Pig Sus scrofa

Footprints and Tracks

Hooves

Pigs have cloven hooves with two bilaterally symmetrical toes (called cleaves). The dew claws (lateral toes) are frequently evident because they are much lower down than those of deer and other ungulate species. When dew claw prints are present, they are behind and to the side of the cleaves. The cleaves are blunter than those of deer and goats, and in general the footprint is wider and rounder. Toe indentations are often splayed away from the central line. Hoof prints are about 50–80mm in length and 40–50 mm in width.

Can be confused with:
Pig footprints can be confused with those of deer, goats, and sheep. However, sheep hoof prints tend to be more pointed at the front, goat hoof prints are more kidney shaped (due to the curve on the inside of the toe), and deer hoof prints are longer and narrower. When deer dew claw prints are present, they are directly behind the main hooves, rather than behind and to the side.

Trails and Runs

Feral pigs can create distinctive trails by trampling through vegetation. Soil can be eroded from the exposed and compacted ground along these routes.

Can be confused with:

Other ungulate (hooved animals), including farm animals such as cattle, can also create trails although feral pig trails are likely to be associated with areas disturbed by their characteristic rooting.

Wallows

Feral pigs take mud baths in wet depressions in the ground to rid themselves of lice and other ectoparasites (unwanted bugs living on their skin). Pig wallows can be found in swamps, gullies, and alongside creeks. Wallows are used year round, but more intensively in summer during hot periods.

Can be confused with:
Wallows used by pigs can be confused with those used by deer. Look for other evidence such as droppings and hoof prints.

Dens and nests

Feral pigs build and use farrowing nests (for giving birth to young) and loafing beds (adult resting sites), although these can be difficult to tell apart. Examples include depressions in the ground lined with grass, bracken, or fern, and flattened areas within dense bracken. They may be located at the base of a tree or underneath a log or bank.

Can be confused with:
Farrowing nests and loafing beds may be confused with resting sites within thick cover used by deer and feral goats. However, deer and feral goats are not known to line resting sites with vegetation.

Vegetation Damage

Understorey (less than 3m)

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!

Bark

Feral pigs will often rub on trees, logs and fence posts. They use the same site repeatedly and may travel some distance to use a favoured rubbing post. Rubbing posts often become coated with mud and pig hair, and sometimes tusk marks are evident. Pigs can kill trees if they rub against them too much, particularly if they remove all the bark.

Can be confused with:
Antler rubbing by deer could be confused with pigs rubbing, but pig rubbing will be low on the tree or fence post and mud and pig hair are likely to be present.

Kill Sign

Fur, feathers or scales (vertebrate)

Birds

In New Zealand, feral pigs have been known to eat ground-nesting birds and their eggs. However, there is little information available regarding characteristic signs that pigs might leave at nests they have preyed on. There are stories that pigs turn kiwi-skins inside out, but it is not clear if the pig killed the kiwi or ate it after it was found dead.

Mammals

In New Zealand, feral pigs have been known to eat mice, rats, young rabbits, possum carrion, and new-born lambs. Lamb predation has very tell tale signs of skins turned inside out with just the hocks and skins remaining , but there is little information available regarding characteristic signs pigs might leave behind for other species.

Lizards and frogs

Feral pigs are known to eat lizards and frogs. There is little information available regarding characteristic signs pigs might leave behind when they devour lizards and frogs. However, it is likely given their small size that they are often eaten whole.

Could be confused with:

Remember that animal remains might have been scavenged by other animals.

Insects or snails (invertebrate)

Feral pigs sometimes dig into or tear apart rotten logs in search of invertebrates. They are known predators of New Zealand’s native land snails Powelliphanta spp. When a land snail has been eaten by a pig, its crushed shell is often found. Pigs also eat amphipods, centipedes, beetles and earthworms caught while rooting. These latter invertebrates will most often be eaten whole.

Eggs

In New Zealand, feral pigs have been known to eat ground-nesting birds and their eggs. However, there is little information available regarding characteristic signs that pigs might leave at nests they have preyed on.

Could be confused with:

Remember, too, that egg remains might have been scavenged by other animals.

Other Clues

Bite marks

Pigs' teeth are adapted to enable them to eat their omniverous diet (both plants and animals).  They have six incisor teeth at the front of the top and the bottom jaw and a single canine tooth on each side behind the incisors, top and bottom. The bottom canines form a tusk on each side, which grows continuously and is kept sharp with friction against the upper teeth. Further back, behind the canines, are the premolars and molars, used for crushing and grinding food.

Little information is available about identifying pig bite marks but pigs (and cattle) are large enough to take an entire chewcard into the mouth and mangle it.

For further guidance and illustrated examples of bite marks in general, see the Manaaki Whenua – Landcare Research chewcard interpretation guide and other more technical identification guides.

Distribution

Pigs are widespread in both North Island and South Island, and currently occur on 13 offshore islands. They were eradicated from Stewart Island by 1965. 

They currently occupy approximately 93,000 km² (34%) of New Zealand.

Smell

Pigs can smell strongly of urine.

Sound

Pigs make grunting sounds. They also make loud squealing sounds when alarmed or when two boars are fighting. Fighting boars can sometimes be heard from a long way off, particularly in areas where the sound is carried across water e.g. around lakes edges or in locations like the Marlborough Sounds.

Body covering

Feral pig hair is longer and coarser than that of domestic pigs. Places where traces might be found include: on trees where a pig has been rubbing its rump; where pigs have forced their way under fences; or embedded in the mud where a pig has been wallowing. Black is the most common colour, but other colour variations include rusty red to ginger, brown with black spots, brown and white, white with or without a black stripe, grey and smoky blue (the latter colour is common in North Canterbury).

Eye shine

Pigs’ eyes reportedly do not reflect colour at night because they lack a tapetum lucidum layer inside the eye. Species lacking eye shine are usually diurnal (active during the day and sleeping at night).

Other

Signs of disturbance to rotten logs could be a sign that feral pigs are present as they sometimes dig into or tear apart rotten logs in search of invertebrates.