likened to the studies into the use of military dolphins. It has also been proposed that remote-controlled rats could be used for the clearing of land mines. Other suggested fields of application include pest control, the mapping of underground areas, and the study of animal behaviour. Development of robots that are capable of performing the same actions as controlled animals is often technologically difficult and cost-prohibitive. Flight is very difficult to replicate while having an acceptable payload and flight duration. Harnessing insects and using their natural flying ability gives significant improvements in performance. The availability of "inexpensive, organic substitutes" therefore allows for the development of small, controllable robots that are otherwise currently unavailable. Similar applications Some animals are remotely controlled, but rather than being directed to move left or right, the animal is prevented from moving forward, or its behaviour is modified in other ways. Shock collars Shock collars deliver electrical shocks of varying intensity and duration to the neck or other area of a dog's body via a radio-controlled electronic device incorporated into a dog collar. Some collar models also include a tone or vibration setting, as an alternative to or in conjunction with the shock. Shock collars are now readily available and have been used in a range of applications, including behavioural modification, obedience training, and pet containment, as well as in military, police and service training. While similar systems are available for other animals, the most common are the collars designed for domestic dogs. The use of shock collars is controversial and scientific evidence for their safety and efficacy is mixed. A few countries have enacted bans or controls on their use. Some animal welfare organizations warn against their use or actively support a ban on their use or sale. Some want restrictions placed on their sale. Some professional dog trainers and their organizations oppose their use and some support them. Support for their use or calls for bans from the general public is mixed. Invisible fences In 2007, it was reported that scientists at the Commonwealth Scientific and Industrial Research Organisation had developed a prototype "invisible fence" using the Global Positioning System (GPS) in a project nicknamed Bovines Without Borders. The system uses battery-powered collars that emit a sound to warn cattle when they are approaching a virtual boundary. If a cow wanders too near, the collar emits a warning noise. If it continues, the cow