The most recent advances in capturing feral deer have been made in New Zealand. Deer can be captured by a multitude of methods, but helicopters have been most widely used in New Zealand. A new innovation has been to shoot a combination drug-dart and radio transmitter dart from a shotgun at a deer to be captured. However, this method requires skill in the interpretation of radio signals and drug handling. Deer are also trapped in nets ejected from the undercarriage of a helicopter, but this method is somewhat dangerous to both deer and catchers. Another method is to jump upon a deer from a helicopter after which it is physically wrestled and restrained. This method is mainly used for capturing fawns. Recently, electrical immobilising apparatus has been used from helicopters.
Trap pens with trip wires or other non-return devices are an effective and popular means of capturing deer. Pens may be ‘baited’ with crops such as swedes or lucerne, or during the rut, with a female. Deer can be driven into traps by the use of helicopters, motorcycles, four-wheel drive vehicles, dogs and/or horses.
The most important problem associated with capture is stress, which often results in post capture myopathy and death. It is therefore important to make every effort to prevent this from occurring. The following approaches will reduce stress:
refrain from chemically immobilising a deer which has been chased too long or too far;
if the drug Fentanyl is used, administer an antidote rapidly;
blindfold or hood a captured deer to quieten it; this also protects the face;
if a deer is to be moved from the point of capture under a helicopter, enclose it entirely in a large bag;
place deer in a darkened, well-ventilated truck for road transport;
after capture, hold deer in a darkened shed for 1 – 2 days, feed and water them, and preferably release them at dusk.
A trap commonly used in New Zealand is constructed of netting with a maximum mesh of 0.3 m and a height of 1.9 m. The most popular pen size is 40 × 20 m. The gates are light and strong, and are made of pipe and netting, preferably diamond mesh. They are selfclosing and are triggered by a fine wire or string connected to a release catch. The wire is set out into the pen across the gateway about 0.5 to 0.6 m off the ground; deer entering the pen trip the wire and the gate closes. A butterfly catch holds the gate shut in the event of the deer hitting it in trying to escape.
To remove deer from the trap, a 10 cm mesh net, about 3.2 m long and 1.9 m high, is erected with one end tied to a post, and the deer are driven into this net. Before captured deer are released into paddocks, it is advisable to hold them for about three days in a close-walled, covered pen and to walk through them at intervals to allow them to get used to human beings. After this, the deer should be released into a paddock at night.
The following methods are used for capturing musk deer:
Chasing: This results in few injuries and high survival rate but is labour intensive;
Noosing: This is economical and easy, with a high capture but low survival rate;
Net-catching: Gives a better survival rate than noosing, but requires much care;
Trapping: With this method the survival rate is high but it requires much manpower.
Musk deer are transported in cages 100 × 50 × 75 cm, with an entrance on one side. During transport the cage should be covered with cloth.
Newly captured musk deer should be kept in a dark, quiet and narrow shed and be fed twice a day with small amounts of grass and water. When they have become accustomed to captivity, they can be released during the day, but have to be shut in at night.
A variety of drugs is available for the immobilisation and capture of deer. All drugs should be used with caution and the operator should acquire a thorough knowledge of damage and antidote rates before application. Some drugs can only be used by veterinarians. There may also be legal requirements to be complied with in the aquisition, possession and use of certain immobilising agents, particularly those that are classified as dangerous drugs in many countries, such as morphine derivatives.
Most ingredients used in tranquilising darts are either analgetics or sedatives, sometimes applied in combination with tranquilizers. The analgetics are pain relievers, the sedatives enhance sleepiness and the tranquilizers influence the ‘psyche’.
Drugs used in New Zealand for immobilization of red deer include Xylazine (‘Rompun’, Bayer) and a Fentanyl-Azaperone mixture (‘Fentaz’, Ethnor Ltd.). Intra muscular dose rates used for red deer are:
Rompun 0.2–5.5 mg/kg (average 0.4 mg/kg) liveweight.
Fentaz 2.0–4.0 ml/100 kg of liveweight.
Both Rompun and Fentaz are required in higher doses on the open range and also for stressed animals.
Fentaz is the drug of choice for capture of red deer by helicopter as its effect is relatively consistent and rapid and an antidote is available. Dose rates of 1 ml/45 kg are recommended for quiet farmed deer and of 1 ml/22 kg for range deer. Xylazine is a slowacting sedative with a considerable safety margin. No antidote can be used with it. Male deer require a higher dosing rate than females.
Fallow deer react differently to drugs than other deer, although a fentanyl in combination with xylazine or azaperone may be used. In New Zealand etorphine with xylazine, in a dose of 2 mg/100 kg body weight for etorphine and 30 mg/100 kg for xylazine are used. In Canada, fentanyl was used in conjunction with either xylazine or azaperone (Haigh, 1977). Jones (1972) used valium (= diazepam) and librium as tranquilizers for moving deer.
Both overdosing (causing breathing depression) and underdosing (causing exhaustion, excitation and hyperthermy) are dangerous.
It should be realised that the drugs routinely used by deer farmers and capturers are potentially lethal because they are readily absorbed through tissues into the blood stream.
Tranquillisers are relatively slow in action and are therefore used in handling rather than actual capture. They are safe, devoid of side effects, and render the animal easier to handle. Their action is generally prolonged, which is a desirable feature for the handling of deer. Best of all, deer have wide dose tolerances of them and they are safe from the human point of view.
Intramuscular injection of immobilizing drugs is effected by syringe if deer are confined to yards. With free ranging or paddocked animals, drugs are administered either by tranquillizer dart guns or by blow darts. The major advantage of a blow dart in confined areas is its lack of noise and hence the decreased likelihood of panic and trampling. Another simple and very effective apparatus in appropriate situations is a syringe with an extended plunger handle, consisting of a piece of wooden dowel about 1 m in length glued to the plunger.
It is important to ensure correct projection of darts for the species concerned because considerable tissue injury is caused by darts which are fired at too high a velocity.