These unfortunate animals are ‘traitors’ to their kind (but we’re the real ones to blame)

While many of us aren’t overly fond of our 9 to 5, these animals take the cake for worst job ever—and have one of the most unappealing titles to go along with it.

For centuries Judas animals, an individual creature isolated from its social herd and used to control the larger group, have been employed by shepherds, farmers, and veterinarians to locate lost flocks and calm large animals during operations or rescues. But now conservationists are also looking to these unwittingly traitorous critters to eradicate feral populations, using them to find others of their kind for elimination.

Not every animal is a good Judas candidate. Most importantly the animal need be a highly gregarious species, dependent upon others for survival. That means when alone or isolated, it will look for its herd or seek out a new one, leading those tracking it the grouping it discovers.

The best Judas animals are also usually leaders of the pack and logically, fond of humans. Pregnant females or those in estrus can be good at the job too, putting off some pretty powerful and alluring odours. Australian researchers have even come up with a way to implant hormones in female goats to extend their cycles and make them more desirous of a herd, and useful for longer. Youngsters are sometimes even used to lure in their mums for transport, tagging, or examination.  

The most famous example of Judas animals at work is the Galapagos goats, used to remove fellow ferals from the famous island ecosystems they had colonised and essentially destroyed, pushing out native icons like the Giant tortoise. But before Judas goats helped cleanse their invasive species from the delicate island-chain, Galapagos pigs and donkeys did the same to their friends and loved ones. And this method, called the Judas control technique, had already been tested out in a few other places and species with varying success rates.

Here’s a quick look at some of the animals worldwide that have already done their solemn duty or are currently unknowingly contributing to the greater good—all by ‘betraying’ their kind.


Goats Worldwide

Goat herd

Goats make some of the best Judas animals—they’re generally friendly, intensely social, and despise being alone. But goats are also an incredibly invasive species that has spread itself far and wide thanks to humans. Their non-discriminating veggie munching nature and fast reproduction rate allows them to alter habitats quickly, making it unsuitable for the other forms of life that once lived there.

Before they depopulated the Galapagos of an estimated 100,000 of their hooved-kind, goats were also at work on much smaller scales in other island nations around the globe.

At the start of the 1990s Americans pulled off major victories in California’s San Clemente Island and Lana`i Hawaii. Radio-collared Judas goats in San Clemente took between one and five days to find their targets, travelling 5km on average a day.

In 1994, 30 or so goats were eradicated from Flinders Island Australia, and shortly after, around 150 or so were eliminated from Auckland, New Zealand. Australia’s King and Bruny Islands were able to remove a similar amount of animals.

Today the tradition continues whenever and wherever goat populations become pests, or impede on native ecosystems and species. In 2010 Australia was back at it, eradicating goats from Kangaroo Island.


Camels in Australia


Researchers from Murdoch University have a new Judas candidate—camels. The critters are a logistical nightmare for trackers looking to cut back on their numbers, given the immense distances the animals can, and normally do, cover.

In the spring female camels were captured in northern Western Australia, fitted with satellite collars, then released back to the site they were taken from. Once they found their herd, hunters culled all its members from a helicopter except for the betraying female, leaving her to move onto the next doomed group.

The researcher’s claim studies have looked into the physiological toll this takes on the female camels undertaking the nasty work and claim it is negligible.


Carp in Tasmania, the United States, and of course… Australia


Veterinarians in the African nation have been sterilising male carp and fitting some with radio-transmitters before re-releasing them in the country’s Central Highlands. Their aim is to naturally cut back on the population by reducing the number of breeding members, but to also use the tagged carp to monitor the location and abundance of the species’ populations.

In some American states, Asian carp are becoming a serious problem, endangering regional rivers and lakes. The species pulls up weeds and aquatic plants from the bottom, which causes the bodies’ of water they accumulate in to become murky and lower in quality. In Minnesota researchers have been testing out the technique to deal with Asian big-head carp since 2008.

To mention Australia’s been tackling their carp problems with this technique too probably goes without saying at this point.


Mustangs in the United States

wild horses

In Idaho wild horse populations (usually mustangs) grow by about a quarter on average per year. That means in order to keep the community in line with their available range, every few years ‘gathers’ must take place in the fall months. Helicopters are used to corral herds together towards a netted-trap and when they’re close enough, wranglers release Judas, or so-called Prada horses, trained to run the anxious group into the trap.

But Judas horses in this case don’t have quite as much to feel bad about. Once they’re secured, the animals are transported to a holding facility and after some vet care, go up for adoption. Similar events take place in other states like Utah.

A shout out again to Australia, who gets a special notation here for having the world’s largest feral horse population—estimated at around 400,000 individuals. The country’s been trying to slowly eradicate the animals from their island for quite some time now, as previously mentioned, but the scale of the problem make the process a lot harder.

Just how officials should go about removing these animals is a sensitive topic. At this size, large culls are really the only feasible option to control the population, which some would argue is actually far more humane than trapping, poisoning, or long-distance relocations.

Donkeys have proven equally useful in many of the same settings and locations around the world as horses—though they don’t look quite as graceful doing their job.


Nutrias in the United States


Back in the 1900s, semi-aquatic South American mammals called nutrias spawned a short-term international trend. The animal, resembling a beaver, was raised like a stockyard animal and then slaughtered for their pelts. At its height, nutrias were being farmed in many regions of the world.

But by the 1930s and 40s people weren’t exactly keen on expensive furs and the industry failed—especially in the United States. Farm owners primarily killed or sold off their animals that were of age, but when it came to youngsters, still requiring month’s worth of pricey feed to reach prime fur-bearing age, many were simply released into the surrounding environment.

In Maryland’s famous Chesapeake Bay nutrias became a serious problem. The digging newcomers began to cause coastal erosion, and the fact they have as many as seven kits per litter made them particularly hard to keep on top of. In the 1990s the watershed’s stakeholders began trying to sort out how to solve the nutria problem, and after two decades, multiple approaches, and lots of funds, they’ve done what they set out to. One of the final steps in their process was the use of Judas nutria to locate remnant strongholds.

In Louisiana government groups kill thousands of the critters each year and the state is trying to come up with a way to use these corpses. So far they’ve endorsed nutria-recipes and nutria pelts as a sustainable fashion trend.


Raccoon dogs in Sweden


Raccoon dogs are endemic to East Asia initially, but fur operations in some European countries and China have grown over the years, slowly feeding feral populations. The canids’ fur markings and softness has allowed raccoon dog pelts to fraudulently be swapped out for that of more desirable species by wholesalers and retailers.

In Sweden, raccoon dogs are being trapped, sterilised, and then released as Judas dogs, altering hunters to the whereabouts of nearby animals.


Snakes and pigs in the US


By now it’s probably not news that exotic species like pythons and boas have become established in more southernly American states like Florida. If you’ve never seen The Python Hunters you’re missing out.

And it’s not just snakes that have taken up shop in the states’ everglades. Caimans and monitors are additionally terrifying examples, but about 50 other reptiles are listed as invasive species.

In the spring of 2013 government officials fitted a female Burmese python with a radio-tag and then released her into the everglades, hoping she’d lead them to male pythons and shed light on the highly elusive animal’s lifestyle.

In the same 2013 experiment Judas pigs were released into the Florida swamplands.

Though they’ve been in the region for a lot longer than their reptilian alien peers, roughly 500 years opposed to around ten, feral pigs have become a major problem in some American states. Wild pigs have a foothold in Texas and Mississippi too, estimated to cost billions of dollars worth of damages to crops and land annually.

In the 2013 trial a novel trick was tested. Judas pigs actually sent researchers an email as to their precise location and movements—ok well not really, but their radio-collars did.


Judas Birds in Australia

Starling Flock

Researchers down under that helped pioneer other invasive-eradication projects with horses, donkeys, goats and camels have also thrown around the idea of using certain types of birds as Judas animals.

A few years back trials were conducted to explore the potential of the idea, using radio-tagged starlings to isolate flocks for destruction. Though it wasn’t all that effective, it usually takes a bit of experimentation to get the process just right. The team ultimately concluded the technique could prove useful in the future for gregarious species like the starling with adjustments.