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Sign-up to receive the latest information from Automatic Trap including discounts and flash sales! Do rats really deserve humane treatment? Download our free e-book to learn more. There's a lot of confusion about the similarities and differences between rats and mice. Most people simply judge the two species by size. If a long-tailed rodent is small then it's usually classified as a mouse, and if the rodent is large it's usually classified as a rat.
Rats have a well-deserved reputation as disease carriers. In fact, rodents have been spreading diseases for most of human history. Newsletter Sign Up Be the first to know about upcoming sales and promos, and stay up to date new Blog posts. Many rat species also live in trees. Overall, rats live to forage and mate. Most rats are nocturnal, though the brown rat is often awake day or night. Rats usually stick together in groups called packs. Brown rats are usually led by the largest male in the pack.
Other rats may have several dominant males or females in a pack. Rats are omnivores, but many prefer meat when they can get it. House and brown rats usually use humans for their primary food source. They will scavenge through trash or eat any food that is left unprotected. Rats have also been known to eat grain or kill insects, water creatures such as snails, fish and mussels, small birds, mammals and reptiles for food.
Before their offspring are born, rats build nests from any material that can be foraged from the area, including branches, grass, trash and paper. These nests are usually built in crevices, in rotting trees or in buildings. Rats, generally, are baby-making machines. 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?
The differences between laboratory rats and wild Norway rats were first noticed and described in the s King and Donaldson, , 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 20 th century, a series of morphological differences were spotted between the Wistar rats and trapped wild rats Richter, 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, 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, Domestication significantly affected their brain morphology too, the neocortex being the most markedly altered brain structure Welniak-Kaminska et al.
There are also significant differences in the circadian rhythm and out-of-nest activity between the laboratory and wild rats Stryjek et al. Compared to their wild counterparts, laboratory rats show less interspecific aggression Barnett et al. Defensive behaviors are also reduced, resulting in smaller reactions to both humans and conspecifics Blanchard et al.
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.
In laboratory, where it is impossible to delineate separate territories, individual rats instead establish social hierarchies Adams and Boice, ; Blanchard et al. Domesticate rats seem to learn more quickly than wild rats Price, , tending to perform better in laboratory learning paradigms Boice, Wild rats have a broad repertoire of swimming-related behaviors, while laboratory rats are reluctant to swim Stryjek et al.
Wild rats build more complex and more durable tunnels and, unlike their laboratory cousins, inhabitable underground burrows Stryjek et al. 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, ; Lockard, 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. Whishaw and Pasztor, 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 , caught wild rats and studied them in his laboratory for decades since s, and in the process developed several techniques for handling them Barnett, Beginning in s, Bennett G Galef also extensively studied wild Norway rats with a specific focus on their feeding behaviors e.
Jaap Koolhaas also conducted experiments with wild caught Norway rats in the late s Koolhaas et al. 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.
In , a new laboratory colony of wild Norway rats was set up in Poland Stryjek and Pisula, 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. Its head is stout with a pointed muzzle and darkly pigmented, slightly bulging eyes. Characteristic of all rodents, rats have large and continuously growing front teeth. The durable enamel on the front surface of these teeth contains an iron-based pigment, which gives them an orange color.
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.
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.
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. Such experiments would be difficult to achieve using standardized laboratory strains. 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, In the interests of transparency, eLife publishes the most substantive revision requests and the accompanying author responses.
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. 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. 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.
Overall, the article is comprehensive and well-researched, with many examples. It would, however, benefit from editing to make the text more succinct.
Taking inspiration from the title, the Introduction could be restructured into three, short paragraphs max 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.
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. 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.
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.
This also needs to be condensed and should avoid introducing too many new concepts that were not discussed in the article. 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 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. 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.
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.
Norway rat, throughout the rest of the article to avoid confusing unfamiliar readers. 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.
Several statements need support references from the literature while some references should be updated. 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.
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. 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 Ecology section has been replaced and now follows the Natural History section. Both sections have been revised. The sections you mentioned above have been rewritten and restructured accordingly. The references have been updated and missing information added. 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. 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. 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.
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.
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