Brown Rat (Rattus norvegicus) lives in urban sewers across Worldwide, except Arctic. It feeds on seeds and grains. Its conservation status is Least Concern.
Fascinating facts about the Brown Rat
- Brown rats can turn two individuals into a bustling colony of 15,000 in just one year. The species can breed year-round, with a female producing up to five litters a year, each gestating only 21 days and often containing up to 14 pups. Newborns weigh a mere 6 g, reach sexual maturity in about five weeks, and a single female can boost the female population by a factor of 3.5 in eight weeks, equating to a ten-fold rise in 15 weeks. This explosive growth explains why rats dominate urban ecosystems and why eradication efforts must be relentless.
- Thought to have originated in northern China and neighbouring areas, it has now spread to all continents except Antarctica. By 1800 the species was present in every European country, and the first New World sighting was recorded in the 1770s as ship stowaways. Today, Norway rats can be found on every continent of the world except Antarctica, thriving wherever humans settle.
- A brown rat can grow as long as a school ruler and weigh as much as a small cat food can. The body reaches up to 28 cm (11 in) with a tail slightly shorter, and adult weight ranges from 140 to 500 g (4.9 to 17.6 oz). The heaviest live specimen recorded weighed 822 g (29 oz) and measured 482.5 mm (19 in) in length. Average individuals are about 399 mm (15.7 in) long and weigh roughly 400 g (14.1 oz). These dimensions give the brown rat a size advantage over many other rodents, helping it dominate diverse habitats.
- Brown rats show a glimpse of human-like thinking. A 2007 study found brown rats to possess metacognition, a mental ability previously only found in humans and some other primates, though later analysis suggested the behavior might stem from simple operant conditioning.
- Eradicating invasive brown rats can bring extinct-on-paper island species back from the brink. On Rábida Island, rats introduced in the 17th-18th centuries devastated native wildlife, eating gecko eggs and disrupting nests. After a precise island-wide baiting campaign removed every rat, park rangers spotted a living Mares's leaf-toed gecko just one year later, the first confirmed sighting in recorded history. This rapid rebound demonstrates how removing a single predator can instantly restore fragile ecosystems.
Sources
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At a glance
RangeWorldwide, except Arctic
HabitatUrban sewers
DietSeeds and grains
About the Brown Rat
In the shadows of human endeavour, the brown rat thrives, its unassuming presence a testament to its remarkable adaptability, as it navigates the hidden labyrinths of our cities with ease, its nimble form darting through narrow crevices and scavenging for sustenance with an unrelenting fervour. With a twitching snout and inquisitive gaze, it probes the urban landscape, ever-vigilant for the next opportunity to exploit, its resourcefulness and cunning allowing it to flourish in even the most inhospitable of environments. As it weaves through the underbelly of our metropolises, the brown rat remains an enduring emblem of resilience, a humble yet formidable creature that has learned to thrive in the margins of our world.
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