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 leaves, grass, moss, bark, and hair. Den sites include burrows dug by woodchucks ("Marmota monax"), red foxes ("Vulpes vulpes"), nutria ("Myocastor coypus"), or beaver and muskrat lodges. North American river otters also may use hollow trees or logs, undercut banks, rock formations, backwater sloughs, and flood debris. The use of den and resting sites is chiefly opportunistic, although locations that provide protection and seclusion are preferred. Aquatic life ties North American river otters almost exclusively to permanent watersheds. The North American river otters favor bog lakes with banked shores containing semiaquatic mammal burrows and lakes with beaver lodges. The North