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Brown or Norway Rat Rattus norvegicus (Berkenhout)
-- Rodentia: Muridae |
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The brown rat (Rattus norvegicus), also known as
the common rat, street rat, sewer rat, wharf
rat, Hanover rat, Norway rat, Norwegian rat and Parisian
rat, is a widespread species of common rat. One of the largest muroids, it is a brown or
grey rodent with a head and body length of up to 28 cm
(11 in) long, and a tail slightly shorter than that. It weighs between 140 and
500 g. This species is thought
to have originated on the plains of northern China and Mongolia and
neighboring areas. It then spread to
other parts of the world sometime in the Middle Ages and has now occurs on
all continents except Antarctica, It is the dominant rat in Europe and much
of North America. The brown rat
usually lives wherever humans live, particularly in urban areas. The question of when brown rats
became coexistent with humans is not known, but as a species, it has
spread and established along routes of human migration and now lives almost
everywhere humans occur. This rat may have been present in
Europe as early as 1553, a conclusion drawn from illustrations and a
description by Swiss naturalist Conrad Gesner in his book Historiae animalium, published
1551–1558. Though Gesner's
description could apply to the black rat, his mention of a large
percentage of albino specimens—common among wild populations of brown
rats—adds credibility to this conclusion.
Reliable reports dating to the 18th century document the presence of
the brown rat in Ireland in 1722, England in 1730, France in 1735, Germany in
1750, and Spain in 1800. It became
widespread during the Industrial Revolution, but did not reach
North America until around the mid 1700's. As it spread from Asia, the brown rat
generally displaced the black rat in areas where humans lived. In addition to being larger and more aggressive,
the change from wooden structures and thatched roofs to brick and tiled
buildings favored the burrowing brown rats over the arboreal black rats. Moreover, brown rats eat a wider variety
of foods, and are more resistant to weather extremes. Selective breeding of the brown rat has
produced the rats that are kept as pets, as well as the laboratory rats used for biological
research. Both kinds are of the domesticated subspecies Rattus norvegicus domestica. Biological Characteristics: The fur is usually brown or dark grey, while the lower
parts are lighter grey or brown. The
brown rat is a rather large animal and can weigh twice as much as a black rat (Rattus rattus) and many times more than
a house mouse (Mus
musculus). The head and
body length ranges from 15 to 28 cm while the tail ranges in length
from 10.5 to 24 cm therefore being shorter than the head and body.
Adult weight ranges from 140 to 500 g. Som large individuals can reach 900 to 1,000 g. but
are not expected except for domestic specimens. Reports of rats attaining sizes as big as cats are
exaggerations, or misidentifications of larger rodents, such as the muskrat. In fact, breeding wild brown rats weigh
less than 300 g. Brown
rats have acute hearing, are sensitive to ultrasound, and possess a very
highly developed olfactory sense. Their average heart rate is 300 to 400
beats per minute, with a respiratory rate of around 100 per minute. The vision of a pigmented rat
is poor, around 20/600, while a non-pigmented (albino) with no melanin in its
eyes has both around 20/1200 vision with a
scattering of light within its vision. Brown rats are able to see colors like a human with red-green colorblindness, bit their color
saturation may be quite faint. Their
blue perception also has UV receptors, allowing them to see ultraviolet
lights that some species cannot. The brown rat is nocturnal and a good swimmer, both on the surface and
underwater, and has been observed climbing slim round metal poles several
feet in order to reach garden bird feeders.
Brown rats dig well, and often excavate extensive burrow systems. A
2007 study found brown rats to possess a mental ability previously only
found in humans and some primates, but further analysis suggested they might
have been following simple operant conditioning principles. Communication Brown
rats are capable of producing ultrasonic vocalizations. As pups, young rats use different types of
ultrasonic cries to elicit and direct maternal search behavior, as well as to
regulate their mother's movements in the nest. Although pups produce ultrasounds around any other rats at the
age of 7 days, by 14 days old they significantly reduce ultrasound production
around male rats as a defensive response.
Adult rats will emit ultrasonic vocalizations in response to predators
or perceived danger; the frequency
and duration of such cries varies with the sex and reproductive status of the
rat. The female rat also emits
ultrasonic vocalizations during mating. Chirping Rats may also emit short, high
frequency, ultrasonic, socially induced vocalization during rough and tumble
play, before mating or when tickled. The vocalization, described as a distinct
"chirping", has been compared to laughter, and is interpreted as
an expectation of a reward. Like most
rat vocalizations, the chirping is too high in pitch for humans to hear
without special equipment. Bat detectors are often used by
pet owners for this purpose. In
research studies, the chirping is associated with positive emotional
feelings, and social bonding occurs with the tickler, resulting in the rats
becoming conditioned to seek the experience.
However, as the rats age, the tendency to chirp tends to decline. REFERENCES: Baker,
H. J.; J. R. Lindsey & S. H. Weisbroth.
1979. The laboratory rat:
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University of New Mexico Press p. 247. Berdoy, M; J. P. Webster
& D. W. MacDonald. 2000. atal
attraction in rats infected with Toxoplasma gondii. Proceedings of
the Royal Society B. 267(1452): 1591–1594. Brudzynski, S. M. 2005. Principles of Rat Communication:
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S.A.; H. N. Shair & M. A. Hofer.
1994. Hypothermic
vocalizations of rat pups (Rattus norvegicus) elicit and direct maternal
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pp. 298–299. Naughton, D. (2012). The
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Toronto: University of Toronto Press. pp. 204–206. Brunelli, S. A.; H. N.
Shair & M. A. Hofer. 1994. Hypothermic vocalizations of rat pups (Rattus norvegicus) elicit and
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C.; W. H. Stickel, L. F. Stickel, R. H. Coleman, A. B. Mickey, L. Schellbach,
A. W. Schorger, N. C. Negus & E. B.
Polderboer. 1948. Aquatic habits of the Norway rat. Journal of Mammalogy 29(3): 299. Davis,
H. N. & J. R. Connor. 1980. Brief Report: Male modulation of female
reproductive physiology in Norway rats: effects of mating during postpartum
estrus. Behavioral and Neural Biology. 29(1): 128–131. Galef,
Junior & G. Bennett. 1980.
Diving for Food: Analysis of a Possible Case of Social Learning in Wild Rats
(Rattus norvegicus). Journal of Comparative and Physiological
Psychology. 94(3):
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M. & K. A. Miczek. 1993. Ultrasounds during agonistic interactions between
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Duffy, Murrell K. Darwin & G. A. Schad.
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M. K. & J. J. Anisko. 1982. Group mating among Norway rats I. Sex
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"Laughing" rats and the evolutionary antecedents of human
joy? Physiology & Behavior. 79(3): 533–47. Price,
A. O. 1977. Burrowing in Wild and Domestic Norway Rats. Journal of
Mammalogy. 58(2): 239–240. Schein,
M. W. & Orgain Holmes. 1953. A Preliminary Analysis of Garbage as Food
for the Norway Rat. American Journal of Tropical Med. Hygiene. 2(6): 1117–1130. Smith,
J. D.; M. J. Beran, J. J. Couchman & M. V. C. Coutinho. 2008. The Comparative Study of
Metacognition: Sharper Paradigms, Safer Inferences. Psychonomic
Bulletin& Review. 15(4):
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D; T. Zivicnjak, A. Marinculic, G. Marucci, G. Andelko, M. Brstilo, L. Pavo
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Trichinella Infection in Brown Rats (Rattus norvegicus) and Domestic
Pigs in Croatia Suggests That Rats are not a Reservoir at the Farm
Level. Journal of
Parasitology. 90(3):
666–670. Thomas,
D. A. & R. J. Barfield.
1985. Ultrasonic vocalization
of the female rat (Rattus norvegicus) during
mating. Animal Behaviour 33(3):
720–725. Webster, J. P.; G. Lloyd & D.
W. Macdonald. 1995. Q fever (Coxiella burnett) reservoir in
wild brown rat (Rattus norvegicus) populations in
the UK. Parasitology. 110:
31–55. White, N.; R. Adox, A. Reddy & R. Barfield. 1992. Regulation of rat maternal behavior by broapudband p vocalizations. Behavioral and Neural Biology. 58(2): 131–137. |
