Castoroides was a genus of enormous beavers that used to inhabit most of the USA and Canada. Casteroides were similar to modern day beavers, but much larger in size, reaching six to eight ft long, had bigger hind feet and had longer tails. Like still surviving beavers, Casteroides were semi-aquatic, but Casteroides didn’t build dams, but built surprisingly long and wide tunnels on sandy banks and islands. Like many other megafauna, casteroides is thought to have went extinct during the end of the Pleistocene, about 10,000 years ago, even though sightings still occasionally occur. Reports of casteroides in the modern day occur in the Laurentian Canadian shield in Manitoba, Central Ontario, and western Quebec as well as northern Michigan and Minnesota. There are also rarer sightings elsewhere, like in the Adirondacks in New Hampshire, Nova Scotia, Yukon and even Great Salt Lake in Utah. Giant beavers and folklore of surviving casteroides are common in First Nations folklore in Ontario, Minnesota, Quebec and Michigan like the Cree Wisagatcak or the Ojibwe kitchi-amik.
Sightings started becoming more common in the 1920’s, which coincided with increasing human activity in the area. Canadian cryptozoologist John Warms interviewed many Cree elders from northern Manitoba and his work became some of the best sources for surviving casteroides reports. In the mid 90’s a Cree man was driving his snowmobile around South Indian Lake when he spotted a large dark animal sitting on the ice. He initially was wondering how a rock got there and how he didn’t notice it earlier, until he got closer, when he saw that it was a massive beaver. He watched as it took several steps towards the water and swam off.
In 2006, there was another sighting, also from South Indian Lake. The witness was goose hunting on the wooded shore of the lake when he was surprised to see a massive beaver ahead of him. Due to his gun not being strong enough to take out the animal, he didn’t attempt to kill it, and instead backed away cautiously as it slid into the water. In the late 2000’s, two women from Nelson House were cranberry picking on a slope beside a small lake when they saw two bear-sized beavers waddle into the water. Around the same time, a man claimed to have seen two giant beavers jump into the water in Apegano Lake, seemingly startled by the noise of his helicopter landing. At an unspecified date, a Cree man named Angus, and his friend, from Pukatawagan were checking their traps when they realized their snare and anchors were gone, which was strange as it easily could hold down a beaver. Later, they spotted one of their anchors, a log, down the Churchill river which was held under by something. When they hauled out the anchor, an enormous dead beaver that must have weighed hundreds of pounds was caught on it. Presumably it was strong enough to escape their snares, but drowned due to the heavy anchor attached to it. It was too heavy to bring it back home, so they skinned it instead. The pelt wasn’t kept by them, but it was estimated by Angus to have been 11 ft adding length and width together.