When people imagine what could bring a major stock market to a halt, they picture a crash, a computer virus, or some grand act of sabotage. They don't usually picture a squirrel. But one of the more memorable outages in Nasdaq's history started with exactly that.
The short answer: in 1987, a squirrel caused a loss of power to Nasdaq's automated trading computer. The outage lasted about 90 minutes and affected some twenty million trades. And that wasn't a one-time fluke. Squirrels have brought down the Nasdaq twice.
How One Squirrel Can Cut the Power
Squirrels are natural climbers, and power poles and cables are just more branches to them. They scramble up poles, run along lines, and climb onto transformers, sometimes looking for food or a spot to stash acorns.
The trouble starts when a squirrel touches two parts of the equipment at different voltages at the same time. Its body becomes a bridge for the electricity. That creates a short circuit that can shut down equipment, and sadly the squirrel usually doesn't survive.
Chewing is the other problem. Like all rodents, squirrels have front teeth that keep growing throughout their lives. They gnaw on branches and, now and then, on electrical cables, chewing right through the insulation.
It Happens More Than You'd Think
The Nasdaq story sounds like a one-in-a-million event, but squirrel outages are surprisingly common. Between Memorial Day and the end of August 2013, at least 50 power outages caused by squirrels were recorded in 24 states.
In 2015, John C. Inglis, a former deputy director of the National Security Agency, said that the number one threat experienced to date by the U.S. electrical grid was squirrels. He meant it seriously. Some commentators have pointed out that real cyberattacks on the grid are much rarer than squirrel trouble.
The Squirrel Index
The problem is taken seriously enough that the American Public Power Association created a tracker called the Squirrel Index. It measures squirrel-caused disruptions per 1,000 customers over time.
The data shows two busy seasons for squirrel trouble, May to June and October to November. Utilities try to fight back with plastic guards and rotating sleeves on equipment, but squirrels are clever. They can get around guards, gnaw through insulation, and squeeze into substations through small openings.
Not Just Power Lines
Squirrels have caused headaches in some unexpected places. At Malmstrom Air Force Base in Montana, ground squirrels have tunneled under fences near underground nuclear missile sites, slipping past motion detectors and setting off thousands of false alarms each year.
Germany has its own famous case. In 2005, a squirrel knocked out power to the whole area south of the River Elster for an hour. And one security researcher joked that squirrel-type outages have happened in all 50 states, including Hawaii, where chickens did the job instead.
The Little Rodent With a Big Reputation
It's easy to laugh at the image of a squirrel taking on a stock market's computers and winning. But the story shows how even the most high-tech systems still depend on ordinary wires strung along poles and running into buildings.
So the next time you watch a squirrel darting along a power line in your backyard, give it a little respect. It belongs to a species with a surprising track record of making headlines.
