“Nice Beaver!”

Childhood stories probably influence how we see familiar creatures. If someone talks about beavers, I think about Narnian beavers. In the delightful C. S Lewis book The Lion, The Witch and The Wardrobe, the good beavers have cozy homes, make tea and are very much on the side of the Pevensie children who are on the run from the malevolent White Witch, who has turned the world into ‘always winter and never Christmas’. Incidentally, I consider this the most concise description of the Ice Age I can think of! Not all cultures had friendly beavers in their legends, however, and not all beavers were the little chaps we think of today.

There’s a legend that was told by the Pocumtuck tribe of Native Americans, of Massachusetts, USA. It’s a curious tale, and one that raises questions about what may have been observed by the earliest people as the great ice sheets of the last Ice Age receded. The Pocumtuck would tell you how the hills near Deerfield, MA were created from the carcass of a giant beaver. This beaver lived in a huge lake near the Sugarloaf Mountains, MA, and it was not a friendly sort. It would raise itself from the lake and drag people back to its dam where it would devour them. The ancient tribes lived in terror of this huge monstrous beaver, and prayed that there would be some kind nature deity who could protect humans against such a powerful enemy. A heavenly giant hunter heard the plea and decided to intervene. He battled with the giant beaver until it was finally killed, and as it sank into the lake it became stone, then heaved suddenly upwards to the skies, becoming a mountain range.

Now, initially this looks like a good story for round a camp-fire. Until, that is, you consider the kinds of animals they had in that region back during the Pleistocene. They had real giant beavers.  The first ever fossils were found in a peaty swamp near Nashport in Ohio, back in the 1830s, and were named Castoroides ohioensis – the Ohio beaver – by the geologist J.W Foster in 1838.  Since then, numerous fossils have been found across North America, from New England to Nebraska. But this was an all-American beaver as it has never been found outside of North America, for all its widespread distribution.

The skeleton of the Giant Beaver (Castoroides ohioensis) on display at the Field Museum Chicago. (Image by Steven G. Johnson from here)

We’ve a pretty good idea about its appearance – especially as there’s an almost complete skeleton in the Science Museum of Minnesota. Based on fossils found, C. ohioensis grew to about 2m in length (longer than the average human). Estimates have put this enormous beaver weighing about the same as a black bear (around 120 kg).  There have been mutterings in palaeontological circles that this beaver could reach the size of a black bear, and some fossils suggest they did grow larger, but it’s unlikely they were bear sized. Not quite the size of a mountain, granted, but still a lot bigger than the modern Castor canadensis, which weighs in at a comparatively measly 32kg! Needless to say, Castoroides was not a direct ancestor of our furry river pals today, more of a cousin a few times removed.

One model of the Giant Beaver. (Image via Ross Barnett)

The gnawing teeth on extant beavers are kind of goofy and slightly endearing, but may have been a little less so on its giant relative. Think of C. ohioensis with huge convex incisors extending about 15cm or more beyond the gums! Those teeth were considerably different from modern beaver species too; extant species have rounded surfaces on their incisors, but the Pleistocene was a harsh and difficult time, and even a playful water creature needed incisors that could handle the most challenging conditions – the teeth were ridged to act like girders, to protect the animals phenomenal gnawing capacity. Yet it’s been hypothesised a couple of years ago that Castoroides ate mostly pond plants. Macrofossil and pollen assemblages found in context with a wonderful find of a Castoroides skull in Erb, Wisconsin, provided a near-perfect palaeoenvironmental study on the Younger Dryas landscape (12,500yrs ago) of North America. The plant material summoned a dramatically accurate image of the post-Ice Age environment of Castoroides. It was a cold, damp one, with various species of Carex (sedges) and Najas flexilis (naiad pond weeds). Nearby were trunks of ancient Populus with telltale gnaw marks. The palaeoecologist who carried out the study, Dr Catherine Yansa, compared C. ohioensis to little hippos, munching on aquatic plants.

There are numerous excellent radiocarbon dates, gleaned from robust dental collagen which suggests the Giant Beaver survived the ice, and continued well into the Younger Dryas, a climatic ‘cold snap’, or stadial, which started around 13,000 years ago, as the glaciers receded. It was possibly caused by a large chunk of glacier breaking off in the Great Lakes region (the Laurentide Ice Sheet), cooling air and water currents and thereby altering them. Of course, palaeoenvironmentalism would be nothing without alternative theories, and one of the newer ones is that the Dryas was caused by a cometary impact. It’s been a compelling argument, and I’d be inclined to think there may be parts of the hypothesis well worth consideration.

Graph illustrating the dip in temperature about 13,000-10,000years ago. The present day is on the left side of the graph, and you go further back in time as you look right. Temperature estimates come from Oxygen isotope measurements in tiny oceanic microfossils. (Image from Wiki Commons)

It cannot be denied that the end of the Ice Age brought massive changes, environmentally and climatically. As the climate warmed up the entire ecosystem started to change. There’s a group of fungi, Sporormiella, which I might have mentioned before with poor Archaeoindris. It’s a fungus which breaks down organic waste material, and was plentiful in megafaunal dung. Without it, the vegetation cover of environments will change. The lack of this fungus is often used as a proxy for megafaunal extinctions during the end of the Pleistocene, and certainly, this has been the case in the USA.  It’s likely that climate change was working strongly against the Giant Beaver, who was supremely equipped for the cold.

The Giant Beaver was a giant. (Image by Jan Freedman)

One of the reasons I am madly in love with palaeoecology is that you can ‘see’ in your minds eye  a whole prehistoric landscape come back to life as the pollen chart builds. Sometimes, when I have been counting pollen, and know what  vegetation is there, I pause and imagine what it would smell like, what birds would sing there, what animals would rustle through the grasses and trees. So, come with me for a moment back to the last days of the Giant Beaver in the North America of maybe 11,000 years ago.

Where the enormous stretch of glaciers receded, wet swamps and marshes fill the hollows left by the retreating ice sheets, fed by the glacial melt-waters. There is a smell of marsh in the air, and it is bitingly cold, so you can see your breath when you walk from the dense clusters of colonising trees towards the sedgy lakes. These wetlands are pretty good habitation spots for beavers to make dams.

But you’ll hear other noises and rustles which are strangely familiar in their footfall; human hunters. The newly ice-free landscape witnessed increasing numbers of humans wandering the forests and wetlands looking for food, armed with the elegant Clovis point lithics, from which we take their identifying name. Castoroides ohioensis was about to come into direct and deadly contact with the Clovis culture, the hardy hunter-gatherers of North America – and those who came afterwards, who refined hunting with the slender and utterly deadly Folsom lithic weapons.

Beautifully intricate Clovis points from Rummells-Maske Cache site, Iowa. (Image by Bill Wittaker, from here)

I’m not detracting from human tenacity to survive the worst of environments, but as an archaeologist I am fascinated (but in truth personally repelled) by how humans elevate hunting into something beyond a function for food. Predators of the animal kingdom consume what they need, yet humanity hunts as a social act, replete with status and ego, especially within hunter gatherer societies and tethered mobility groups. It’s understandable to hunt the Giant Beaver for a dense, water-resistant pelt in a bitter cold climate, but it’s pretty likely that it took more than the odd successful trapper to push the species onto the endangered lists of the Pleistocene.

The overlap of Castoroides ohioensis and humans is relatively brief, and it’s uncertain if hunting was 100% responsible for their entire extermination – environment and climate changes had probably already decreased the populations of the great creature.  It’s most likely that the last of the Giant Beavers of North America were pushed into extinction by humans who had no idea they were destroying the last of a line.  Castoroides was left to fireside stories, and the dreams of wide- eyed children, who would always see them as the size of mountains and with the ferocity of lions.

Written by Rena Maguire (@JustRena)

A link to one of the best sight gags ever, from the Naked Gun (source of this article’s title)

Further Reading:

More about the research from Dr C Yansa and the Erb Site here.

More information about the Clovis culture here.

Abbott, K. (1907), ‘Old paths and legends of the New England Borders’. Knickerbocker Press. [Book]

Boulanger, M. T, et al. (2015), ‘AMS Radiocarbon Dates for Pleistocene Fauna from the American Northeast’. Radiocarbon. 57 (1). pp.1-4. [Full article]

Boulanger, M. T, & Lyman, R. L. (2014), ‘Northeastern North American Pleistocene megafauna chronologically overlapped minimally with Paleoindians’, Quaternary Science Reviews.  85. pp.35-46. [Full article]

Buchanan, B, O’Brien, M. J, and Collard, M. (2014), ‘Continent-wide or region-specific? A geometric morphometrics-based assessment of variation in Clovis point shape’. Archaeological and Anthropological Sciences. 6. pp.145-162. [Full article]

Engels, W. L. (1931). ‘Two new records of the Pleistocene beaver, Castoroides ohioensis’. American Midland Naturalist. 12(12). pp.529-532. [Full article]

Grootes, P. M., et al, (1993), ‘ Comparison of oxygen isotope records from the GISP2 and GRIP Greenland ice core’. Nature. 366. pp.52–554. [Abstract only]

Kurten, B, & Anderson, E. (1980), Pleistocene mammals of North America. New York: Columbia University Press. [Book]

Martin, R. A. (1969), ‘Taxonomy of the giant Pleistocene beaver Castoroides from Florida’, Journal of Paleontology. pp.1033-1041. [Full article]

McDonald, H. G, & Glotzhober, R. C. (2008), ‘New radiocarbon dates for the giant beaver, Castoroides ohioensis (Rodentia, Castoridae), from Ohio and its extinction’. Unlocking The Unknown: Papers Honoring Dr. Richard J. Zakrzewski. Fort Hays Studies, Special Issue, 2. pp.51-59.

Melott, A. L., Thomas, B. C., Dreschhoff G.,  & Johnson, C. K., (2010), ‘Cometary airbursts and atmospheric chemistry: Tunguska and a candidate Younger Dryas event’ Geology.  38. pp.355–358. [Full article]

Miller, R. F., Harington, C. R., & Welsh, R. (2000), ‘ A giant beaver (Castoroides ohioensis Foster) fossil from New Brunswick, Canada. Atlantic Geology, 36(1). [Full text]

Muller-Schwartz, D. (2011). Living Beavers, Now and Then: The Species, Including Fossils. New York: Cornell University Press. [Book]

Redmond, B. G & Tankersley, K. (2011). ‘Species Response to the Theorized Clovis Comet Impact at Sheriden Cave, Ohio’. Current Research in the Pleistocene. 28.

Surovell, T. A., et al., (2009), ‘An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis’ Proceedings of the National Academy of Sciences of the United States of America. 106. pp.18155–18158. [Abstract only]