If you picture squirrels as quiet backyard residents, historical accounts from 19th-century America sound like fiction. In the 1800s, newspapers, farmers, and explorers frequently documented jaw-dropping spectacles involving squirrel migrations. Millions of gray squirrels marched across states, swam across massive rivers like the Ohio, Mississippi, and Niagara, and took weeks to pass through a single town.
Even legendary naturalist John James Audubon was baffled by the scale of these events. Because of this, he mistakenly believed migrating gray squirrels were an entirely different species.
How Many Squirrel Migrations Have Been Recorded?
Pinning down an exact number is impossible because 19th-century local newspapers recorded dozens of localized events that went unarchived on a national scale. However, historians note that these mass movements occurred periodically throughout the 18th and 19th centuries.
Notable major recorded migrations include:
- 1807: Early travelers documented wide movements, including brief notes from the era.
- 1819 & 1822: Massive waves swept through the Midwest, because the 1822 “invasion” caused severe agricultural damage in places like Indianapolis.
- 1845 & 1857: Large-scale movements occurred across Ohio, Indiana, and Texas, while historians heavily study the 1857 Texas migration.
- 1866: A famous migration crossed the Niagara River.
- 1968: Scientists tracked a massive migration across the Eastern United States.
- 1998: A notable regional squirrel surge occurred in Arkansas and neighboring states, meaning wildlife biologists consider this the last true localized migration event of this scale.
Small vs. Large Squirrel Migrations: Do They Vary?
These squirrel migrations exist on a vast spectrum, ranging from localized neighborhood scuttles to continental spectacles:
- Small Emigrations: These happen more frequently every few years, because a specific forest experiences a food crunch or sudden population spike. This causes thousands of squirrels to push outward into surrounding towns looking for space.
- Large Emigrations: These are the legendary events of the 1800s and 1968. Spanning multiple states, these mega-events involved millions of animals. Furthermore, squirrels marched in a single direction, plunged into lakes and rivers where thousands drowned, and pressed forward until exhaustion claimed them.
What Actually Causes Squirrel Migrations?
For centuries, old-timers and scientists argued over the cause. Some blamed fleas, others blamed red squirrels, and many assumed the animals were starving.
However, University of Maryland zoologist Dr. Vagn Flyger studied the 1968 migration in real-time and unlocked the truth:
- The Boom-and-Bust Cycle: These migrations result from too much success. In the year prior, a region experiences a bumper crop of nuts like acorns. Well-fed squirrels breed successfully, creating an unprecedented population boom.
- The Sudden Crash: The very next year, nut production fails entirely. Consequently, the forest can no longer feed the massive population.
- The Urge to Spread Out: Driven by overcrowding, the squirrels hit a breaking point. They did not move because they were starving nomads—many were quite fat when they started. Instead, they moved simply because too many squirrels crowded one area, forcing them to find empty forest habitat.
Will We Ever See These Migrations Again?
We will likely never see squirrel migrations on the biblical scale of the 1800s. Human development, roads, and fragmented forests have altered modern landscapes. Without vast, unbroken seas of nut-bearing trees, billions of squirrels will never march across the American landscape again. Today, these events are mostly reduced to small-scale dispersals or young squirrels looking for new territory.