HELICOPTER NET GUN CAPTURE
The helicopter netgun technique has proven very efficient for capturing free-ranging wild ungulates, including bighorn sheep. Animals can be located, captured, delivered to a processing site, assessed and loaded onto transport vehicles in a timely manner.
However, the use of aircraft is stressful (a short chase is often necessary), costs are typically high (~$1,000/animal) and the risk of injury to both the animals and capture crews is greater than ground-based techniques. Public perception of the method makes it somewhat controversial as well; to the uninformed, airborne capture operations may appear to be nothing more than wildlife harassment. Despite the negative aspects, the efficiency of the technique has seen it used extensively throughout North America, and exclusively for capture of South Thompson sheep, with great success.
Considerable success has been had drawing free-ranging bighorn sheep into specially designed corral traps with various desirable baits, such as alfalfa hay and apple mash. Bighorn sheep managers in Oregon have suggested that if sheep are accustomed to the presence of people, buildings and vehicular traffic, they should enter a corral type trap (C. Foster, Oregon Department of Fish and Wildlife, personal communication).
If animals are not habituated to human activity, the acclimatization period may require up to two years. The Oregon experience also suggested that these animals will exhibit trap avoidance behaviour if they see their compatriots enter a trap and disappear as the door is closed behind them.
The TIB, with the financial support of the Habitat Conservation Trust Fund, constructed, installed and monitored a trap for bighorn sheep during the winter of 2002/03.
Unfortunately, the trap failed to attract any sheep. Perseverence and/or re-evaluation of the trap location may produce results. Alternative trapping options might include a new large corral-type trap based on a pre-European contact (1830s) Shuswap design featuring long ‘wings’, which would serve to funnel animals into the main body of the structure, or the installation of a partial fence line situated on a known movement corridor which would lead animals into a corral trap at one end.
These options, as with the standard corral trap, would require regular monitoring, perhaps baiting and an indefinite period of acclimatization for the sheep.