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Behavior

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Information on communication in Polynesian rats is not available. However, as mammals, it is likely that they use some visual signals in communication. Tactile communication is undoubtedly present, especially between mates and between a mother and her offspring. Scent cues are probably used, also.

Communication Channels: visual ; tactile ; acoustic ; chemical

Perception Channels: visual ; tactile ; acoustic ; chemical

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Conservation Status

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Rats are an exotic species in Hawaii and are not protected by law. The rats can be controlled by any method consistent with state and federal law regulations. Mongoose and monitor lizards were introduced to the Pacific islands to attempt to control R. exulans.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Benefits

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Polynesian rats are a major agricultural pest throughout Southeast Asia and the Pacific region. Crops damaged by this species include root crops, cacao, pineapple, coconut, sugarcane, corn, and rice.

Negative Impacts: crop pest

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Nancy Shefferly, Animal Diversity Web
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Benefits

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Polynesian rats have no positive economic importance to humans.

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Nancy Shefferly, Animal Diversity Web
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Associations

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As a prey species, these animals undoubtedly affect predator populations. In their foraging, they affect plant communities, as well as populations of small invertebrates upon which they prey.

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Nancy Shefferly, Animal Diversity Web
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Trophic Strategy

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Polynesian rats eat a variety of foods, including broad leaf plants, grasses, seeds, fruits, and animal matter. They prefer fleshy fruits such as guava, passion fruit, thimbleberry, and their favorite sugar cane. Rats that live on the edges of sugar cane fields consume sugar cane as 70% of their diet. To acquire the other additional proteins it will eat earthworms, spiders, cicadas, insects, and eggs of ground nesting worms.

Animal Foods: eggs; insects; terrestrial non-insect arthropods; terrestrial worms

Plant Foods: leaves; seeds, grains, and nuts; fruit

Primary Diet: omnivore

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Distribution

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Polynesian rats (Rattus exulans) have an extensive distribution from Southeast Asia and New Guinea through the Pacific. They spread to several thousands islands in the western and central Pacific Ocean through the colonizing efforts of the Polynesian people. The rats were carried along on the large sea-going canoes with pigs, dogs and jungle cocks.

Biogeographic Regions: palearctic (Introduced , Native ); oriental (Introduced , Native ); australian (Introduced ); oceanic islands (Introduced )

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Habitat

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Rattus exulans can live in a variety of habitats including grassland, scrub and forests, provided that it has adequate food supplies and shelter. It is not a good swimmer, but is able to climb trees for food. Other habitats include the those created by humans, such as houses, granaries, and cultivated lands. These rats usually lives below 1,000 m in elevation, where there is good ground cover and well-drained soil.

Range elevation: 1,000 (high) m.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest ; scrub forest

Other Habitat Features: urban ; suburban ; agricultural

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Life Expectancy

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The lifespan of Polynesian rats is up to one year in the wild. In capitivity this species can live up to 15 months.

Typical lifespan
Status: wild:
1 (high) years.

Typical lifespan
Status: captivity:
12 to 15 months.

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Morphology

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Rattus exulans has a slender body, pointed snout, large ears and relatively delicate feet. Its back is a ruddy-brown color, with a whitish belly. Mature Polynesian rats are 11.5 to 15.0 cm long from the tip of the nose to the base of the tail. Average weoght is between 40 and 80 g. The tail has fine, prominent, scaly rings, and is about the same length as the head and body combined. Female R. exulans have eight nipples. The skull size has been shown to vary with latitudem with those from cooler climates being larger than those living in warmer climates. A useful feature to distinguish this rat from other species is a dark outer edge on the upper side of the hind foot near the ankle while the rest of the foot is pale.

Range mass: 40 to 80 g.

Range length: 11.5 to 15 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Associations

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The infestation of Polynesian rats has destroyed the sugar cane fields, especially in Hawaii. To protect the fields in Hawaii, Indian mongooses (Herpestes auropunctatus) were introduced from the West Indies to help control the rats. Barn owls and dogs have also been used to get rid of Polynesian rats.

Known Predators:

  • Indian mongooses (Herpestes auropunctatus)
  • barn owls (Tyto alba)
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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Chris Yahnke, University of Wisconsin-Stevens Point
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Reproduction

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Polynesian rats breed throughout the year with peak breeding occuring in summer and early fall.

Reproduction varies among geographic areas and is influenced by the availability of food, weather, and other factors. Females have an average of 4 litters per year with and average of 4 young per litter. In New Zealand, gestation is 19 to 21 days and weaning occurs at 2 to 4 weeks. Sexual maturity is reached by 8 to 12 months, though adult size can be achieved during the same season as birth.

Breeding interval: These rats can breed up to four times per year, depending on weather, food availability and climate.

Range number of offspring: 1 to 4.

Average number of offspring: 4.

Range gestation period: 19 to 21 days.

Range weaning age: 2 to 4 weeks.

Range age at sexual or reproductive maturity (female): 8 to 12 months.

Range age at sexual or reproductive maturity (male): 8 to 12 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous

Not much is known about the parental care of Polynesian rats. They are placental mammals that have dependent young. Young are probably altricial, as is common in the genus. While they develop, they probably live in some sort of nest, where they are nurse, groomed, and protected by their mother.

Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female)

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Warren, D. 2004. "Rattus exulans" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_exulans.html
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Donna Warren, University of Wisconsin-Stevens Point
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Polynesian rat

provided by wikipedia EN

The Polynesian rat, Pacific rat or little rat (Rattus exulans), 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 originated in Southeast Asia, and like its relatives has become widespread, migrating to most of Polynesia, including New Zealand, Easter Island, and Hawaii. It shares high adaptability with other rat species extending to many environments, from grasslands to forests. It is also closely associated with humans, who provide easy access to food. It has become a major pest in most areas of its distribution.

Description

The Polynesian rat is similar in appearance to other rats, such as the black rat and the brown rat. It has large, round ears, a pointed snout, black/brown hair with a lighter belly, and comparatively small feet. It has a thin, long body, reaching up to 6 in (15 cm) in length from the nose to the base of the tail, making it slightly smaller than other human-associated rats. Where it exists on smaller islands, it tends to be smaller still – 4.5 in (11 cm). It is commonly distinguished by a dark upper edge of the hind foot near the ankle; the rest of its foot is pale.

Distribution and habitat

The Polynesian rat is widespread throughout the Pacific and Southeast Asia. Mitochondrial DNA analysis suggests that the species originated on the island of Flores.[2] The IUCN Red List considers it native to Bangladesh, all of mainland Southeast Asia, and Indonesia, but introduced to all of its Pacific range (including the island of New Guinea), the Philippines, Brunei, and Singapore, and of uncertain origin in Taiwan.[3] It cannot swim over long distances, so is considered to be a significant marker of the human migrations across the Pacific, as the Polynesians accidentally or deliberately introduced it to the islands they settled. The species has been implicated in many of the extinctions that occurred in the Pacific amongst the native birds and insects; these species had evolved in the absence of mammals and were unable to cope with the predation pressures posed by the rat. This rat also may have played a role in the complete deforestation of Easter Island by eating the nuts of the local palm tree Paschalococos, thus preventing regrowth of the forest.[4][5]

Although remains of the Polynesian rat in New Zealand were dated to over 2,000 years old during the 1990s,[6] which was much earlier than the accepted dates for Polynesian migrations to New Zealand, this finding has been challenged by later research showing the rat was introduced to both the country's main islands around A.D. 1280.[7]

Behaviour

Polynesian rats are nocturnal like most rodents, and are adept climbers, often nesting in trees. In winter, when food is scarce, they commonly strip bark for consumption and satisfy themselves with plant stems. They have common rat characteristics regarding reproduction: polyestrous, with gestations of 21–24 days, litter size affected by food and other resources (6–11 pups), weaning takes around another month at 28 days. They diverge only in that they do not breed year round, instead being restricted to spring and summer.

Diet

R. exulans is an omnivorous species, eating seeds, fruit, leaves, bark, insects, earthworms, spiders, lizards, and avian eggs and hatchlings. Polynesian rats have been observed to often take pieces of food back to a safe place to properly shell a seed or otherwise prepare certain foods. This not only protects them from predators, but also from rain and other rats. These "husking stations" are often found among trees, near the roots, in fissures of the trunk, and even in the top branches. In New Zealand, for instance, such stations are found under rock piles and fronds shed by nikau palms.

Rat control and bird conservation

New Zealand

In New Zealand and its offshore islands, many bird species evolved in the absence of terrestrial mammalian predators, so developed no behavioral defenses to rats. The introduction by the Māori of the Polynesian rat into New Zealand resulted in the eradication of several species of terrestrial and small seabirds.

Subsequent elimination of rats from islands has resulted in substantial increases in populations of certain seabirds and endemic terrestrial birds, as well as species of insects such as the Little Barrier Island giant wētā. As part of its program to restore these populations, such as the critically endangered kākāpō, the New Zealand Department of Conservation undertakes programs to eliminate the Polynesian rat on most offshore islands in its jurisdiction, and other conservation groups have adopted similar programs in other reserves seeking to be predator- and rat-free.[8]

However, two islands in the Hen and Chickens group, Mauitaha and Araara, have now been set aside as sanctuaries for the Polynesian rat.[9]

Rest of the Pacific

NZAID has funded rat eradication programs in the Phoenix Islands of Kiribati in order to protect the bird species of the Phoenix Islands Protected Area.[10]

Between July and November 2011, a partnership of the Pitcairn Islands Government and the Royal Society for the Protection of Birds implemented a poison baiting programme on Henderson Island aimed at eradicating the Polynesian rat.[11] Mortality was massive, but of the 50,000 to 100,000 population, 60 to 80 individuals survived and the population has now fully recovered.[12]

References

  1. ^ Ruedas, L.; Heaney, L. & Molur, S. (2008). "Rattus exulans". IUCN Red List of Threatened Species. 2008. Retrieved 6 February 2010.old-form url
  2. ^ Thomson, Vicki; Aplin, Ken P.; Cooper, Alan; Hisheh, Susan; Suzuki, Hitoshi; Maryanto, Ibnu; Yap, Grace; Donnellan, Stephen C. (2014-03-17). Lalueza-Fox, Carles (ed.). "Molecular Genetic Evidence for the Place of Origin of the Pacific Rat, Rattus exulans". PLOS ONE. 9 (3): e91356. Bibcode:2014PLoSO...991356T. doi:10.1371/journal.pone.0091356. ISSN 1932-6203. PMC 3956674. PMID 24637896.
  3. ^ Ruedas, L. (2016-08-17). "IUCN Red List of Threatened Species: Rattus exulans". IUCN Red List of Threatened Species. Retrieved 2021-01-08.
  4. ^ Flenley, John R. (2003) The enigmas of Easter Island
  5. ^ Diamond, Jared (2005). Collapse: How Societies Choose to Fail or Succeed. Penguin Group. ISBN 978-0-670-03337-9.
  6. ^ Holdaway, R. N. (1996). "Arrival of rats in New Zealand". Nature. 384 (6606): 225–226. Bibcode:1996Natur.384..225H. doi:10.1038/384225b0. S2CID 22648001.
  7. ^ Wilmshurst, J. M.; Anderson, A. J.; Higham, T. F. G.; Worthy, T. H. (2008). "Dating the late prehistoric dispersal of Polynesians to New Zealand using the commensal Pacific rat". Proceedings of the National Academy of Sciences. 105 (22): 7676–7680. Bibcode:2008PNAS..105.7676W. doi:10.1073/pnas.0801507105. PMC 2409139. PMID 18523023.
  8. ^ Auckland Conservancy. 2006. Kiore / Pacific Rat/ Polynesian Rat Archived 2010-05-18 at the Wayback Machine New Zealand Department of Conservation
  9. ^ Tahana, Yvonne (3 June 2010). "Rare rats off the hook as DoC gives them island sanctuary". The New Zealand Herald. Retrieved 3 November 2011.
  10. ^ Jamieson, Regen (18 April 2014). "Removing Rats and Rabbits: An Interview with Ray Pierce". New England Aquarium - Phoenix Islands Blog. Retrieved 25 January 2015.
  11. ^ Royal Society for the Protection of Birds. "Henderson Island Restoration Project". Retrieved 28 May 2012.
  12. ^ Amos, W.; Nichols, H. J.; Chuchyard, T.; Brooke, M. de L. (2016). "Rat eradication comes within a whisker! A case study of a failed project from the South Pacific". Royal Society Open Science. 3 (4): 160110. Bibcode:2016RSOS....360110A. doi:10.1098/rsos.160110. PMC 4852649. PMID 27152226.

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Polynesian rat: Brief Summary

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The Polynesian rat, Pacific rat or little rat (Rattus exulans), 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 originated in Southeast Asia, and like its relatives has become widespread, migrating to most of Polynesia, including New Zealand, Easter Island, and Hawaii. It shares high adaptability with other rat species extending to many environments, from grasslands to forests. It is also closely associated with humans, who provide easy access to food. It has become a major pest in most areas of its distribution.

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