Possum Trichosurus vulpecula

About this pest

Key Clues

Distinctive features: Furry body, long bushy tail, shorter front legs, pair of fused toes on hind feet, protruding brown eyes, pointed snout with pink nose, pointed ears without fur on the inside.

Size: Similar size to a cat.

Droppings: Crescent shaped pellets, in groups or single.

Footprints: Five-toed fore-feet, different hind-feet, claw marks.

Kill signs: Messy eaters, regurgitated pellets, egg shell fragments pushed into the egg.

Vegetation damage: Ragged edges on leaves, often in tree tops. Partially eaten leaves, leaf stems, fruits and flowers on the ground.  Bark chews and scratches.

Eye shine: Red

Distribution: North Island, South Island, Stewart Island, Chatham Island and other islands. Eradicated from some offshore islands.

Why are possums pests?

Ecological impacts

Possums threaten New Zealand’s ecology because they can increase to population densities where their browsing pressure can defoliate canopy and understorey vegetation.  They also compete with and prey on our native fauna.

Possums damage our native forests by browsing on foliage, flowers and fruit, especially of some preferred plant species. Their browsing can reduce flowering and fruiting, kill trees, and result in forest canopy collapse. The forest’s ability to regenerate is reduced because fewer seeds are produced. Some possum-preferred plant species have disappeared in some areas, but no species has become extinct in New Zealand because of possums.

Because possums eat the same food that native birds rely on the food available for native fauna is reduced. Less food means reduced breeding success for native birds and insects.

Possum competition and predation can also cause bird populations to decline. Possums compete for nest sites with hole-nesting birds such as kiwi, parakeets and saddlebacks, and eat the eggs, nestlings and adults of native birds. Possums eat large native land snails like Wainuia, Powelliphanta and Placostylus, which include many rare species. A single possum can eat more than 60 Powelliphanta per night!

Other impacts

Possums also carry bovine tuberculosis (TB). They spread the disease to New Zealand’s cattle and deer herds, which threatens the meat export industries. Possums can also damage horticultural and garden crops.

Read more about possums.


Clues

Droppings

Separate

Droppings (pellets) are long and cigar or crescent shaped, like jellybeans, with slightly pointed ends.  They are called pellets, can be found singly or in groups, and are usually about 15-30 mm long and 5-14 mm wide.  The colour and texture vary with diet, but they are often various shades of green, darkening with age.  Possum pellets can have a distinctive smell rather like pickled onions.  In spring when pine pollen cones are common the pellets can be bright yellow.

Can be confused with:

Droppings are quite different to deer or goat pellets because of their elongated shape, whereas ungulate pellets are round.. Possum droppings are often found on logs and stumps, while deer and goat droppings are mostly found on the ground and often in pellet heaps. Large weta droppings can sometimes be mistaken for those of juvenile possums.

Clumped

Droppings (pellets) are long and cigar or crescent shaped, like jellybeans, with slightly pointed ends.  They are called pellets, can be found singly or in groups, and are usually about 15-30 mm long and 5-14 mm wide.  The colour and texture vary with diet, but they are often various shades of green, darkening with age.  Possum pellets can have a distinctive smell rather like pickled onions.  In spring when pine pollen cones are common the pellets can be bright yellow.

Can be confused with:

Droppings are quite different to deer or goat pellets because of their elongated shape, whereas ungulate pellets are round.. Possum droppings are often found on logs and stumps, while deer and goat droppings are mostly found on the ground and often in pellet heaps. Large weta droppings can sometimes be mistaken for those of juvenile possums.

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Footprints and Tracks

Paws and feet

Forefeet are hand-like but the hind feet are quite different.  The forefoot has five fingers, each with a strong curved claw, and cushiony pads.  The hind foot has an opposable ‘thumb’ without a claw and the second and third digits are fused for most of their length except the tips.  The fusion of two toes is called syndactyly toe, and these toes are used for grooming fur. The claws can’t retract.

You won’t often see complete possum (fore and hind) prints on tracking paper, because possums don’t fit in standard tunnels.  Usually you see front paws only, which are impressions of four or five cushion pads plus four or five toe pads 1 to 1.5 cm out in front.  If you do find fore and hind foot prints then the hind foot will be placed just behind (or slightly overlapping) the forefoot on the same side (e.g. both are left feet).  Five or six cushion pads on the hindfoot might be visible.  The cushion pads of the 2nd and 3rd digits are fused.  The toe pad of the ‘thumb’ is usually visible and one or both of the 4th and/or 5th digit toe pads.  The toe pads for the 2nd and 3rd digits may or may not show, but are not fused.  The fur on the feet can smudge the prints.

Possums walk on all four feet when on the ground and the gait length is about 10 to 12 cm between placement of left and right feet.  They make half bounds (short jumps) on steeper terrain and between branches and big bounds on tree trunks.  The tail holds on to a branch until all feet are touching a solid surface.  Possums can swim but don’t much like water.

It is difficult to confuse possum prints with anything else as they are usually much larger than those of other species of small mammal in New Zealand.  The toe pad marks are quite small relative to the cushion pad marks and the toe pads are spaced further than those of other species. 

Can be confused with:

Rat, hedgehog, or ferret footprints. However, rat footprints are very much smaller and show less toe, especially on the hind foot. Hedgehog prints are smaller and quite circular in outline.  Ferrets can also mess up tracking paper but the cushion pads and toe pads are in quite a different arrangement to that of possums.

Trails and Runs

Possum trails (called pads or runs) are seen most often on the forest edge near pasture, made when possums come out from the forest at night to eat pasture species and crops. Possum runs can also be found inside a forest, especially near denning sites, if there are lots of possums. 

Can be confused with:

Many animals will create trails to get from one place to another.  You may need to check for footprints to see who is using the track.  Runs from forest into grassland are most often made by possums but also by hares, and wallabies where these occur.  Tracks up and down spurs are often made by ungulate species such as deer and goat.

Dens and nests

Possums sleep (during the day) in holes (called dens) above the ground, in hollow tree branches or building ceiling cavities, or at or below ground level.  A possum can have several dens and can change dens several times per night.

Can be confused with:

Dens can be used by a range of species; you will need to check for fur, footprints and smell to see if possum was one of these.

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Vegetation Damage

Tree Tops (Canopy taller than 3m)

Damage to the forest canopy is often caused by possums, but native birds, insects, and weather can cause damage too.  Clues are; many bare branches, only a few leaves left, large parts of the tree dead, and ragged looking leaves.  In New Zealand the density of possums (number per area) is only limited by the amount of food.  So possum numbers always increase to the point where they damage or eliminate tree and plant species. Check the damage with binoculars; possums chewed leaves are usually ‘torn’ roughly with midribs and occasionally lower portions of leaves left uneaten.

Can be confused with:

Birds like kereru can also strip leaves from a tree and cause ragged edges.  However kereru bites have round tips. 

Insects can also damage leaves and fruits, but usually they cause smaller holes and holes away from the leaf edge. 

Bad storms and salt-spray can cause leaves to fall off too.  If all species in an area are affected, rather than just the ones possums really like, then it may be a weather event.

Understorey (less than 3m)

Possums can leave the ground littered with partially eaten leaves, flowers and fruits, and can leave chew marks and scratches on bark – but it can be one of many other culprits too!   One useful clue is how far up you can see the same type of damage.  If it goes all the way up into the canopy then it could be possum.  If it only occurs in the understorey then it may be one of the other culprits. 

Can be confused with:

Many other species.  Check out the signs of vegetation damage left by other species, including: fallow deer, red deer, rusa deer, sambar deer, sika deer, white-tailed deer, rabbit, Norway rat, ship rat, kiore, mouse, feral pig, and feral goat. 

Bark

Short horizontal bark biting on bark are most likely to be possum. Possums chew bark as a way to mark territory and they often use the same tree year after year.  You should be able to see two parallel lines with a narrow higher strip in between (left by incisor teeth).  If the incisor marks are wider then 5mm it is most likely a possum. 

You might also see claw scratches as they climb up and down – scratches from claws often wrap around the trunk on a slant.

Can be confused with:

Many other species bite bark, but mostly more up and down.  The tooth-marks of possums are also quite different to that of other species.  Check out the other species and other vegetation sign to make sure. Other culprits are; fallow deer, red deer, rusa deer, sambar deer, sika deer, white-tailed deer, rabbit, Norway rat, ship rat, kiore, mouse, cat, feral pig, and feral goat. 

plant leaves

Possums are messy eaters and the ground beneath a tree is often littered with partially eaten leaves.  Possum chewed leaves are usually ‘torn’ roughly with midribs and occasionally lower portions of leaves left uneaten.  They only eat the leaf-stalks of some species, like fivefinger.  Possum preferred species include pohutukawa, rata, kohekohe, tree fuchsia, totara, mahoe, heketara, toro, tutu, mamaku, kamahi, pahautea, pine (exotic) and many other species.  They don’t like pigeonwood.

Possum veg confuse sqx100Can be confused with:

Many other species like deer, goats and farm animals.  Birds like kereru can also strip leaves from a tree and cause ragged edges.  However kereru bites have round tips. Insects can also damage leaves.

 

Fruits and Flowers

Possums love fruits and flowers.  Look for chew marks: if the width of the incisor marks is greater than 5 mm then possums are the most likely culprit. Possums particularly like fruits with lots of energy and nutrients, like tawa, taraire, puriri, kohekohe, kahikatea, karaka, five-finger, kiekie, nikau (fleshy stem only), and hinau.  Possums like the rind on citrus fruit including lemons! Surprisingly perhaps they also like the seeds inside rewarewa capsules. 

They also like the flowers of kiekie, nikau (fleshy stem only), puriri, kohekohe, five-finger, kowhai, pohutukawa, rata, rewarewa, rose, pinecone and kahikatea ‘flower-cones’ and many others.  Sometimes possums eat so many of the flowers that the plants never have a chance to set fruit. 

Can be confused with:

Rats and mice.  If the incisor marks are wider than 5 mm it is most likely possum, between 5 and 2 mm one of the rat species, and less than 2 mm a mouse.  However, juvenile possum teeth can make marks very similar to rat teeth.  Larger mammals will likely swallow the fruit whole. Fruit can also be damaged by native birds such as kaka, kea, kakariki and exotic birds such as rosella.

Flowers can also be eaten by native birds such as kaka, kea, kakariki and exotic birds such as rosella.  Flowers in the understorey can be eaten by fallow deer, red deer, rusa deer, sambar deer, sika deer, white-tailed deer, Norway rat, ship rat, kiore, feral pig, and feral goat.

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Kill Sign

Fur, feathers or scales (vertebrate)

Birds

Small bird prey remains may include chewed feathers, and regurgitated feather and bone remains.  Eggshell and other material are sometimes chewed into a 'pellet' that is coughed up. Birds and nestlings often are only partially eaten, favoured areas being the head and chest, with wing and rear being less favoured.

Mammals

Possums are known to scavenge on deer and pig carcasses and are often caught in traps baited with rabbit meat to catch ferrets or stoats.  Scavenging carcasses is thought to be one way that bovine TB is spread between animals.

Lizard and frogs: 

Possums are opportunistic feeders and possibly may eat lizards and frogs if they can catch them but there are no confirmed records of this occurring..

Can be confused with:

The messy feeding sign can be confused with that of ship rat or other rodents, and mustelids like stoats. A key differentiator may be the presence or absence of feather and bone or eggshell 'pellets' produced by possums.  Stoats often kill with a distinctive bite mark to the back of the head and prefer to drag their prey under cover. Remember, too, that animal remains might have been scavenged.

Insects or snails (invertebrate)

Possums eat large New Zealand land snails by biting through the shell and pulling the snail out. They eat snails like Wainuia, Powelliphanta and Placostylus, which include many rare species. A single possum can eat more than 60 Powelliphanta per night!  

Can be confused with:

Rats also prey on snails but they leave smaller teeth marks and a smaller hole.  Pigs tend to completely crush larger shells and swallow smaller shells whole.  Weka peck neat holes through the central whorl of the shell to access the meat.  Thrushes kill and eat only small snails, leaving shatter holes (a hole with breaks and shell fragments radiating out from it) through the outer whorl.  Hedgehog sign is similar to that of thrushes

Eggs

Possums leave relatively whole but crushed eggshells.  The edges of the shell are pushed inwards. They are suspected of predating on kiwi eggs. One egg had an 80-120 mm hole chewed in the top or side of egg.

Can be confused with:

Rats, but they leave numerous small fragments and jagged edged shells.  Stoats and ferrets, but they tend to create a hole rather than crush the egg and the edge of the hole will be serrated. Remember, too, that egg remains might have been scavenged.

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Other Clues

Smell

Possums have multiple scent glands including a red-brown gland on the chest between the front legs (sternal), near their bottoms and in the pouch region. They commonly rub these glands on the bases of tree trunks, or mix the scent with urine or droppings, to mark territory. They can release different scents when scared or handled, and will often release urine or droppings too.


The sternal gland on the chest has a sweetish musky odour. One pair of anal (bottom) glands contain a white substance with a penetrating acid smell rather like pickled onions. A second pair of anal glands secrete cells suspended in a clear viscid fluid, but have no distinctive odour.

Sound

Possums are mostly solitary but make a range of noises at night when there are other possums around including screeches, grunts, growls, hisses and chatters (aggressive), zook-zook noises and squeaks with dependent juveniles, and males make shook-shook and clicking noises when courting a female.

Body covering

When possums fight with each other they will leave tufts of hair behind.  Possum fur is very soft and luxurious (the reason why they were introduced into NZ).  In colour it is grey or dark brown on the head, back and tail and white or dirty yellow on the belly.  However, possums come in grey and dark forms and there also are occasional albino animals.  The fur is about 4-6 cm in length with a dense cushioned undercoat.  The possum fur is much prized because it doesn't shed and is anti-static.  The hair has a hollow structure which helps to store heat (it is the third warmest fur in the world) and is combined with merino wool to make a fibre that is used for making clothes.

Bite marks

Possums have six incisor teeth at the front of the jaw (four up and two down) designed for cutting plant matter; a relatively small canine part way back; and premolars/molars at the back for crushing and grinding plant matter.

For guidance on identfying possum bite marks go to Landcare Research, 'Possums' heading or pages 6-15 of their identification guide.

Eye shine

Possums are nocturnal (only come out at night) and if you shine a torch in the trees at night you might see their large eyes reflecting a red light.

Distribution

North and South Island, Stewart Island, Chatham Island, Kawau Island, Ruapuke Island, Native Island and Bravo Island (in Paterson Inlet). Possums occur in a wide range of habitats from open country to deep in the forest, from rain forest to arid areas but tend to be rare at high altitudes (mountain tops).

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More about Possums

Origin

Introduced for the fur-trade from Australia; New South Wales, Victoria and Tasmania.

Description

Possums have a furry body, with a long prehensile (can hold on to things) bushy tail for climbing.  They have a pointed snout with pink nose and long dark whiskers and brown eyes.  The large pointed ears are furless on the inside.  Possum fur is fluffy grey or dark brown on the head, back and tail and white or dirty yellow on the belly and there are several colour forms [link to fur].  Mature possums have a brown stain (the sternal gland) between their front legs.  The front legs are shorter than the hind legs.  Front paws are rather hand-like, and rear paws rather longer with a pair of fused digits.

Possums are marsupials, so they give birth to very small young that climb into the mother’s pouch.  They stay in the pouch for at least 120 days.

Size and weight

Males and females are similar in size; between 650 and 930 mm, including a tail of 250 to 405 mm.  That is about the size of a cat.  Adults weigh between 1. 4 and 6.4 kg.

Behaviour

Possums are nocturnal and come out of their dens about 30 minutes after sunset.  The main feeding activity tends to occur about two hours after they have come out of the den.  Sick animals can sometimes been seen in the afternoon.  Heavy rain may delay possums from leaving their dens.  Possums spend most of their time in trees and may only spend 10-15 % of their time on the ground.

Possums live in dens. They prefer to den in holes above the ground like hollow tree branches or trunks, ceiling cavities of buildings, but can also den at or below ground level in holes or beneath vegetation and structures on the ground..  A possum can have several dens, and can change dens several times per night.  The dens are not exclusive; more than one possum may use it, but preferably not at the same time. 

Juvenile females will establish territories close to the mother’s territory, but juvenile males shift further away.  This means that in areas of possum trapping you are more likely to catch a male wandering in from adjacent areas.  Heavier possums are dominant (the boss) over smaller ones, and females tend to be dominant over similar sized (or smaller) males.  The main breeding season is autumn but in some locations a second breeding season occurs in spring. Usually only one young is born per litter, though twins do very occasionally occur.  Young become independent after 6-9 months.

Possums communicate by smell, scent-marking tree trunks with oil from special glands, and urine and droppings.  They also have a range of screeches, grunts, growls, hisses and chatters. 

Diet

Possums are opportunistic herbivores.  They feed mainly on leaves but also eat buds, flowers, fruits, ferns, bark, fungi, insects, land snails, birds and their eggs, and scavenge carcasses.  Diet can vary seasonally with invertebrates being common during certain times (depending on where and what habitat).  Possums particularly love eating some plant species and can eat these species to death or totally strip the fruit crop, but this preference can be regional. 

Habitat

Possums are widespread and known to inhabit pastoral land, beech forest, podocarp forest, and sub-alpine areas. Densest populations occur in mixed hardwood forest and forest/pasture margins and can be as high as 25 per ha.

Distribution

North and South Island, Stewart Island, Chatham Island, Kawau Island, Ruapuke Island, Native Island and Bravo Island (in Paterson Inlet).  Not found at high altitude e.g. tops of Mts Taranaki and Ruapehu.  Have been eradicated from many off-shore islands, notably Rangitoto, Motutapu, Kapiti, Codfish, Whanganui and Tarakaipa, all of which have outstanding conservation importance.  Possums are still spreading into new areas.  Possums are native to the Australian mainland, Tasmania and some other Australian islands.

Other

‘Opposum’ is what brushtail possums used to be called but now more commonly refers to a completely different marsupial from America.

How to get rid of possums

Contact your local DOC or Regional Council office for advice (see Next Steps).  Possums can be controlled by spotlight (night) shooting, using live- or kill-traps baited with carrot or apple, bait stations (variety of toxic baits available) and, in larger areas, aerial sowing of baits.  Correct placement of the traps or stations can be important to successfully controlling possums so get advice from DOC or your local council.

A vaccine has been developed to stop possums from breeding so fast, and is being tested.


FIND MORE INFORMATION IN:

Barton, Ian (1990). A handbook for the assessment of noxious animal damage in Auckland forests. Unpublished report, Auckland  Regional Council, Auckland.

Brown, K., Innes, J., and Shorten, R. (1993).  Evidence that possums prey on and scavenge birds’ eggs, birds and mammals. Notornis, 40, 169-177.

Coleman M.C., Parkes J.P., & Walker K.J. (2001). Impact of feral pigs and other predators on macro-invertebrates, D'Urville Island. Conservation Advisory Science Notes No. 345 (p. 16). Department of Conservation, Wellington, New Zealand.

Cowan P.E. (2005). Brushtail possum. In TKing, C.M., (Ed.), The handbook of New Zealand mammals (pp. 56-81).Auckland, New Zealand: Oxford University Press.

Department of Conservation. (Undated). Draft Predator Control Manual. Unpublished report. Wellington: Author.

Kean R.I. (1967). Behaviour and territorialism in Trichosurus vulpecula (Marsupialia). Proceedings of the New Zealand Ecological Society, 14, 71-78.

McLennan, J.A. (1988). Breeding of North Island brown kiwi, Apteryx australis mantelli, in Hawke's Bay, New Zealand.  New Zealand Journal of Ecology, 11, 89-97.

Malcolm, T.  (2009). Private landowners' guide to possum control: control tools and techniques. National Possum Control Agencies, Wellington.

New Zealand plant conservation network. (2014). Possums. Retrieved from http://www.nzpcn.org.nz/page.aspx?threats_animal_pests_mammalian_pests_possums

Parks and Wildlife Service, Tasmania. (2014). Brushtail possum Trichosurus vulpecula. Retrieved from http://www.parks.tas.gov.au/index.aspx?base=4871

Pest Control Education Trust. (2014). 1080: The Facts. Retrieved from http://www.1080facts.co.nz/