■ Dart guns are also commonly referred to as dart projectors, remote delivery systems (RDS) or remote chemical injection (RCI) and are used to remotely deliver liquid anaesthetic or medical agents to animals that cannot be routinely handled such as wild, dangerous or escaped animals
■ Consideration should be given as to whether darting is suitable in a given situation and whether more benign methods (e.g. oral medication, hand injection, pole syringe (jab sticks), physical restraint, animal training) could be deployed safely. Dart guns are a projectile weapon and as such carry risk of injury to operators, bystanders and the animals themselves, independent of the pharmaceutical agents they are delivering. Dart systems are a firearm and should be respected like any other gun or rifle
■ A variety of different dart guns are available on the market and consideration should be given to the requirements of the operator prior to purchase. This should include: the species darting may be required for; effective range, accuracy and consistency; dart volume required; dart velocity and impact energy; operator familiarity and ease of use; availability of parts, budget and long-term disposable costs
■ Dart guns, including blowpipes, are considered as Section 5 prohibited firearms under the Firearms Act 1968, with an exemption available if they are to be used for tranquilizing or treating animals. Even with the exemption from a suitable firearm certificate, appropriate secure storage facilities, and in some cases Secretary of State authority, are both required before a dart gun can be purchased
■ Knowledge of the dart system’s function, including how to accurately sight a rifle or pistol and how to respond in different environments, are essential to effective use. Experience combined with regular practice is vital and demonstrable training is often required before a firearms licence will be given.
Dart guns are classified as Section 5 prohibited firearms under the Firearms Act 1968, and its subsequent amendments. Such prohibited weapons include stun guns, rocket launchers, mini-guns and ‘any weapon of whatever description designed or adapted for the discharge of any noxious liquids, gas or other thing’ (Section 5(1)(b)), which includes dart guns (and blowpipes). Under Section 8 of the Firearms (Amendment) Act 1997, a Secretary of State’s authority is not required for the possession of a dart rifle, gun or blowpipe if it is designed or adapted for tranquilizing or otherwise treating an animal, and if the professional has a firearm certificate subject to a condition restricting its use to the treatment of animals.
As such, a suitable firearm licence must be obtained before purchase or handling of a prohibited weapon. Currently, a Section 5 firearm offence carries a 6 month summary prison sentence or fine or both, and on indictment 10 years or a fine or both. A person commits an offence if they do not have a licence for, or if they have in their possession, or purchase, acquire, manufacture, sell or transfer, any of the prohibited weapons and ammunition listed in Section 5(1) of the 1968 Act. In simple terms, if a person does not have a licence for a specific weapon, they are committing an offence by handling or firing any type of darting equipment. In certain cases there are exemptions to this (e.g. licensed firearms dealers at specified sites as part of training programmes).
Firearms law and licensing is in place to allow the legitimate possession and use of firearms by those judged safe to do so. A firearm certificate is granted allowing application to the local police force under the Firearms Acts 1968 to 1997. In general, the licence needs to be renewed every 5 years. Before being granted, the chief officer of police must be satisfied that the applicant can be permitted to have in their possession the firearm and ammunition without danger to public safety or to the peace. As such the local police force will be able to provide veterinary surgeons with the specific details required to be met, which usually consist of:
■ Formal application for a firearm licence, which includes all types of firearm and their ammunition proposed to be held along with personal details, signed photographs of proposed licence holders, medical statements, personal references and statements of intent. This is followed by an interview with the local firearms officer before a licence can be issued
■ Demonstration of secure storage for the proposed dart gun (and any other firearms). Legislation does not specify the level of security; however, there may be stipulated levels required by the local police authority depending on the weapon and the local environment. It is usual to have a commercially available gun cabinet of sufficient size and space (BS7558 standard). In some cases, additional security such as barred windows, metal access doors, a separate armoury, alarms or CCTV may be requested prior to acquisition, depending on the individual’s situation
■ A specified maximum amount of ammunition may be held, all of which must be locked in a secure gun cabinet, preferably separate to where the dart gun itself is held. All components of the darts (e.g. needles, darts) must also be secure. Ammunition is also considered Section 5 prohibited and the number of darts that can be held is specified on the individual’s firearm licence
■ Specified conditions on the firearm licence may stipulate limited use of a weapon (e.g. ‘the rifle may only be used within zoo grounds’ or ‘the rifle may be used anywhere following logged communication with the local police authority’). It is prudent to discuss with the issuing police authority any limitations that may be enforced by proposed conditions as they may be prohibitive to a general practitioner’s needs. There is variation within each county police force’s requirements in the UK and it is down to the practitioner to discuss any additional conditions prior to the licence being issued. In some instances derogations can be provided from conditions whereby each movement of a dart system is communicated and logged with the police.
Separate to the firearm licensing requirements and the duty of care that comes with holding the dart projector, the veterinary surgeon must comply with the relevant legislation for dispensing, storage and use of any anaesthetic or other veterinary medicinal products (VMPs) utilized within the dart itself – namely the Veterinary Medicines Regulations (VMR) and the Misuse of Drugs Regulations. Often this is simple if the veterinary surgeon is also the person delivering the dart. However, it should be noted that there are several lay capture teams that utilize darting systems and these may request VMPs or anaesthetic agents to be delivered using dart guns, often without the presence of a veterinary surgeon: in such cases advice should be sought from the Veterinary Medicines Directorate (VMD) or the Professional Conduct Team at the Royal College of Veterinary Surgeons (RCVS) as to the legality or appropriateness of supplying medicines in these situations. Examples include the police with respect to dangerous dogs or specialist capture teams for the translocation of deer.
Types of device
Dart delivery systems can be classified as falling into one of three groups based on the methodology utilized to project the dart:
■ Manual (lung-powered) systems
■ Pressurized gas systems
■ Powder-charged systems.
Manual dart systems are limited to blowpipes and pole syringes. Whilst not a dart system in itself, consideration should be given to pole syringes (also known as jab sticks), which may be a suitable alternative to a darting system and do not require the practitioner to have a firearm licence. Pole syringes are effectively an extension of the clinician’s arm and can be used over very short distances, usually 1–2 m (determined by pole length). They are useful in crush cages, over animal boards or in places where hand injection is inappropriate. Pole syringes are available as gas-driven or hand-driven at the time of injection.
Blowpipes require considerable practice and user skill. They have an effective range of 10–15 m, and are a cheap and effective tool in the hands of a competent operator, but they still require the level of security of any of the high-end rifles and firearms on the market. The advantages of blowpipes should not be overlooked when considering purchasing a darting system. In addition to being cheap and effective they are quiet, can be used for any size of animal and come in to their own for smaller animals were there may be a risk of injury from some of the higher pressured systems. However, they require operator skill and experience to a level not required with some of the more advanced systems, therefore they are used less frequently.
Pressurized gas systems mostly use carbon dioxide to deploy the dart, although there are foot-pump air-driven systems available that are equally as effective. These are the most common systems used by capture teams and zoos as they have an effective working range of up to 75 m, which meets the needs of most professionals. Pressurized systems are available as pistols, rifles or hybrids that have interchangeable barrels allowing a variety of different dart sizes to be used and greater flexibility in their use. There are even double-barrelled systems that can deploy a second dart without having to reload. In all of the commercially available pressurized systems, a release valve allows the user to directly fill a compression chamber to a designated pressure determined by the size of the dart and the distance required for the dart to travel. As the trigger is depressed, the gas is released and propels the dart through the barrel, towards the target. This effectively replaces the lungs and any variability seen in the manual systems. If sighted and utilized properly, these systems should be consistent with each shot.
Powder-charged systems are similar to pressurized systems except that they typically use a .22 calibre blank charge to propel the dart. Various charges are used for different distances and these can be further dampened using venting ports that allow the operator to dial down a distance from the maximum setting for that charge. Powder-charged systems have the longest range, from 40–100 m depending on the system, but are often limited in their flexibility.
Selecting a device
There is a range of options available when selecting a darting system and it is important that consideration is given to the situations where a dart system will be used in practice. Primary considerations should include:
■ Effective range
■ Dart volume required (determined by the range of species and medicines to be used)
■ Dart velocity
■ Impact energy
■ Operator skill and knowledge required for safe use
■ Ease of use
■ Frequency of use (to some degree this influences operator skill and experience required to operate the system e.g. if infrequent then use a system that requires low operator skills supported by laser sites)
■ Availability of parts and disposables (especially if the system is to be used overseas)
■ Cost and financial return for practice
■ Willingness to meet legislative requirements.
The type of dart that can be used with the system should also be considered in the selection process. Specific brands have little crossover and once committed to a dart system often only specifically associated darts can be used with that firearm. The biggest limitation is the maximum volume that a dart can hold and this selection criteria is essential when considering the purchase of a darting system. For instance, one dart projector has a range of over 100 m yet can only hold a maximum volume of 1 ml, which limits the range of applications.
There are two main types of dart available. These are classified by the method utilized to drive the plunger on impact. Like the dart delivery systems, the darts can either have pressurized gas or explosive charge driven plungers, the former being recyclable and the latter disposable in most commonly available systems. The darts vary between brands in the level of complexity to build them, from simple active straight out of the packet to complex darts that have up to eight components to put together.
The generic anatomy of a dart comprises a liquid medicine chamber that contains the agent to be delivered, a plunger delivery system, a stabilizer and a needle (with or without a sleeve depending on the plunger delivery mechanism). Needles vary depending on species requirement and consideration must be given to needle length and width to ensure that the medicine delivered is injected, usually, intramuscularly. Needles can have a variety of barbs or collars. They may be smooth or, with some systems, have gelatine collars that melt after a period, facilitating removal. Compressed gas-driven plungers have needles with side ports that must be covered with a sealing sleeve; on impact, the sleeve slides backwards exposing the ports and the medicine is injected. Typically, the exposed charge darts are open ended, although some have side ports as well (triports), with no active pressure until the explosive charge activates as the dart hits the animal (or the dart is dropped).
Some manufacturers offer alternative dart types such as biopsy darts or bear scare darts, which simply make a noise. These have specialist roles and are not capable of delivering medicines. Blowpipe darts are often lighter than other systems and as such cause the least impact injury. Some dart brands can be reused. In such cases it is imperative that the dart is cleaned and maintained to the manufacturer’s recommendations to avoid dart plunger failure.
Range finders are an extremely useful addition to any dart box. They are used to accurately estimate the distance between the dart system operator and the target animal. With all of the non-manual dart systems, a control system will allow a deployment pressure for the dart to be set which corresponds to the distance the dart is to travel. The pressure, be it explosive or gas pressure, needs to take into consideration the volume of the dart (weight) and the distance. All darts are designed to be fired full and so must be topped up with water for injection if required and, as such, the only variable is distance. Inaccurate estimation of distance, and hence failure to select the correct pressure, is the most common cause of unsuccessful darting. The use of a range finder addresses this potential error in the darting process.
Sights are commonly supplied with darting systems, except blowpipes. They are only useful if they are accurately aligned and it is therefore important that sights are regularly assessed. Some rifles have both a laser and telescopic sight – in this case it can be useful to have one scope set at a long distance and the other for closer work. If more than one person uses the dart system it is important to write on the rifle the distances that the scopes are set at to ensure accuracy when darting.
Equipment maintenance, for both dart projectors and darts, is essential to ensure accurate darting, guaranteed delivery on impact, safety for both animal and operator, improved welfare from reduced darting failure and decreased darting times. Manufacturer’s guidelines should be followed at all times.
Health and safety
Darting should be considered a relatively traumatic event – even with the correct pressure, a dart can cause considerable bruising, a fractured limb or in worst case scenarios the death of the target animal either from darting trauma or from poor management of the darting environment.
All dart systems are firearms and it is imperative that gun safety is followed at all times and the systems are treated with the utmost respect. Only suitably licensed firearm licence holders must handle and use the firearm, and sensible precautions must be taken during the darting process. These include, but are not limited to:
■ The dart projector must be secure until imminent use is expected
■ The dart projector should be carried in a secure gun bag or case to the site where it is to be used
■ When out of the case, if not in use, the safety catch must be on, any firing pins or bolts open or removed and the barrel must always point directly at the floor or sky so it is clearly obvious to bystanders that the firearm is not in a ‘ready to fire’ state
■ The dart projector should never be pointed at an individual or anything that is not intended to be shot
■ The darting area must be considered – safe lines of sight, darting techniques that take into account the species of animal being darted, accurate dart placement, area to be targeted, any risks of either ricochet or animal behaviour once darted that may compromise the animal or capture team’s safety
■ The dart projector should not be loaded until ready to fire.
In addition to gun safety, consideration must be given to the agents placed into the dart. Many of the anaesthetic agents used are either opioids (e.g. etorphine or carfentanil) or highly concentrated agents (e.g. ketamine 200 mg/ml or medetomidine 40 mg/ml), all of which are extremely dangerous if inappropriately exposed to the operator or any bystanders. In addition, other VMPs such as vaccines and antibiotics are not benign and large doses, injected or inhaled in an aerosolized form, can be extremely dangerous. Written standard operating procedures (SOPs) and emergency procedures must be available and discussed prior to every darting activity with all stakeholders. Where anaesthetic agents are used, it is essential that a buddy system is utilized where a second trained member of the team is available to administer antagonists or provide life support until the emergency services arrive for any accidental exposure of the primary operator of the dart system. Sufficient in date doses of antagonists are an essential part of the emergency response. Advice from your local hospital or doctor is advised prior to offering darting services to your clients to ensure both parties are adequately prepared to manage emergency events.
The high risk areas that need consideration are:
■ Loading of darts and the pressurization process
■ Removal of the dart from the animal, especially if there still remains agent in a partially discharged dart
■ Storage of used darts prior to disposal or cleaning
■ Cleaning of the darts where there will be residual anaesthetic agents or similar in the darts.
Risks assessments and suitable personal protective equipment (PPE) should be available and used for all of these areas, in addition to the actual darting event itself. For air pressurized darting systems, all darts should be assessed and, if required, depressurized (de-vented) prior to removal from the animal to prevent any risk of spray. Some brands offer commercial solutions to these problems, others require diligence on the part of the operator.
Another area for consideration is the safety of the operator and bystanders during the induction and recovery period. Both the safety of the animal and the capture team is of paramount importance, and assessment of the darting environment must take into consideration any common and avoidable eventualities. If considered unsafe, all attempts must be made to move the animal to a safer environment that facilitates darting, safe induction and mitigates any risk to bystanders.
Standard operating procedures
General darting system use safety
■ Complete, practicable and written risk assessments in a format consistent with current Health and Safety Executive requirements should be carried out for the following areas:
- Firearm storage
- Firearm transportation
- Dart system use (specific to each system, if more than one is used)
- Dart loading
- Dart cleaning/disposal
- Risk assessments for particular medicines used (e.g. potent opioids)
- Emergency procedure in the event of accidental injection or exposure to agents to be used in the system.
■ The use of the darting system (and all firearms) is restricted to people who have been approved and licensed to use them by the Firearms Officer at the local police force. No one else is allowed access to or use of the darting system unless they hold a current firearms licence with the darting system listed on the licence.
■ All staff should be briefed on the appropriate risk assessments and the potential agents used in the system, especially if the operator is not cleaning the darts and potent opioids or high concentration anaesthetic agents are to be used.
■ Suitable PPE should be available as part of the basic kit. This should include nitrile gloves and suitable eye protection when building, removing or cleaning darts.
Dart management and safety
Explosive discharge darts are typically single-use only darts and must be disposed of in a suitable fashion following use. Extreme care must be taken in handling these darts as, if dropped, they can discharge. Some of the older brands can be reloaded with a charge; this type of dart may still be seen in zoos. These are less reliable compared to some of the newer systems, but are still effective with experienced use. Newer brands are typically clear plastic darts in which the liquid chamber can be seen. A blob of silicone gel can be placed in the nib of the needle to prevent loss of injectable agent, but is not necessary for effective deployment.
The pressurized gas type darts utilize either compressed gas from a can or, more commonly, air injected with a syringe. In both cases, a no-return valve retains this compressed gas. The dart should be held with the needle pointing upwards to enable the no-return valve to drop into place and allow effective filling. A needle sleeve, if available, should be put over the needle to prevent accidental exposure if, during building, the dart has been incorrectly assembled. Once the gas is injected, the dart is armed and must be de-vented to make safe. This can easily be assessed by inverting the dart – with the needle down, the no-return valve drops away from the dart if not pressurized or remains where it is if pressurized. An alternative method to allow quick visual assessment of armed status is to leave a very small air bubble in the liquid chamber. Once armed, this becomes compressed allowing confirmation that the dart is pressurized and ready to be fired. The volume of air to be injected is determined by the size of the dart and the brand requirements as set out by the manufacturer. This should only be done immediately prior to the dart being loaded into the firearm. Darts can lose pressure over time, but this also minimizes the risk of exposure from accidental discharge if armed darts are to be transported.
Following induction, and once the target animal has been assessed and safely approached, the dart must be removed from the animal. To do this the dart should be reviewed carefully. The liquid chamber should be checked visually to ensure that all of the contents have been injected and, in the case of pressurized gas darts, the no-return valve position should also be checked. If any medicine remains extreme care must be taken to prevent exposure to the residual agent on removal. Often, darts fail to discharge due to poor dart cleaning technique or inadequate pressure within the air chamber; however, in some species tissue pressure can be greater than that of the air chamber and on removal the dart effectively discharges any residual agent. To avoid this risk the dart should be de-vented using the supplied pin, which is simply pushed through the no-return valve. Explosive darts should not discharge, but care must still be taken. In some cases the liquid agent may leak out from the needle entry wound and the area should be liberally washed and marked in the case of some of the more potent anaesthetic agents to avoid accidental contamination, especially if the animal is to be physically handled or moved.
Darts should be immediately placed into a designated dart storage receptacle or sharps bin, depending on the choice of the veterinary surgeon. If recycling gas pressurized darts these should be cleaned on the day of use to prevent drying and crystallization of the medicine impairing plunger movement. All manufacturers’ guidelines must be followed as to safe and effective cleaning. If using potent anaesthetic agents, cleaning darts is as dangerous as loading and equal care must be taken at this time. Needles should also be assessed at cleaning and injection ports checked for patency – dried blood or tissue cores can block side ports and prevent injection if not suitably cleaned. It is useful to have cleaning protocols with written instructions on safety and expected levels of maintenance.
BSAVA members have online access to Jonathan Cracknell's Darting Manual.
Dart systems are extremely effective when deployed safely and in an appropriate fashion. There is considerable variation between the different commercial systems and each must be assessed following internal audit for the needs of the practice and the range of uses where such a system may be required. In all cases safe firearm use must be practiced and the manufacturers’ guidelines for safe use, maintenance and cleaning must be followed.
References and further reading
Cracknell J (2013) Remote chemical immobilization: darting in practice. In Practice 35, 17–23
Home Office (2005) Firearms security: a brief guide
Home Office (2014) Guide on firearms licensing law
Kock MD and Burroughs R (2012) Chemical and physical restraint of wild animals: a training and field manual for African species, second edition. International Wildlife Veterinary Services, South Africa