Physically capturing and handling wild deer (typically to affix tracking collars and take morphological data) is crucial for advancing our knowledge of critical management factors such as movement, habitat use, population dynamics and distribution. In contrast to studies which attempt to model these factors using theoretical algorithms, these physical studies allow us a deeper understanding of the actual behaviour of wild deer in a level of detail that in-field and static camera observations cannot.
Key points:
- First evaluation of this methodology in Australia
- Promising animal welfare outcomes reported
- Promising signs to open up relevant research to aid practical deer management
Most of the efforts to capture wild deer in Australia have involved chemical immobilisation from the ground or from helicopters (dart guns) and, to a lesser degree, static trapping methods (e.g. clover traps). These methods can be both time and labour intensive and carry their own risks of harm to the captive deer.
Helicopter net-gunning was developed in New Zealand in the 1970s for the farmed venison industry. Animals are captured using a weighted net fired by a shooter in a helicopter and are usually physically restrained and handled without chemical immobilisation. Helicopter net- gunning is standard practice for capturing several species of wildlife in North America and it has been used to capture deer for research in New Zealand and South America.
A newly released Australian paper describes two helicopter net-gunning operations in which researchers sought to evaluate the feasibility of net-gunning for the capture of wild fallow deer (Dama dama) in Australia. The researchers report that they are aware of only one other study that has used helicopter net-gunning to capture fallow deer.
Pleasingly, this report provides a level of accountability for researchers with regards to animal welfare. Along with the efficacy of the methodology, the authors also report pursuit and animal handling time, types of injuries incurred, post-release activity and survival. The authors claim that this is the first such description of helicopter net-gunning in Australia and of net-gun capture of fallow deer worldwide.
The results reported are encouraging, the authors found that:
- Helicopter net-gunning was an effective method for capturing multiple wild fallow deer per day with no mortality of captured deer.
- They were able to capture 1 deer per 44 minutes of flying time, averaging 5.4 deer per day.
- Captured deer did not sustain any serious injuries during capture and none died within 30 days of capture during winter and spring.
- The frequency and severity of injuries were particularly low when compared with alternative capture methods used recently in Australia.
These results suggest that net-gunning of deer is likely to become a regularly used method where habitat and population densities allow.
Further reading:
Andrew J. Bengsen, Jordan O. Hampton, Sebastien Comte, Sean Freney and David M. Forsyth (2021). Evaluation of helicopter net-gunning to capture wild fallow deer (Dama dama). Wildlife Research https://doi.org/10.1071/WR21007
Hampton, J. O., Amos, M., Pople, A., Brennan, M., and Forsyth, D. M. (2021). Minimising mortalities in capturing wildlife: refinement of helicopter darting of chital deer (Axis axis) in Australia. Wildlife Research 48, 304–313. doi:10.1071/WR20106
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