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Rattus: the main pest of crops

Rattus: the main pest of crops

Brown rat (Rattus norvegicus)

Black rat (Rattus rattus)


(Globally there are more than 1,000 species of rats and mice).
Family: Muridae
The Murids are classified in 5 subfamilies, around 150 genera and approximately 710 species.
1-Deomyinae (spiny mice, brush furred mice, link rat).
2-Gerbillinae (gerbils, jirds and sand rats).
3-Leimacomyinae (Togo Mouse)
4-Lophiomyinae (Crested Rat).
5-Murinae (Old World rats and mice including the vlei rats)
Subfamily: Murinae
Genus: Rattus
The genus Rattus proper contains 66 extant species. A subgeneric breakdown of the species has been proposed, but does not include all species.

The list of 66 species of Genus Rattus (Typical rats)

+Incertae sedis (uncertain placement)
1-Annandale's Rat (Rattus annandalei) – IndonesiaMalaysia, and Singapore.
2-Enggano Rat (Rattus enganus) – Indonesia.
3-Philippine Forest Rat (Rattus everetti) – the Philippines.
4-Polynesian Rat (Rattus exulans) –Fiji and most Polynesian islands, New ZealandEaster Island, and Hawaii.
5-Hainald's Rat (Rattus hainaldi) – Indonesia.
6-Hoogerwerf's Rat (Rattus hoogerwerfi) – Indonesia.
7-Korinch's Rat (Rattus korinchi) – Indonesia.
8-died Maclear's Rat (Rattus macleari) – Christmas Island.
9-Nillu Rat (Rattus montanus) – Sri Lanka.
10-Molaccan Prehensile-tailed Rat(Rattus morotaiensis) – Indonesia.
11-died Bulldog Rat (Rattus nativitatis) – Christmas Island.
12-Kerala Rat (Rattus ranjiniae) – India.
13-New Ireland Forest Rat (Rattus sanila).
14-Andaman Rat (Rattus stoicus) –Andaman Islands.
15-Timor rat (Rattus timorensis) –Timor.
+Rattus norvegicus group
16-Himalayan Field Rat (Rattus nitidus) – BangladeshBhutanChina, India, Indonesia, LaosMyanmarNepal,Palau, the Philippines, Thailand, and Vietnam
17-Brown Rat or Norway Rat (Rattus norvegicus) – worldwide except Antarctica.
18-Turkestan Rat (Rattus pyctoris; obs.Rattus turkestanicus) –Afghanistan, China, India, Iran, KyrgyzstanNepal, and Pakistan.
+Rattus rattus group
19-Sunburned Rat (Rattus adustus) –Enggano Island, Indonesia.
20-Sikkim Rat (Rattus andamanensis) – BhutanCambodia, China, India, Laos, Myanmar, Nepal, Thailand, and Vietnam.
21-Rice-field Rat (Rattus argentiventer) – Southeast Asia
22-Summit Rat (Rattus baluensis) –Malaysia.
23-Aceh Rat (Rattus blangorum).
24-Nonsense Rat (Rattus burrus) – India.
25-Hoffmann's Rat (Rattus hoffmanni) – Indonesia.
26-Koopman's Rat (Rattus koopmani) – Indonesia.
27-Lesser Rice-field Rat (Rattus losea) – China, LaosTaiwan, Thailand, and Vietnam.
28-Mentawai Rat (Rattus lugens) – Indonesia.
29-Mindoro Black Rat (Rattus mindorensis) – the Philippines.
30-Little Soft-furred Rat (Rattus mollicomulus) – Indonesia
31-Osgood's Rat (Rattus osgoodi) – Vietnam.
32-Palm Rat (Rattus palmarum) – India.
33-Black Rat (Rattus rattus) – worldwide except Antarctica.
34-Sahyadris Forest Rat (Rattus satarae).
35-Simalur Rat (Rattus simalurensis) – Indonesia.
36-Tanezumi Rat (Rattus tanezumi) – Afghanistan, Bangladesh, Cambodia, China, Cocos (Keeling) Islands, Fiji, India, Indonesia, Japan, North KoreaSouth Korea, Laos, Malaysia, Myanmar, Nepal, Pakistan, the Philippines, Taiwan, Thailand, and Vietnam.
37-Tawi-Tawi Forest Rat (Rattus tawitawiensis) – the Philippines.
38-Malayan Field Rat (Rattus tiomanicus) – Indonesia, Malaysia, the Philippines, and Thailand.
+Rattus xanthurus group
39-Bonthain Rat (Rattus bontanus; obs. Rattus foramineus) – Indonesia.
40-Opossum Rat (Rattus marmosurus) – Indonesia.
41-Peleng Rat (Rattus pelurus) – Indonesia.
42-Southeastern Xanthurus Rat (Rattus salocco) – Indonesia.
43-Yellow-tailed Rat (Rattus xanthurus) – Indonesia
+Rattus leucopus group (New Guinean group).
44-Arfak Rat (Vogelkop Mountain Rat) (Rattus arfakiensis).
45-Western New Guinea Mountain Rat (Rattus arrogans).
46-Sula Rat (Rattus elaphinus) – Indonesia.
47-Spiny Ceram Rat (Rattus feliceus) – Indonesia.
48-Giluwe Rat (Rattus giluwensis) –Papua New Guinea.
49-Japen Rat (Rattus jobiensis) – Indonesia.
50-Cape York Rat (Rattus leucopus) –Australia, Indonesia, and Papua New Guinea.
51-Eastern Rat (Rattus mordax) – Papua New Guinea.
52-Moss-forest Rat (Rattus niobe) – Papua New Guinea, Indonesia.
53-New Guinean Rat (Rattus novaeguineae) – Papua New Guinea.
54-Arianus's Rat (Rattus omichlodes).
55-Pocock’s Highland Rat (Rattus pococki).
56-Spiny Rat (Rattus praetor) – Indonesia, Papua New Guinea, andSolomon Islands
57-Glacier Rat (Rattus richardsoni) – Indonesia.
58-Stein's Rat (Rattus steini) – Indonesia and Papua New Guinea.
59-Van Deusen's Rat (Rattus vandeuseni) – Papua New Guinea.
60-Slender Rat (Rattus verecundus) – Indonesia and Papua New Guinea
+Rattus fuscipes group (Australian group).
61-Dusky Rat (Rattus colletti) – Australia.
62-Bush Rat (Rattus fuscipes) – Australia.
63-Australian Swamp Rat (Rattus lutreolus) – Australia.
64-Dusky Field Rat (Rattus sordidus) – Australia, Indonesia, and Papua New Guinea.
65-Pale Field Rat (Rattus tunneyi) – Australia.
66-Long-haired Rat (Rattus villosissimus) – Australia.

Two worldwide species

1-Brown Rat or Norway RatRattus norvegicus (Berkenhout, 1769)

The brown rat, common rat, street rat, sewer rat, Hanover rat, Norway rat, brown Norway rat, Norwegian rat, or wharf rat (Rattus norvegicus) is one of the best known and most common rats.
One of the largest muroids, it is a brown or grey rodent with a body up to 25 cm long, and a similar tail length; the male weighs on average 350 g and the female 250 g. Thought to have originated in northern China, this rodent has now spread to all continents except Antarctica, and is the dominant rat in Europe and much of North America - making it the most successful mammal on the planet after humans. Indeed, with rare exceptions, the brown rat lives wherever humans live, particularly in urban areas.
Selective breeding of Rattus norvegicus has produced the laboratory rat, an important model organism in biological research, as well as pet rats.
Naming and etymology
Originally called the "Hanover rat" by people wishing to link problems in 18th century England with the House of Hanover, it is not known for certain why the brown rat is named Rattus norvegicus (Norwegian rat), as it did not originate from Norway. However, the English naturalist John Berkenhout, author of the 1769 book Outlines of the Natural History of Great Britain, is most likely responsible for popularizing the misnomer. Berkenhout gave the brown rat the binomial name Rattus norvegicus, believing it had migrated to England from Norwegian ships in 1728, although no brown rat had entered Norway at that time.
By the early to middle part of the 19th century, British academics were aware that the brown rat was not native to Norway, hypothesizing (incorrectly) that it may have come from Ireland, Gibraltar or across the English Channel with William the Conqueror. As early as 1850, however, a more correct understanding of the rat's origins was beginning to develop. The British novelist Charles Dickens acknowledged the misnomer in the 2 June 1888 edition of his weekly journal, All the Year Round, writing:
"Now there is a mystery about the native country of the best known species of rat, the common brown rat." 
Academics began to understand the origins and corrected etymology of the brown rat towards the end of the 19th century, as seen in the 1895 text Natural History by American scholar Alfred Henry Miles:
"The brown rat is the species common in England, and best known throughout the world. It is said to have travelled from Persia to England less than two hundred years ago and to have spread from thence to other countries visited by English ships.”
Though the assumptions surrounding this species' origins were not yet entirely accurate, by the 20th century, it was established among naturalists that the brown rat did not originate in Norway, rather the species came from central Asia and (likely) China. Despite this, this species' common name of "Norway rat" is still in use today.
The fur is coarse and usually brown or dark grey, while the underparts are lighter grey or brown. The length can be up to 25 cm, with the tail a further 25 cm , the same length as the body. Adult body weight averages 550 g in males and about 350 g in females, but a very large individual can reach 900 g. Rats weighing over 1 kg are exceptional, and stories of rats as big as cats are exaggerations, or misidentifications of other rodents, such as the coypu and muskrat.
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 nonpigmented (albino) with no melanin in its eyes has both around 20/1200 vision and a terrible scattering of light within its vision. Brown rats are dichromates which perceive colours rather like a human with red-green colorblindness, and their colour saturation may be quite faint. Their blue perception, however, also has UV receptors, allowing them to see ultraviolet lights that some species cannot.
Biology and behavior
The brown rat is usually active at night and is a good swimmer, both on the surface and underwater, but unlike the related black rat (Rattus rattus), they are poor climbers. Brown rats dig well, and often excavate extensive burrow systems. A 2007 study found brown rats to possess metacognition, a mental ability previously only found in humans and some primates, but further analysis suggested they may have been following simple operant conditioning principles.
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 will produce ultrasounds around any other rats at 7 days old, 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 depends on the sex and reproductive status of the rat. The female rat will also emit ultrasonic vocalizations during mating.
Rats may also emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, before receiving morphine, or mating, and when tickled. The vocalization, described as a distinct "chirping", has been likened to laughter, and is interpreted as an expectation of something rewarding. 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 clinical 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 tickling. However, as the rats age, the tendency to chirp appears to decline.
Rat chirp also can be used for mosquito control.
Other ultrasonic vocalisations, including a lower-frequency 'boom' or 'whoom' noise can be produced by bucks in a calm state, when grooming or settling down to sleep.
Audible communication
Brown rats also produce communicative noises capable of being heard by humans. The most commonly heard in domestic rats is bruxing, or teeth-grinding, which is most usually triggered by happiness, but can also be 'self-comforting' in stressful situations, such as a visit to the vet. The noise is best described as either a quick clicking or 'burring' sound, varying from animal to animal.
In addition, they commonly squeak along a range of tones from high, abrupt pain squeaks to soft, persistent 'singing' sounds during confrontations.
The brown rat is a true omnivore and will consume almost anything, but cereals form a substantial part of its diet.
Martin Schein, founder of the Animal Behavior Society in 1964, studied the diet of brown rats and came to the conclusion that the most-liked foods of brown rats include scrambled eggs, macaroni and cheese, and cooked corn kernels. According to Schein, the least-liked foods were raw beets, peaches, and raw celery.
Foraging behavior is often population-specific, and varies by environment and food source. Brown rats living near a hatchery in West Virginia catch fingerling fish. Some colonies along the banks of the Po River in Italy will dive for mollusks, a practice demonstrating social learning among members of this species. Rats on the island of Norderoog in the North Sea stalk and kill sparrows and ducks.
Reproduction and life cycle
The brown rat can breed throughout the year if conditions are suitable, with a female producing up to five litters a year. The gestation period is only 21 days, and litters can number up to 14, although seven is common. They reach sexual maturity in about five weeks. The maximum life span is up to three years, although most barely manage one. A yearly mortality rate of 95% is estimated, with predators and interspecies conflict as major causes.
When lactating, female rats display a 24 hour rhythm of maternal behavior, and will usually spend more time attending to smaller litters than large ones.
Brown rats live in large, hierarchical groups, either in burrows or subsurface places, such as sewers and cellars. When food is in short supply, the rats lower in social order are the first to die. If a large fraction of a rat population is exterminated, the remaining rats will increase their reproductive rate, and quickly restore the old population level.
Social behavior
Rats commonly groom each other and sleep together. As with dogs, rats create a social hierarchy, and each rat has its own place in the pack. Rats are said to establish an order of hierarchy, so one rat will be dominant over another one. Groups of rats tend to "play fight", which can involve any combination of jumping, chasing, tumbling, and boxing. Play fighting involves rats going for each other's necks, while serious fighting involves strikes at the others' back ends. If living space become limited, rats may turn to aggressive behavior, which may result in the death of some animals, reducing the burden over the living space.
Rats are known to burrow extensively, both in the wild and in captivity, if given access to a suitable substrate. Rats generally begin a new burrow adjacent to an object or structure, as this provides a sturdy "roof" for the section of the burrow nearest to the ground's surface. Burrows usually develop to eventually include multiple levels of tunnels, as well as a secondary entrance. Older male rats will generally not burrow, while young males and females will burrow vigorously.
Burrows provide rats with shelter and food storage, as well as safe, thermoregulated nest sites. Rats use their burrows to escape from perceived threats in the surrounding environment; for example, rats will retreat to their burrows following a sudden, loud noise or while fleeing an intruder. Burrowing can therefore be described as a "pre-encounter defensive behavior", as opposed to a "postencounter defensive behavior", such as flight, freezing, or avoidance of a threatening stimulus.
Distribution and habitat
Likely originating from the plains of Asia, northern China and Mongolia, the brown rat spread to other parts of the world sometime in the Middle Ages.The question of when brown rats became commensal with humans remains unsettled, but as a species, they have spread and established themselves along routes of human migration and now live almost everywhere humans do.
The brown rat may have been present in Europe as early as 1553 (from an illustration and description by Swiss naturalist Conrad Gesner in his book Historiae animalium, published 1551-1558).
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, becoming widespread during the Industrial Revolution. It did not reach North America until around 1750-1755.
The only brown rat-free zones in the world are the Arctic, the Antarctic, some especially isolated islands, the province of Alberta in Canada, and certain conservation areas in New Zealand.
Rat Island in Alaska was infested with brown rats after a Japanese shipwreck in 1780.
In New Zealand, first arriving before 1800 (perhaps on James Cook's vessels),brown rats have posed a serious threat to many of New Zealand's native animals. In 2001, the sub-Antarctic Campbell Island had the highest population density of brown rats in the world.
Similar to other rodents, brown rats may carry a number of pathogens,which can result in disease, including Weil's disease, rat bite fever, cryptosporidiosis, viral hemorrhagic fever, Q fever and hantavirus pulmonary syndrome. In the United Kingdom, brown rats are an important reservoir for Coxiella burnetii, the bacterium that causes Q fever, with seroprevalence for the bacteria found to be as high as 53% in some wild populations.
This species can also serve as a reservoir for Toxoplasma gondii, the parasite that causes toxoplasmosis, though the disease usually spreads from rats to humans when domestic cats feed on infected brown rats.The parasite has a long history with the brown rat, and there are indications that the parasite has evolved to alter an infected rat's perception to cat predation, making it more susceptible to predation and increasing the likelihood of transmission.
Surveys and specimens of brown rat populations throughout the world have shown this species is often associated with outbreaks of trichinosis. but the extent to which the brown rat is responsible in transmitting Trichinella larvae to humans and other synanthropic animals is at least somewhat debatable. Trichinella pseudospiralis, a parasite previously not considered to be a potential pathogen in humans or domestic animals, has been found to be pathogenic in humans and carried by brown rats.
Brown rats are sometimes mistakenly thought to be a major reservoir of bubonic plague, a possible cause of the Black Death. However, the bacterium responsible, Yersinia pestis, is commonly endemic in only a few rodent species and is usually transmitted zoonotically by rat fleas-common carrier rodents today include ground squirrels and wood rats. 
Some of the common methods used to control the number of Norway rats include:
Using traditional break-back traps, glue traps, live cage traps and other humane traps
There are many types of poison available for the purpose of controlling the Brown rat. The use of poison is controlled in most of the countries in the world so its important to check your state legislations.
Prevention is the best cure, There are ways to stop the infestation occurring at the first place e.g. Blocking access points, better waste management, better sewage design etc.

2-Black rat (Rattus rattus)

The black rat (Rattus rattus) is a common long-tailed rodent of the genus Rattus (rats) in the subfamily Murinae (murine rodents). The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe by the 1st century and spreading with Europeans across the world.
The black rat was one of the many species originally described by Linnaeus in his 18th century work, Systema Naturae, and it still bears its original name of Rattus rattus. It is the type species of the genus Rattus. Alternate names include ship rat, roof rat, house rat, Alexandrine rat, and old English rat.
A typical adult black rat is 32.4-46.4 cm long, including a 17-25 cm tail, and weighs 110-340 g. Despite its name, the black rat exhibits several colour forms. It is usually black to light brown in colour with a lighter underside.
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, which is responsible for the Justinianic plague and Bubonic plague. According to epidemiological models, Yersinia pestis originated outside of Europe which indicates that Western and central Europe have never had any natural rodent plagues.
Black rats eat a wide range of foods, including seeds, fruit, stems, leaves, fungi, and a variety of invertebrates and vertebrates. They are generalists, 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, and spread to the Near East and Egypt, and then throughout the Roman Empire, reaching England as early as the 1st century. Europeans subsequently spread it throughout the world. The black rat is again largely confined to warmer areas, having been supplanted by the brown rat (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 plant, and cause devastation to the plantings of subsistence farmers; this phenomenon, Mautam, is happening currently in parts of India.
Black rats are thought to have arrived in Australia with the First Fleet, and subsequently spread to many coastal regions in the country.
In New Zealand, 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.
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 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.
It is nocturnal and omnivorous, 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.
Rats appear to den and forage in separate areas in their home range depending on the availability of food resources.
All other habitat variables showed little to no correlation.While this specie's relative, the Brown (Norway) Rat prefers to nest near the ground of a building the black rat will prefer the upper floors and roof. Because of this habit they have been given the common name Roof Rat.
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.
Black rats (or their ectoparasites) are able to carry a number of pathogens, of which bubonic plague (via the rat flea), typhus, Weil's disease,  toxoplasmosis  and  trichinosis  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. This theory has, however, been deprecated, as the dates of these displacements do not match the increases and decreases in plague outbreaks.[19]
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 bacterium are disease causing agents in humans. In some cases, these diseases are incurable.
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 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.
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 and mohua.
Pesticides, such as pindone 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, is also used along with coloured 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.
Source: Brown rat-
                                                                       Edited and posted by Hồ Đình Hải
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