Polynesian Rat
Encyclopedia
The Polynesian Rat, or Pacific 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 originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji
and most Polynesia
n islands, including New Zealand
, Easter Island
and Hawaii
. It shares the ability to easily adapt to many different types of environments, from grasslands to forests. Its habits are also similar, becoming closely associated with humans because of the easy access to food. As a result it has become a major pest in almost all areas within its distribution.
and South-east Asia. They cannot swim over long distances and are therefore considered to be a significant marker of the human migration
s across the Pacific, as the Polynesia
ns accidentally or deliberately introduced them to the islands they settled. The species has been implicated in many of the extinction
s that occurred in the Pacific amongst the native birds and insects; these species had evolved in the absence of mammal
s and were unable to cope
with the predation pressure posed by the rats. It has also been suggested that the rats may have played a role in the complete deforestation
of Easter Island
by eating the nuts of the local palm tree
, and thus preventing regrowth of the forest.
Although remains of the Polynesian Rat in New Zealand were dated to over 2000 years old during the 1990s, which was much earlier than the accepted dates for Polynesian migrations to New Zealand, this finding has been overturned by later research showing that the rat was introduced to both of the country's main islands around AD 1280.
species: eating seeds, fruit, leaves, bark, insects, earthworms, spiders, lizards, avian eggs and hatchlings. Polynesian Rats have been observed to often take pieces of food back to a safe place in order 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
.
Subsequent elimination of rats from islands has resulted in substantial increases in populations of certain seabirds and endemic terrestrial birds. As part of its program to restore populations of sea birds and endemic terrestrial birds such as the endangered kakapo
, 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.
However, two islands in the Hen and Chickens group, Mauitaha and Araara, have now been set aside as sanctuaries for the Polynesian Rat.
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
in the world behind 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....
and Black Rat
Black Rat
The black rat is a common long-tailed rodent of the genus Rattus in the subfamily Murinae . 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.-Taxonomy:The black rat was...
. The Polynesian Rat originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...
and most Polynesia
Polynesia
Polynesia is a subregion of Oceania, made up of over 1,000 islands scattered over the central and southern Pacific Ocean. The indigenous people who inhabit the islands of Polynesia are termed Polynesians and they share many similar traits including language, culture and beliefs...
n islands, including 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...
, Easter Island
Easter Island
Easter Island is a Polynesian island in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian triangle. A special territory of Chile that was annexed in 1888, Easter Island is famous for its 887 extant monumental statues, called moai, created by the early Rapanui people...
and Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
. It shares the ability to easily adapt to many different types of environments, from grasslands to forests. Its habits are also similar, becoming closely associated with humans because of the easy access to food. As a result it has become a major pest in almost all areas within its distribution.
Description
The Polynesian Rat is similar in appearance to other rats like the Black and Brown Rats. It has large round ears, a pointed snout, black/brown hair with a lighter belly, but comparatively small feet. They have thin, long bodies, reaching up to 6 inches (15.2 cm) in length from the nose to the base of the tail, making them slightly smaller than other human-associative rats. Where they exist on smaller islands they tend to be smaller still (e.g. 4.5 inches (11.4 cm)). They are commonly distinguished by a dark upper edge of the hind foot near the ankle. The rest of their foot is pale.Distribution and habitat
Polynesian Rats are widespread throughout the PacificPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
and South-east Asia. They cannot swim over long distances and are therefore considered to be a significant marker of the human migration
Human migration
Human migration is physical movement by humans from one area to another, sometimes over long distances or in large groups. Historically this movement was nomadic, often causing significant conflict with the indigenous population and their displacement or cultural assimilation. Only a few nomadic...
s across the Pacific, as the Polynesia
Polynesia
Polynesia is a subregion of Oceania, made up of over 1,000 islands scattered over the central and southern Pacific Ocean. The indigenous people who inhabit the islands of Polynesia are termed Polynesians and they share many similar traits including language, culture and beliefs...
ns accidentally or deliberately introduced them to the islands they settled. The species has been implicated in many of the extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
s that occurred in the Pacific amongst the native birds and insects; these species had evolved in the absence of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s and were unable to cope
Island tameness
Island tameness is the tendency of many populations and species of animals living on isolated islands to lose their wariness of potential predators, particularly of large animals. The term is partly synonymous with ecological naïvete, which also has a wider meaning referring to the loss of...
with the predation pressure posed by the rats. It has also been suggested that the rats may have played a role in the complete deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
of Easter Island
Easter Island
Easter Island is a Polynesian island in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian triangle. A special territory of Chile that was annexed in 1888, Easter Island is famous for its 887 extant monumental statues, called moai, created by the early Rapanui people...
by eating the nuts of the local palm tree
Paschalococos
Paschalococos disperta , formerly Jubaea disperta, was the native cocoid palm species of Easter Island...
, and thus preventing regrowth of the forest.
Although remains of the Polynesian Rat in New Zealand were dated to over 2000 years old during the 1990s, which was much earlier than the accepted dates for Polynesian migrations to New Zealand, this finding has been overturned by later research showing that the rat was introduced to both of the country's main islands around AD 1280.
Behaviour
Polynesian Rats are nocturnal like most rodents, and are adept climbers, often nesting in trees. In winter, when food is scarce, it is common for them to 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 the fact that they do not breed year round, instead restricting it to spring and summer.Diet
R. exulans is an omnivorousOmnivore
Omnivores are species that eat both plants and animals as their primary food source...
species: eating seeds, fruit, leaves, bark, insects, earthworms, spiders, lizards, avian eggs and hatchlings. Polynesian Rats have been observed to often take pieces of food back to a safe place in order 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
Nikau
Nikau is a palm tree, the only palm endemic to New Zealand.-Etymology:Nīkau is a Māori word; in the closely related Eastern Polynesian languages of the tropical Pacific, it refers to the fronds or the midrib of the coconut palm.- Distribution:The Nikau palm is the only palm species endemic to...
.
Rat control and bird conservation
In New Zealand and its offshore islands, many bird species evolved in the absence of terrestrial mammalian predators and developed no behavioral defenses to rats. The introduction by the Maori 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 part of its program to restore populations of sea birds and endemic terrestrial birds such as the endangered kakapo
Kakapo
The Kakapo , Strigops habroptila , also called owl parrot, is a species of large, flightless nocturnal parrot endemic to New Zealand...
, the New Zealand Department of Conservation
New Zealand Department of Conservation
The Department of Conservation , commonly known by its acronym, "DOC", is the state sector organisation which deals with the conservation of New Zealand’s natural and historic heritage...
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.
However, two islands in the Hen and Chickens group, Mauitaha and Araara, have now been set aside as sanctuaries for the Polynesian Rat.