When Lightning Strikes

If you think lightning never strikes twice in the same place, think again. The USDA's recently retired Chief Meteorologist Albert Peterlin says, "Lightning is not just a random event natural killer, but more an opportunist taking advantage of a preferred pathway. Where lightning has struck a tree in the past, it will likely hit again. An area of pasture that has been deadly once could be again. With lightning, the past is a prologue to the future."

For horse owners, the message is clear--to help safeguard livestock from lightning strikes, learn what lightning likes, then either remove the attractant or remove the livestock.

Lightning Turn-Ons

Lightning is biased toward tall objects and easy pathways. "The primary goal of a lightning bolt is to seek the easiest pathway to Earth," explains Peterlin. "Any pathway offering less resistance than air standing between the bolt in the blue and the Earth's surface is at risk. The most likely area for a strike is toward higher elevations."

Higher elevations include hilltop or hillside pastures, states Peterlin. Other attractants include tall (relatively speaking) objects, including single trees or even animals. Pathways to the Earth can also include power lines and wire or metal fences.
Mix in a little rain to moisten the ground, add a few horses, and your horse pasture has become a tempting playground for lightning, and the horse a pathway to the ground.

Even ungrounded barns can be a problem. "Livestock can be injured even in a structure, depending on size, grounding, and the size and location of any open areas," says Peterlin. "A very small barn without grounding is not a protected environment when it comes to lightning."

Dean Scoggins, DVM, equine extension veterinarian at the University of Illinois, agrees. "If there is a lightning strike on a metal barn, it can almost explode from the impact of the voltage."

Lightning attractants in wooden barns include metal screens, metal automatic waterers, water conduits, etc.
"We don't hear about that being so much of a problem," he says, "but people dealing with lightning rod services stress that if there is such a strike, it will pretty well destroy all the electrical panels and everything in the barn."


While one cannot guarantee a risk-free environment from lightning, there are several things a horse owner can do to reduce that risk. If possible, bring horses into a safe, well-grounded barn when electrical storms are imminent. "A wooden barn is best, or a well-grounded metal barn topped with lightning rods," says Scoggins. "Make sure that conduit and water pipes are well-grounded."

Also make sure that lightning rods have been properly installed and maintained.

For horses which live outside, provide safe havens such as a stand of trees, lower elevations, or access to a properly grounded shed. Because lightning is biased toward a single tree rather than one in a large group of trees, avoid that kind of situation in your pasture.

"Lightning can strike tall trees and spread to the animals sheltered beneath the branches," explains Scoggins. "Once there, the lightning bolt may bounce between animals, including several in the group. Also, lightning frequently goes down the tree, and if it's a shallow-rooted tree, it will travel out through the roots so the ground will be involved as well."

If you have individual trees in the pasture, Scoggins suggests fencing them off with wood, vinyl, or other nonconductive fencing. Use nonconductive fencing for paddocks when they attach to a metal barn, or at least provide some sort of insulated area between the building and the fence so lightning won't jump from the barn to the fence and travel.

Provide nonmetal water tanks and, regardless of what the tank is made of, don't put it on top of a hill. "Whatever is in contact with the tank or adjacent to it is just as susceptible as being under a tree," he warns. "The same thing for horses standing in ponds; sometimes in hot, humid weather there are lots of flies, so horses will take sanctuary in ponds."

When Lightning Strikes

An animal struck by lightning can suffer severe consequences. Michel Levy, DVM, Dipl. ACVIM, large animal medicine clinician at Purdue University, says, "Often when lightning strikes, it causes sudden nervous shock with temporary unconsciousness or immediate death. The nervous system is mostly affected--the animal may stay unconscious for minutes to hours. When consciousness is regained, the animal may be normal, or show depression or blindness. Usually, lightning strikes are fatal."
Scoggins agrees. "A couple of things occur during a lightning strike that normally kill horses. One is nerve damage and the immediate destruction of the brain. The other, usually with lesser strikes, involves problems related to the heart. The heart is primarily controlled by electrical mechanisms as far as the strength of beat and the rate. Frequently, the heart will have some ventricular fibrillation; those cases will normally die within a short period of time."

In nonfatal cases, most injuries are nervous system-related. "One may end up with a horse that has its eyesight, hearing, or both destroyed," says Scoggins. "The horse may suffer brain damage to the point where it has trouble functioning."

Levy says animals electrocuted by lightning seldom have burns on the body, so diagnosis is partly based on proximity to trees or other dead animals nearby. "It's partly a detective game," adds Scoggins. "Usually the horse totally collapses in whatever position it was in. When there's no struggle involved, the fact they died so quickly and the report of an electrical storm in the area leads one to consider the possibility of a lightning strike. Many times, there will be something else that will indicate a strike--a tree that's been struck, burn marks on the ground, a horse found dead under a tree or on a hill, a group of horses that's involved, or horses standing next to a wire or metal fence."

Definitive diagnosis is made post-mortem. "And the sooner, the better," Scoggins states. "One of the things that occurs with lightning strike is that animals will bloat more quickly. Organs in the horse will become distended with gas more rapidly than normal. Usually, we find no burns, but if we do find burns, they frequently will be over the withers, down the legs, or will run down the jugular groove on the side of the neck."

Treatment of survivors is done symptomatically. Levy recommends stimulants for the nervous system and oxygen/ventilation support. "But practically speaking, most horses are either dead or have recovered before treatment can be instituted," he says. Scoggins sometimes adds corticosteroids to the regimen, and occasionally sedatives for hyperexcitable horses.

Prognosis ranges from complete recovery to permanent injury. "Damaged nerves do not heal very well," says Scoggins, "so the horse may or may not improve from its injured state. If a horse is going to respond, it will be in the first two or three weeks. If it hasn't recovered by then from whatever damage is left, whether it is blindness, deafness, lameness because of nerve damage, etc., the horse probably isn't going to get any better."

What Are The Risks?

Levy says he's never been called to look at a horse which possibly was struck by lightning. However, he says, "I had one client who had three dead cows close to a tree in the pasture with burn marks on the ground."

Scoggins found records indicating that the largest single-strike kill involved 20 head of cattle gathered under a tree. He notes that discussions with other practitioners indicate that a lightning strike to livestock "is not an uncommon thing at all."

In fact, Peterlin says that the USDA estimates that lightning causes 80% of all accidental livestock deaths. "Almost all parts of the United States face some risk of threat by lightning, although the risk is more remote west of the Rocky Mountains and in New England. The greatest risk is centered over Florida and stretches northwestward to Colorado and northward to the Carolinas (see page 50).

"Lightning is a common occurrence and an uncommon threat," Peterlin adds. "Lightning is not recognized by many people as a threat because of its very nature--it is frequent and familiar, and familiarity can lead to underestimation. Lightning's victims at any moment are few in number, so there is not a massive outpouring of publicity as in many other types of natural disasters. Finally, we have all taken that chance and run into the house in a thunderstorm. Do that a few times and the likelihood of thinking of the risk in the future diminishes."

It's a familiarity and risk that could have fatal consequences to whomever--and whatever--remains outside and unsheltered during an electrical storm. 

Horses and Storms

When horses huddle in a group or seek shelter during a thunderstorm, it might be the wind and rain from which they’re seeking shelter, and not a killer bolt from the sky.

Sue M. McDonnell, PhD (reproductive physiology and behavior), head of the Equine Behavior Lab at New Bolton Center, University of Pennsylvania, has formally studied horses which are pastured most or all of the time, equids at liberty or in very large pastures, and a semi-feral herd.

McDonnell notes that during thunderstorms, most horses show no noticeable response to either thunder or lightning independent of the severity of the rain and the wind.

"We consistently observe that with thunder and lightning preceding a storm, horses just continue on as they would, doing whatever else they were doing before the weather change. But when the wind picks up and the rain picks up, horses may seek natural or artificial shelter. So, we conclude that it is not the electrical storm from which they are seeking shelter."

McDonnell also found that stabled horses didn’t exhibit any changes during thunderstorms. They just continued to munch their feed and continued their activities, oblivious of the thunderclaps and lightning flashes.

"It could be a hellacious storm, and still no change," she says.

When thunderstorms are accompanied by wind and rain, horses will seek the shelter of trees and natural changes in the terrain, says McDonnell. "For example, they’ll often go down to the creekbeds, which are typically lined with trees. They usually stand on the side of the creek. That makes sense in terms of having the wind and rain at their back. They often huddle in their social groups and become more tightly compacted, just as they would in a driving snowstorm or torrential rain that’s independent of thunder and lightning."

McDonnell notes that outside horses also seek refuge in man-made shelters--if nothing else is available.

"With our semi-feral herds, it is only after all the natural terrain spaces are taken that lower ranking individuals or groups get the shed. Here at the university, our indications of horse behavior concerning the three-sided run-in shed we provided is that it’s not the preferred shelter, but they will use it when the other spaces are occupied."

About the Author

Marcia King

Marcia King is an award-winning freelance writer based in Ohio who specializes in equine, canine, and feline veterinary topics. She's schooled in hunt seat, dressage, and Western pleasure.

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