Aerial Survey FAQs

​​​General aerial survey questions​​

Why was the survey ar​​ea chosen?

Because this area holds the largest concentration of wild fallow deer in Tasmania. This area was extended by a small amount to allow the population of Forester kangaroos to be surveyed at the same time.

​Why wa​​s an aerial survey chosen?

Aerial surveys are a valuable method of estimating the abundance, density and distribution of medium to large mammals over wide geographic areas.

How​ was the aerial survey conducted? 

The survey was conducted from a helicopter along transects 10km apart. Three observers in the helicopter detected wild fallow deer and Forester kangaroos. Thermal imagery was also used, experimentally, to detect deer.

At ​​what height and how fast was the helicopter flying?

The helicopter flying 200 feet above the ground at a speed of 50 knots (90 km per hour).  

Wh​​o conducted the aerial survey and how were they selected?

EcoKnowledge was awarded the contract to conduct the aerial survey through a public tender process. EcoKnowledge is an Australian owned and operated company with  extensive experience in conducting surveys of wildlife across Australia.

What precautions were taken to ensure the safety of wedge-tailed eagles?

All known wedge-tailed eagle nests were in the survey mapping technology and were avoided, with deviations from the survey line to ensure this. During the flight the pilot and observers were looking for any eagles observed to be flying near the helicopter.  

What precaut​ions were taken to ensure the safety of livestock?

The pilot took precaution to avoid livestock, with deviations from the survey line taken where necessary. Continuous observations ensured livestock were not herded by the helicopter.

What precautions were tak​en to protect privacy of dwelling occupiers on the survey route?

Deviations were taken to ensure the helicopter did not fly over private dwellings.

Whe​re was the survey conducted?

To see a map of the survey area and transects please see dpipwe.tas.gov.au/deer-survey.

Who analyse​​d the results from the survey?

EcoKnowledge analysed the results as part of its contract. This analysis has been reviewed by two independent experts.

Why​​ aren’t the raw numbers observed reported?

The raw numbers are considered a sample so they must be scaled up using advanced mathematics to give a reliable estimate of the actual wild fallow deer and Forester kangaroo populations.

How​​ much did the aerial survey cost?

Approximately $150,000.

​​What was Game Service Tasmania’s role in the aerial survey and analysis of data?

As a part of its contract, EcoKnowledge provided a Game Services Tasmania (GST) Senior Wildlife Management Officer with professional development opportunities. The GST Officer was involved in all aspects of the project including survey method, logistics, data collection and analysis.  

Will another a​​erial survey be conducted in the future?

EcoKnowledge recommended the aerial survey is repeated every four to five years. This survey is the first of its kind in Tasmania and provides a baseline population estimate of wild fallow deer and Forester kangaroos. Future surveys can therefore be used to determine the impacts of management strategies on the wild deer population and validate annual on-ground survey methods used to monitor trends.  

The c​hance of seeing an animal is greater the closer one is to that animal so how did the survey take account of this?

The distance of the wild fallow deer or Forester kangaroo away from the helicopter (transect) was recorded using distance gradients on sighting poles mounted to either side of the helicopter. This well-used method, known as distance sampling, takes account of the increased probability of seeing an animal close to the helicopter.

photograph of a helicopter on the ground with the sighting pole attached to the side

Sighting poles used to identify the five distance zones of observations made from the helicopter. The yellow tape corresponds to the view of the front seat observer and the green tape corresponds to rear seat observer, after being calibrated. Zone 1: 0–20 m, 2: 20–40 m, 3: 40–70 m, 4: 70–100 m, 5: 100–150 m.

​​How were wild fallow deer and Forester kangaroo observations recorded?

Each observer had a customised electronic keypad strapped to their leg that was linked to a Global Navigation System. This keypad was used to record species, the number observed, the distance zone it was observed in and the habitat type it was observed in.  

An image of the electronic keypad, that was customised for the survey, strapped to the observer’s leg in the helicopter.

Customised electronic keypads strapped to the observer’s leg

​​How is the number o​f wild fallow deer or Forester kangaroos counted used to calculate an estimate of the overall population?

The number of wild fallow deer or Forester kangaroo counted along predetermined sample lines that are not deliberately chosen because of presence or absence of deer can be considered a random sample of the population abundance. This can then be used in mathematical techniques that allow abundance of the overall population to be estimated. These techniques have been validated by many different scientists working with many different animal species in many different ecosystems.

​​Why is the number of wild fallow deer and Forester kangaroos reported as an estimate of their population?

Because it is not possible to count every wild fallow deer or Forester kangaroo as would happen with domestic livestock or a human population census. A sampling technique is therefore used to estimate the population within an acceptable accuracy.

​​How do we know the population estimates of wild fallow deer and Forester kangaroos is accurate?

The analysis of aerial survey data by EcoKnowledge has been reviewed and endorsed by two independent reviewers, professionals in this field, declaring the analysis as credible and robust. Further, EcoKnowledge has used analysis methods commonly used in wildlife surveys. The level of variation (19 per cent deer, 23 per cent Forester) is relatively low, indicating a satisfactory level of precision.  

Was time ​of day taken into account when doing the aerial observations?

Yes, this is very important. All flights were conducted within three hours following first light and three hours preceding last light

Why were surveys conducted within the time frames that they were?

This is the optimal time to conduct aerial surveys for crepuscular/nocturnal species and is commonly used for aerial surveys elsewhere. This is the time when these species are generally most active during daylight hours when it is safe to fly.  

In what direction were the survey​​ transects flown?

All transects (excepting 8F and 9D) were flown in an east-west, or west-east, direction to avoid observers looking into the sun.  

What m​​odel of helicopter was used in the survey?

A Bell LongRanger (206L) helicopter.  

If you did the survey again now would you get the same results?

The survey results are a reflection of the population at the point in time of the survey. Populations respond to changes, such as births, deaths, environmental changes, all influencing population size. It cannot be predicted if additional surveys would generate the same results.

Thinking of the ​property I shoot on I estimate it to carry 1000 deer on its 5000 hectares. If I scale this up to the area surveyed the population should be about 15 million so why isn’t this so?

Deer are not distributed evenly over the landscape so simply scaling up the population will dramatically overestimate the overall population. This is also why scientifically valid sampling and analysis procedures are required.

Can drone​​s and other techniques be used to survey wild fallow deer and Forester kangaroos? 

Currently there is little known about the validity of using drones to survey wildlife in Tasmania. With improved knowledge, through trial of drone surveys collecting data by flying relatively small sample areas, more conclusions can be drawn.  Drones do not have the capacity to fly the full extent of large geographic areas. Currently the benchmark standard remains as helicopter surveys.

Ho​​w do you know you didn’t double count any wild fallow deer or Forester kangaroos?

Transects were spaced approximately 10km apart, allowing for a survey width of approximately 2km, and sufficient space between transects to ensure deer were not double counted due to flushing from one transect to the next.

How do you know that you saw​​ and counted all the wild fallow deer and Forester kangaroos present along the transects?

Three trained observers (and a thermal camera experimentally for wild fallow deer) were used to count and record wild fallow deer and Forester kangaroos along the survey transect. A technique known as Distance Sampling corrects for the fact that animals further from the line of flight of the aircraft are less likely to be seen. The mathematics of the data analysis account for factors affecting sight ability of animals when estimating the population. The observers are well trained, each having at least 200 hours of experience.

Now that this work has been d​one do take returns still have to be provided?

Yes, because the results of this survey provide a baseline estimate of the populations. Take returns are important in monitoring and predicting population trends. Accurate take returns remain an important input to understanding how wild fallow deer and Forester kangaroo populations change over time. 



​Wild fallow deer aerial survey questions​

​What is​​ the need for a ‘statewide census’ of wild fallow deer in Tasmania?

The 2017 report by the Legislative Council Government Administration Committee-A on its Inquiry into Wild Fallow Deer in Tasmania, concluded there was no science-based quantitative estimate of the wild fallow deer population in Tasmania to inform management. The Tasmanian Government responded to this report by committing to undertake a ‘comprehensive statewide census of wild fallow deer in Tasmania’.   

Why was​ a survey chosen not a census?

A census is a total count of individuals in a population at one point in time. It is not possible to conduct a census of wild animals because they are not easily seen and move around the landscape. It is more efficient (in time and cost) to estimate population size by surveying a sample of an area known to support a species, rather than trying to count every individual at one point in time.  

If you did no​​t count all the wild fallow deer in the survey area how can you say how many there are?

It is not possible to count every individual in a population of wild animals within a very large range so a science-based sampling technique is used. This involves counting a sample of the population in an unbiased manner and then using statistical procedures to estimate the number in the total population. This sampling technique is widely used and validated in all fields of science. Distance sampling estimates the number of Forester kangaroos occurring along the flight path by correcting for the fact that animals further from the line of flight of the aircraft are less likely to be seen. Results from the area along the flight path are then extrapolated to the entire survey area

Why wasn’t t​​he whole state surveyed for wild fallow deer?

Aerial surveying is more appropriate in areas of medium to high densities of animals, without deploying impractical levels of resources. It was decided to survey areas where deer are found in medium to high densities and where the majority of hunting occurs. Other areas of the state supporting a low densities of deer population will be surveyed using camera trap surveys and citizen science.

Where wa​s the survey for wild fallow deer conducted? 

The grey lines on the below map indicate the aerial survey flight paths. The area surveyed can be viewed on LISTmap​.

map of north east Tasmania showing the transect lines flown during the wild fallow deer survey

Transects (grey lines) flown during the 2019 wild fallow deer aerial survey. Transects 17–22 were outside the deer survey area and were used to survey Forester kangaroos (see Part B: baseline aerial survey of Forester kangaroo population, Tasmania).

What was the size of th​​e survey area for wild fallow deer?

19,905km2.

What wa​​s the total length of all survey transects in the survey area for wild fallow deer?

1986km.

What is the p​​opulation estimate of wild fallow deer in the survey area?

The population estimate is 53,660.

Where were w​ild fallow deer detected in the survey area?

Green crosses on the map below represent wild fallow deer detections.

map of north east tasmania showing where wild fallow deer were detected

Wild fallow deer detections in the survey area based on observer counts (green crosses).

What i​s the population density estimate of wild fallow deer in the survey area?

The average density of wild fallow deer within the total survey area was estimated to be 2.7 deer per square kilometre. However, in high-density areas on average the density ranged from 10 wild fallow deer per square kilometre to 25 wild fallow deer per square kilometre.  

map of north east tasmania showing wild fallow deer population density hotspots detected by the survey

Density hotspots per square kilometre of wild fallow deer within the survey area.

How accurate is the population estimate of wild fa​llow deer in the survey area?

The reliability of the estimate is influenced by the number of observations of wild fallow deer made using the survey method, which is regarded as world best practice. The measure of this reliability is called the Coefficient of Variation (CV), which for this deer survey was 19 per cent as compared to the generally accepted upper limit of 25 per cent for this type of survey. Generally, accuracy of the estimate increases with decreasing CV but as the CV gets lower the additional resources required to further reduce it increases exponentially. 

​Were wild fallow deer easily seen from the helicopter? Was the helicopter going too quick?

Wild fallow deer were clearly detected by survey observers from the helicopter. A Senior Wildlife Management Officer from Game Services Tasmania participated in 30 per cent of the survey and was able to clearly detect deer from the helicopter.

How could the observers tell farmed f​​allow deer from wild fallow deer?

Records of deer farms were uploaded to flight path maps. If a deer farm was on or near a survey line observers were notified. Further, farm deer are contained within high fences which were obvious from the helicopter.

Has this method been used for other wild de​er surveys in Australia?

Yes, similar aerial surveys have been undertaken elsewhere in Australia and overseas.

How​ well were wild fallow deer able to be identified from the thermal camera footage?

Wild fallow deer have a distinctive image in thermal camera footage and were able to be identified from other wildlife and animals such as livestock.

Can I find out how many wild fallow deer were observed on my property?

The survey was not intended to count the wild fallow deer on individual properties.

What will the results of the aerial survey be used for? 

The results will give more accurate information on distribution and numbers of wild fallow deer in Tasmania. DPIPWE will use information from the aerial survey to better inform management strategies across different areas of the Tasmanian landscape and to develop a proposed Wild Fallow Deer Management Plan. Importantly, the aerial survey provided a baseline population estimate, which can be used to monitor changes in the population against management regimes.​

Will the aerial survey be repeated ever​y year to monitor the wild fallow deer population? 

No, the wild fallow deer population will be monitored annually using spotlight surveys, which have been shown to be a reliable indicator of deer population trends. The consultants recommended that aerial surveys be repeated every four to five years to validate spotlight surveys, determine population number, and track management regimes.  

How will the population estimate affect future wil​​d fallow deer management in Tasmania?

The population estimate provides baseline data that can be used to inform development and implementation of future wild fallow deer management strategies, but this is a separate task to undertaking the survey.

What are the additi​onal stages of the ‘statewide census’ of wild fallow deer?

In the future, additional surveys incorporating citizen science and camera trap surveys will be implemented as a part of the statewide census of wild fallow deer in Tasmania.  

Is this the beginning of deregulation​​ for wild fallow deer?

No. It is proposed that a Wild Fallow Deer Management Plan will be developed using the results of the census and other inputs, including consultation with stakeholders, to provide the overarching framework for collating existing and potential new management strategies for wild fallow deer.    

Will the results affe​ct game seasons and game licence tag limits for hunting male wild fallow deer?

This may be considered as part of a future wild fallow deer management plan.

Will the results affect Crop Protection​ Permit periods and tag limits for taking wild fallow deer? 

This may be considered as part of the wild fallow deer management plan.

Will the survey be used to promote the commercial use of wild fallow deer? 

The question of utilising deer taken by landholders and hunters for commercial use is subject to a separate project examining the feasibility of a trial. 



​Forester ka​ngaroo aeri​al survey questions

​What is the need for an aerial survey of Forester kangaroos in Tasmania?

The aerial survey of wild fallow deer provided an opportunity for the first time to survey the whole Forester kangaroo range in an attempt to estimate its population. The results will provide important baseline population estimate that can inform future management strategies for this species.

Why wasn’t the whole ​state surveyed for Forester kangaroos?

Forester kangaroos occur only in limited areas of Tasmania. The survey covered the range of where almost all Forester kangaroos are known to exist.  

If you did not count all the kang​​aroos in the survey area how can you say how many there are?

It is not possible to count every individual in a population of wild animals within a very large range so a science-based sampling technique is used. This involves counting a sample of the population in an unbiased manner then using mathematics to calculate an estimate of the whole population. This sampling technique is widely used and validated in all fields of science.  Distance sampling estimates the number of Forester kangaroos occurring along the flight path by correcting for the fact that animals further from the line of flight of the aircraft are less likely to be seen. Results from the area along the flight path are then extrapolated to the entire survey area.

Where ​was the survey for Forester kangaroo conducted?

The grey lines on the below map indicate the aerial survey flight paths. The area surveyed can also be viewed on LISTmap.

map of north east tasmania showing the helicopter transect lines for the forester kangaroo aerial survey

Transects (grey lines) flown during the 2019 Forester kangaroo aerial survey.

​​What was the size of the survey area for Forester kangaroos?

21,958 km2.

W​​hat was the total length of all survey transects in the survey area for Forester kangaroos?

A: 2170 km.

What is th​e population estimate of Forester kangaroos in the survey area?

30,327.

Where were Fore​ster kangaroos detected in the survey area?

On the map below green crosses represent Forester kangaroo detections.

a map of north east tasmania showing where forester kangaroos were detected during the aerial survey

Forester kangaroo detections in the survey area based on observer counts (green crosses).

What is the population density es​​timate of Forester kangaroos in the survey area?

While it was estimated to be 1.381 Forester kangaroos per square kilometre over the entire survey area. Much of the area surveyed does not contain Forester kangaroos, therefore negatively influencing the population density. In hotspot areas of high abundance densities ranged from five Forester kangaroos per square kilometre to 25 Forester kangaroos per square kilometre.  ​

a map of north east Tasmania showing the density of forester kangaroo populations in the area

Density hotspots of Forester kangaroo per square kilometre within the survey area.

How acc​​urate is the population estimate of Forester kangaroos in the survey area?

The reliability of the estimate is influenced by the number of observations of wild fallow deer made using the survey method, which is regarded as world best practice. The measure of this reliability is called the Coefficient of Variation (CV), which for the Forester survey was 23 per cent as compared to the generally accepted upper limit of 24 per cent for kangaroo surveys. Generally, accuracy of the estimate increases with decreasing CV but as the CV gets lower the additional resources required to further reduce it increases exponentially. 

Were Forester ​kangaroos easily seen from the helicopter? 

Forester kangaroos were clearly detected by survey observers from the helicopter.

How coul​​d the observers tell Forester kangaroos from Bennett’s wallaby?

Observers received training on detecting Forester kangaroos over Bennett’s wallaby. Additionally Forester kangaroos are generally larger than Bennett’s wallabies and have a different gait and responsive behaviour to the helicopter.

Has this method be​​en used for other kangaroo surveys in Australia:

Yes, aeri​al surveys of this type are widely used in other parts of Australia to survey kangaroos.

How well were Forester kan​​garoo able to be identified from the thermal camera footage?

Forester kangaroos were not able to be identified from other wallabies on the thermal camera footage. This was known before the survey was conducted.  

Can I find out h​​ow many Forester kangaroos were observed on my property?

The survey was not intended to count the kangaroos on individual properties.

What will the results of the aerial survey be used for? 

The results will give more accurate information on spatial distribution and numbers of Forester kangaroo in Tasmania. DPIPWE will use information from the aerial survey to better inform management strategies across different areas of the Tasmanian landscape. Importantly, the aerial survey provided a baseline population estimate, which can be used to monitor changes in the population against management regimes, and to help ensure Forester kangaroos are managed in a sustainable manner.  

Will the aerial survey​ be repeated every year to monitor the Forester kangaroo population? 

No, the monitoring of Forester kangaroo population will be reviewed. On-ground monitoring will be used to monitor trends in the population in core areas. It is recommended that aerial surveys be repeated every four to five years to validate on-ground monitoring determine population number and track management regimes.  

How will the popula​tion estimate affect future Forester kangaroo management in Tasmania?

The population estimate provides baseline data that can be used to inform development and implementation of future Forester kangaroo management strategies, but this is a separate task to undertaking the survey.

Will the results affect Crop Protecti​on Permit and Commercial Crop Protection Permit tag limits for taking Forester kangaroos?

This may be determined as part of the overall state Forester Kangaroo management plan.

Contact

Game Services Tasmania
GPO Box 44
Hobart TAS 7000
Phone: 03 6165 3225
Email: gameservicestas@dpipwe.tas.gov.au

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