BBC Two: Big Life Fix – Sheep Rustling

Deterring Sheep Rustlers With Smartphones and Security Ink

Thousands of sheep are stolen every year in the UK, at a cost of millions to the industry. Trying to prevent theft is seemingly impossible, as an average farm can easily total 600 Acres of pasture (about 500 football pitches), and is services by dozens of roads. The problem only gets more difficult, considering that the unit cost of a sheep is relatively low (£70-£80) compared to cows and horses which are so expensive they actually have passports!


This low price also means that regulatory authorities do not have sufficient impetus to invest in a more advanced ‘closed loop’ database of sheep registration. For example, unlike your car’s numberplate, a new sheep’s ear tag can be acquired, and does not need to be ‘decommissioned’, so a thief can simply cut a ear identification (Ear ID) tags off and replace them with his own – and it’d be hard to detect the fraud when the sheep is sold.

Although some stolen sheep might be sold at market (with switched ear tags), the vast majority are sold on the black market as meat. Indeed, when sold in this manner, the sheep’s head, guts and fleece are removed in haste, rendering any tagging or even tracking collars useless. Mike explained that the remnants are usually left in the abandoned trailer, which is usually stolen. He went on to explain in a heist, sheep will sadly be treated brutally and will suffer hugely in their final moments through overcrowding and the unregulated butchery.


The Fix Team explored the scope of this ever-expanding problem. Jude and Zoe met other farmers who had lost sheep recently, and also police from the Rural Crimes division in Wiltshire. They explained that although existing methods had been attempted, such as fitting motion-sensitive alarms to gates, or IR motion detectors at roadsides – these did not prevent criminals, as when even when the alarm was sounded, it was often in the middle of the night, and over 200 sheep could be rustled into a trailer in under 5 mins, or less.



The realities of trying to protect miles of fences, hedges and walls is highly impractical – as a criminal gang would often just drive over a fence or knock down a wall in a secluded place, making perimeter alerts useless.


Jude and Zoe both grew up in the rural England, and had remembered hearing lambs and ewes bleating as they carefully walked through fields. They wondered whether a microphone could be used to ‘listen’ for when sheep’s bleating changed from ‘normal’ to ‘distressed’.

Prairie Dogs and Sonograms for different threats. Image Credit: Prairie Dog Chatters Channel


Jude remembered seeing a documentary on Prairie Dogs having distinct ‘barks’ for different threats, and wondered if sheep might also have evolved different bleats for calling to each other or for warning of potential predators. Jude was able to make what he called a ‘Bleat-o-Meter’, which allowed him to detect changes in sound volume. It would need further development to develop the ‘screening’ of different bleats.



However, when they put the prototype to the farmers for review – they realised that they had omitted a key issue: Ewes only bleat when their young are near. So in fact, a herd of only ewes could be rustled – in relative silence. The problem was not getting easier to solve!


The Fix Team’s failed or imperfect concepts were now stacking up:

  • IR Sensors/Trip-Beams [too slow to sound alarm]

  • Cameras [Too expensive to install everywhere]

  • Number Plate Recognition [Vehicles were stolen and afterwards abandoned anyway]

  • Better locks on gates [Impractical to implement. Thieves knock-down fences/walls/etc.]

  • Bleat-o-Meter [Not enough noise from ewes only]

  • GPS Collars on Sheep [Not cost-effective. Easily cut off. Strangulation risk is high]


Even if GPS collars were to be made economically viable for sheep – Mike explained that this had been tried in the past, but often resulted in the animal strangling itself in some unfortunate way. Furthermore, the device couldn’t be fitted to a sheep as snugly as a horse or cow, as the wool got in the way – and hence, the looser fit allowed it to be easily slipped off by a theif.


After discussing this at length with the both police and a local veterinary school, it became clear that any single device was not going to be the ‘magic bullet’. They needed a series of deterrents. In addition to using some of the existing security measures to increase security on a farm, Zoe and Jude wondered how they could improve the Ear Tags.


The Fix Team had been thinking about how the Tag couldn’t be made impossible to remove, and neither could it realistically house GPS electronics – but it perhaps could be made tamper-evident? If suspicion was raised, somehow it could provide the evidence for an investigation by the police, which might eventually result in a conviction.



Taking inspiration from the retail industry, which uses ‘tamper-evident’ security tags, which leak dye all over clothing if tampered with, Jude looked at how the Ear Tag could be modified to contain security ink. After examining a large Ear Tag, he realised that the central ‘locking pin’ was quite large – and similar in proportion to the glass vials in the retail tags.



The intention was to use the same ink that is used by banks to ‘spoil’ banknotes in a heist. This ink is very permanent. Zoe also wondered if UV-Smart water could also be used as a secondary trace to catch criminals ‘red handed’ as it were.


Jude experimented with numerous ways to house a few milliliters of the dye-cocktail in the central pin. It was clear if one were cut through, this would only leave a relatively small stain, but in the process of cutting off multiple ‘inky ear tags’, the cumulative effect would be noticeable, (as show after only 5 tags were removed in the programme).

The ink would accumulate on the tools and hands of the criminals’ hands, as well as the ears and bodies of the sheep. The latter would potentially rouse suspicion if the sheep were trying to be sold at a legitimate auction (for a higher price than black market).

Jude drew inspiration from the RFID Tags you see stuck on roasting joints in supermarkets, that trigger an alarm at the store exit if not deactivated. He wondered if this could also be incorporated into the Inky Ear Tags as a further means of authentication – and which could be linked to a database, which would know if a flock were registered as stolen.



Although the farmers felt that the inky ear tags could a credible deterrent, they pointed out that it was still an overt solution – could the Fix Team come up with something more covert? This is when the assignment got a lot more complex, as Zoe and Jude considered how to put a tracing device inside a sheep (without it turning into something from a movie, like The Dark Knight’s intestinal mobile phone scene).



This ‘mineral bolus’, as is is known, does not ‘pass through’ the sheep, as they have multiple stomachs designed to ingest objects such as stones, which sit in the reticulum (the pit of the first stomach). These hard objects actually helps to break down the fresh grass. If they could make a bolus-sized tracking device, it could potentially stay in the sheep and transmit a tracking and identification signal, that would be picked up in close proximity of a detector or smartphone.


The Fix Team set about reading around the subject of oral supplements for livestock. They had found academic studies trialing such ideas with larger animals like cows. Again, the issue of cost was clear a driving factor. However, cows could swallow much larger device than a sheep, as their oesophagus was much larger.

Excerpt from “Retention of different sizes of electronic identification boluses in the forestomachs of sheep”. J. J. Ghirardi et al.


Jude and Zoe realised they needed to miniaturise a tracking device a considerable amount. They managed to find one of the smallest Bluetooth transmitters available. After careful examination Jude reduced the size of the circuit board by a further 20% to fit it in a porcelain capsule, Zoe had cast, which was within the tolerable size of a sheep’s bolus.

Jude, Ross and Ryan were able to modify the signal of the transmitter to ‘signal’ as a stronger intensity, but at a lower duty cycle (i.e. stronger signal, less often). Meaning the device would last for about 2 years, sending a signal every 1 second (which is a long time in transmitters).

The signal could be detected by the ‘race’ detectors already installed in auction marts, where a sheep would pass within range within in a couple seconds of transmissions. The ‘twist’ was that the Fix Team realised that our smartphones also have the capability to detect Bluetooth signals – making any phone capable of ‘calling foul’ if it comes within range of a sheep with a tracking bolus, which has been registered as stolen. This concept exists in the form of a product called Tile, which relies on a network of people signing up to ‘catch’ a lost or stolen device if it passes within range, although Tile was not designed to be put inside humans or animals!

Although this device would be expensive, it need not be applied to every sheep. And the ‘Russian Roulette’ approach of bolusing every 1 in 10 sheep would make it a gamble for a criminal gang to steal a flock. The police pointed out that actively sign-posting the warning that a flock is ‘protected by electronic tagging’ is 90% of the task. Just as a ‘neighbourhood watch’ sticker does not protect your house, it does nonetheless act as a deterrent to a would-be thief.


When Zoe and Jude tested this device, it seemed to work on different smartphones if they were within a couple meters of the sheep. Mike and the auction market team were impressed at the combination of the two solutions, and were keen to know how it would be implemented.



The App/Bolus Solution and Inky Ear Tag Prototype would need to be reviewed by government organisations, as neither concept could work without buy-in from these organisations, so that the databasing of all the information was correctly coordinated with the Police. The project will be submitted for review to the relevant bodies for consideration, but stands as a compelling proof of concept at upgrading security to sheep farmers globally.