Bayou Petit Caillou, whose French name means “little pebble,” is part of the remnant Lafourche Delta created when the Mississippi River flowed through this area 800 to 2,500 years ago. At that time, Bayou Lafourche, Bayou Terrebonne, and Bayou Petit Caillou were distributaries of the Mississippi, and bald cypress swamps and freshwater marshes flourished here, sustained by spring floods that overtopped natural levees built up by river sediment. After the Mississippi shifted to a more eastern route to the Gulf of Mexico, Bayou Petit Caillou and nearby wetlands remained stable because Bayou Lafourche still connected the area to the river and supplied water and sediment. In 1905, a man-made levee at Donaldsonville severed Bayou Lafourche from the Mississippi to stop seasonal flooding, interrupting the natural delta cycle and allowing salt water to push north into the coastal bayous, which gradually became tidal arms of the Gulf. As fresh flow declined, wetlands weakened and disappeared, bald cypress and freshwater marsh gave way to brackish salt marsh, trees died, and salt-tolerant grasses spread. Canals dug for drainage, logging, oil and gas drilling, navigation, and transport further disrupted natural water flow and carried salt water deeper into freshwater marshes, accelerating change in this fragile landscape. Although these wetlands remain threatened, nature has adapted again, and Bayou Petit Caillou and other small bayous in Terrebonne Parish now support salt-tolerant plants and animals and provide habitat for birds including least bittern, clapper rail, roseate spoonbills, herons, egrets, ibis, and white and brown pelicans. The area is also known for birding, fresh seafood, boating, offshore oil and gas related industry, and coastal research and education.