AnimalTracks.wiki

What the sources say

Brown RatRattus norvegicus

Every figure, record and mechanism on the Brown Rat profile was written from a source, and this is the working table behind it: 55 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

Profile updated

Source
01

Animal Diversity Web, University of Michigan

Rattus norvegicus. Animal Diversity Web, University of Michigan.

The page saysEvery continent except Antarctica, including sewers, basements, open fields and woodlands
The source saysToday, Norway rats (also known as brown rats) can be found on every continent of the world except Antarctica.Note: stats.habitat
The page saysincluding sewers, basements, open fields and woodlands
The source saysThey occupy a variety of habitats including garbage dumps, sewers, open fields and woodlands, basements, and nearly anywhere else that food and shelter might be found.Note: stats.habitat
The page saysOmnivore, mostly discarded human food in cities
The source saysIn metropolitan areas, they survive mainly on discarded human foodNote: stats.diet
The page saysOmnivore
The source saysPrimary Diet omnivoreNote: stats.diet
The page saysFeels its way through total darkness with paws and whiskers, backed by a spectacular sense of smell
The source saysfeel their way through total darkness with their paws and whiskers. However, these rats would not have such an advantage over all other foragers if it were not for their spectacular sense of smellNote: stats.superpower
The page saysthey can feel their way through total darkness with their paws and whiskers
The source saysfeel their way through total darkness with their paws and whiskers
The page sayslives on every continent except Antarctica
The source sayscan be found on every continent of the world except Antarctica
The page saysThey weigh 140 to 500 g
The source saysweigh 140 to 500 g
The page saysaverage 399 mm from nose to tail
The source saysAverage length 399 mm
The page saysmales usually larger
The source saysMales are usually larger than females.
The page saysIn cities, brown rats survive mainly on discarded human food
The source saysIn metropolitan areas, they survive mainly on discarded human food
The page saysSome rats living near the sea have been observed catching fish with their paws
The source saysSome Norway rats living near the sea have been observed catching fish with their paws.
The page saysone wild rat's stomach in Germany held 4000 items, most of them plants
The source saysExamination of a wild R. norvegicus stomach in Germany revealed 4000 items, most of which were plants
The page saysEats Almost Anything
The source saysthey survive mainly on discarded human food, and anything else that can be eaten without negative consequencesNote: heading

Source
02

AnAge: The Animal Ageing and Longevity Database, Human Ageing Genomic Resources

AnAge entry for Rattus norvegicus. AnAge: The Animal Ageing and Longevity Database, Human Ageing Genomic Resources.

The page sayswild rats rarely live more than a year
The source saysIn the wild, rats experience a high mortality and rarely live more than 1 year
The page saysone large study found a captive maximum of 3.8 years
The source saysArguably the most accurate data comes from one large study with thousands of animals in which maximum longevity was 3.8 years
The page saysAnAge says wild rats rarely live more than 1 year, though exceptional ones can live up to 3 years
The source saysrarely live more than 1 year, though in exceptional cases they can live up to 3 yearsNote: faq
The page saysIn captivity, a study of thousands of rats recorded a maximum of 3.8 years
The source saysone large study with thousands of animals in which maximum longevity was 3.8 yearsNote: faq 1
The page saysweightKg: 0.3
The source saysAdult weight 300 gNote: battleStats.weightKg, typical adult (#1117)

Source
03

Modlinska & Pisula 2020

Modlinska & Pisula (2020). The Norway rat, from an obnoxious pest to a laboratory pet. eLife.

The page saysbreeds all year
The source saysR. norvegicus can breed all year longNote: tagline
The page saysquickly learns to shun the taste of food that once made it ill
The source saysRats quickly develop strong aversion to the taste of substances which have caused illnessNote: tagline
The page saysWild rats reach sexual maturity at about 11 weeks, stay pregnant for 21 to 24 days and give birth to litters of about 7 or 8 pups
The source saysWild 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.
The page saysThey can breed all year and average 3 to 5 litters a year
The source saysR. norvegicus can breed all year long and has 3–5 litters per year on average.
The page saysThe pups arrive almost naked, blind and totally dependent on their mother
The source saysthe young are born almost naked, blind and totally dependent on the mother
The page saysstart leaving the nest and eating solid food at about 14 days
The source saysThe young start leaving the nest and ingest solid foods at about 14 days after birth.
The page saysWild Norway rats have relatively poor eyesight and are sensitive to sharp light
The source saysWild Norway rats have relatively poor eyesight and are sensitive to sharp light
The page saysTheir main sensory input is touch from the facial whiskers, plus a particularly well-developed sense of smell
The source saysthe main sensory input is touch from the facial whiskers (or vibrissae) and a particularly well-developed sense of smell
The page saysThey hear from about 0.25 to 80 kHz, which enables them to communicate with ultrasound
The source saysThey can detect sounds between about 0.25–80 KHz ( Heffner et al., 1994 ), which enables them to communicate with ultrasound
The page sayscalls humans cannot hear without special equipment
The source saysThese vocalizations are inaudible to humans without the use of specialized equipment.
The page saysRats develop preferences for particular foods by sniffing at the mouth and fur of an individual who has finished eating
The source saysRats develop preferences for particular foods by sniffing at the mouth and fur of an individual who has finished eating
The page saysThey also have no sweat glands. They regulate body temperature through behavior, such as hiding in burrows, and the sparsely haired tail plays a part
The source saysRats 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
The page saysthe Norway rat most likely originated in Asia
The source saysDespite its name, the Norway rat most likely originated in Asia.
The page saysreached North America between 1750 and 1775
The source saysThe Norway rat reached North America between 1750 and 1775
The page saysAfter an unfamiliar food, they markedly reduce what they eat
The source saysThey also markedly reduce their food intake after they are introduced to an unfamiliar food.
The page saysthey develop an aversion to foods that cause adverse effects within up to 6 hours
The source saysRats develop an aversion to foods that cause adverse effects within up to 6 hours
The page saysThat often limits the effectiveness of traditional pest control
The source sayswhich often limits the effectiveness of traditional pest control procedures
The page saysLike the black rat, the Norway rat often lives close to humans and may carry various pathogens and parasites
The source saysLike 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
The page saysPeople once believed it reached England from Norway on ships in the 18th century
The source saysit was believed to have immigrated to England from Norway aboard ships in the 18 th centuryNote: faq
The page saysreached Europe from there via Russia
The source saysthe species originally arrived in European countries from Asia via RussiaNote: faq
The page saysTheir hearing spans about 0.25 to 80 kHz, and they use ultrasound to communicate
The source saysThey can detect sounds between about 0.25–80 KHz ( Heffner et al., 1994 ), which enables them to communicate with ultrasoundNote: faq
The page saysit most likely originated in Asia
The source saysthe Norway rat most likely originated in AsiaNote: faq 2
The page saysa rat has no sweat glands
The source saysRats have no sweat glandsNote: faq 4
The page saysIt controls its temperature with behavior instead, for example by sheltering in a burrow, and its thinly haired tail helps with thermoregulation too
The source saysregulate their body temperature through behavior, for example, by hiding in burrows. The sparsely haired tail also plays a part in thermoregulationNote: faq 4
The page saysSniff test
The source saysRats develop preferences for particular foods by sniffing at the mouth and fur of an individual who has finished eatingNote: heading/lead-in label only
The page saysWired for Whiskers and Scent
The source saysthe main sensory input is touch from the facial whiskers (or vibrissae) and a particularly well-developed sense of smellNote: heading
The page saysA person needs specialized equipment to pick up those calls
The source saysThese vocalizations are inaudible to humans without the use of specialized equipment.Note: faq 3
The page saysYet rats are cautious about new things
The source saysRats are highly inquisitive and eager to explore new environments but exhibit neophobia (i.e., caution towards new objects; Pisula, 2009 )
The page saysBuilt to Multiply
The source saysR. norvegicus can breed all year long and has 3–5 litters per year on average.Note: heading
The page saysEats Almost Anything, Wary of New Food
The source saysThey also markedly reduce their food intake after they are introduced to an unfamiliar food.Note: heading
The page saysRats develop preferences for particular foods by sniffing at the mouth and fur of a rat that has just eaten
The source saysRats develop preferences for particular foods by sniffing at the mouth and fur of an individual who has finished eatingNote: vibe.reason
The page saystheir sense of smell is particularly well developed
The source saysthe main sensory input is touch from the facial whiskers (or vibrissae) and a particularly well-developed sense of smellNote: vibe.reason

Source
04

Hulme-Beaman, Orton & Cucchi 2021

Hulme-Beaman, Orton & Cucchi (2021). The origins of the domesticate brown rat (Rattus norvegicus) and its pathways to domestication. Animal Frontiers.

The page saysIts indigenous range is often cited as northern China, Mongolia and/or south-eastern Siberia
The source saysThe indigenous distribution of the brown rat is often cited as the northern regions of China, Mongolia, and/or south-eastern Siberia
The page saysmost likely transported globally on ships, apparently sometime in the 1700s
The source saysthe brown rat was later transported globally, most likely on ships ( Puckett et al., 2020 ). This appears to have occurred sometime in the 1700s
The page saysAn Asian Rat That Went Global
The source saysFrom its native distribution in East Asia, the brown rat was later transported globallyNote: heading

Source
05

Biancolini & Johnson 2026

Biancolini & Johnson (2026). Rattus norvegicus. The IUCN Red List of Threatened Species 2026: e.T19353A286459858.

The page saysLeast Concern
The source saysIUCN Red List category: Least Concern (LC).Note: stats.conservationStatus

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.