Kiore Rattus exulans
About this pest
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A kiore (Pacific rat).
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Kiore and ship rat comparison.
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Preserved specimen of a kiore, or Pacific rat.
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Kiore (or Pacific rats) on Little Barrier Island eating nikau seeds.
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Dorsal (back) view of the four rodent species in New Zealand.
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Ventral (belly) view of the four rodent species in New Zealand.
KEY CLUES
Distinctive features: Brown fur, white-tipped grey fur on belly, pale feet with dark mark on outer edge of hindfeet. Eight nipples on female belly. Ears cover eyes when pulled forward. Thin tail about the same length as body.
Size: Smaller than other rats in New Zealand, maximum body length is 180mm without tail, and they usually weigh 60g - 80g, maximum 180g.
Droppings: Small cylindrical pellets, 6.4mm -9.0mm long.
Footprints: Four-toed forefeet and five-toed hindfeet.
Kill signs: Similar to ship rats, including shell fragments in preyed-on nests, parallel double incisor marks in chewed flesh, neatly chewed holes in snail shells.
Vegetation damage: Similar to ship rats, such as seeds with neatly chewed holes to access contents, larger fruit may show parallel double incisor marks, damage to growing tips of some species may occur.
Eye shine: TBC
Distribution: Kiore are found throughout the Pacific. In New Zealand they are restricted to parts of the South Island and some offshore islands.
WHY ARE KIORE PESTS?
Ecological impacts
Kiore were the first rat species to arrive in New Zealand and they were brought here either deliberately or accidentally with the first human voyagers. The date of arrival of both kiore and humans has been estimated at about 1280 A.D. Kiore feed on plants, insects, lizards and birds and have had a very large impact on the ecology of New Zealand.
When kiore arrived in New Zealand, they found a land without mammalian predators and fauna that had no experience of defending itself against mammals and were therefore easy prey. Some of the best evidence for the impacts of kiore comes from islands where they have subsequently been removed.
Nine species of large, flightless invertebrates such as weta and giant earwigs appeared on one island following the removal of kiore and rabbitsThey were probably there all along, but their numbers were kept low by kiore so they hadn’t been recorded. On the same island, the populations of geckos and skinks have increased dramatically. Kiore are known to affect tuatara populations through predation of eggs and juveniles, and through food competition. A small island in the Mokohinau group was invaded by kiore in 1977 and they were removed in 1978. In this short time, they had such an impact on lizards and their invertebrate prey that the lizard population was reduced in numbers and diversity for at least seven years, probably longer. Birds aren’t safe either, particularly small seabirds that breed on the ground or in burrows on islands. There are records of almost complete breeding failures in some years on islands where kiore coexist with small petrels and shearwaters. The ‘extinct’ storm petrel was only rediscovered after kiore were removed from Little Barrier Island (Hauturu).
On the New Zealand mainland, kiore have had impacts on large flightless insects and land snails. In conjunction with land clearance and hunting by early Maori, they contributed to the decline or even extinction of several land bird species.
Plants make up a large part of kiore diet and their feeding on flowers, fruits and seeds can reduce or prevent regeneration of certain species, including karo (Pittosporum crassifolium), tawapou (Planchonella costata), turepo (Streblus banksii), coastal maire (Nestegis apetala) and various other native species.
Kiore are now restricted to small areas of New Zealand (see below) so their continuing impacts on ecosystems are much less serious compared to the other rat species which are far more widespread.
Other impacts
Store houses built by Maori in pre-Europen times were built on poles in an attempt to protect food from kiore damage.
Droppings
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Kiore droppings.
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Photographs of kiore droppings required.
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Compare the droppings of the rodent species found in New Zealand.
Separate
Kiore droppings are smaller than those of other rats in New Zealand (see photograph “Dropping comparison between three main rodent species found in New Zealand”) and resemble small ship rat droppings. Kiore droppings range from 6.4mm to 9.0mm in length. Droppings are deposited singly in small groups along commonly used tracks and at feeding sites.
Can be confused with:
It may be difficult to distinguish ship rat droppings from kiore droppings. Kiore are absent from large part of mainland New Zealand, and this may help decide if the droppings belong to kiore or not. Wētā droppings can resemble kiore droppings but tend to be thinner, have blunter ends and are often ridged lengthwise, as in the example at right. The ridging can be darker, resulting in a striped appearance, which fades with time.
Stick-insect droppings are even thinner and can look like a tube of stacked circular disks, especially when dry.
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Footprints and Tracks
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Kiore footprints.
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Compare footprints of rodents found in New Zealand.
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How to distinguish rat from stoat prints.
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The underside of a kiore hindfoot.
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Photo of kiore footprints needed.
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Tracking tunnel paper showing rat footprints (upper right) and mouse footprints (lower left).
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Tracking tunnel paper showing rat, stoat and weta tracks.
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Rat footprints on tracking tunnel paper (species unknown).
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Kiore nest.
Paws and feet
Kiore forefeet have four toes and the hindfeet have five toes, all with non-retractable claws. The hindfeet of adult kiore are 24.5mm to 31.0mm long, but the prints are usually shorter with only the toes showing. Kiore have a distinctive black diamond on the outer edge of their hind feet, while the rest of the foot and toes are pale. This can be a good way to distinguish between kiore and ship rats (which usually have dark hind feet).
Rat footprints show up clearly in tracking tunnels and forefeet and hindfeet are easily distinguished. In prints, the toes of the forefeet are widely spaced in a circular pattern, while the three central toes of the hindfeet are in a line with the two edge toes set slightly back. The forefeet have three main pads that are visible in tracks, while the hindfeet have around five pads. An adult forefoot print will be about 11.1mm wide and 15mm long. The hindfeet prints are about 15mm wide by 14mm long.
Rats have two main gaits on the ground – walking and running. If tracks are found in soft sediment it is possible to distinguish the gait from the arrangement of the footprints. When rats are walking, the prints are evenly spaced with distinct fore- and hind-footprints visible. When they are running, all four paw prints will be close together as the animal bounds along the ground.
Can be confused with:
Kiore footprints can be confused with Norway rat and ship rat prints as they can overlap in size at different ages.
Rat footprints from tracking tunnels can be confused with mustelid prints. They can be distinguished by drawing a line between toes 1 and 4 (A and B in photo “How to distinguish rat from stoat prints”) on the forefoot and 1 and 5 on the hindfoot. In rats, this line will either bisect the central pad or be slightly behind it. In mustelids, the line will be in front of the central pad.
Dens and nests
Food remains can be found around tree roots where kiore like to feed. They will dig small scrapes looking for food, but do not burrow. Kiore make nests in tree holes, behind loose bark and in tree stumps.
Can be confused with:
Other rat species.
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Vegetation Damage
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Kiore eating nikau seeds.
Fruits and Flowers
Kiore are likely to damage fruit, flowers and seeds in the same way as ship rats and Norway rats.
Can be confused with:
Damage by ship rats and Norway rats.
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Kill Sign
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Kiore: this Cook’s petrel was eaten by a kiore.
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Kiore-chewed snail shell or other invertebrate kill sign.
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Kiore egg predation.
Fur, feathers or scales (vertebrate)
Birds
Populations of some seabirds increased after kiore were eradicated from Little Barrier-Hauturu Island. In 2004, the Department of Conservation carried out an operation to eradicate kiore from the 2,800 hectare island. The following breeding season, Cook’s petrels had a 70% breeding success rate compared with 5% in previous years.
Lizards and frogs
Kiore can have a significant impact on lizards but some lizard species are more susceptible to rat predation than others. Kiore colonised a small island in the Mokohinau Group (Hauraki Gulf) during 1977 and caused a dramatic drop in lizard numbers.
Can be confused with:
Predation of other rats, mustelids (stoat, ferret, weasel) and cats. Remember, too, that animal remains might have been scavenged.
Insects or snails (invertebrate)
Kiore chew a hole in snail shells to access the soft tissues inside. Like other rodent species they are also likely to eat insects and other invertebrates.
Can be confused with:
Predation of other rat species.
Eggs
Kiore are likely to behave similarly to other rodents. Rodents may remove eggs from nests and eat them elsewhere. If the eggs are eaten in the nest there will be a few large fragments and several smaller fragments. Droppings may be present and the nest lining is likely to be disturbed as the animal searches for bits it has dropped.
Can be confused with:
It will be difficult to distinguish between ship rat- and kiore-predated nests. Remember, too, that egg remains might have been scavenged.
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Other Clues
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Kiore distribution in New Zealand.
Distribution
Though once more widespread, kiore are now only found in parts of Fiordland, Southland and South Westland on the mainland and on several islands, including Stewart Island.
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MORE ABOUT KIORE
Origin
Kiore evolved in South East Asia and were spread throughout the Pacific by people. They arrived in New Zealand around 1280 A.D . Once kiore arrived in New Zealand, they spread throughout suitable habitat on the three main islands and many offshore islands. The arrival of three European rodent species (ship rat, Norway rat, and house mouse) coincided with the decline of kiore across much of the country. The reasons behind the kiore decline are unclear, but may have been a result of competition, predation or both.
Description
Kiore have brown fur which is darker along the spine. The belly is grey and white. The feet are pale and have a distinctive dark outer edge on the hindfeet. The tail is dark and is around the same length as the head and body combined.
Size and weight
Adult head-body length is around 180mm and the typical weight is 60-80g, but individuals weighing up to 180g have been recorded. Adult kiore are smaller than adult ship rats, but juvenile ship rats may be mistaken for kiore based on size.
Behaviour
Kiore feed on the ground and in trees and are good climbers. Nests are mainly on the ground, but also sometimes in small holes.
Diet
Kiore have a very broad diet of plants and animals.
Habitat
Prior to their population decline (see below), kiore were found in a wide range of habitats from grasslands to mature forests. Their range is now restricted, so their habitat choices are limited to those available within this range.
Distribution
See distribution clue.
Other
Kiore were an important food source for Maori and it is possible that they were brought to New Zealand deliberately. They were actively hunted and kiore bones are present at archaeological sites spanning the whole pre-European period to more recently.
How to get rid of kiore
Contact your local DOC or Regional Council office for advice (see Next Steps). Trapping or poisoning.
FIND MORE INFORMATION IN:
Atkinson I.A.E., & Towns D.R. (2005). Kiore. In King, C.M., (Ed.), The handbook of New Zealand mammals (pp. 159-174).Auckland, New Zealand: Oxford University Press.
Booth, A. M., Minot, E. O., Fordham, R. A., & Innes, J. G. (1996). Kiore (Rattus exulans) predation on the eggs of the little shearwater (Puffinus assimilis haurakiensis). Notornis, 43, 147-153.
Gillies C., & Williams D. (2002). A short guide for identifying footprints on tracking tunnel papers. Draft Standard Operating Procedure. Unpublished. Waikato: Department of Conservation.
McCallum, J. (1986). Evidence of predation by kiore upon lizards from the Mokohinau Islands. New Zealand Journal of Ecology, 9, 83-87.
Rayner, M. J., Hauber, M. E., Imber, M. J., Stamp, R. K., & Clout, M. N. (2007). Spatial heterogeneity of mesopredator release within an oceanic island system. Proceedings of the National Academy of Sciences, 104, 20862-20865.
Towns D., R., Simberloff D., and Atkinson I., A. E. (1997). Restoration of New Zealand islands: Redressing the effects of introduced species. Pacific Conservation Biology, 3(2), 99-124.
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, USA, 105(22), 7676-7680.