Thousand Islands – Frontenac Arch is one of four ecoregions of the Mixedwood Plains. The Thousand Islands in the Saint Lawrence River have a distinctive flora and fauna and are a part of the biological corridor. The bedrock is mostly gneiss, granite and marble, more than a billion years old. The Frontenac terrain is the youngest of the Ontario portions of the arch, dated at 1.2 billion years old. These rocks were once part of a large mountain chain of the ancient supercontinent of Rodinia. There is also a meteor crater near Holleford, where the shield meets the limestone plains of southeastern Ontario. The area
North American river otter analyzed. However, many other studies did not report any findings of North American beaver remains in the scat sampled. The North American river otter has few natural predators when in water. Aquatic predators include the American alligator ("Alligator mississippiensis"), American crocodile ("Crocodylus acutus"), and killer whale ("Orcinus orca"), none of which commonly coexist with the North American river otter and thus rarely pose a threat. On land or ice, the North American river otter is considerably more vulnerable. Terrestrial predators include the bobcat ("Lynx rufus"), mountain lion ("Felis concolor"), coyote ("Canis latrans"), domestic dog ("Canis lupus familiaris"), wolf ("Canis lupus"),