Beavers and Carolina Bays

One of the intriguing aspects of the Carolina Bays is that they frequently overlap one another. Prouty reasoned that bays impinging on other bays were the result of multiple, serial, impacts with the last in the sequence retaining the common Carolina Bay form. A problem with this method of creating Carolina Bays is that the rim height of ostensibly later formed bays is generally about the same height as the rim of those bays that were impinged upon. It is difficult to find a convincing way for multiple impacts to produce a bay within a bay with a rim height that matches the bay that contains it. The gloss over to this hard to account for property is that the bays are so shallow that virtually any rim height would be enough to bring later formed bays up to about the level of the earlier formed bays. This is a weak explanation and also points to another problem with a direct impact model—the shallowness of the features.

If we examine how beavers go about constructing their semi-aquatic environment however, the relationship of bays to one another becomes less of a problem to explain. In pursuit of fresh trees for food and construction, beavers build canals as well as multiple dams along these water paths to function as locks—they do not like to drag logs for long distances. Also, as the family or colony expands in the number of reproducing couples, new ponds, often nearby, are produced.

Below are a few examples of how beavers alter their immediate environment. These images are from a wonderful book published in 1914, The Romance of the Beaver, by A. Radclyffe Dugmore. One can see by comparing the aerial photos and Prouty’s drawing of clustered Carolina Bays how direct the relationship seems between beaver pond arrangement and Carolina Bay occurrence. It is also obvious that the beaver ponds would not all have the same surface area to depth relationship and so would not flash into steam simultaneously. This would allow a sequence of bay formation as Prouty proposed in the numbered drawing below.

The streams shown in dotted line were dammed at A and B; as the water rose it formed two other outlets, a and D. At these points additional dams were put. Later, to reinforce the principal structure, supporting or subsidiary dams, E, F, G and H, were built. On the island, I, formed by the rising water was the first lodge. On the west side arc the roads, J, to the birch and maple trees. To the north-east is a canal, E, built in order that the beavers might have access to the groves of aspens, which was situated on rising ground and necessitated making the canal with three dams to hold the water at the different levels. Toward the end of the east wing of the canal is B straight line, L, indicating the small aqueduct or ditch cut by the beavers in order that water might be diverted from the streamlet to ensure an ample supply for the canal. Other small canals, M, arc for the purpose of making short cuts when transporting food supplies. The upper pond, N, was made by the second pair of beavers, who had been driven from their own home by fire. The dam forming this pond is O, with subsidiaries P, Q. The lodge, R, on a point of land which has been formed into an island by cutting a ditch. The second lodge was built by one of the young from the first lodge.

A.R. Dugmore, 1914

Beavers and Bays