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 range from . Large male North American river otters can exceed a weight of . It differs from the European otter by its longer neck, narrower visage, the smaller space between the ears and its shorter tail. A broad muzzle is found on the North American river otter's flat head, and the ears are round and inconspicuous. The rhinarium is bare, with an obtuse, triangular projection. Eyes of the animal are small and placed anteriorly. A short, broad rostrum for exhaling and a long, broad cranium define the relatively flat skull. The North American river otter's nostrils and ears close