Understorey (less than 3m)

Possum

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. 

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Rabbit (European)

Rabbits will graze favoured vegetation to the point that there is nothing left but bare earth. They also suppress the growth and regeneration of favoured species, leading to changes in vegetation composition.

Can be confused with:

Sheep can graze pasture to very low levels, but not to quite the same extent as rabbits and often without much bare earth.

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Brown hare

Hares can stand on their hind legs and browse plants up to about 1 m high and can reach higher if the terrain or site conditions (such as snowdrifts) allows. At times, their browsing can create very short and dense pasture or grassland swards. Observations have shown that hares can affect nearly all the plants in areas of new tree, shrub and crop planting, even at low hare densities. Hares strip leaves off plants or bite off stems at a 45⁰ angle. In plantings, hares tend to prefer plants with wider foliage such as Coprosma species and will often leave the smaller leaved plants, such as manuka or kanuka, alone.  Studies of hare diet in alpine areas have shown that hares eat a range of plant species, the proportions of which in the diet reflect the abundance of the plant species in the habitat. The winter diet in alpine areas of mainly tussocks (Chionochloa species) and mountain daisies (Celmisia species) changes to more grass-like species such as Poa colensoi in summer, probably because Poa colensoi is more available after the snow has melted.

Hares are known to nip off low branches and bite bark off citrus and other fruit trees, often leaving branches uneaten around the base of the tree. Hares damage market garden crops by biting off asparagus spears, and eating crops like cabbages, cauliflowers and lettuces, as well as grains like corn, wheat and maize.

Can be confused with:

Hare browse can be difficult to distinguish from rabbit browse, as both species will browse vegetation of less than 1 metre in height. Rabbits are a bit shorter than hares and may only reach as high as 0.8 m when standing on their hind feet, though in areas where food is limited it is not uncommon to find they have clambered up into shrubs and fed on them a metre or two above the ground! The browse of other larger herbivorous (plant eating) animals like deer, goats, chamois, wallabies and sheep can be distinguished from hares and rabbits if it extends higher than 1 metre above the ground. Plants browsed by larger herbivores may look more ragged and twigs will lack the 45⁰ angled cut characteristic of hares and rabbits. Look for other distinguishing sign as well, such as droppings that hares often leave near plants they have eaten. Signs of digging down to plant roots, is more likely to be caused by rabbits or Bennett’s wallabies.

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Dama wallaby

Due to the small size of dama wallaby (height about 0.5 m), they typically browse the leaves of seedlings, saplings, grasses and ferns that are below 1 m. The leaves are often bitten in half and resemble browse from other introduced mammals. They eat many native species including kamahi (Weinmannia racemosa), māhoe (Melicytus ramiflorus), Coprosma spp, Mānuka/kānuka, ferns, supplejack (Ripogonum scandens), and broadleaf (Griselinia sp.)

Vegetation surveys near Rotorua have shown that hangehange (Geniostoma ligustrifolium), kotukutuku (Fuchsia excorticata), raurēkau (Coprosma grandifolia), karamū (Coprosma robusta), pate (Schefflera digitata) and five finger (Pseudopanax arboreus) are particularly heavily browsed by dama wallabies. Where dama wallabies have access to pasture or grassed clearing a high percentage of their diet consists of pasture species therefore they are considered potential pasture pests.  They occasionally damage to pine and eucalyptus seedlings.

Can be confused with:

Understorey browse by dama wallabies can be confused with browse by deer, feral goats and livestock.

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Bennett's (red-necked) wallaby

Bennett’s wallaby are primarily grazers of open grassland, eating grasses and herbs, including indigenous species, such as the large daisy Celmisia spectabilis, that sheep do not eat. In forests, they can severely deplete the understorey and prevent regeneration of palatable species by browsing foliage and digging with their forepaws to feed on the roots of forest and shrub species.

Can be confused with

Bennett's wallaby grazing on farmland pasture cannot easily be differentiated from that of sheep. They can leave a distinctive ‘browse line’ in scrub and forest; however, this can be confused with species, like sheep, goats, and hares that also feed at a similar height to wallabies. Wallabies' scratching and digging sign can be confused with species like rabbits, hares and possums.

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Goat

When feral goats are abundant they can denude vegetation and change the composition of species in the forest understorey. Despite their reputation as eating almost anything, like deer, goats have preferences and will first select palatable species such as broadleaf (Griselinina littoralis), kiekie (Freycinetia banksii) and mahoe (Melicytus ramiflorus), quickly reducing their abundance in an area. Goat are more likely to eat prickly species such as mingimingi (Leucopogon fasciculatus) and gorse than deer.

Can be confused with:
The impact of goats on the understorey can look similar to that of deer and other browsing ungulates. Goats will eat a wider range of of species, including those with prickly foliage, and will often crop plants closer to the ground than deer.

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Chamois

Chamois usually occur in low densities, thus feeding sign is more likely to be caused by other browsers. Chamois feeding sign can include large clumps of grass or tussocks pulled from the ground or grazed, or shrubs that have been browsed. Chamois eat lichens, grasses, herbs and woody plants. Signs of their feeding can be found in alpine and subalpine grasslands, herb fields, shrublands and mire (swamp) communities where chamois commonly occur. In alpine grassland they favour tussocks, grasses and alpine herb species with fleshy leaves such as the Mt Cook buttercup. Chamois are also found in lower altitude forests, especially on the West Coast, where they will browse on understorey vegetation, finding broadleaf (Griselinia littoralis) and kamahi (Weinmannia racemosa) particularly palatable.

Can be confused with:

It is difficult to distinguish chamois damage from that of other ungulates (hoofed animals) tahr, deer species, sheep, cows and goats.

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Himalayan Tahr (thar)

Tahr are predominantly grazers, feeding on grasses and herbs, but they do browse the leaves of shrubs particularly when grasslands and tussocklands are snow-covered. Signs of Himalayan tahr grazing on vegetation is most likely to be found in alpine and subalpine zones. They are known to graze snow tussock (Chionochloa spp.), native broom (Carmichaelia spp.) and Mount Cook buttercup (Ranunculus lyallii) and can kill entire plants. Changes in plant community composition could also be a sign: decreases in snow tussock, increases in turf grasslands (Poa colensoi) and, in areas of high tahr density, a change from Chionochloa dominance to shorter Festuca tussock species or even areas of bare ground.

Himalayan tahr can browse alpine shrubland species, e.g. matagouri (Discaria toumatou), and short podocarp (Podocarpus nivalis).

Can be confused with:

Chamois, red deer, sheep, brushtail possums and brown hare all co-exist with Himalayan tahr over much of their range and can be mistaken for tahr browse. Red deer are more likely to occur below the treeline in areas with significant helicopter hunting pressure but can also be found, along with the other species, browsing in the sub-alpine and alpine areas. Possum browse on some shrub species might be distinguishable as possums often leave the midrib uneaten. It might be difficult to attribute the browse to particular species, so look for other clues such as droppings or foot prints.

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Fallow deer

In the understorey, there are certain plant species that fallow deer prefer to eat (this is known as selective browsing). They especially like broadleaf (Griselinia littoralis), other broad-leaved subcanopy trees and some ferns. Over time, their selective browsing can lead to the removal of these species from areas, leading to an increase in unpalatable ‘browse resistant’ species.

Can be confused with:
Fallow deer browse can be confused with browse by other deer species, cows, goats, and sheep.

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Sika deer

Sika deer browse most of the understory species that other deer species do e.g. broadleaf (Griselinia littoralis), Pseudopanax species, fuchsia (Fuchsia excorticata), wineberry (Aristotelia serrata) and Coprosma species. However, they also eat the seedlings and saplings of beech tree species and ferns in addition to these highly preferred species, including species that are considered less palatable to other deer species. This is because they may be better adapted to digesting fibrous forage.

Can be confused with:
Browse by sika deer can be confused with browse by other deer species, sheep, and goats.

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Rusa (Javan) deer

Rusa deer prefer to graze farm pastures and root crops, as well as grasses and forbs in forest clearings, if they have access to these habitats. In the scrub-hardwood forest of the Galatea Valley (south east of Rotorua), rusa deer browse on three-finger, bracken, flax tips and young manuka.

Can be confused with:
Other deer species also browse on the same plant species.

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White-tailed deer

In the Lake Wakatipu area, the effects of white-tailed deer browsing are noticeable on trees and shrubs. Palatable species such as broadleaf (Griselinia littoralis), Pseudopanax spp. and Coprosma spp. are scarce. On the northern and eastern coasts of Stewart Island, broadleaf and the leaves, stems and fruit of supplejack (Ripogonum scandens) comprised >50% of white-tailed deer diet. Many other species were eaten in small quantities.

Can be confused with:
White-tailed deer browse can be confused with the browse of other deer species, cows, sheep, goats, and pigs.

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Sambar deer

Sambar deer graze and browse the understorey, but they are believed to not have as great an impact on the vegetation as other deer species. They primarily graze but are flexible feeders and will, at least in their home range, switch to feeding on leaves, buds flowers and fruits. Sambar deer may not be as selective as other deer species, which can completely eliminate favoured plant species from the understorey. It may also be because Sambar deer also eat a lot of other foods, in addition to shrubs, including native and introduced grasses, flax and reeds. However, sambar deer have been shown to have a significant impact in Australia where they were also introduced, and it is not known whether the lack of effects seen here is due to lower sambar deer density, insufficient research, or because there are truly minimal impacts on native vegetation.

Can be confused with:
Sambar deer browsing sign can be confused with that of other deer species, sheep, and goats.

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Red deer

In the understorey, red deer prefer to eat certain plant species (this is known as selective browsing). Examples include tree species like broadleaf (Griselinia littoralis) and weeping matipo (Myrsine divaricata), and herbs such as Astelia nervosa. Over time, this selective browsing can lead to the removal of these species from the forest, changing vegetation composition and leading to an increase in unpalatable ‘browse resistant’ species.

Red deer most commonly browse vegetation from ground level to about 2m above the ground, but can reach higher if they can stand on something with their front feet. However, they won’t climb as high as goats.

Can be confused with:
Red deer browse can be confused with browse by other deer species, sheep, cows, and goats.

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Wapiti

Fiordland wapiti feed on a wide variety of valley floor vegetation including trees, shrubs, lianes, trees, ferns, sedges and grasses. They will also feed on lichens, mosses and bark. In montane to low alpine areas just above treeline, they feed on snowgrass and a range of herbaceous and woody shrubland vegetation.

Dietary studies have revealed that wapiti favour broadleaf (Griselinia littoralis), kamahi (Weinmannia racemosa), sedges and lancewood (Pseudopanax crassifolius) where these species are present. The preference for eating particular plant species is known as selective browsing. Over time, this selective browsing can lead to the removal of these species from the forest, changing vegetation composition and leading to an increase in unpalatable ‘browse resistant’ species. Wapiti can reach higher branches than red deer can. Usually plants browsed by wapiti have a ragged or torn look. If there is limited pressure from helicopter hunters, wapiti will spend much of their time feeding on grasses and tussocks above treeline.

Can be confused with:

Wapiti browse and the effects it has on the condition and composition of the understorey can be confused with browse by other deer species, sheep, cows and goats.

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Pig

Rooting (digging up the soil with their noses) by feral pigs can do an enormous amount of damage to the ground surface. Rooting is a foraging behaviour (food gathering), and is often undertaken systematically in deep regular patterns. It is the most common and evident sign of the presence of feral pigs. Pig rooting can sometimes be so severe that almost the entire ground surface in a given location has been uprooted. It occurs most commonly in somewhat damp areas (wet gullies, the base of hills). Pigs may also pull apart rotten logs and roll large boulders. Pig rooting has the potential to impact long-term ecosystem processes such as nutrient cycling and the composition of plant species in forests.

Pigs are omnivorous. On the two main islands of New Zealand they are known to eat fruit from native trees and sweet briar. They also are known to eat the roots of Carex appressa, Aciphylla spp., nettles (Urtica spp.), thistles (Cirsium spp.), supplejack (Ripogonum scandens), and bracken. They will also eat the base of nikau palm (Rhopalostylis sapida) fronds, roots of young palms, fungi, grasses and the base of tussock tillers.

Can be confused with:
Pig rooting can’t really be confused with anything else, except ploughing by humans!

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Hedgehog

Analysis of hedgehog stomach contents in New Zealand often found some vegetation, especially mosses, grass and clover leaves, dead podocarp leaves, occasional seeds (mainly grass seed), and berry seeds.

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Australian magpie

Ground-level vegetation, such as grassland, can be damaged when Australian magpies search the ground for their main food, invertebrates. They will stab their beaks in the ground to extract food, which could leave holes in the ground.

Can be confused with:

Other birds such as rooks, blackbirds, thrushes, seabirds (such as black-backed gull) and wading birds (such as variable and South Island pied oystercatcher) can sometimes also dig up invertebrates in fields. Pūkeko can also pull up seedlings.  These similar types of damage may be hard to attribute to a particular species unless they are caught in the act.

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Rook

Rooks can pull up large clots of dirt when digging in grassland looking for grubs or seeds. Large bare patches in grassland with holes poked in to the ground may be caused by rooks (if these occur in your locality).

Can be confused with:

Other species that cause similar field damage include pūkeko pulling up seedlings; pigs furrowing; birds such as blackbirds, thrushes, magpies, seabirds and wading birds also sometime dig for invertebrates in fields. Weka can cause extensive ‘grubbing’ in pasture and kiwi also use their beaks to search for invertebrates and leave round holes. Unless sighted in the act, it is difficult to determine the particular species.

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Canada goose

Canada geese eat only plants and often graze agricultural grasslands. They prefer short grasses, clover and other legumes but will also eat cereal crops. Their grazing can result in swards of very short grass where goose sign (feathers and droppings) will be obvious.

A researcher in Canada found that Canada geese are altering the floral composition of East Coast Vancouver Island estuaries with adverse effects on the estuary. Within Pauatahunui Inlet, north of Wellington, high numbers of Canada geese within a small bird sanctuary are reported to alter the indigenous intertidal salt-marsh vegetation.

Can be confused with:

Short grass can also result from grazing by other waterfowl such as mute swans, black swans, greylag goose, Cape Barren goose and ducks; and by stock such as sheep and goats. Look for other clues such as feathers, droppings and footprints.

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