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The Challenge
Deer were brought to Australia for hunting and farming in the 1800s.
Over time feral populations established, but until recently their impacts were not widely recognised.
Today the extensive population growth poses threats to Australia’s primary production, environment and communities.
The species that established include red, fallow, chital, sambar, rusa and hog deer. In the 1990s, numbers of feral deer increased following a decline in the venison and velvet market, and the subsequent escape or release of farmed deer.
Feral deer populations are now large and well established in many parts of Australia, and their impacts on the environment, primary production and communities are getting worse.
Deer are in all states and territories of Australia, but they are in largest numbers in the eastern parts of Victoria and New South Wales, where they are spreading quickly. For example, in New South Wales, the six species of feral deer now inhabit 22 per cent of the State, where their distribution has spread by 35 per cent since 2016. Populations are smaller and more isolated to the west of the Great Divide and in other states and territories, but even some of these populations number in the tens of thousands.
2011 Feral Deer Distribution
Predictive models, based on habitat requirements of feral deer, indicate that one or more deer species could potentially spread to most parts of Australia.
Our challenge is to stop the current spread of feral deer.
Where it could go...
Potential distribution of deer (six species), estimated using the Climatch algorithm. Dark red shows the areas where the habitat and climate is most suitable for one or more species of deer. Green shows areas less suitable for deer.
Some farmland regions in NSW have
30 feral deer per km2
Such densities require expensive helicopter culls to get them under control.
The number of feral deer in Australia poorly understood, but there could be between one and two million feral deer.
In the absence of culling and when conditions are favourable, populations of feral deer can increase by between 34 and 50 per cent per year. Without culling, a small herd of 30 feral deer can grow to 500 in 10 years.
Intensive culling has the capacity to moderate deer population growth. For example, in Tasmania, recreational hunting has limited the average population growth rate to about 5 per cent per year; a rate that sees the population double every 15 years.
Our other challenge in protecting Australia’s valuable assets is to stop existing deer populations from getting out of control, to protect our most valued assets. Because feral deer readily move across property boundaries, neighbours and communities need to work together across whole landscapes to pool and coordinate efforts. In order to counter natural population growth, communities should use best practice control measures to reduce feral deer populations by at least 35 each year.
Listen to a podcast about the challenges of managing deer
At least 35% of feral deer need to be removed from a local population, each year, to have on-going reductions in impacts.
Impacts to Agriculture
Feral deer cause severe economic, environmental and social impacts. Economic impacts for the agricultural sector include their consumption of and damage to crops, pastures, and saplings. They also flatten fences and damage infrastructure. Additionally, feral deer pose a biosecurity risk through the transmission of diseases and parasites to livestock. Increasingly, they are also a pest of backyard gardens, particularly in peri-urban areas.
Fast Fact: How much of my pasture does a deer eat?
A fallow deer eats 1.8 to 2.3 times as much as a sheep (Dry Sheep Equivalent). A red or rusa deer eats 2.8 to 3.6 times as much as a sheep.
Fast Fact:
Fallow deer in Tasmania cost the state’s agricultural industry at least
$10 million annually.
Let's hear from the farmers...
“If I didn’t have a deer problem, I could run an extra 500 sheep on top of the 800 I farm. They are also changing the ecosystem and reducing biodiversity on my land”
– Simon, sheep farmer
“The few hundred deer on my land increased ten fold in six years. We move livestock around to let pasture recover, but deer just eat the paddocks we are resting. We use a professional shooter and if I have a spare hour, I also go shoot deer”
– Harvey, cattle farmer
“I used to have 50 cows in a paddock. When deer came, I had to reduce this to 20 cows and feed them. One day I had 150 deer in that paddock. Long nights of shooting took it’s toll on me. If you have a few deer, get on top of them before they become such a huge problem. They are really impacting our business”
– Mal, cattle farmer
“We weren’t concerned with deer in the landscape until we put in a barley crop. The deer hit that in numbers. We tried to control with night shooting and a fencing program. Work with your neighbours, get a harvester, start your shooting program as the escalation of numbers is dramatic.”
– Michael, crop farmer
“We were shooting 300 to 500 deer a year, impacts on pasture and fences and the risk of biosecurity was a major concern. Our commercial deer operator has been very effective. Now our pasture production has improved and we are spending less nights shooting deer. Deer are very mobile and it doesn’t matter who owns the land – you have to all work together”
– Ted, cattle farmer
“Impacts are constant, like loss of production and carrying capacity of livestock. Deer also attract illegal poachers, who cut fences and leave rotting carcasses. Deer also damage our fencing, which then allows other pests onto our property”
– Brett, sheep farmer
Biosecurity Risk
Feral deer pose a biosecurity risk through the transmission of diseases and parasites to livestock. Biosecurity risks include Brucellosis, Bovine Tuberculosis, Johne’s disease, Cattle tick, Leptospirosis and Foot and Mouth Disease (not currently in Australia).
In other countries, Foot and Mouth Disease outbreaks result in export bans on livestock products, and low market prices. Containing such outbreaks in feral deer populations is difficult and expensive.
Fast Fact:
A small Foot and Mouth Disease outbreak, controlled in 3 months, could cost Australia around $7.1 billion, while a large 12-month outbreak would cost $16 billion.
Impacts to the Environment
Feral deer threaten biodiversity and ecosystems including in National Parks and Reserves and heritage listed rainforest areas.
Deer have profound impact on the composition of plant species in a native environment. They browse on young trees and foliage, damage or destroy mature trees through ringbarking and can spread weeds. In addition as hooved animals they impact vegetation through trampling and pugging waterways.
By changing the structure and composition of vegetation other levels of the ecosystem are impacted, for example native flora.
In New South Wales, environmental impacts of deer are listed as a key threatening process under the State’s Threatened Species Act 1995.
Two sisters discuss impacts of feral deer:
Feral deer impacts are now occurring in areas where they are native. Watch the below video to learn about how the reduction of feral deer impacts in Yellowstone National Park not just transformed the ecosystem but also its physical geography.
Fast Fact:
In Victoria, Sambar are listed as a potentially threatening process to native vegetation, including threatened Alpine Sphagnum Bog communities. The Victorian Deer Control Strategy 2021 suggests that over a thousand native plant and animal species would benefit from deer control efforts across the state.
“The only way that Parks Victoria and Friends of Helmeted Honeyeater can create new habitat for the helmeted honeyeater is to surround that vegetation with expensive deer exclusion fencing”
– Gaye Gadsden.
“In order to be Wold Heritage you have to maintain the natural and cultural values for which you are listed and feral deer put that at risk because what they’re doing is undermining some of the specific criteria for which World Heritage was granted.”
– Christine Milne – Ambassador for Invasive Species Council
Impacts to bushfire affected regions
Feral deer significantly impact bushfire recovery.
Firstly, feral deer directly affect success of regeneration. A post-bushfire environment is vulnerable to trampling by hard hooved animals like feral deer. Additionally, deer graze on saplings which emerge as a natural course of bushfire regeneration, preventing their establishment and ringbark remaining trees.
Secondly, feral deer populations increase in size and in spread post-bushfires, placing further pressure on the recovering land. For example, after the bushfires in Royal National Park in 1994, local deer densities rose from <500 to 2500 in 1999. Increased densities of feral deer can be supported due to the high level of nutritious saplings. Spread is facilitated by necessity to move into unburnt areas, and increased access to land that was previously impenetrable.
The figure above shows areas of above-normal fire conditions for the 2019-20 fire season are marked in red (Supplied: BNHCRC), and 2021 feral deer distribution marked in black (Supplied: Invasive Species Council).
In addition to direct impact to natural bushfire recovery, feral deer have significant impact on regeneration attempts
“There is absolutely no point being involved in bushcare recovery if you can’t also protect the forest from the deer” – Kieran Tapsell
To reduce the pressure of herbivory on restored forests, protective guards for individual plants or exclusion fences around plots of planted seedlings are frequently used. The requirement for deer-proof equipment increases the cost and time required for regeneration attempts.
Impacts to road and human safety
Social impacts of feral deer include vehicle collisions and fears of them. Additionally, deer attract poachers, who sometimes trespass, use firearms illegally, cut fences and frighten residents. Land managers struggling to control feral deer report declines in their wellbeing and problematic relationships with neighbours who do not control their feral deer.
In vegetation impact studies, most thrashing of vegetation by feral deer occurs along roadside verges. These findings suggest deer use roads to move through their range and thrashed vegetation advertises their presence to other males in the area.
Fast Fact:
Deer are the 4th most commonly hit animal in Australia, and the number of collisions is increasing each year.
