Sandscript #30 – Antelope darting protocols in Chad

Read here the fifth article of Sandscript 30th issue

The tele-anesthesia and chemical immobilization of wild antelopes that the Government of Chad, the Environment Agency – Abu Dhabi (EAD) and SaharaConservation strive to conserve falls under the responsibility of EAD veterinarians. The ultimate goal is to safely anesthetize individual animals from a distance to allow veterinarians and researchers to undertake the required procedures.

There are a few ways of delivering anesthetics drugs to wild animals. In the Ouadi Rimé – Ouadi Achim Game Reserve, we use a modified .22 caliber bolt action rifle powered by blank rounds. The gas of those cartridges propels a 50-caliber ballistic dart, loaded with a combination of anesthetics to the animal. The darts have a small charge of compressed air that, upon impact, propels the plunger to inject the drugs intramuscularly.

Shooting from a modified rifle is more complicated than shooting from a regular rifle. To deliver the anesthetic effectively the dart has to penetrate those areas of the animals with large muscles. The dart should also penetrate the animal as close to perpendicular as possible. A dart landing diagonally can cause the dart to be deflected. The dart also needs to be fired using the appropriate force based on the distance. To achieve this, different gas cartridges and different power settings are available to produce the right impact force. Wind direction and speed must be considered too, as the darts are not travelling as fast as bullets and are much heavier.

This process requires of a well-organized and coordinated team. The darting is undertaken from all terrain vehicles. The driver must be able to locate the vehicle in the appropriate direction, taking into consideration distance, angle, wind, sun direction and risk of having other animals passing by at the moment of shooting. Constant communication between the veterinarian and the driver is essential. Missing a shot could spook the animals or hit an unintended target.

To anesthetize wild antelopes in Chad, we use a combination of drugs. This is called balanced anesthesia and allows us to use less dosage of each substance, reducing the undesirable side effects of each drug and being able to modulate the effects easier. The darts are loaded with a dosage according to the species, weight and mood of the animals (a stressed animal will require a higher dose than a calm animal, for example).

Another advantage of using a combination of drugs is that they can be reversed once the procedure is finished. The reversal drugs are injected and the effects of the anesthetics disappear very quickly. The animal regains consciousness and is able to return with the herd almost immediately. This is very important, especially with wild animals. After a quick in situ evaluation of the recovery of the animal, the monitoring team will check on the animal to ensure that there is no renarcotization or any undesirable side effect in the following hours/days.

The usage of some substances poses a significant risk for humans, as they are extremely toxic. Just a tiny drop on the skin can have fatal consequences (cardiorespiratory arrest). Given that the darting is done in a remote area, hours away from the closest medical facility, it is very important for the veterinarian to protect himself while manipulating those substances. The preparation of the darts is always done using personal protective equipment’s, separated from the rest of the team, with the wind blowing away and under supervision of a trained person who has the antidote loaded and ready to be injected.

Once the animal has been darted, the process of induction should not take more than 5 minutes. During this time, the animal is followed from a safe distance. When the drugs act and the animal falls asleep, the team will proceed to put a blindfold and horn guards and ensure an appropriate position to avoid aspiration pneumonia and to facilitate the procedures to be done.

While the animal is under anesthesia, a health check will be performed together with any other required procedure (collaring, sampling, biometrics, etc.). The veterinarian monitors the animal to ensure that there are no issues. Reflexes, temperature, heart and breathing rate are some of the parameters usually observed to evaluate that the anesthesia is safe and done to the required depth.

The procedures carried out in the field are usually within the duration of the anesthesia given, but if required, a top up of drugs can be given to modulate the length or depth of the anesthesia.

Once the procedure is finished, all the non-essential personnel and material are cleared from the area and the animal is reversed. The handling team will ensure that the animal maintains a proper posture until it regains full consciousness. Just before being released, the horn guards and blindfold will be removed. All the data collected (drugs, dosages, gun settings, weather conditions, timings, effects….) is recorded in anesthesia sheets.

Since 2020, 27 wild scimitar-horned oryx and addax have been anesthetized in the field by the Veterinary team. All the procedures were carried with no side effects or fatalities and the animals recovered without any problem, proving that the protocol, dosage and drugs selected are appropriate.

Jon Llona Minguez
Veterinarian
Terrestrial & marine Biodiversity
Environment Agency – Abu Dhabi

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