Common Brushtail Possum - A Pest in New Zealand
Updated: Jul 28, 2021
The following map shows the density of possum populations around New Zealand.
New Zealand possums inhabit both islands. They prefer bushy, forest areas, but can also be found in urban areas. The most loved places on North Island are Coromandel, Te Urewera, and Raukumara Forest Park. On South Island, possums prefer west coast areas and Stewart Island.
Possums are a pest in New Zealand. What damage can they cause? How can we reduce their numbers to preserve the most valuable asset of New Zealand - its natural heritage?
The common brushtail possum is a nocturnal, semi-arboreal marsupial of the family native to Australia. It was naturalized and became the second-largest pest in New Zealand. This piece of writing presents an overview of the animal’s origin and gives an idea of what it looks like. It then examines the damage caused by possums. Finally, it presents the ways and means of reducing their numbers in New Zealand.
Behavior and Background
Possums have had a wide natural distribution only in a few countries. They are marsupial species native to Australia. They have a thick, bushy tail, pointed snouts, and long ears. Possums can be either grey or black depending on their coloring around ears and eyes.
According to the Department of Conservation (n.d.), “adult possums are between 65 and 95 cm in length, and can weigh anywhere between 1.4 and 6.4 kg”.
Their behavior is based on the search for forests and varied food supplies. They were brought from Australia in 1837 to establish a fur trade but became a great threat to the environment in New Zealand. “People did not realize the harm possums would cause to the forest. The wildlife would be much greater than any value their fur provided”, (Possum facts, 2013).
Below are possum characteristics and traits:
Possum Diet: Herbivorous, Omnivorous
*Preferred Food: Leaves, buds, flowers, fruits, ferns, bark, fungi, invertebrates, native birds and eggs, native snails, carrion
Characteristics: Marsupial, Solitary, Nocturnal, Arboreal, Herbivorous, Omnivorous
Color: Grey or black
Length: 65 - 95cm
*The population peaked at about 50 million to 70 million. Now there are thought to be about 30 million
*Possums are nocturnal, although in winter starving animals may emerge to feed in the afternoon.
*They can live in any place that has shelter and a varied food supply. This excludes the high-rainfall, mountainous terrain of Fiordland.
*Forests are their main habitat, especially hardwood mixed forests. Their densities are particularly high there. Forest-pasture margins are also known to support very dense populations.
*At the height of the fur trade, trappers killed 20 million possums each year, but that did not make much of a dent in their numbers.
*They love eating native species such as pohutukawa, rata, totara, kowhai, and kohekohe.
*Adopted from (Possum facts, 2013)
Possums affect the ecosystem in New Zealand as there are no predators and lots of very palatable vegetation. Their dietary habits make them very destructive. Their preferred diet includes leaves and berries. Still, they also prey on invertebrates, eggs, bark, carrion, and crops.
Different types of damage are caused by possums. In order, from left to right: Yellow-Eyed Penguin eggs, crops, trees, and bark - all serve as a meal for them.
Kiwi birds suffer from possum hunting them down as well!
Rachelle (1994) points out that possums harm major flora and fauna in Auckland. They prey on Pohutukawa/rata hybrid forest in Rangitoto Island, Hardwood forest, and Hochstetter’s frog habitat.
Possums have led to the loss of diversity and extinction of species. They eat leaves of native trees, prey on species, intrude on farmers, leaving them with no harvest. Plenty of food enables them to grow in numbers very fast.
You can imagine that their eating habits are a big issue in New Zealand, but there is another issue too. Possums are carriers of infectious diseases, among which is bovine tuberculosis (TB). It can infect cattle. TB in wild animals tends to affect trade in agricultural products such as dairy, beef, and deer as Montague has stated (2000). This, in turn, has another impact on farms, bringing considerable losses to individual farmers.
New Zealand Invasive Species Management
It should be noted that possums are not a problem in Australia, where it is prohibited to hunt for them. In Australia, their numbers are well managed by nature. According to “Possum facts” (2013), Australian trees are out of danger as they have spines, prickles, and poisonous leaves.
Possums are protected in Australia but not in New Zealand. In New Zealand, various organizations offer pest control services for people hunting for them. These organizations organize pest control and management campaigns to contain pest numbers.
As mentioned before, two causes of damage of possums to the ecosystem exist in New Zealand: eating habits and bovine tuberculosis. The latter can be tackled by vaccination of livestock against TB but it will not help in the future when possums increase in numbers.
The only solution is to manage the numbers. Thus, different techniques are applied today. They include poisoning, toxicants, trapping, shooting, and developing vaccines to stop possums breeding. To do all these, tracking and monitoring must be carried out.
According to the broadcast of “OneNews” (2013), drones are used to track possums and help farmers hunt them. They spot clusters of possums from the air and carry out better-targeted poison drops and trapping.
A list of control methods are listed below:
Control methods chart. Out of all methods trapping is most common in New Zealand while others such as shooting and poisoning are used specifically to target possums inhibiting farm lands or forests.