Wild ponies take their annual swim to Chincoteague

Photo: Mark Wilson/Getty Images

Sea ponies

A herd of wild Chincoteague horses endure heavy rain while swimming across the Assateague Channel on July 24.

Every year, the famous ponies are rounded up on Assateague Island by Salt Water Cowboys and herded to Chincoteague, Va., where they are auctioned off. Although the practice has roots dating back to the 17th century, the official "Pony Penning" event first took place in 1925 as a fundraiser for the local fire company.

The exact origin of the wild Chincoteague horses is unknown, but it's largely believed the feral breed developed after 17th century colonists released a herd of horses on the island to avoid livestock taxes and laws on the mainland.

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Catie Leary is a photo editor at Mother Nature Network. Follow her on Twitter and Google+.