 or 8 pups. Female rats build nests before giving birth, and the young are born almost naked, blind and totally dependent on the mother (Burton and Burton, 2002). The young start leaving the nest and ingest solid foods at about 14 days after birth. R. norvegicus can breed all year long and has 3–5 litters per year on average. Its life expectancy is slightly more than 1 year (Davis, 1953).
Behavior and senses
The Norway rat is primarily nocturnal. It prefers small, dark, confined places and avoids moving in open and well-lit spaces. It tends to move on four limbs with its fur and whiskers in contact with the walls and large objects. It can also jump (Himmler et al., 2014), and swim and dive (Galef, 1980; Stryjek et al., 2012). Rats have no sweat glands and regulate their body temperature through behavior, for example, by hiding in burrows. The sparsely haired tail also plays a part in thermoregulation (Owens et al., 2002).
In rats, the main sensory input is touch from the facial whiskers (or vibrissae) and a particularly well-developed sense of smell (Uchida and Mainen, 2003). Wild Norway rats have relatively poor eyesight and are sensitive to sharp light (Finlay and Sengelaub, 1981; Prusky et al., 2002). They have dichromatic color vision thanks to two classes of cone cells on the retina: one sensitive to ultraviolet light and the other most sensitive to the middle wavelengths of the visible spectrum, such as the color green (Jacobs et al., 2001). They can detect sounds between about 0.25–80 KHz (Heffner et al., 1994), which enables them to communicate with ultrasound (Portfors, 2007; Burke et al., 2018). These vocalizations are inaudible to humans without the use of specialized equipment.
Exploration and neophobia
Rats are highly inquisitive and eager to explore new environments but exhibit neophobia (i.e., caution towards new objects; Pisula, 2009). They also markedly reduce their food intake after they are introduced to an unfamiliar food. This "food neophobia" is typified by the initial avoidance of the new food, followed by gradual sampling (Barnett, 1958). If the new food does not become associated with adverse body symptoms, the rats will eat more (Barnett, 2009; Mitchell, 1976). Rats develop an aversion to foods that cause adverse effects within up to 6 hours (Misanin et al., 2002; Revusky and Bedarf, 1967), which often limits the effectiveness of traditional pest control procedures.
Social behavior
Rats live in groups and establish social relations. In favorable conditions they can form colonies of several hundred individuals. The colonies comprise groups with an adult male and a few females with their young. These groups inhabit certain areas, called territories, which are delineated and marked with scent cues (Adams, 1976; Barnett, 2009). The males defend their territories against intruders from other groups (referred to "resident-intruder aggression"; Koolhaas et al., 2013). Social aggression in males may increase while cohabiting with females (Albert et al., 1988). When individual rats meet, they examine each other thoroughly, relying on scent to learn about the sex, age, health, reproductive status and nutrition of the other rat. If an individual is not recognized as a representative of its own group, the intruder may be attacked and will often retreat from the territory (Miczek and de Boer, 2005). Female rats defend their nests and offspring against intruders and their social aggression increases in the postpartum period (Consiglio and Lucion, 1996).
Juvenile rats engage in play-fighting (Pellis and Pellis, 1987). Rats in the same group groom each other, sleep in tight groups and huddle. The group also provides a setting for rats to learn from each other about food sources and food quality. Rats develop preferences for particular foods by sniffing at the mouth and fur of an individual who has finished eating (Galef, 1993). There is no evidence that aversion to foods that have made a specific individual sick is transmitted from one individual to the next.
Early history of research with the laboratory rat
The Norway rat is often considered the first mammal to have been domesticated for research purposes (Richter, 1959). Although some scientists point to the sporadic use of rats in experiments prior to 1850, the first known documented experiment conducted on these animals was a study of the effects of adrenalectomy published in 1856 in France (Philipeaux, 1856). In 1863, a study on the nutritional quality of proteins was conducted on mixed colored rats (Savory, 1863). The rat was first used in psychological studies by Adolph Mayer, a well-known American psychiatrist (Logan, 1999). After 1893, American neurologist Henry Herbert Donaldson started to use rats in biomedical experiments conducted at Chicago University (Lockard, 1968). When he took a post of the director of the Wistar Institute, he brought with him four pairs of albino rats that he then used in multidisciplinary studies conducted together with a large group of scientists. Donaldson intended to standardize the albino rat to create a universal model suited for biomedical research (Lindsey and Baker, 2005). Researchers at the Wistar Institute developed special breeding and reproduction techniques for rats. They designed special cages and entire buildings adapted specially for rat breeding. In 1912, the Wistar Institute began supplying laboratory rats to other research institutions (Lindsey and Baker, 2005).
The breeding colony established by Donaldson inspired his PhD student John Broadus Watson to conduct further experiments which resulted in ground-breaking discoveries in behavioral studies. In 1914, Watson published the book Behavior: An Introduction to Comparative Psychology, which became a major text in the field of animal psychology. His work was developed by Curt Paul Richter, who published numerous studies on topics such as domestication, stress, the biological clock and adrenalectomy between 1919 and 1977 (Lindsey and Baker, 2005).
Comparison with other animal models
Rats are often used in similar studies to mice (Phifer-Rixey and Nachman, 2015), though their larger size means they are more useful in some experiments, such as those involving surgery and imaging (Jonckers et al., 2011). Rat models are also considered more reliable than mouse models in the study of certain addictions (Vengeliene et al., 2014), cancer immunotherapy (Bergman et al., 2000), and diabetes and related conditions (Obrosova et al., 2006). Some research areas in which rats are commonly used models now make more and more use of other animal models instead, such as the zebrafish (Danio rerio; Parichy, 2015; Stewart et al., 2012: Kari et al., 2007).
Variety of strains and stocks
Numerous strains of laboratory rat have been created to ensure control over the genetic variation in experimental subjects. However, the roots of the phylogenetic tree of the laboratory rat strains have not yet been established. Some researchers suggest several independent domestication pathways (e.g., Festing, 1979), but there is no consistent evidence to support this notion. More recent genetic studies based on the measurements of mutation rates in different parts of the rat genome have clarified the relationships between the different strains and led to a shared phylogenetic tree for most inbred strains (Thomas et al., 2003).
Based on their breeding history, laboratory rats may be broadly divided into outbred stocks and inbred strains (Table 1). The outbred stocks are usually used for general study purposes where homozygosity is not crucial and are well suited for behavioral studies. The inbred strains are used for researching issues related to genetic and phenotypic characteristics (Sharp and Villano, 2012). Rat models are also created in laboratories by means of electrical, pharmacological and surgical techniques that induce changes in the animals (e.g., Calcutt, 2004; Teixeira and Webb, 2007; Relton and Weinreb, 2008; Obenaus and Kendall, 2009).
Rat strains differ significantly in their morphology: their body weight and the size of internal organs may vary greatly, while the body length remains the same (e.g., Reed et al., 2011). For example, albino strains consistently exhibit impaired vision, while other strains appear to have the wild-type or even enhanced visual acuity (Prusky et a., 2002). Metabolism and behavior differ between certain strains as do the way these characteristics change with age (Clemens et al., 2014). Differences may also occur where social behaviors are concerned: for example, when play-fighting, juvenile Wistar rats initiate significantly fewer playful attacks than Fisher 344 rats (Schneider et al., 2014).
As many breeding colonies have been isolated for several decades, the inbred animals have different phenotypes than their counterparts bred elsewhere (e.g., Goepfrich et al., 2013). Environmental conditions and specific breeding settings lead to epigenetic differences, while several decades of breeding may result in a cumulation of mutations, which subsequently hinders the generalization of results even to the animals of the same strain (Box 3).
Box 3.
Unanswered questions about the natural history of the laboratory rat.
Even though the rat is one of the oldest model organisms used in scientific studies, there are still many gaps in our knowledge about this species. By the same token, the common use of rats in scientific research generates new questions and doubts.
Do the differences in morphology, physiology or behavior among rats of the same strain obtained from different breeders have a significant effect on the replicability of studies? What is the genetic variability within and between the laboratory populations of R. norvegicus? In other words, how stable and robust is the rat model based exclusively on the characteristics of a single strain?
Nocturnal activity, a tendency to stay close to ground level, and a dominant sense of smell are all traits that rats likely share with the common ancestor of all mammals (Finlay and Sengelaub, 1981), but to what extent are the results obtained in studies conducted on rats also true of mammals in general and to what extent are they typical of rats only?
The value of animal models in studying the effectiveness of, for instance, treatment strategies in clinical tests has remained controversial. To what extent can a single-species animal model, like the rat, accurately represent a process occurring in humans?
Controversial aspects of using animals in scientific research, such as inflicting pain on animals, also raise questions. How often is it possible to use alternative methods and models for those experiments that have routinely used rats in the past?
What is the genetic and epigenetic basis of their physiological and behavioral plasticity which allows rats to adapt to diverse environments? How will wild rat populations cope with rapid environmental changes, like climate change or the ubiquity of pharmacological substances in food and water?
Changes occurring in the process of laboratorization of Rattus norvegicus
Morphological and physiological changes
The differences between laboratory rats and wild Norway rats were first noticed and described in the 1920s (King and Donaldson, 1929), when it was seen that laboratory rats differed from their wild counterparts in morphology and behavior after only 10 generations of inbreeding. In the second half of the 20th century, a series of morphological differences were spotted between the Wistar rats and trapped wild rats (Richter, 1952). The laboratory rats were smaller at maturity but did not differ significantly in their skeletal structure and teeth anatomy. The liver, heart, brain and adrenal glands were smaller, while the gonads and secondary sex organs developed at an earlier age (Richter, 1952). Domesticated female rats reached sexual maturity earlier and had bigger litters, which may indicate that domestication accelerated sexual development and increased reproductive success (Clark and Price, 1981). Domestication significantly affected their brain morphology too, the neocortex being the most markedly altered brain structure (Welniak-Kaminska et al., 2019). There are also significant differences in the circadian rhythm and out-of-nest activity between the laboratory and wild rats (Stryjek et al., 2013).
Behavioral changes
Compared to their wild counterparts, laboratory rats show less interspecific aggression (Barnett et al., 1979). Defensive behaviors are also reduced, resulting in smaller reactions to both humans and conspecifics (Blanchard et al., 1986). Longitudinal studies of social behavior, such as play-fighting in juvenile rats, show that laboratory rats initiate more playful attacks and are more likely to defend themselves. Wild Norway rats are however more likely to use evasive actions to defend their nape than to wrestle with their partner (Himmler et al., 2014; Himmler et al., 2013).
In laboratory, where it is impossible to delineate separate territories, individual rats instead establish social hierarchies (Adams and Boice, 1989; Blanchard et al., 1988). Laboratory rats present a lower neophobia level (Calhoun, 1963; Cowan, 1977; Tanaś and Pisula, 2011), however early claims that laboratory rats exhibit lower food neophobia (Barnett, 1958; Mitchell, 1976) were not replicated in a more recent study (Modlinska et al., 2015).
Both laboratory and wild rats explore their environments, but the response to a novel object in a familiar environment is less pronounced in wild subjects (Tanaś and Pisula, 2011). Domesticate rats seem to learn more quickly than wild rats (Price, 1972), tending to perform better in laboratory learning paradigms (Boice, 1981).
Wild rats have a broad repertoire of swimming-related behaviors, while laboratory rats are reluctant to swim (Stryjek et al., 2012). Wild rats build more complex and more durable tunnels and, unlike their laboratory cousins, inhabitable underground burrows (Stryjek et al., 2012).
Impact of domestication on research and research results
Differences between laboratory rats and wild rats had previously prompted several scientists to question the legitimacy of generalizing the results of studies conducted on laboratory rats to the species as a whole, or other organisms (Beach, 1950; Lockard, 1968). Yet comparative studies have shown that domestication rarely modifies an animal’s behavioral repertoire to any significant extent (Price, 1999; Stryjek et al., 2012; Modlinska et al., 2015). Instead, most changes tend to affect the frequencies of certain behaviors, or the thresholds at which a stimulus will trigger a response.
Some features of domestication have also unintentionally increased the utility of rats as a model organism. For instance, the laboratory rats’ reluctance to swim and their determined attempts to get out of water are crucial to the Water Morris Test, a popular protocol in the study of memory and learning (cf. Whishaw and Pasztor, 2000).
Attempts to recreate new laboratory rat populations from wild colonies
Several researchers aware of the problems arising from the domestication of the rat conducted experiments on wild Norway rats and comparative studies of both lines. Samuel Anthony Barnett, the author of the classic text "The Rat: A Study in Behaviour" (first published in 1963), caught wild rats and studied them in his laboratory for decades since 1950s, and in the process developed several techniques for handling them (Barnett, 2009). Beginning in 1970s, Bennett G Galef also extensively studied wild Norway rats with a specific focus on their feeding behaviors (e.g., Galef and Clark, 1971), and Robert J Blanchard spent many years investigating the defensive and aggressive behaviors of these animals (e.g., Blanchard et al., 1986).
Jaap Koolhaas also conducted experiments with wild caught Norway rats in the late 1990s (Koolhaas et al., 1999). He studied stress and aggression, and the wild rats were particularly well suited for those experiments due to their poor adaptation to the laboratory setting and their emotional constitution. His work on wild rats resulted in the creation of a wild line of R. norvegicus – the Wild-type Groningen rats.
In 2006, a new laboratory colony of wild Norway rats was set up in Poland (Stryjek and Pisula, 2008). The new line was named WWCPS, which short for Warsaw Wild Captive Pisula Stryjek (Figure 1). In order to prevent the development of domestication features in the breeding colony and maintain the animals’ ‘wild’ genetic status, the colony was systematically enlarged with captured rats in various locations. Since it was established, comparative studies involving rats from this colony have added to the list of known differences between wild rats and laboratory rat lines (Stryjek et al., 2012; Modlinska et al., 2015; Himmler et al., 2014; Himmler et al., 2013; etc.).
It is important, however, to note that wild rats are not easily handled or manipulated. The fact that these animals are less suited to a laboratory setting can impact the results obtained from them. Wild rats in a laboratory have a higher level of stress hormones in their blood plasma than domesticated laboratory rats; they also exhibit stronger responses to emotional stressors and novel objects (Naumenko et al., 1989; Plyusnina et al., 2011; Koizumi et al., 2019). These factors must be taken into consideration when interpreting results and may constrain the kind of studies that are feasible using wild rats. Before conducting experiments with wild individuals, researchers may need to develop special procedures that better approximate the natural conditions of these animals (i.e., that have "high ecological validity"). Efforts must be made to reduce the stress involved in the breeding and experimental manipulations, as it may affect rat welfare. Nevertheless, studies on wild animals, that have not been subjected to the domestication process, could help the community to assess the generality or specificity of results obtained with laboratory lines. The fact that wild rats show more variability between individuals with regard to many biological traits may also be useful when studying the impact of various stimuli (e.g., environmental changes) on such complex and variable populations. Such experiments would be difficult to achieve using standardized laboratory strains.
Conclusion
Many of the traits that make Norway rats a pest in the wild are the same traits that have contributed to its success as a model organism. Nevertheless, the domestication of the rat for research purposes has also resulted in significant changes. Rather than viewing the rat as a simple model, a "pest" or a "pet", it is important to recognize it as a complex mammal in its own right, and one that is highly adapted to its environment (Burn, 2008). Research on rats in the laboratory will be benefited by researchers who understand the animals they are working with; this includes having an appreciation of the rat’s natural history.
Data availability
No data was generated as part of this work.
References
-
Development of dominance in domestic rats in laboratory and seminatural environmentsBehavioural Processes 19:127–142.https://doi.org/10.1016/0376-6357(89)90036-3
-
Molecular phylogeny and divergence time estimates for major rodent groups: evidence from multiple genesMolecular Biology and Evolution 18:777–791.https://doi.org/10.1093/oxfordjournals.molbev.a003860
-
Non-linear spatial modeling of rat sightings in relation to urban multi-source fociJournal of Infection and Public Health 11:667–676.https://doi.org/10.1016/j.jiph.2018.05.009
-
Experiments on neophobia in wild and laboratory ratsBritish Journal of Psychology 49:195–201.https://doi.org/10.1111/j.2044-8295.1958.tb00657.x
-
BookEcologyIn: Whishaw IQ, Kolb iB, editors. The Behavior of the Laboratory Rat. New York: Oxford University Press. pp. 15–24.
-
Comparison of in vitro antibody-targeted cytotoxicity using mouse, rat and human effectorsCancer Immunology, Immunotherapy 49:259–266.https://doi.org/10.1007/s002620000120
-
Defensive behavior of laboratory and wild Rattus norvegicusJournal of Comparative Psychology 100:101–107.https://doi.org/10.1037/0735-7036.100.2.101
-
Leptospira infection in rats: a literature review of global prevalence and distributionPLOS Neglected Tropical Diseases 13:e0007499.https://doi.org/10.1371/journal.pntd.0007499
-
Behavioral comparability of wild and domesticated ratsBehavior Genetics 11:545–553.https://doi.org/10.1007/BF01070009
-
What is it like to be a rat? rat sensory perception and its implications for experimental design and rat welfareApplied Animal Behaviour Science 112:1–32.https://doi.org/10.1016/j.applanim.2008.02.007
-
Pain Research55–65, Modeling diabetic sensory neuropathy in rats, Pain Research, Humana Press, 10.1385/1-59259-770-x:225.
-
BookThe Ecology and Sociology of the Norway RatBethesda, Maryland: U.S. Department of Health, Education and Welfare.
-
Murine typhus: an unrecognized suburban vectorborne diseaseClinical Infectious Diseases 46:913–918.https://doi.org/10.1086/527443
-
Neophobia and neophilia: new-object and new-place reactions of three Rattus speciesJournal of Comparative and Physiological Psychology 91:63–71.https://doi.org/10.1037/h0077297
-
Management of rodent populations by anticoagulant rodenticides: toward Third-Generation anticoagulant rodenticidesDrug Metabolism and Disposition 45:160–165.https://doi.org/10.1124/dmd.116.073791
-
The characteristics of rat populationsThe Quarterly Review of Biology 28:373–401.https://doi.org/10.1086/399860
-
The Laboratory RatInbred strains, The Laboratory Rat, 1, Academic Press, 10.1016/C2013-0-10325-X.
-
Toward a neuroethology of mammalian vision: ecology and anatomy of rodent visuomotor behaviorBehavioural Brain Research 3:133–149.https://doi.org/10.1016/0166-4328(81)90044-9
-
Antimicrobial resistance of bacterial organisms isolated from ratsEast African Medical Journal 78:646–649.https://doi.org/10.4314/eamj.v78i12.8934
-
Diving for food: analysis of a possible case of social learning in wild rats (Rattus norvegicus)Journal of Comparative and Physiological Psychology 94:416–425.https://doi.org/10.1037/h0077678
-
Social factors in the poison avoidance and feeding behavior of wild and domesticated rat pupsJournal of Comparative and Physiological Psychology 75:341–357.https://doi.org/10.1037/h0030937
-
The Laboratory Rat3–16, History, strains and models, The Laboratory Rat, Academic Press.
-
Audiogram of the hooded Norway ratHearing Research 73:244–247.https://doi.org/10.1016/0378-5955(94)90240-2
-
How domestication modulates play behavior: a comparative analysis between wild rats and a laboratory strain of Rattus norvegicusJournal of Comparative Psychology 127:453–464.https://doi.org/10.1037/a0032187
-
Cone-based vision of rats for ultraviolet and visible lightsThe Journal of Experimental Biology 204:2439–2446.
-
A global perspective on Hantavirus ecology, epidemiology, and diseaseClinical Microbiology Reviews 23:412–441.https://doi.org/10.1128/CMR.00062-09
-
Zebrafish: an emerging model system for human disease and drug discoveryClinical Pharmacology & Therapeutics 82:70–80.https://doi.org/10.1038/sj.clpt.6100223
-
Rodents: Habitat, Pathology and Environmental Impact1–21, Rodents in urban ecosystems of Russia and the USA, Rodents: Habitat, Pathology and Environmental Impact, Nova Science Publishers Inc.
-
Synanthropic and agrophilic rodents as invasive alien mammalsRussian Journal of Biological Invasions 1:301–312.https://doi.org/10.1134/S2075111710040089
-
BookThe Life Processes and Size of the Body and Organs of the Gray Norway Rat During Ten Generations in Captivity (No. 14 of the American Anatomical Memoirs)Philadelphia: Wistar Institute.
-
Novel objects elicit greater activation in the basolateral complex of the amygdala of wild rats compared with laboratory ratsJournal of Veterinary Medical Science 81:1121–1128.https://doi.org/10.1292/jvms.19-0040
-
Coping styles in animals: current status in behavior and stress-physiologyNeuroscience & Biobehavioral Reviews 23:925–935.https://doi.org/10.1016/S0149-7634(99)00026-3
-
The Resident-intruder paradigm: a standardized test for aggression, violence and social stressJournal of Visualized Experiments 77:e4367.https://doi.org/10.3791/4367
-
Aboriginal and invasive rats of genus Rattus as hosts of infectious agentsVector Borne and Zoonotic Diseases 15:3–12.https://doi.org/10.1089/vbz.2014.1629
-
The albino rat: a defensible choice or a bad habit?American Psychologist 23:734–742.https://doi.org/10.1037/h0026726
-
The Laboratory Rat147–164, Reproduction and breeding, The Laboratory Rat, Academic Press, 10.1016/B978-012074903-4/50009-1.
-
The Behavior of the Laboratory Rat: A Handbook with TestsAggressive, Defensive, and Submissive Behavior, The Behavior of the Laboratory Rat: A Handbook with Tests, Oxford University Press, 10.1093/acprof:oso/9780195162851.003.0032.
-
The interaction of age and unconditioned stimulus intensity on long-trace conditioned flavor aversion in ratsDevelopmental Psychobiology 40:131–137.https://doi.org/10.1002/dev.10018
-
Experiments on neophobia in wild and laboratory rats: a reevaluationJournal of Comparative and Physiological Psychology 90:190–197.https://doi.org/10.1037/h0077196
-
Food neophobia in wild and laboratory rats (multi-strain comparison)Behavioural Processes 113:41–50.https://doi.org/10.1016/j.beproc.2014.12.005
-
Mammal Species of the World: A Taxonomic and Geographic ReferenceSuperfamily Muroidea, Mammal Species of the World: A Taxonomic and Geographic Reference, JHU Press.
-
Behavior, adrenocortical activity, and brain monoamines in Norway rats selected for reduced aggressiveness towards manPharmacology Biochemistry and Behavior 33:85–91.https://doi.org/10.1016/0091-3057(89)90434-6
-
Encyclopedia of Basic Epilepsy ResearchIMAGING. Structural Magnetic Resonance Imaging of Epilepsy, Encyclopedia of Basic Epilepsy Research, Academic Press, 10.1016/b978-012373961-2.00139-9.
-
Handbook of Pharmacogenomics and Stratified MedicineAnimal Models in Pharmacogenomics, Handbook of Pharmacogenomics and Stratified Medicine, Academic Press.
-
Thermoregulatory control of sympathetic fibres supplying the rat's tailThe Journal of Physiology 543:849–858.https://doi.org/10.1113/jphysiol.2002.023770
-
Note sur l'extirpation des capsules servenales chez les rats albios (Mus Rattus)Comptes Rendus Hebdomadaires Des Seances De l’Academie Des Sciences 43:904–906.
-
BookCuriosity and Information Seeking in Animal and Human BehaviorUniversal-Publishers.
-
Effect of domestication on aggression in gray Norway ratsBehavior Genetics 41:583–592.https://doi.org/10.1007/s10519-010-9429-y
-
Types and functions of ultrasonic vocalizations in laboratory rats and miceJournal of the American Association for Laboratory Animal Science: JAALAS 46:28–34.
-
Domestication and early experience effects on escape conditioning in the Norway ratJournal of Comparative and Physiological Psychology 79:51–55.https://doi.org/10.1037/h0032552
-
Behavioral development in animals undergoing domesticationApplied Animal Behaviour Science 65:245–271.https://doi.org/10.1016/S0168-1591(99)00087-8
-
Variation in visual acuity within pigmented, and between pigmented and albino rat strainsBehavioural Brain Research 136:339–348.https://doi.org/10.1016/S0166-4328(02)00126-2
-
CNS Regeneration. Basic Science and Clinical Advances373–388, Strategies to inhibit signaling through Nogo receptor 1 for spinal cord injury and stroke, CNS Regeneration. Basic Science and Clinical Advances, Academic Press, 10.1016/b978-012373994-0.50018-x.
-
Symposium: Light from animal experimentation on human heredity: 1. Domestication of the Norway rat and its implication for the study of genetics in manAmerican Journal of Human Genetics 4:273–285.
-
Conditioned taste aversions: a behavioral index of toxicityAnnals of the New York Academy of Sciences 443:272–292.https://doi.org/10.1111/j.1749-6632.1985.tb27079.x
-
Dating of divergences within the Rattus genus phylogeny using whole mitochondrial genomesMolecular Phylogenetics and Evolution 49:460–466.https://doi.org/10.1016/j.ympev.2008.08.001
-
GIS-modelling the distribution of Rattus norvegicus in urban Areas using non toxic attractive baitHystrix the Italian Journal of Mammalogy 19:.https://doi.org/10.4404/hystrix-19.1-4410
-
Adolescent peer-rejection persistently alters pain perception and CB1 receptor expression in female ratsEuropean Neuropsychopharmacology 24:290–301.https://doi.org/10.1016/j.euroneuro.2013.04.004
-
Modeling anxiety using adult zebrafish: a conceptual reviewNeuropharmacology 62:135–143.https://doi.org/10.1016/j.neuropharm.2011.07.037
-
Warsaw wild captive pisula stryjek rats (WWCPS) - Establishing a breeding colony of Norway rat in CaptivityPolish Psychological Bulletin 39:67–70.https://doi.org/10.2478/v10059-008-0011-x
-
Response to novel object in Wistar and wild-type (WWCPS) ratsBehavioural Processes 86:279–283.https://doi.org/10.1016/j.beproc.2010.12.018
-
BookThe RhoA/Rho-Kinase Signaling Pathway in Vascular Smooth Muscle Contraction: Biochemistry, Physiology, and PharmacologyIn: Lip G. Y, Hall J. E, editors. Comprehensive Hypertension. Elsevier Health Sciences. pp. 167–181.https://doi.org/10.1016/b978-0-323-03961-1.50019-2
-
Population genomics reveals speciation and introgression between Brown Norway rats and their sibling speciesMolecular Biology and Evolution 34:2214–2228.https://doi.org/10.1093/molbev/msx157
-
Phylogenetics of rat inbred strainsMammalian Genome 14:61–64.https://doi.org/10.1007/s00335-002-2204-5
-
BookPest Control: RodentsUSDA National Wildlife Research Center - Staff Publications.
-
Speed and accuracy of olfactory discrimination in the ratNature Neuroscience 6:1224–1229.https://doi.org/10.1038/nn1142
-
Factors influencing the density of the Brown rat (Rattus norvegicus) in and around houses in AmsterdamScientific Journal 56:77–91.
-
Circadian rhythms in white adipose tissueProgress in Brain Research 199:183–201.https://doi.org/10.1016/B978-0-444-59427-3.00011-3
Decision letter
-
Stuart RF KingReviewing Editor; eLife, United Kingdom
-
Peter RodgersSenior Editor; eLife, United Kingdom
-
Stuart RF KingReviewer; eLife, United Kingdom
-
Amelie DesvarsReviewer; Research Institute of Wildlife Ecology, Austria
In the interests of transparency, eLife publishes the most substantive revision requests and the accompanying author responses.
Acceptance summary:
The "lab rat" is a classical model organism but less is known about its former life in the wild. This wide-ranging review gives an interesting introduction to laboratory rats from an ecological perspective, discussing how they compare with their wild counterparts, and covering the history of the domestication of this model species. The revisions have strengthened the article and it will soon make a welcome addition to our collection on the natural history of model organisms. This work should be of special interest to researchers who study rats in the laboratory.
Decision letter after peer review:
Thank you for submitting your article "The Natural History of Model Organisms: The Norway rat, from an obnoxious pest to a laboratory pet" for consideration by eLife. Your article has been reviewed by two peer reviewers and the evaluation has been overseen by two Features Editors at eLife (Stuart King and Peter Rodgers). The following individual involved in review of your submission has agreed to reveal their identity: Amelie Desvars.
The reviewers have discussed the reviews with one another and the Associate Features Editor has drafted this decision to help you prepare a revised submission.
Summary:
This essay is being considered as part of a series of articles on "The Natural History of Model Organisms":https://elifesciences.org/collections/8de90445/the-natural-history-of-model-organisms. Each article should explain how our knowledge of the natural history of a model organism has informed recent advances in biology, and how understanding its natural history can influence/advance future studies.
The "lab rat" is perhaps the archetypical model organism and would thus make a welcome and interesting addition to this collection of articles. The paper is also timely. Rats remain a key laboratory animal for much research, especially in the behavioral and neural sciences, yet there is a nagging suspicion about the consequences of over a hundred years of domestication.
This wide-ranging review explores the history of laboratory rats, their uses and how they compare with their wild counterparts. The conclusion is that laboratory rats retain sufficient physiological and behavioral characteristics of wild rats to be suitable as animal models for many questions. It also concludes that all strains, or stocks thereof, including wild rats, have to be thoughtfully matched to the research question being asked. This will be a valuable resource in guiding researchers to use rats as animal models more effectively, nevertheless revisions are needed to strengthen the article.
Essential revisions:
1) Structure of the article
Overall, the article is comprehensive and well-researched, with many examples. It would, however, benefit from editing to make the text more succinct. Restructuring would also help its ideas to flow more fluidly and make its central message/conclusion clearer.
Below are some general suggestions as to how this could be achieved.
- Introduction
Taking inspiration from the title, the Introduction could be restructured into three, short paragraphs (max 150 words each). The first paragraph could briefly introduce wild rats as one of the most important vertebrate pest species (with risks to public health, animal health, wildlife, agriculture and infrastructures), and explain how they are widely disliked by the public. The second paragraph could then contrast this by describing laboratory rats as a popular model organism with a long history in research. The third paragraph should highlight the concerns about the "laboratorisation" of rats and briefly describe the objectives or central theme for the rest of the article. The third paragraph is the most critical one in the Introduction. All three paragraphs should offer a high level perspective, with more detail given later in the main text.
- Main text
Most sections would benefit from being more concise. For many sections, the word count could be cut by about a third without reducing the scope. The reviewers felt that some topics were discussed in inappropriate sections (i.e. "diet" is currently combined with "behaviour", and "reproduction" is included under "physical traits".
The section on "Natural history" should focus on the origin, evolution, phylogenetics, biogeography of wild rats. The section on Ecology could be a sub-section of this section, and should discuss the distribution of rats in cities more.
Difference between lab and wild rats are currently described in three consecutive sections: "Laboratorisation of R. norvegicus", "New laboratory rat populations recreated from wild colonies" and "Comparative studies on wild and laboratory rats". These three sections could be revised and restructured to describe i) the changes that occurred when wild rats were domesticated for use in the lab, ii) how this subsequently limited the usefulness of lab rats for some research, and iii) how researchers try to overcome these limitations by creating new lab rat populations from wild colonies (with mentions of the advantages and limitations of these new stocks).
- Conclusion
This also needs to be condensed and should avoid introducing too many new concepts that were not discussed in the article.
- Box 1: Disease and pest control
This also needs to offer a high level perspective and can be cut back to avoid too much detail on specific examples of diseases spread by rats. It would be good to instead briefly cover public opinion of rats (as dirty animals, living in sewage and feeding on garbage), and the impact of rats on crops, infrastructures and endangered wildlife. It would be interesting to mention here how humans have tried for centuries to eliminate, or at least control, rat populations, and that research on rodenticide resistance involves both lab and wild rats.
2) Figures and tables
The current manuscript has a photo as one figure and three boxes to discuss specific topics that would otherwise disrupt the flow of the text. The reviewers felt that the authors should consider moving some of the details currently written in the text into new tables or figures. For example, the information about the systematic groups in the genus Rattus (subsection “Natural history”, second paragraph) should be removed from the text, and presented as a table, or perhaps as a figure with a phylogenetic tree. A map could help the author explain how the Norway rat colonized different geographic regions (see the last two paragraphs of the aforementioned subsection), and the information displayed in Box 2, "The most common stocks and strains of the laboratory rat", would be more easily read if it was presented in a table.
3) Species common name
It would also be interesting if the authors could briefly explain why this rat is called the "Norway rat" when its origins are thought to be in Asia. A few sentences in the appropriate section would likely satisfy a reader's curiosity.
On a related point, it would be good if the article could also list the other common names, besides brown rat, for completeness – i.e. sewer rat, water rat, city rat, common rat – but then continue to use one name, i.e. Norway rat, throughout the rest of the article to avoid confusing unfamiliar readers.
4) Wild or lab rats?
In some sections, especially under the heading Characteristics of the species", it is unclear whether the text refers to wild rats, laboratory strains or both. Please go through the text and make this clearer. It may help if that specific section is renamed "Characteristics of wild Norway rats, and any comparison to laboratory rats is made explicit, or saved for a later section.
5) References
Several statements need support references from the literature while some references should be updated.
6) Part of a collection
Lastly, since this article is part of a series that has already covered 12 other model organisms (including two other rodents), it would be good if the authors could do more to highlight similarities/differences between rats and any of the other model organisms in the series. For example, when discussing life history traits that make rats a good choice for a model organism, it'd be interesting to note other models that have similar traits, and cite the relevant articles already in the collection to help readers see the connections [https://elifesciences.org/collections/8de90445/the-natural-history-of-model-organisms].
https://doi.org/10.7554/eLife.50651.sa1Author response
Essential revisions:
1) Structure of the article
Overall, the article is comprehensive and well-researched, with many examples. It would, however, benefit from editing to make the text more succinct. Restructuring would also help its ideas to flow more fluidly and make its central message/conclusion clearer.
Thank you for this comment. The manuscript has been restructured and edited to make it more concise.
Below are some general suggestions as to how this could be achieved. The Associate Features Editor will contact you separately with more specific edits.
- Introduction
Taking inspiration from the title, the Introduction could be restructured into three, short paragraphs (max 150 words each). The first paragraph could briefly introduce wild rats as one of the most important vertebrate pest species (with risks to public health, animal health, wildlife, agriculture and infrastructures), and explain how they are widely disliked by the public. The second paragraph could then contrast this by describing laboratory rats as a popular model organism with a long history in research. The third paragraph should highlight the concerns about the "laboratorisation" of rats and briefly describe the objectives or central theme for the rest of the article. The third paragraph is the most critical one in the Introduction. All three paragraphs should offer a high level perspective, with more detail given later in the main text.
Following your advice, we have rewritten the Introduction section. As you suggested, we have divided the section into three paragraphs, and in the first part we have presented the rat as a nuisance, in the second part we have considered the rat as a laboratory model, and in the last part we have briefly described the controversy around using the domesticated form of the species.
- Main text
Most sections would benefit from being more concise. For many sections, the word count could be cut by about a third without reducing the scope. The reviewers felt that some topics were discussed in inappropriate sections (i.e. "diet" is currently combined with "behaviour", and "reproduction" is included under "physical traits". As mentioned above, the Associate Features Editor will contact you separately with specific edits to help address these issues.
The manuscript has been restructured and edited to make it more succinct. The word count has been cut substantially. The different sections have been reordered.
The section on "Natural history" should focus on the origin, evolution, phylogenetics, biogeography of wild rats. The section on Ecology could be a sub-section of this section, and should discuss the distribution of rats in cities more.
The Ecology section has been replaced and now follows the Natural History section. Both sections have been revised.
Difference between lab and wild rats are currently described in three consecutive sections: "Laboratorisation of R. norvegicus", "New laboratory rat populations recreated from wild colonies" and "Comparative studies on wild and laboratory rats". These three sections could be revised and restructured to describe i) the changes that occurred when wild rats were domesticated for use in the lab, ii) how this subsequently limited the usefulness of lab rats for some research, and iii) how researchers try to overcome these limitations by creating new lab rat populations from wild colonies (with mentions of the advantages and limitations of these new stocks).
The sections you mentioned above have been rewritten and restructured accordingly.
- Conclusion
This also needs to be condensed and should avoid introducing too many new concepts that were not discussed in the article.
The conclusion section has been shortened, and it is now only a brief summary.
- Box 1: Disease and pest control
This also needs to offer a high level perspective and can be cut back to avoid too much detail on specific examples of diseases spread by rats. It would be good to instead briefly cover public opinion of rats (as dirty animals, living in sewage and feeding on garbage), and the impact of rats on crops, infrastructures and endangered wildlife. It would be interesting to mention here how humans have tried for centuries to eliminate, or at least control, rat populations, and that research on rodenticide resistance involves both lab and wild rats.
The section has been revised and the first paragraph shorted as per reviewer’s comments. The references have been updated and missing information added.
2) Figures and tables
The current manuscript has a photo as one figure and three boxes to discuss specific topics that would otherwise disrupt the flow of the text. The reviewers felt that the authors should consider moving some of the details currently written in the text into new tables or figures. For example, the information about the systematic groups in the genus Rattus (subsection “Natural history”, second paragraph) should be removed from the text, and presented as a table, or perhaps as a figure with a phylogenetic tree. A map could help the author explain how the Norway rat colonised different geographic regions (see the last two paragraphs of the aforementioned subsection), and the information displayed in Box 2, "The most common stocks and strains of the laboratory rat", would be more easily read if it was presented in a table.
As you suggested, we have transferred the information about the systematic groups in the genus Rattus to a separate box. We have also moved the description of methods for creating rat models in the laboratory to Box 2 (the most common stocks and strains of the laboratory rat). The presentation of stocks and strains in Box 1 has also been rewritten and reformatted into a table.
3) Species common name
It would also be interesting if the authors could briefly explain why this rat is called the "Norway rat" when its origins are thought to be in Asia. A few sentences in the appropriate section would likely satisfy a reader's curiosity.
On a related point, it would be good if the article could also list the other common names, besides brown rat, for completeness – i.e. sewer rat, water rat, city rat, common rat – but then continue to use one name, i.e. Norway rat, throughout the rest of the article to avoid confusing unfamiliar readers.
A brief explanation of the origin of the name "Norway rat" has been added to the Natural History section. The commonly used names have been listed in the Introduction.
4) Wild or lab rats?
In some sections, especially under the heading "Characteristics of the species", it is unclear whether the text refers to wild rats, laboratory strains or both. Please go through the text and make this clearer. It may help if that specific section is renamed "Characteristics of wild Norway rats", and any comparison to laboratory rats is made explicit, or saved for a later section.
We have revised the characteristics of the species to make sure it only described the characteristics of the wild rat. Changes that had occurred during the domestication process have been presented in a separate section "Changes occurring in the process of laboratorisation of Rattus norvegicus".
5) References
Several statements need support references from the literature while some references should be updated.
The references have been revised and updated according to the reviewer’s suggestions.
6) Part of a collection
Lastly, since this article is part of a series that has already covered 12 other model organisms (including two other rodents), it would be good if the authors could do more to highlight similarities/differences between rats and any of the other model organisms in the series. For example, when discussing life history traits that make rats a good choice for a model organism, it'd be interesting to note other models that have similar traits, and cite the relevant articles already in the collection to help readers see the connections [https://elifesciences.org/collections/8de90445/the-natural-history-of-model-organisms].
A brief comparison with other animal models has been presented in a separate section "Comparison with other animal models", and relevant articles from the series have been cited.
https://doi.org/10.7554/eLife.50651.sa2Article and author information
Author details
Funding
Narodowe Centrum Nauki (UMO-2015/19/D/HS6/00781)
- Klaudia Modlinska
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Publication history
- Received:
- Accepted:
- Version of Record published:
Copyright
© 2020, Modlinska and Pisula
This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 43,289
- views
-
- 1,339
- downloads
-
- 45
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Further reading
-
- Ecology
Tracking wild pigs with GPS devices reveals how their social interactions could influence the spread of disease, offering new strategies for protecting agriculture, wildlife, and human health.
-
- Ecology
- Neuroscience
In nature, animal vocalizations can provide crucial information about identity, including kinship and hierarchy. However, lab-based vocal behavior is typically studied during brief interactions between animals with no prior social relationship, and under environmental conditions with limited ethological relevance. Here, we address this gap by establishing long-term acoustic recordings from Mongolian gerbil families, a core social group that uses an array of sonic and ultrasonic vocalizations. Three separate gerbil families were transferred to an enlarged environment and continuous 20-day audio recordings were obtained. Using a variational autoencoder (VAE) to quantify 583,237 vocalizations, we show that gerbils exhibit a more elaborate vocal repertoire than has been previously reported and that vocal repertoire usage differs significantly by family. By performing gaussian mixture model clustering on the VAE latent space, we show that families preferentially use characteristic sets of vocal clusters and that these usage preferences remain stable over weeks. Furthermore, gerbils displayed family-specific transitions between vocal clusters. Since gerbils live naturally as extended families in complex underground burrows that are adjacent to other families, these results suggest the presence of a vocal dialect which could be exploited by animals to represent kinship. These findings position the Mongolian gerbil as a compelling animal model to study the neural basis of vocal communication and demonstrates the potential for using unsupervised machine learning with uninterrupted acoustic recordings to gain insights into naturalistic animal behavior.