Black Rat

Black Rat

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The black rat is a common long-tailed rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

 of the genus Rattus (rats) in the subfamily Murinae
Murinae
The Old World rats and mice, part of the subfamily Murinae in the family Muridae, comprise at least 519 species. This subfamily is larger than all mammal families except the Cricetidae and Muridae, and is larger than all mammal orders except the bats and the remainder of the...

 (murine rodents). The species originated in tropical Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 and spread through the Near East
Near East
The Near East is a geographical term that covers different countries for geographers, archeologists, and historians, on the one hand, and for political scientists, economists, and journalists, on the other...

 in Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 times before reaching Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 by the 1st century and spreading with Europeans
European ethnic groups
The ethnic groups in Europe are the various ethnic groups that reside in the nations of Europe. European ethnology is the field of anthropology focusing on Europe....

 across the world.

Taxonomy



The black rat was one of the many species originally described by Linnaeus
Carolus Linnaeus
Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...

 in his 18th century work, Systema Naturae
Systema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...

, and it still bears its original name of Rattus rattus. It is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 of the genus Rattus. Alternate names include ship rat, roof rat, house rat, Alexandrine rat, and old English rat.

Description


A typical adult black rat is 12.75 to 18.25 in (32.4 to 46.4 cm) long, including a 6.5 to 10 in (16.5 to 25.4 cm) tail, and weighs 4 to 12 oz (113.4 to 340.2 g). Despite its name, the black rat exhibits several colour forms. It is usually black to light brown in colour with a lighter underside. In the 1920s in England, several variations were bred and shown alongside domesticated brown rat
Brown Rat
The brown rat, common rat, sewer rat, Hanover rat, Norway rat, Brown Norway rat, Norwegian rat, or wharf rat is one of the best known and most common rats....

s. This included an unusual green tinted variety.

Origin of Rattus rattus


Rattus rattus bone remains that date back to the Norman Period have been discovered in Britain. Evidence also suggests that R. rattus existed in prehistoric Europe as well as Levant (eastern Europe) during post-glacial periods. The specific origin of the black rat is uncertain due to the rat's disappearance and reintroduction. Evidence such as DNA and bone fragments also suggests that rats did not originally come from Europe, but migrated from southeast Asia.

Rats are resilient vectors for many diseases because of their ability to hold so many infectious bacteria in their blood. Rats played a primary role in spreading bacteria, such as Yersinia pestis
Yersinia pestis
Yersinia pestis is a Gram-negative rod-shaped bacterium. It is a facultative anaerobe that can infect humans and other animals....

, which is responsible for the Justinianic plague and Bubonic plague
Bubonic plague
Plague is a deadly infectious disease that is caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexandre Yersin. Primarily carried by rodents and spread to humans via fleas, the disease is notorious throughout history, due to the unrivaled scale of death...

. According to epidemiological models, Yersinia pestis originated outside of Europe which indicates that Western and central Europe have never had any natural rodent plagues.
The modern Roman rat arose from an ancestor that originated in Malaysia. The number of chromosomes these Malaysian rats and the Mediterranean Black Rats differ by four chromosomes. Therefore, it seems that speciation could have occurred when the rats colonized southwest India, which was a primary country where Romans obtained their spices. Because Rattus rattus is a passive traveler, they could have easily traveled to Europe during the trading between Rome and the southwestern Asian countries. Evidence also suggests that, in 321-331 BC, Egyptian birds were preying on Mediterranean rats, though this is not enough to prove that Egypt was the source of the rats.

Diet


Black rats are considered omnivores and eat a wide range of foods, including seeds, fruit, stems, leaves, fungi, and a variety of invertebrates and vertebrates. They are generalists
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...

, and thus not very specific in their food preferences, which is indicated by their tendency to feed on any meal provided for cows, swine, chickens, cats, and dogs. They are similar to the tree squirrel in their preference of fruits and nuts. They eat about 15 grams per day and drink about 15 ml per day. Their diet is high in water content. They are a threat to many natural habitats because they feed on native birds and insects. They are also a threat to many farmers since they feed on a variety of agricultural-based crops, such as cereals, sugar cane, coconuts, cocoa, oranges, and coffee beans.

Distribution and habitat



The black rat originated in India and Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

, and spread to the Near East
Near East
The Near East is a geographical term that covers different countries for geographers, archeologists, and historians, on the one hand, and for political scientists, economists, and journalists, on the other...

 and Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

, and then throughout the Roman Empire
Roman Empire
The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

, reaching England as early as the 1st century. Europeans
European ethnic groups
The ethnic groups in Europe are the various ethnic groups that reside in the nations of Europe. European ethnology is the field of anthropology focusing on Europe....

 subsequently spread it throughout the world. The black rat is, again largely confined to warmer areas, having been supplanted by the brown rat
Brown Rat
The brown rat, common rat, sewer rat, Hanover rat, Norway rat, Brown Norway rat, Norwegian rat, or wharf rat is one of the best known and most common rats....

 (Rattus norvegicus) in cooler regions and urban areas. In addition to being larger and more aggressive, the change from wooden structures and thatched roofs to bricked and tiled buildings favored the burrowing brown rats over the arboreal black rats. In addition, brown rats eat a wider variety of foods, and are more resistant to weather extremes.

Black rat populations can explode under certain circumstances, perhaps having to do with the timing of the fruiting of the bamboo
Bamboo
Bamboo is a group of perennial evergreens in the true grass family Poaceae, subfamily Bambusoideae, tribe Bambuseae. Giant bamboos are the largest members of the grass family....

 plant, and cause devastation to the plantings of subsistence farmers; this phenomenon, Mautam
Mautam
Mautam is a cyclic ecological phenomenon that occurs every 48 years in the northeastern Indian states of Mizoram and Manipur, which are thirty percent covered by wild bamboo forests, as well as Chin State in Burma, particularly Hakha, Thantlang, Falam, Paletwa and Matupi Townships, creating a...

, is happening currently in parts of India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

.

Black rats are thought to have arrived in Australia with the First Fleet
First Fleet
The First Fleet is the name given to the eleven ships which sailed from Great Britain on 13 May 1787 with about 1,487 people, including 778 convicts , to establish the first European colony in Australia, in the region which Captain Cook had named New South Wales. The fleet was led by Captain ...

, and subsequently spread to many coastal regions in the country.

In New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, black rats have an unusual distribution and importance, in that they are utterly pervasive through native forests, scrublands, and urban parklands. This is typical only of oceanic islands that lack native mammals, especially other rodents. Throughout most of the world, black rats are found only in disturbed habitats near people, mainly near the coast. Black rats are the most frequent predator of small forest birds, invertebrates, and perhaps lizards in New Zealand forests, and are key ecosystem changers. Controlling their abundance on usefully large areas of the New Zealand mainland is a crucial current challenge for conservation managers.

Black rats adapt to a wide range of habitats. In urban areas they are found around warehouses residential, buildings, and other human settlements. They are also found in agricultural areas, such as in barns and crop fields. In urban areas they prefer to live in dry upper levels of buildings, so they are commonly found in wall cavities and false ceilings. In the wild, black rats live in cliffs, rocks, the ground, and trees. They are great climbers and prefer to live in trees, such as pines and palm trees. Their nests are typically spherical and made of shredded material, including sticks, leaves, other vegetation, and cloth. In the absence of trees, they can burrow into the ground. Black rats are also found around fences, ponds, riverbanks, streams, and reservoirs.

The black rat, along with the brown rat, is one of the most widespread rats and animal species in the world.

Home range


Home range
Home range
Home range is the area where an animal lives and travels in. It is closely related to, but not identical with, the concept of "territory".The concept that can be traced back to a publication in 1943 by W. H. Burt, who constructed maps delineating the spatial extent or outside boundary of an...

 refers to the area in which an animal travels and spends most of its time. It is thought that male and female rats have similar sized home ranges during the winter, but male rats increase the size of their home range during the breeding season. Along with differing between rats of different gender, home range also differs depending on the type of forest in which the black rat inhabits. For example, home ranges in the beech forests
Beech
Beech is a genus of ten species of deciduous trees in the family Fagaceae, native to temperate Europe, Asia and North America.-Habit:...

 of South Island, New Zealand appear to be much larger than the non-beech forests of North Island. Due to the limited number of rats that are studied in home range studies, the estimated sizes of rat home ranges in different rat demographic groups are inconclusive.

Behavior


It is nocturnal
Nocturnal animal
Nocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....

 and omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...

, with a preference for grains and fruit. Compared to the brown rat, it is a poor swimmer, but more agile and a better climber, tending even to flee upwards. In a suitable environment it will breed throughout the year, with a female producing three to six litters of up to ten young. Females may regulate their production of offspring during times when food is scarce, producing as few as only one litter a year. R. rattus lives for about 2–3 years. Social groups of up to sixty can be formed.

Nesting behavior


Through the usage of tracking devices such as radio transmitters, rats have been found to occupy dens located in trees, as well as on the ground. In Puteki, a kauri
Kauri, New Zealand
Kauri is a locality in Northland, New Zealand. State Highway 1 passes through the area. Kamo is to the south, and Hikurangi is to the north. Mt Parakiore is a volcanic dome rising 391 m to the southwest...

 forest, rats have been found to form dens together. Rats appear to den and forage in separate areas in their home range depending on the availability of food resources. Research shows that in New South Wales, the black rat prefers to inhabit lower leaf litter of forest habitat. There is also an apparent correlation between the canopy height and logs and the presence of black rats. This correlation may be a result of the distribution of the abundance of prey as well as available refuges for rats to avoid predators. As found in North Head, New South Wales, there is positive correlation between rat abundance, leaf litter cover, canopy height, and litter depth. All other habitat variables showed little to no correlation.

Foraging behavior


As generalists, Black rats express great flexibility in their foraging behavior. They are predatory animals and adapt to different micro-habitats. They often meet and forage together in close proximity within and between sexes. Rats tend to forage after sunset. If the food cannot be eaten quickly, they will search for a place to carry and hoard to eat at a later time.
Although black rats eat a broad range of foods, they are highly selective feeders; only a restricted number of the foods they eat are dominant foods. When black rat populations are presented with a wide diversity of foods, they eat only a small sample of each of the available foods. This allows them to monitor the quality of foods that are present year round, such as leaves, as well as seasonal foods, such as herbs and insects. This method of operating on a set of foraging standards ultimately determines the final composition of their meals. Also, by sampling the available food in an area, the rats maintain a dynamic food supply, balance their nutrient intake, and avoid intoxication by secondary compounds.

Ecology


Black rats (or their ectoparasites) are able to carry a number of pathogens, of which bubonic plague
Bubonic plague
Plague is a deadly infectious disease that is caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexandre Yersin. Primarily carried by rodents and spread to humans via fleas, the disease is notorious throughout history, due to the unrivaled scale of death...

 (via the rat flea
Rat flea
The Oriental rat flea , also known as the tropical rat flea, is a parasite of rodents, primarily of the genus Rattus, and is a primary vector for bubonic plague and murine typhus. This occurs when the flea has fed on an infected rodent, and then bites a human...

), typhus
Typhus
Epidemic typhus is a form of typhus so named because the disease often causes epidemics following wars and natural disasters...

, Weil's disease, toxoplasmosis
Toxoplasmosis
Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid family. Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself...

 and trichinosis
Trichinosis
Trichinosis, also called trichinellosis, or trichiniasis, is a parasitic disease caused by eating raw or undercooked pork or wild game infected with the larvae of a species of roundworm Trichinella spiralis, commonly called the trichina worm. There are eight Trichinella species; five are...

 are the best known. It has been hypothesized that the displacement of black rats by brown rats led to the decline of the Black Death
Black Death
The Black Death was one of the most devastating pandemics in human history, peaking in Europe between 1348 and 1350. Of several competing theories, the dominant explanation for the Black Death is the plague theory, which attributes the outbreak to the bacterium Yersinia pestis. Thought to have...

. This theory has, however, been deprecated, as the dates of these displacements do not match the increases and decreases in plague outbreaks.

Cultivation



Very few people currently keep black rats as pets. Most pet rats (or fancy rat
Fancy rat
The fancy rat is a domesticated brown rat , which is the most common type of pet rat. The name fancy rat derives from the idea of animal fancy or the phrase "to fancy" ....

s) are domesticated brown rats.

Predators and parasites


The black rat serves as prey to cats and owls in domestic settings. In less urban settings, rats are preyed upon by weasels, foxes, and coyotes. These predators have little effect on the control of the black rat population because black rats are agile and fast climbers. In addition to agility, the black rat also makes use of its keen sense of hearing to detect danger and quickly evade mammalian and avian predators.
Rats serve as outstanding vectors for transmittance of diseases because they have the ability to carry bacteria and viruses in their systems. A few parasites that are common to rats include Streptococcus pnuemoniae, Corynebacterium kutsheri, Bacillus piliformis, Pasteurella pneumotropica, and Streptobacillus moniliformis, to name a few. All of these parasites are disease causing agents in humans. In some cases, these diseases are incurable.

Damage caused by R. rattus


After Rattus rattus was introduced to the northern islands of New Zealand, it has influenced them by feeding on the seedlings in the area. Even after eradication of R. rattus the negative effects may take decades to reverse. When consuming these seabirds and seabird eggs, these rats reduce the pH of the soil. This harms plant species by reducing nutrient availability in soil, thus decreasing the probability of seed germination. For example, research conducted by Hoffman et al. indicates a large impact on sixteen indigenous plant species directly preyed on by R. rattus. These plants displayed a negative correlation in germination and growth in the presence of black rats.
Rats prefer to forage in forest habitats. In the Ogasawara islands, they prey on the indigenous snails and seedlings. Snails that inhabit the leaf litter of these islands showed a significant decline in population upon the introduction of Rattus rattus. The black rat shows preference for snails with larger shells (greater than 10mm). This is the reason for the great decline in population of snail with larger shells upon the introduction of black rats to the Ogasawara islands of Japan. This interaction is a result of the lack of prey refuges, which causes these snails to be less adapted to avoiding the black rat.

Complex pest


The black rat has been considered a complex pest, which is a pest that influences the environment in both harmful and beneficial ways. In many cases, after the black rat is introduced into a new area, the population size of some native species declines or goes extinct altogether. This is often due to the fact that the black rat is a good generalist with a wide dietary niche
Niche
Niche may refer to:*Niche , an exedra or an apse that has been reduced in size;*Niche , Colombian/Spanish football player, full name Víctor Manuel Micolta Armero*Niche , a British Thoroughbred racehorse...

 and a preference for complex habitats; this causes strong competition for resources among small animals. This has led to the black rat completely displacing many native species in Madagascar, the Galapagos, and the Florida Keys. In a study by Stokes et al., habitats suitable for the native bush rat, Rattus fuscipes, of Australia are often invaded by the black rat and are eventually occupied by only the black rat. When the abundances of these two rat species were compared in different micro-habitats, both were found to be affected by micro-habitat disturbances, but the black rat was most abundant in areas of high disturbance; this indicates it has a better dispersal ability.
Despite the black rats tendency to displace native species, it can also aid in increasing species population numbers and maintaining species diversity. The bush rat, a common vector for spore dispersal of mycorrhiza commonly known as truffles, has been extirpated from many micro-habitats of Australia. In the absence of a vector for spore dispersal of these truffles, the diversity of truffle species will decline. In a study conducted by Vernes et al. in New South Wales, Australia it was found that although the bush rat consumes a diversity of truffle species, the black rat consumes as much of the diverse fungi as the natives and is an effective vector for spore dispersal. Since the black rat now occupies the many of the micro-habitats that were previously inhabited by the bush rat, the black rat plays an important ecological role in the dispersal of fungal spores. By eradicating the black rat populations in Australia, the diversity of fungi would decline, potentially doing more harm than good.

Control methods


Large-scale rat control programs have been taken to maintain a steady level of the invasive predators in order to conserve the native species in New Zealand such as kokako
Kokako
The Kōkako is a forest bird which is endemic to New Zealand. It is slate-grey with wattles and a black mask. It is one of three species of New Zealand Wattlebird, the other two being the endangered Tieke and the extinct Huia...

 and mohua. Pesticides, such as pindone
Pindone
Pindone is an anticoagulant drug for agricultural use. It is commonly used as a rodenticide in the management of rat and rabbit populations.It is pharmacologically analogous to warfarin and inhibits the synthesis of Vitamin K-dependent clotting factors....

 and 1080 (sodium fluoroacetate), are commonly distributed via aerial spray by helicopter as a method of mass control on islands infested with invasive rat populations. Bait, such as brodifacoum
Brodifacoum
Brodifacoum is a highly lethal vitamin K antagonist anticoagulant poison. In recent years, it has become one of the world's most widely used pesticides...

, is also used along with colored dyes in order to kill and identify rats for experimental and tracking purposes. Another method to track rats is the use of wired cage traps, which are used along with bait, such as rolled oats and peanut butter, to tag and track rats to determine population sizes through methods like mark-recapture and radio-tracking. Poison control methods are effective in reducing rat populations to nonthreatening sizes, but rat populations often rebound to normal size within months. Besides their highly adaptive foraging behavior and fast reproduction, the exact mechanisms for their rebound is unclear and are still being studied.

In 2010, the Sociedad Ornitológica Puertorriqueña (Puerto Rican Bird Society) and the Ponce Yacht and Fishing Club
Club Náutico de Ponce
The Club Náutico de Ponce is a sports complex located in Ponce, Puerto Rico. The club is located on Isla de Gatas , near the La Guancha recreational and cultural area, and next to the Port of Ponce....

 launched a campaign to eradicate the black rat from the Isla Ratones (Rats Island) and Isla Cardona (Cardona Island) islands off the municipality of Ponce, Puerto Rico
Ponce, Puerto Rico
Ponce is both a city and a municipality in the southern part of Puerto Rico. The city is the seat of the municipal government.The city of Ponce, the fourth most populated in Puerto Rico, and the most populated outside of the San Juan metropolitan area, is named for Juan Ponce de León y Loayza, the...

.

Endangerment and conservation


Although predators like R. rattus are often a threat to native species on islands, there is evidence that R. rattus is becoming endangered in Great Britain. Rattus rattus populations were common in Great Britain, but began to decline after the introduction of the brown rat in the eighteenth century. R. rattus populations remained common in seaports and major cities until the late nineteenth century but have been decreased due to rodent control and sanitation measures. There are currently two natural populations of R. rattus left, one on Lundy Island and one in the Shiant Islands of Great Britain. Although rats pose a threat to native seabird species and their eggs, seabird populations have remained stable and large, and therefore control options for R. rattus have not been used.

See also


in*Brown rat
Brown Rat
The brown rat, common rat, sewer rat, Hanover rat, Norway rat, Brown Norway rat, Norwegian rat, or wharf rat is one of the best known and most common rats....

  • Karni Mata temple, Deshnoke, Rajasthan, India.
  • Polynesian rat
    Polynesian Rat
    The Polynesian Rat, or Pacific Rat , known to the Māori as kiore, is the third most widespread species of rat in the world behind the Brown Rat and Black Rat. The Polynesian Rat originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji and most Polynesian...

  • Rat flea
    Rat flea
    The Oriental rat flea , also known as the tropical rat flea, is a parasite of rodents, primarily of the genus Rattus, and is a primary vector for bubonic plague and murine typhus. This occurs when the flea has fed on an infected rodent, and then bites a human...

  • Black Rats, nickname of Road Policing Unit
    Road Policing Unit
    The Road Policing Unit is the term for the Highway patrol within the majority of British police forces.-Responsibilities:RPUs work with the National Roads Policing Strategy, which has five strands:* Casualty reduction.* Counter-terrorism....

    Officers (also known as UK Police Traffic Officers)

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