Pests

Possums In The Bay Of Plenty

Introduction

In 1937, the Common Brushtail Possum or Trichosurus Vulpecula made its first appearance in New Zealand. Since then they have spread throughout the country with only a few remote islands remaining untouched. The possums, which are indigineous to Australia, pose a major threat to the New Zealand ecosystem. The Common Brushtail Possum can grow up to 95cm and can weigh up to 5kg and it’s The colours are silver-grey, black, brown and golden. Not to be confused with the American Opossum which is grey, black and white. They are voracious eaters and every possum in New Zealand combined can eat 20,000 tonnes of vegetation per night.

Possums have become a major problem in The Bay of Plenty. This Report will discuss what can be done to mitigate the possums in The Bay of Plenty.

What Effect Do Possums Have On The Food Chain?

Possums have a major effect on the food chain because of their diet. The possums diet consists of the berries of more than 60 native trees. Usually in nature, birds will eat the berries and spread them. So when possums eat the berries, they are limiting the spread of native trees and the food of native birds. The plant life in Australia has evolved to grow natural defences against possums such as: tough and thick bark, chewy leaves and sometimes even poisonous berries. When possums were brought to New Zealand, the plant life here did not have these defences so the possums had free reign and seemingly unlimited food. Possums were previously thought to only eat plants but have since been caught eating native hatchlings and eggs. This means that they are dramatically reducing the bird population.

Possums also spread Bovine Tuberculosis (TB), which is a type of deadly disease found in cattle. When they possums pass TB on cattle, they are killing the food of humans. From 1837 to 1849, possums were a legally protected animal in New Zealand, until it became clear they were doing more harm than good. Possums usually only bear one offspring every year, but because of the excellent conditions and food in New Zealand, they are able to bear two every year. Making twice as many possums affecting the food chain in New Zealand.

How Did Possums Get To New Zealand And Where Did They Come From?

Possums originally come from Australia. They were brought to New Zealand in 1837 by settlers from Australia to establish the fur industry. The first release of possums in 1837 was unsuccessful and a second release 20 years later was required for them to be introduced. From 1858 to 1922 possums were released around the country. In total, possums were released at 450 different places in New Zealand.

What Are We Currently Doing About The Possum Problem In New Zealand?

In New Zealand we are doing our best to keep possum numbers down, but despite trapping, shooting and poisoning, there are still around 30 million possums in New Zealand today. There are two types of traps used in New Zealand. The first is a leg hold trap which clamps onto one leg of a possum so that the trapper can come and tag it or kill it. The second trap is a kill trap. The kill trap usually needs baiting and resetting but there are self-resetting traps that can kill 12 possums without needing to be reset. After that the carbon dioxide canister needs to be replaced. We also use poison such as 1080 and brodifacoum. In 2019, the New Zealand government spent $110 million on possum control.

Is There Any Place In The World Where They Have Control Of The Possum Population And If So What Methods Do They Use?

We all know that possums are a pest in New Zealand. In Australia they are a legally protected animal. In Tasmania however, because possums are only partly protected, they are shot and trapped to protect crops and livestock. Tasmania uses similar methods to New Zealand, such as trapping and poisoning but they use different traps such as the Mersey Box Trap and the Stubby Tent Trap.

What Is The Best Method To Control The Possum Population And Why?

We believe that Biological control is the best way to control the possum population in New Zealand. Biological control is where scientists capture a possum and insert a toxin or a vaccine into it. The toxins will produce antibodies that will destroy the possums reproductive proteins. This means that the possum, and any possum it comes in contact with, will be unable to reproduce. These biocontrols will stop the possum population from becoming larger.

After the vaccines have stopped the possums from spreading, traps and poisons will still be needed to catch those possums that have managed to dodge the toxins.

Unlike other methods of control, biological control only affects the targeted species. So other native species will be safe. Biological control is expensive but effective as it only needs to be injected a few possums for the toxins to spread and work. It is also incredibly humane as it does not hurt the possum at all. (Link To PMI Analysis)

It is good to see that some of the experts in this field of work agree with our thesis. (Link to Interview With Colin Hewens)

Conclusion

Possums in New Zealand have been a major problem for over a century. We believe that with the help of new technologies, persistent volunteers and hunters, that we can get this problem under control.

References

(n.d.). Retrieved from https://www.cabi.org/isc/datasheet/61405#toDistributionMaps

(n.d.). Retrieved from https://www.waikatoregion.govt.nz/services/plant-and-animal-pests/possums/#e4484

Delivering biocontrol agents to possums. (n.d.). Retrieved from https://www.sciencelearn.org.nz/resources/1086-delivering-biocontrol-agents-to-possums

Guthrie, K. (2017, May 17). Trojan Possums – are they the next step? Retrieved from https://predatorfreenz.org/trojan-possums-are-they-the-next-step/

Meyer, G. (n.d.). Trichosurus vulpecula (silver-gray brushtail possum). Retrieved from https://animaldiversity.org/accounts/Trichosurus_vulpecula/

NHNZ, P. B. (n.d.). Possum a New Zealand Nightmare. Retrieved from https://www.nzgeo.com/video/possum-a-new-zealand-nightmare/

New Zealand Ministry for Culture and Heritage Te Manatu Taonga. (2012, July 13). Impact on native animals. Retrieved from https://teara.govt.nz/en/possums/page-4

New Zealand Ministry for Culture and Heritage Te Manatu Taonga. (2020, February 20). Impact on native plants. Retrieved from https://teara.govt.nz/en/possums/page-3

New Zealand Ministry for Culture and Heritage Te Manatu Taonga. (2015, June 29). Possums in New Zealand. Retrieved from https://teara.govt.nz/en/possums/page-1

New Zealand Ministry for Culture and Heritage Te Manatu Taonga. (2020, January 08). Spread of possums. Retrieved from https://teara.govt.nz/en/possums/page-2

Newshub. (2017, September 07). DOC champions humane possum trap. Retrieved from https://www.newshub.co.nz/environmentsci/doc-champions-humane-possum-trap-2011072818

Pest animals: Bay of Plenty Regional Council: Toi Moana. (n.d.). Retrieved from https://www.boprc.govt.nz/environment/pests/pest-animals

Possum facts. (n.d.). Retrieved from https://predatorfreenz.org/resources/introduced-predator-facts/possum-facts/

Possums. (n.d.). Retrieved from https://www.doc.govt.nz/nature/pests-and-threats/animal-pests/possums/#:~:text=They occur in high numbers,but possums are opportunistic omnivores.

Wildlife. (2019, June 18). Possums. Retrieved from https://www.wildlife.vic.gov.au/managing-wildlife/possums

Page updated

Report abuse