WEBVTT - How Did the Bear-Sized Beaver, Castoroides, Work? 0:00:01.920 --> 0:00:06.960 Welcome to Brainstuff, a production of iHeart Radio, Hey brain Stuff, 0:00:07.000 --> 0:00:12.680 Lauren Bobo bomb Here. Mammoths, mastodons, and sabretooth cats weren't 0:00:12.720 --> 0:00:16.959 the only giants roaming ancient America. The Palistocene was a 0:00:17.000 --> 0:00:20.520 global epoch that kicked off two point six million years ago. 0:00:21.079 --> 0:00:23.880 It lasted right up until Earth's most recent ice age, 0:00:24.000 --> 0:00:28.240 ended about eleven thousand, seven hundred years before the present day. 0:00:29.120 --> 0:00:32.240 When you live in a cold environment, being big has 0:00:32.240 --> 0:00:36.440 its advantages. Large animals tend to conserve body heat more 0:00:36.479 --> 0:00:39.199 easily than smaller ones, and this is one of the 0:00:39.240 --> 0:00:42.839 major reasons why colossal mammals were so widespread during the 0:00:42.880 --> 0:00:48.640 frigid Pleistocene. Castroides was very much a product of its time. 0:00:49.479 --> 0:00:53.760 The largest rodent in Pleistocene North America, this very big 0:00:53.800 --> 0:00:56.800 beaver grew to more than seven ft long from tail 0:00:56.840 --> 0:00:59.520 to snout that's over two meters, and could have weighed 0:00:59.520 --> 0:01:01.440 as much as two hundred and twenty pounds or a 0:01:01.520 --> 0:01:07.040 hundred kilos or more, rivaling the American black bear in size. 0:01:07.440 --> 0:01:12.400 Casteroids utterly dwarfed the beavers that live today. Modern Eurasian 0:01:12.400 --> 0:01:15.400 and American beaver species clock in it just around three 0:01:15.440 --> 0:01:18.160 ft long, a bit less than a meter, and weigh 0:01:18.240 --> 0:01:21.440 somewhere between twenty nine and seventy seven pounds that's about 0:01:21.480 --> 0:01:26.640 thirteen to thirty five kilos. Proportionately, Casteroids had a narrower 0:01:26.680 --> 0:01:30.200 tail and shorter legs, albeit with bigger hind feet than 0:01:30.280 --> 0:01:34.120 it's extant relatives. We also know that it didn't eat 0:01:34.160 --> 0:01:37.920 the same foods. Woody plants are a crucial part of 0:01:38.000 --> 0:01:42.600 every living beaver's diet. The critters used chisel like incisors 0:01:42.640 --> 0:01:45.600 that's their front teeth to gnaw through bark and take 0:01:45.640 --> 0:01:50.240 down trees. But even though casteroids incisors grew to be 0:01:50.240 --> 0:01:54.280 a whopping six inches or fifteen centimeters long, the teeth 0:01:54.360 --> 0:01:58.920 had duller edges. By comparison, dental differences would have made 0:01:58.920 --> 0:02:01.800 it a lot harder for casteroids to eat tree bark, 0:02:02.440 --> 0:02:05.360 and indeed, it looks like this was not really on 0:02:05.400 --> 0:02:10.960 their menu. Using isotropic signatures in casteroid's teeth from Ohio 0:02:11.080 --> 0:02:14.760 and the yukon En study found that the giant beaver 0:02:15.080 --> 0:02:19.239 mostly ate softer aquatic plants. The findings say a lot 0:02:19.280 --> 0:02:22.520 about the rodents ecological niche and why it might have 0:02:22.600 --> 0:02:28.280 died out For starters casteroids probably didn't build dams, not 0:02:28.400 --> 0:02:32.120 that there's anything unusual about that. The earliest known beavers 0:02:32.160 --> 0:02:36.079 appeared during the Eocene epoch, which lasted between about fifty 0:02:36.120 --> 0:02:40.000 six and thirty four million years ago. New evidence suggests 0:02:40.040 --> 0:02:43.600 that the wood harvesting specialists came along much later, perhaps 0:02:43.600 --> 0:02:47.320 around twenty million years ago. In all likelihood, these bark 0:02:47.400 --> 0:02:50.400 fanciers used wood as a food source before any of 0:02:50.400 --> 0:02:56.079 them started constructing dams. Since casteroids fed on aquatic plants, 0:02:56.400 --> 0:03:00.360 its survival would have depended on wetland habitats. The animal 0:03:00.400 --> 0:03:04.520 was highly successful for a time. Casteroids fossils representing at 0:03:04.600 --> 0:03:08.000 least two distinct species have been documented in the Great Plains, 0:03:08.120 --> 0:03:15.520 the Great Lakes, the American South Alaska, and numerous Canadian provinces. Unfortunately, 0:03:15.560 --> 0:03:19.120 for the mega sized beaver, North America became warmer and 0:03:19.320 --> 0:03:23.040 drier after the Last Ice Age ended, wetlands grew scarcer 0:03:23.120 --> 0:03:27.360 as a result. Today's beavers used their logging skills to 0:03:27.480 --> 0:03:29.760 reshape the land around them so that it meets their 0:03:29.760 --> 0:03:33.400 own needs. With some well placed wood in the nearest stream, 0:03:33.440 --> 0:03:38.480 a determined beaver can engineer brandon new ponds. Yet, if 0:03:38.520 --> 0:03:42.160 casteroids didn't harvest wood or build dams. It couldn't have 0:03:42.200 --> 0:03:46.760 followed suit. So theoretically, the decline in natural wetlands left 0:03:46.800 --> 0:03:50.360 the giant beaver more susceptible to extinction. The last of 0:03:50.400 --> 0:03:58.880 these creatures perished around ten thousand years ago. Today's episode 0:03:58.880 --> 0:04:01.360 was written by Mark man Scene and produced by Tyler Clang. 0:04:01.760 --> 0:04:03.880 For more and listen lots of other big topics, visit 0:04:03.920 --> 0:04:06.640 how stuff works dot com. Brain Stuff is production of 0:04:06.680 --> 0:04:09.040 I Heart Radio. For more podcasts to my heart Radio, 0:04:09.200 --> 0:04:11.800 visit the i heart Radio app, Apple Podcasts, or wherever 0:04:11.840 --> 0:04:13.160 you listen to your favorite shows.