One persistent mystery of the natural world is that of mass animal deaths. There are countless instances of vast numbers of animals of all kinds suddenly seeming to just drop dead, but while many of these are eventually explained, there are others that remain firmly within the realm of mystery. Here we will look at a selection of cases of partiucularly bizarre mass animal deaths that have managed to conjure up mysteries, strange clues, and conspiracies, and which may never be truly solved.
Our earliest and perhaps strangest one is a case that has long stirred controversy and conspiracy theories. On March 17, 1968, a manager of a livestock company came across 3,000 dead sheep littering a field at Skull Valley, located in east Tooele County, Utah, United States. Over the next several days, grazing sheep continued to die off by the hundreds, seemingly dropping dead in their tracks, until the area was a veritable sea of sheep carcasses, an estimated 6,000 to 6,400 in total. Among these was the occasional live sheep, which were found shambling about, dazed and disoriented as if they were zombies or just sitting there eerily staring into space. At the time veterinarians could find no obvious cause for the deaths or the symptoms for those found alive, and the bizarre incident was soon hitting headlines around the country.
The fact was not lost on anyone that these sheep were dying not too far from a place called the Dugway Proving Ground, which is a sprawling, 800,000-acre military facility run by the U.S. Army, located around 85 miles (137 km) southwest of Salt Lake City, Utah. The vast facility is a hodgepodge of target ranges, dispersal grounds, laboratories, and military bunkers, with one of its main purposes being to test United States and Allied biological and chemical weapon defense systems and other unconventional military hardware in a secure and isolated environment. With all of the sheep dying off at the same time, all eyes immediately turned to the mysterious top-secret installation and there were rumors that the military had carried out some sort of nefarious test of a chemical or biological weapon.
At the time, the main idea was that some sort of nerve agent had been tested in the area by the military, but there were some problems with this theory. For one, tests performed on the sheep turned up no evidence of a nerve agent, and there was also the fact that only sheep had died and no other animals. However, on March 13, it turns out the military had indeed carried out a series of tests at the facility. One of these was a test firing of a chemical artillery shell, in the second 160 gallons of the nerve agent compound VX were burned in an open pit at the base, and the third was a jet aircraft spraying nerve agent in a specific designated target area. These were all fairly routine tests at the base, business as usual, but it was this third test that was turning heads. It was thought that some of the VX nerve agent on board the plane had either leaked out of the aircraft or been blown by winds to settle onto those sheep, and it certainly would have done the trick. Long a controversial weapon, the tasteless, odorless VX compound is three times as toxic as Sarin, and a lethal dose, about a single drop, will cause will cause convulsions, paralysis, and death within around 10 minutes for a full grown adult human.
When confronted with this, the U.S. Army at first denied having had anything to do with the sheep deaths, underscoring that all of the tests performed had been routine and done far from populated areas in a remote area of the Utah desert. However, they would later admit that the VX spraying run had indeed experienced a bit of a mishap. It was explained that a spray nozzle had malfunctioned during the test, and that one of the canisters had not completely emptied and had begun leaking a small amount of VX as it flew over the area climbing to higher altitudes. Considering that there had been high winds at the time and that the sheep had begun dying off the next day, it seemed obvious that this was the culprit. Other testimony came forward that further fueled this theory, when Skull Valley resident Ray Peck claimed that he had seen numerous dead birds and a dying rabbit on his remote property, and that he had also experienced strange physical symptoms including violent headaches, numbness, and an earache. Adding to the ominous conspiratorial tone of the story was that he also claimed that an Army helicopter had landed at his home and that military personnel had quickly collected the dead bodies, performed blood tests on the family, and left without explanation.
It is all quite sinister, but the military denied having ever gone to Peck’s property, and they also insisted that the amount of VX that had leaked was too small and too far away from Skull Valley to have killed so many sheep so quickly. They also showed that their tests on the sheep carcasses had turned up no trace of VX, and pointed out that the symptoms of the surviving sheep did not fit those of the nerve agent. Veterinarians agreed, explaining that the sheep either wandered around or sat unmoving on the ground, but breathed normally and did not exhibit the asphyxiation or seizures that should have come from VX. There was also the fact that, despite Peck’s claims, no other animals of any type, including cows, horses, dogs, or even small animals like rabbits, mice, or birds had been found dead, so why was it only sheep if this was the work of VX? It was all pretty mysterious.
In the meantime, the Army continued to deny their part in the sheeps' deaths and refused to take any responsibility for it. Despite these reassurances and the contradictory evidence that this had been the doing of VX, the damage had already been done. The public had been whipped up into a state of outrage that forced the U.S. military to change its policy, and it led to President Richard Nixon's decision to ban all open-air chemical weapon testing in 1969. In later years, a report unreleased to the public up until then would come to light that showed that researchers from the U.S. Army's Edgewood Arsenal in Maryland had indeed found traces of VX in in both snow and grass samples of the area three weeks after the incident, and had deemed the amount found to be capable of killing the sheep. Nevertheless, the U.S. Army continued to deny involvement, and we are still left with the fact that no other animals died in the incident, leaving it shrouded in mystery. What really happened out there to those sheep? We may never know for sure.
Moving along into more recent years, a very tragic and bizarre case happened in May of 2015 in the Uzbeki steppe lands of Kazakhstan, when thousands of a type of dog-sized antelope with outsized snouts called saiga began turning up dead by the thousands. Locals were finding the animals, which wander over large tracts of Central Asian grassland, strewn out over the steppe in large numbers, in positions that suggested that they had just collapsed to drop dead on the spot. Over the course of just two weeks during the animals' summer calving season, a staggering 60,000 of the animals, male, female and newborn alike, with some estimates even higher, had died practically simultaneously, in a very sudden fashion and for no clear reason. It was an unprecedented mass animal die-off, and especially worrying since the saiga is considered to be a critically endangered species, brought to the brink of extinction through poaching for their body parts, used in traditional medicines in China and Southeast Asia, as well as habitat loss. With such low numbers, it is estimated that this one catastrophic event had wiped out around 60% of their total population in a matter of days. It was so alarming that delegates from Russia, Kazakhstan, Uzbekistan, Mongolia and China convened an emergency meeting to discuss the issue and try to get some answers. Few were forthcoming.
There were many strange clues in the mass saiga die-off. One was that it had affected only saiga and no other animal species in the area. There was also the fact that the animals seemed to have died nearly instantaneously, usually having collapsed or fallen face down in a manner that suggested they just had suddenly dropped dead rather than gotten sick and died over time, and they were also well-fed and seemingly healthy in every other respect. There was no deterioration or wasting away present to suggest they had died of a disease or toxin. Another oddity was that the deaths had occurred over an area spread across 65,000 square miles, roughly the size of Florida, yet it had all hit all of the animals at about the same time and it had hit them in astronomical numbers and without warning. The animals had no sign of sickness or injury, they had simply all dropped dead. Also eerie was that there were no records of mass die-offs of saiga in the past, so this was completely unprecedented. How is it that so many healthy saiga had suddenly and practically simultaneously died across such a vast area? No one had a clue. Richard Kock, a veterinarian and conservationist from the Royal Veterinary College who went to investigate the scene would say of it:
Mass mortality events are never nice things and I’ve experienced quite a few. But the experience of the saiga was unprecedented, and unworldly. What is surprising and of great concern in this case is the size and extent of the event -- entire herds suffered near-100 percent mortality. Even after 40 years of work, I just said: I don’t understand.
An investigation did not turn up many answers. There were found no signs of toxins in the animals’ systems or in the soil, so the main idea became that they must have died from some sort of disease, perhaps in combination with changes in weather or vegetation, but it is not clear what sort of disease would do this over such a short amount of time and in such a devastating manner. Also, even the worst diseases typically don’t have such a complete mortality rate, and in this case every single one of the animals in the affected area had been killed. One vertinarian would say of it:
In biology, there’s certain rules, you know? We accept that sometimes microbes can cause us harm, but not like this. Even very severe viral diseases or anthrax don’t do this. A good proportion of the animals would be fine.
Other theories went into conspiracy territory, with ideas that included that it had been caused by radiation, some secret government experiment, or even aliens. Scientists eventually found that the deaths had likely been caused by a bacteria called Pasteurella multocida, which had spread through the circulatory system to cause massive internal bleeding and organ failure, but this only created new mysteries and posed even more questions. Pasteurella multocida normally live in the respiratory tract of the saiga and it is typically completely harmless, a totally benign part of the saiga’s microbiome, so how is it that it had just suddenly gone berserk and killed these animals off and why only in this one area? Scientists figured there had to have been a trigger, and considered everything from climate change, to insect bites, or an accompanying viral infection that had caused the bacteria to go rogue. The main theory is that it was somehow caused by global warming, but in the end there was nothing found that could conclusively account for it, and it has not really been adequately explained why more than half of the world’s population of saiga died so rapidly and mysteriously. The most tragic part of the story is that after the collapse of the Soviet Union poaching declined and there were conservation efforts put in place that had been sending the numbers of saiga up, to the point where it was hoped that they would improve their endangered species status, but this mega-death managed to wipe out decades of conservation work within days. What happened to these animals and how can we prevent it from happening again? We may never know for sure.
From the following year we have another unusual and inexplicable case. In August of that year, hunters in a remote area near Hardangervidda, in the southern part of Norway, came across a ghastly and macabre sight. There scattered about, their bodies sprawled over the rugged terrain, sometimes heaped on top of one another, were a total of 323 dead reindeer. Like the saiga, they seemed to have all spontaneously dropped dead at about the same time, and there was nothing to indicate that they had been injured or suffered from any disease or malnutrition. It was as if they had just somehow been turned off. The hunters had never seen anything like it.
Authorities arrived and were equally baffled. Samples were taken and found no signs of toxins, diseases, nothing. The best anyone could come up with was that the animals had possibly been huddled together in fear during a thunderstorm and then killed by a lightning strike, but this was a bit odd. How does lightning kill 323 large reindeer in one fell swoop? The deadliest lightning strike for animals ever recorded was 68 cows killed in Australia, and the deadliest of all time was when 91 people were killed by a lightning strike 1971, and that was only because it hit their plane and they crashed into the Amazon jungle. A whopping 323 reindeer being killed by lightning would be by far the deadliest ever recorded, but how could it happen and would it have been one strike that killed them all or multiple bolts like a rain of lightning? NNI spokesman Knut Nylend would say of it:
We’ve heard about animals being struck by lightning and killed, but I don’t remember hearing about lightning killing animals on this scale before. We don’t know if it was one or more lighting strike; that would only be speculation. They may have gathered even closer together out of fear during the thunderstorm.
This is the prevailing theory, that the animals were close together and one or more strikes brought them down, but the carcasses were spread out over an area measuring 50 to 80 meters in diameter (165 to 263 feet) so they weren’t all exactly up against each other and touching, so how could lighting kill all of them in one shot like that? John Jensenius, a lightning safety expert from the National Oceanic and Atmospheric Administration explained how this might happen in an interview with The Verge, saying:
Animals do tend to group together in storms and huddle under trees. If lightning strikes the tree or somewhere nearby, the entire group can be killed. We don’t know how common this is because it’s hard to track, though usually it’s herds of 10 or 20 animals that get killed. In the case where the animals are huddling under a tree, oftentimes you’ll see some visible signs on the tree, though you may not see any visible signs on the animals themselves. In this case, it’s hard to know where lightning struck based on the pictures, but there may be an animal among the dead animals that has visible signs, like a bit of charring on the skin. When animals or people are in groups, most are being killed by the ground current. First, there’s a direct strike — this is what most people think of when they think of lightning — that hits the tree or maybe the ground nearby. The energy then spreads along the ground surface, and if you’re anywhere near that lightning strike, you absorb it and get shocked. Lightning goes up one leg and down another. Animals are more vulnerable because their legs are spread out more, so the ground currents travel more easily in their bodies. It doesn’t matter if they’re touching, or exactly how close they are, it matters that they were all in the area hit by lightning.
Ground currents are the thing that’s responsible for the most lightning deaths and injuries in both people and animals. In this case, the animals seem to be in an area that was 50 to 80 meters in diameter and on a hillside, which gives you some idea that lightning can travel a good distance and still be deadly. Lightning doesn’t always travel deep into the ground. There’s also the side flash. That’s when an animal or person is standing close to the tree, the tree is hit by lightning, and then the lightning jumps from tree to person or animal. The side flash usually kills one or a small number of animals, not large ones like with ground currents.
The thing is, there was no evidence of a lightning strike on any tree in the vicinity or the animals themselves, and it is unclear whether there was really any thunderstorm in the area at the time at all because it is so remote. In the end, although the lightning strike theory seems to be the most plausible possibility, not one is really sure how so many reindeer just suddenly dropped dead like that, and it remains a very bizarre case of a mass animal death. Even more recently is an incident that happened in 2020 in the Okavango Delta of Botswana, in Africa. Beginning in early May of 2020, clusters of large numbers of elephants began turning up dead in the wilderness. Some seemed to have just suddenly dropped dead very rapidly, as many of them had fallen flat on their faces, chest-first, or seemingly in mid stride. There was no sign of injury or sickness, and they still had their tusks, meaning that it wasn’t the work of poachers. And the elephants kept dying. By mid-June, the number had more than doubled, and it continued through the year scattered across the remote, roughly 3,000-square-mile region until more than 350 elephants of all ages and both sexes had died, probably even more because carcasses can be difficult to spot in the rugged territory, in what experts called a “conservation disaster.”
Authorities were stumped, and there were very few clues to go on. Local witnesses claimed that they had seen elephants in the area acting in a strange way, walking around in circles in a disoriented manner before collapsing, and 70% of the deaths were found to have occurred near waterholes, but this did little to provide any real answers. The odd behavior is indicative of a possible neurological disorder, but what kind? The presence of so many carcasses near water holes suggested poisoning of some sort, but no other types of wildlife coming to drink had been affected. Oddly, when authorities arrived on the scene they reported that there was an odd smell, and that nothing had really scavenged the animals, only maggots, which was seen as very odd in a place full of scavengers and where carcasses don’t typically last long. So what had killed these animals? No one had a clue.
Not helping matters was that the Botswana government had been slow to act on an investigation and generally mishandled and bungled the search for answers. The country is notoriously poor and low on resources for such things, and not helping matters at all was that this was going on in the middle of the COVID-19 pandemic, making it all even more sluggish. There was also the fact that the government just didn’t seem to consider it a big priority and were very uncooperative, despite the fact that much of their income comes from eco-tourism from people coming to see the elephants, which comprises between 10-12% of Botswana’s GDP, second only to diamonds.
Elephants Without Borders, a Botswana-based conservation group, did everything they could to speed up the investigation, sending GPS coordinates and photographs of elephant carcasses to the government and even offering to go to the site and fund an aerial survey of the area and remove the tusks to prevent poachers from stealing them, but the Botswana wildlife department gave them no response at all. The Botswana Wildlife Producers Association, a group representing game farmers and professional hunters, also offered to help by sending a team of local veterinarians and ecologists to go in and take and prepare samples, but they were denied and told that everything was under control. Due to these issues, samples were taken too late and were consequently of low quality, to the point that some researchers who received them classified them as practically useless, and on top of this they were not initially sent to any reputable lab. Mary Rice, executive director of the Environmental Investigation Agency in London, lamented at the time:
We had the opportunity to thoroughly investigate the cause of these mortalities and manage potential future episodes. But unfortunately we’ve missed it. There is real concern regarding the delay in getting the samples to an accredited laboratory for testing in order to identify the problem – and then take measures to mitigate it. The lack of urgency is of real concern and does not reflect the actions of a responsible custodian. There have been repeated offers of help from private stakeholders to facilitate urgent testing which appear to have fallen on deaf ears … and the increasing numbers are, frankly, shocking. It’s a conservation disaster – it speaks of a country that is failing to protect its most valuable resource.
The Botswana government dragged its feet with its own testing, and in the meantime the samples were sent by conservation organizations to a number of independent laboratories with more advanced, specialized equipment, but a series of mishaps broke some of the glass containers and still others were mislabeled, and they were of such low quality that they could only be tested for certain things. They also lacked enough funding to test all of the samples they had, yet even with all of the hurdles some things could be ruled out. The labs ruled out anthrax, as well as cyanide, which is sometimes used by poachers, and tests also ruled out encephalomyocarditis, a viral infection thought to be spread by rodents. Indeed, these independent tests with these degraded samples could find no explanation at all for the deaths.
As this was going on there was immense international pressure for answers and the news of these mysterious elephant deaths had made worldwide headlines. After several delays from the Botswana government, basically saying “we’re working on it” and keeping the media at bay, they finally buckled under the pressure and came out with a response. Their verdict? The elephants had died from cyanobacteria neurotoxins, which are poisons released by blue-green algae that bloom in stagnant, nutrient-rich water. They explained that the elephants had drunk in these bacteria and then succumbed to the neurotoxins attacking the nervous system, but there was immediate disagreement from numerous scientists and labs on this explanation, and the mysteries would only get deeper from there.
According to many experts following the investigation, cyanobacteria neurotoxins were an unlikely candidate. The most obvious reason was that no other animals had died from drinking the water, only elephants, so why would it only target them? There was also the fact that at least two laboratories claimed that they had found no evidence of the presence of this type of bacteria, and the earliest of the mysterious deaths had occurred during the rainy season when flowing water usually washes away blue-green algae. On top of this, many of the bodies were found on floodplains where this type of bacteria typically doesn’t exist and a 14-month review of documents and investigation by National Geographic found that much of the evidence leading to the blue-green algae diagnosis was unreliable. The elephants had also died extremely quickly and suddenly, which did not seem consistent with the bacteria. For all of these reasons, there was a nearly unanimous response from wildlife researchers, scientists, and veterinarians that the cyanobacteria neurotoxin diagnosis was premature, not based on any good evidence, and not a logical explanation, and that more investigation needed to be done to find the real culprit. However, the Botswana government stood by their verdict and considered it case closed.
Considering that the elephants stopped dying not long after this and the fact that the available carcasses are long since gone, meaning there are no new samples to test, there seems to be very little left to solve the mystery and we are forced into mere speculation. Many questions still swirl. What killed so many elephants in such a strange fashion in such short order? Was it perhaps a new, unidentified type of cyanobacteria toxin? Was it maybe a combination of toxins? Could it have been some new kind of disease? Why did it only target elephants and why would it just kill them so suddenly to send them sprawled out face-first into the dirt? At the moment it is unknown, we still don’t have the answers to any of these questions, and the mystery remains.
What are we dealing with in these scenarios? What managed to just strike these animals down in such large numers and seemingly without warning? Is there something being covered up in some cases, and if so, why? These are among some of the strangest mass animal die-offs out there, and there are numerous questions we may never truly have the answers to.