Beavers

The 1804-1805 Lewis and Clark journals provide the first reliable biological documentations of beaver (Castor Canadensis) for the Missouri and Columbia River corridors between St. Louis and the Pacific Ocean.^[2]Through decades of intensive scientific research since the Lewis and Clark Expedition, the beaver has been studied extensively in a wide geographic range from tree to sea level and the subarctic to … Continue reading

Commercial Objective

A primary objective, among others, of the Lewis and Clark Expedition as envisioned by President Thomas Jefferson, dealt in the realm of economic nationalism. With commerce being the primary objective, Jefferson was especially interested in advancing US participation and expansion in the fur trade, the major economic enterprise of the day, and one of the principle forces that had generated competitive imperial rivalries for control of the North American fur trade dominated at the time by the British. Jefferson wanted detailed information as to how Americans could take over the fur trade by learning more about British trade practices and trading methods used with Missouri River tribes.

From the collective effort of the expedition emerged an impressive compilation of detailed information on beaver distribution, relative abundance, scarcity, beaver kills, beaver signs, dens, dams, food, observations, habitats, and trade items, in the Upper Missouri and Columbia River corridor regions. Prior to the middle of the nineteenth century, beaver exemplified the Upper Missouri country. When trappers and fur traders referred to the Upper Missouri as “beaver country,” they were actually admitting to a physical, biological, hydrological, and geographic reality that bonded mountain to plain, sky to water, and cottonwood-willow bottomlands to beaver. The Lewis and Clark Expedition would superbly document that the Upper Missouri basin provided for a dynamic biological landscape that was nurtured and sustained by the heartbeat of the main arterial stem of the Missouri and its interlacing network of perennial tributaries. The unfolding picture we visualize, thanks to Lewis’ observant eye and active pen, is one highly colored with enlightening biological happenings.

Beaver, which have historically been traced back to the Cenozoic Eocene Series, some 55 million years ago, are believed to have crossed the Bering Strait from Eurasia into North America. Before their near extirpation by trapping in North America, the beaver’s geographical home range extended from the arctic tundra to the deserts of northern Mexico, and from the Atlantic to the Pacific Ocean. One may assume with reasonable certainty that the beaver population in North America during pre-European times numbered in the millions, quite probably in the tens of millions. Some historians have speculated that beaver demographics ranged from 60 to 200 million, which seems impractical, especially when such estimates did not take into consideration the variability of suitable habitat present throughout their extensive range or fluctuating climatic changes.

Decades after the Lewis and Clark Expedition, 25 subspecies of beaver were identified by taxonomists in North America, with each subspecies having superficial morphological differences (size, shape, color) and geographical isolation at the time of discovery.^[3]Species—the kind of animal–usually is the smallest unit recognized in zoological field work, but specialists working closely with many individuals of the same species from different parts of the … Continue reading Of these subspecies, the Missouri River beaver, Castor canadensis missouriensis would have been the one observed and documented by the Lewis and Clark Expedition.^[4]Distinctions among the 25 subspecies of beavers are based primarily on slight morphological differences and geophysical isolation at the time of discovery. Today, modern taxonomic techniques use … Continue reading

First Beaver Trapped

The first beaver trapped on the Missouri, as reported in the journal of Patrick Gass, occurred on 22 July 1804, near present day Council Bluffs, Iowa. A total of 38 beaver were trapped and killed (shot) by expedition members between Camp Wood and Fort Mandan during 1804. George Drouillard, the leading expedition trapper, accounted for eighteen of the beaver taken.

The beaver trapped on 22 July was the first of many to be eaten by expedition members. Lewis gave the beaver high marks for its excellent flavor: “the men prefer the flesh of this animal, to that of any other which we have, or are able to procure at this moment. I eat very heartily of the beaver myself, and think it excellent; particularly the tale, and liver.”^[5]Gary E. Moulton, ed., The Journals of the Lewis and Clark Expedition, 13 vols. (Lincoln: University of Nebraska Press, 1983-2001), 4:48. Beaver meat is similar tasting to lean beef, but care must be … Continue reading One beaver, according to Lewis, provided enough meat for two men. The abundance of beaver in the Missouri Riv.er plains country would become acutely meaningful when, during the following year, members of the expedition looked back with hunger pangs from the limited game animals, including beaver, in the Bitterroot-Cascade mountain ranges, and the sterile plains of the Columbia Basin.

The Beaver Ecosystem

After departing from Fort Mandan, expedition members observed beaver to be numerous wherever bottomland cottonwood and willow were sufficiently abundant in providing an adequate food supply. “[B]ark is their only food,” writes Lewis on 16 April 1805, “and they appear to prefer that of the Cotton wood and willow; as we have never met with any other species of timber on the Missouri which had the appearance of being cut by them.”^[6]Moulton, Journals, 4:46. “[B]ark is their only food” needs clarification. Beaver are herbivores and eat a variety of woody and herbaceous species. Willows, cottonwood, mountain alder, and … Continue reading At a later 11 June 1805 date, Lewis, with an observant eye, was quick to note that the narrow-leaf cottonwood (Populus angustifolia—a new discovery to science) was the beaver’s preferred species of cottonwood, due to its having a deeper and softer bark than the other two species of cottonwood (Populus deltoids and Populus trichocarpa).

At the south end of present-day Townsend, Montana, we see Lewis’ observational competency being expressed in his 24 July 1805, journal entry. We gain the distinct impression that his sensitivity to natural systems harbors the vibrant stirrings of an ecological awareness. It is here where he classically describes how beavers serve as nature’s hydraulic engineers and as keystone animals in the shaping of stream ecosystems and surrounding landscapes.

[W]e saw many beaver and some otter today; the former dam up the small channels of the river between the islands and compell the river in these parts to make other channels; which as soon as it has effected that which was stoped by the beaver becomes dry and is filled up with mud sand gravel and drift wood. the beaver is then compelled to seek another spot for his habitation wher he again erects his dam. thus the river in many places among the clusters of islands is constantly changing the direction of such sluices as the beaver are capable of stoping or of 20 yds. in width. this anamal in that way I beleive to be very instrumental in adding to the number of islands with which we find the river crouded.^[7]Moulton, Journals, 4:422-23.

“[A]dding to the number of islands” is Lewis’ way of saying how beavers act as agents in promoting topographical succession, thereby paving the way for increasing plant and animal biodiversity through such expansion. Lewis was actually viewing–seen as a time-lapse video–the dynamic view of a species range expansion that would, through the years, appear something like a gigantic squid extending its tentacles as it slowly invades suitable adjoining habitat due to its own active movements. The sequence begins with beaver arriving, building a dam, creating a pond, digging canals, creating a lodge, thus creating a niche-filling habitat Small increases in stream flow spread water and nutrients beyond the stream banks to widen riparian zones and increase riparian vegetation, providing for fresh water meadows.

It has been well documented that during their many eons of existence, beavers have modified almost every watershed in the North American continent. Flooding is the key eco-system process creating suitable sites for seed dispersal and seeding establishment, and controlling vegetation succession. Beaver made an especially dramatic contribution to northern landscapes by recolonizing ice-gouged valleys after glacial retreats. On numerous occasions, geologists and ecologists have found that the first layer of organic matter lying above glacial deposits was an ancient beaver pond with twigs and stems, showing markings of beaver teeth.

The journals document that the Three Forks of the Missouri headwaters, the Jefferson River, and its numerous tributaries functioned as a loadstone of exceptionally high-quality beaver habitat. “[A]ll the water courses in this quarter emence number of Beaver & orter maney thousand enhabit the river & Creeks near the 3 forks,” writes Clark who is impressed with what he has observed on 25 July 1805.^[8]Moulton, Journals, 4:428.

Based on the large numbers of beaver, otter, and other game observed in the Three Forks area, Lewis recommended the Three Forks as the location site of a trading post. In year 1810, a party under Colonel Pierre Menard, representative of trader Manuel Lisa and the St. Louis Missouri Fur Company, was to establish a post at the Three Forks, but Blackfeet hostility forced its abandonment that same year.^[9]Ferris, Historic Places, 21.

On 30 July 1805, an exhausted Lewis waded through an extensive maze of scattered beaver ponds, dams, and lodges while ascending the Jefferson River.^[10]The upper Jefferson watershed area encompasses approximately 734 square miles in Jefferson and Madison Counties. Much of the river is braided and has a natural tendency to migrate within the flood … Continue reading As he waded through a series of ponds with water up to his waist, he had no knowledge that with each step he was walking over a deep layer of anaerobic muck consisting of decomposed organic matter (wood and bark) provided by beavers. The bacterial and biochemical decomposition of the organic material produces nitrogen and phosphorus and other pond nutrients which are made available to a wide variety of single-celled organisms, thereby increasing a stream’s fertility and capacity at the lowest food web level to support everything from microbes to mammals. Beaver serve as a keystone agent in strengthening the food web at every level and increasing the fertility of entire river systems.

A Wealth of Information

Lewis’ primary objective for examining the Marias River was to see if the Marias drained northern reaches, and if so, would give further territorial claims to the United States under the Louisiana Purchase. Documentations of beaver activities, although important, would not be a high priority. This was evident from only one journal report (20 July 1806) on beaver. “[T]here is much appearance of beaver on this river, but not any of otter.”^[11]Moulton, Journals, 8:119. For the history of beaver trapping in the Marias River region, see on this site, The Golden Triangle. Lewis was hoping that the Marias would provide Americans with access to the Saskatchewan River country and its fur trade. Lewis’ encounter with eight Piegan Blackfeet on 26 July 1086 provided information that the tribe traded with whites on the Saskatchewan, trading furs for guns, ammunition, liquor, and blankets.

Upon returning to the Missouri after their hastened departure from the Marias, and joining the Ordway-Gass detachments, Lewis dispatched Colter and Collins on 29 July 1806 to hunt. Both hunters rejoined Lewis on 12 August 1806 and reported killing six buffalo, thirteen deer, five elk, and 31 beaver. The assumption can be made that that the beaver skins would be taken back to St. Louis to be sold or traded.

[T]he expedition members involved in trapping beaver would unknowingly provide a wealth of biological information in reference to beaver geographic distribution and relative abundance. Neither President Jefferson nor Lewis, it appears, had formulated any plans to use beaver trapping as a tool for collecting biological data.

Thomas Jefferson was particularly interested in advancing the nation’s participation in the fur trade, which was a major economic enterprise at the time, and one of the principal forces that had generated the longtime imperial rivalries for control of North America. Therefore, it was imperative that Lewis and Clark collect as much information on beaver as time and circumstances permitted. The captains collected a wealth of information on the distribution and abundance of beaver, as well as additional beaver activities of interest.