Pests

Ship Rat

Summary & Description

Species: Rattus rattus
Origin: Europe
Breeding Cycle: Approx. 32 days
Diet: Birds, eggs, plants, invertebrates
Home Range (ha): 0.01 - 0.02
Head-Body Length (mm): max. 225
Adult Weight (g): 120 - 160

Originating in India, the ship rat spread throughout Europe and the UK, making it’s way to NZ some 200 years ago with the arrival of Europeans. The ship rat quickly displaced the Norway rat as the most common and widespread rodent in NZ.  They are identifiable by their large ears and a long tail.

Biology & Ecology

Ship Rat skull.

Ship rats spend a large amount of their time in trees, their arboreal nature allowing easy access to birds' nests. They have a varied diet, eating a wide variety of native and introduced birds, plants, and invertebrates.

Ship Rat poo.

They are efficient swimmers, establishing populations on pest-free islands up to 750 m away.

Threat & Impact

Ship Rat eating a kiekie fruit.

Rats in NZ have been implicated in the extinction and decline of a large proportion of native bird species. The spread of ship rats in the North Island coincided with the declines of korimako (bellbird), toutouwai (robin), hihi (stichbird) , and tieke (saddleback.)

NZ robin eggs are consumed by ship rats.

The inclusion of native plants and fruits in their diet also put rats in direct competition with native birds, contributing to their decline. In addition to the destruction of native species, rats also can cause a lot of damage to property.

What you can do

Use Detector cards to locate the best trapping site.

Rat control can be done by everybody, no matter how big your backyard. Establishing a good network of traps around your sensitive sites Getting an understanding of rat locations is important so be sure to set out detector cards before setting your trap.

Goodnature A24 Rat & Stoat trap.

By detecting, not guessing, you can quickly locate rat populations and tailor your pest control. Be sure to place your traps a distance from food sources like compost.

Norway Rat

Summary & Description

Species: Rattus norvegicus
Origin: Europe
Breeding Cycle: Approx. 32 days
Diet: Birds, eggs, plants, invertebrates
Home Range (ha): 0.01 - 0.02
Head-Body Length (mm): 184 - 192 mm
Average adult Weight (g): 150 - 300

New Zealand was virtually mammal free prior to the arrival of pacific islanders around 700 years ago, with them came the pacific rat or Kiore. Nearly 250 years later, Europeans brought the ship rat and the Norway rat. Of the three species, the Norway rat is the largest and is most easily identified by their short tail and small ears.

Biology & Ecology

Rat Skull.

Commonly found in waterways and in urban areas, Norway rats are efficient swimmers and are sometimes referred to as the "water rat". They have been known to swim passages greater than 600 m. Able to climb when required, they are more likely to

Cylindrical (Pastille shaped), avg 16 mm long.

be found in burrows around populated areas and buildings. These rats are omnivorous and take an opportunistic approach to food. The average adult Norway rat eats around 10% of their body weight per day.

Threat & Impact

Rat scavenging.

Rats in New Zealand have been implicated in the extinction and decline of many native bird species. Due to their size, the Norway rat is capable of targeting adult seabirds, an example being the southern New Zealand dotterel (tuturiwhatu), now only found on Stewart Island.

Southern NZ dotterel.

The inclusion of native plants and fruits in their diet has also put these rats in direct competition and contributing to the decline of native birds. Around the home, Norway rats are likely to cause damage to electrical wiring and soil food.

What you can do

Use Rodent Detector Cards to locate a trapping site.

Rat control is easily undertaken and using detector cards prior to installing your A24 is a great way to find the best locations to trap. A couple of A24's around the home and

Goodnature A24 Rat and Stoat trap.

garage will provide continued suppression of rats and mice - remember to add a little pre-feed regularly to have the best effect.

Mice

Summary & Description

Species: Mus musculus
Origin: Europe via Australia
Breeding Cycle: 20 - 30 days
Diet: Omnivorous
Home Range (ha): Average 0.6
Average Length (mm): without tail, max 115
Average weight (g): 15 - 20

Mice are small, nocturnal mammals that arrived in New Zealand on Ruapuke Island accidently with the grounding of the flax ship, the Henrietta in 1824. So foreign to the locals, they became known as Henriettas. Mice are well established across New Zealand but not on Stewart Island.

Biology & Ecology

Mouse skull.

Mice tend to avoid animals larger than themselves and rely heavily on their sense of smell and hearing to avoid predators. They tend to reach greatest densities in thick ground cover. The mouse diet of invertebrates and plants is seasonal.

Mice poo is 3.9-7.6 mm long. Singular.

Mice are found throughout New Zealand, and are a significant threat to wrens in alpine regions in Fiordland but can be found in bush, pasture, farms and urban settings.

Threat & Impact

Mouse on a birds nest.

Mice deficate and urinate in food making it a health hazard for humans, this leads to economic loss through wasted food. Mice are generally oportunistic feeders but are the food staple of stoats and cats. The mouse dietary requirement is high,

Petrel eggs are eaten by mice.

they need to consume around 4.4 g of invertebrates, or 969 rimu seeds daily. On sub-Antarctic Gough Island, mice have learned that petrel and albatross chicks are a good food source and will eat chicks alive on the nest.

What you can do

Trapping at 25 m intervals is needed.

The most difficult part of mouse control is the small home range they occupy. To control mice across the landscape, a network with traps set at 25 m intervals is needed. Around the home, a couple of traps

Goodnature A24 Rat & Stoat trap.

will keep control of the little fellas coming inside at the start of the colder seasons. Keep their numbers low in summer and they are less likely to be a bother by winter.

Possum

Summary & Description

Species: Trichosurus vulpecula
Origin: Australia
Breeding Cycle: Predominantly seasonal
Home Range (ha): 0.7 - 2.7
Adult Length (mm): Between 650 - 930
Adult Weight (g): Range from 1400 - 6400

Introduced in 1837 to establish a fur trade, possums have thrived in a predator free New Zealand. Their diet includes a wide range of native fauna and flora, and due to the abundance of food, they have become somewhat generalist in their food selection. This has had a massive impact on New Zealand's delicate ecosystems.

Biology & Ecology

Possum skull.

Possums have a diverse habitat, predominantly forests, but only sparsely found throughout the mountainous terrain of Fiordland. In their native environment of Australia, possums are said to spend 90% of their time eating and 10% socialising. In New Zealand, this is the inverse with such an

 

Cresent shapped fecal pellets, slightly pointed ends.

abundance of food. Their diet mainly consists of leaves but they will eat whole plants, fungi, invertebrates, birds and eggs, snails and carrion (decaying animals). Possums use a range of scent glands to mark territory or to attract mates.

Threat & Impact

Possum damage to native fern.

The browse feeding habits of possums cause damage to our native forests, killing trees and causing forest canopy collapse. This also reduces the availability of food for native fauna, contributing to the reduction of breeding success.

Weta are eaten by possums.

Possums are carriers of a range of diseases and are the principal host in New Zealand for Bovine TB, transmitting the bacterial infection to livestock. This has severe economic impact on the deer, beef and dairy industry.

What you can do

Typical possum damage.

Often possums will make their presence known with their raspy calls in the small hours of the night or by eating your roses or lemon tree. A good sign possums are around are their ‘runs’, scratch or bite marks on trees, and scattered branches at the base

Goodnature A12 Possum Trap.

of trees. By putting a dab of possum paste at the base of a few trees and where you see the signs of their visits, you can habituate possums and prepare them to pop their head in an A12 trap.

Stoat

Summary & Description

Species: Mustela erminea
Origin: Eurasia & North America
Breeding Cycle: Single litter yearly
Diet: Carnivore
Home Range (ha): 60 - 200
Average Length (mm): 256 - 284
Average Weight (g): Male: 324, female: 207

Stoats were introduced to New Zealand with ferrets and weasels in the mid 1870's to control rabbits, which had become major agricultural pests. They had legal protection until 1936, by the time it was removed they were abundant on the North and South Island. They are still absent from Stewart Island. Stoats are distinguished from other mustelid by the black tip on their tail.

Biology & Ecology

Stoat skull.

Stoats have high metabolisms and a heart rate of up to 300BPM. They commonly raid nests while adults are absent and cache the kill in their den to consume over time. They are capable of carrying animals 10 times their own weight. Typically, all females of a litter are impregnated before dispersal meaning

Stoat poo is 40-80 mm with twist on ends.

90% of all females stoats are pregnant from December to September when they are likely to have a litter of 6-8 kits. The ability to delay impregnation is specific to stoats. Stoats are active day and night and are remarkable swimmers, capable of swimming 1.5 km.

Threat & Impact

A penguin killed by a stoat.

There are few predators that have had a bigger impact on native species in New Zealand than the stoat. North Island brown Kiwi have a 5% chance of survival in the wild due to stoats and feral cats resulting in a total population decline of nearly 2%.

Mohua eggs are consumed by stoats.

Stoats are directly implicated in the decline of the takahe, kaka, mohua and Whio but also dine on lizards and insects. Partial to chickens, stoats attack the neck and back of the head, often killing and leaving the bird.

What you can do

Community groups target species such as the stoat.

Because of a stoat's large home range, a good network is important to keep the population low. By placing traps at 100 m intervals on tracks up to 600 m apart, you can effectively maintain low stoat

Goodnature A24 Rat & Stoat trap.

densities for sustained periods. Goodnature's A24 has passed the National Animal Welfare Advisory Committee's standards for humanness and is one of the best ways to control stoats.

Weasel

Summary & Description

Species: Mustela nivalis vulgaris
Origin: West & Central Europe
Breeding Cycle: Up to 3 yearly
Diet: Carnivore
Home Range (ha): Male: (5-25), female (1-10)
Average Length (mm): 182 - 217
Average Weight (g): Male: 128.8, female: 57.5

Weasels were imported with stoats and ferrets to control rabbits in the 1870's. The weasel has the distinction of being the smallest carnivore in the world and can be identified apart from stoats by their white tummy, small size and lack of black tip on the end of their short tails.

Biology & Ecology

Weasel Skull

During the months between September and March, weasels can have up to three litters of 4-5 kits. If there is an abundance of food, weasels can breed in the year of their birth. They are opportunistic feeders eating insects, lizards, mice and small birds.

Droppings 30-60 mm in length. Twist at each end.

Mice are their most common food source. Populations of weasels can be found throughout the country (with the exception of Stewart Island) but are far less common than stoats or ferrets.

Threat & Impact

A weasel scavenging a birds egg.

Weasels have had significant impacts on populations of the now nationally endangered Whittaker's skink in New Zealand. Like the stoat, they will attack prey much larger than themselves meaning nesting birds are easy targets.

Tui eggs are consumed by weasels.

Because weasels are found in all areas of New Zealand, their diet is varied. They tend to exist in pockets of high population where they are many. There are also no weasels on Stewart or Great Barrier Island.

What you can do

Simple trapping networks can be very effective.

Because the weasel has a relatively small home range, you can maintain the population to low levels with a simple network of traps. A well-placed A24 will

Goodnature A24 Rat & Stoat Trap.

keep populations to low numbers. Use detector cards prior to installing your A24 as a great way to find the best locations to trap.

Hedgehog

Summary & Description

Species: Erinaceus europaeus    
Origin: Europe    
Breeding Cycle: Average 2 litters a year    
Diet: Mainly insects, small animals.    
Home Range (ha): Average 2 - 5 
Average Length (mm): 150 - 266    
Average weight (g): Generally 620 - 700

Originally brought to New Zealand to remind European settlers of home, hedgehogs soon became successful predators of not only garden invertebrates but also native birds and insects.

Biology & Ecology

Hedgehog skull, robust and box like.

Abundant through lowland areas, braided riverbeds and coastal areas, hedgehogs are less likely to be found in hilly environments. They are excellent swimmers and climbers. Although they both hibernate during winter by building dens under tree roots or deep dry litter, males tend to be the first to settle in. 

Poo is 30-50 mm long and 7-10 mm wide.

These nocturnal animals remain solitary until they briefly pair for breeding. Hedgehogs are usually heard moving and snuffling before they are seen and if you get to close they roll tightly into a ball and use their spines for protection. Their droppings are black, and can contain tightly packed fragments of invertebrate exoskeletons.

Threat & Impact

A hedgehog feeding on a frog.

Hedgehogs are mainly insectivorous, posing a threat to native weta. They often eat around 160 g invertebrates per day. They will however, eat animals such as mice, lizards, frogs. They have been proven to be a major predator of eggs of riverbed breeding birds such as banded dotterel and

Hedgehog prey on species such as the Otago skink.

black-fronted tern, and have been known to kill and eat chicks of a variety of ground-nesting birds. Hedgehogs have been known to eat the native New Zealand snail Wainuia urnula. While not a host of bovine TB, TB is likely to be present in hedgehogs living in densely infected possum areas.

What you can do

Use Rodent Detector Cards to locate a trapping site.

Don't be afraid to control hedgehogs, they are an introduced pest to New Zealand and in many locations; they are the primary cause of decline of nesting birds.

Goodnature A24 Rat & Stoat Trap.

A well-placed A24 will keep populations to low numbers. Use detector cards prior to installing your A24 as a great way to find the best locations to trap.