Wildlife Services in Mississippi conducted a survey to determine whether Clemson Beaver Pond Levelers they had installed were meeting landowners' objectives. Wildlife Services is a program in the U.S. Department of Agriculture Animal and Plant Health Inspection Service. The survey considered:

• Management objectives
• The length of time since the leveler was installed
• Watershed characteristics
• Physical attributes of the stream and the beaver dam
• Beaver activity

Twenty of the forty Clemson Beaver Pond Levelers evaluated were operating and regarded as successful by the landowner. The landowners' original management objectives correlated with the operational status of the device and the owner's satisfaction with it. Devices installed to manage wetlands (primarily waterfowl habitat) generally were considered successful, while devices installed to provide perpetual waterflow were deemed less successful. At least six of the unsuccessful devices had been removed by the landowner, usually because the owner wanted more waterflow.

Most factors considered in the survey were not repeated consistently among sites, confounding comparisons and making the results more like a series of case studies than a replicated experiment. However, general patterns or trends could be deduced. Successful devices tended to have been installed more recently (21.5 months) than unsuccessful devices (32 months). A few levelers had been installed within the past 6 months. All of those were considered successful. But several devices that had been installed for longer than 48 months were still in good condition.

There was no apparent relationship between the likelihood that a device would be successful and the characteristics of the beaver dam. Watershed characteristics and stream attributes also were unrelated to owner satisfaction, although these attributes often were tied to management objectives. For example, both successful and unsuccessful devices often were located on small drainages with intermittent flow, but the successful and unsuccessful devices were not necessarily installed for the same reason. Devices installed for wildlife management objectives invariably were placed on small drainages with intermittent flow.

Maintenance had been performed on 70 percent of the 20 operating Clemson Beaver Pond Levelers installed by Wildlife Services. Usually, maintenance involved adjusting the riser to manipulate water levels. Owners had adjusted risers on 11 of the 20 successful devices, while only four attempts were made to adjust risers on the 20 unsuccessful devices. Vegetation was cleared near two of the successful devices and secondary dams were removed near three of the successful devices. The failure of nine devices regarded by landowners as unsuccessful was attributed to secondary dams. It is difficult to assess whether removal of dams, additional devices, population reduction, or a combination of these measures would have improved landowner's perceptions of the device's performance.

Population control measures appeared to increase the success of Clemson Beaver Pond Levelers. Population control measures were practiced on 95 percent of the sites considered successful. The actual density of beavers on these sites before and after control measures is unknown. It is impossible to determine an optimum density of beavers for successful operation of these devices. However, these data suggest that a density threshold probably does exist. When the beaver population exceeds that threshold, a device is less likely to meet a landowner's objectives.

Population control measures alone do not ensure successful operations. Population reduction measures were practiced on 50 percent of the sites where landowners were not satisfied with the results. Perhaps beaver densities remained too high at those sites. Six devices were removed by landowners to increase waterflow without regard to whether they were plugged. These findings reflect the recommendations for using the Clemson Beaver Pond Leveler. The Clemson University Cooperative Extension Service says that "the leveler is not a panacea for eliminating all beaver problems" and "the leveler does not negate the need for direct control of beaver populations where problems are both extensive and severe; however, it may reduce this need."

A Massachusetts pamphlet considered the Clemson Beaver Pond Leveler to be:

• "An effective tool in situations where water input to a pond is from a small stream or spring"
• "Suitable only for small watersheds"
• "Susceptible to problems related to the inability of the device to handle large amounts of water during periods of unusually high rainfall"

A Minnesota Department of Natural Resources pamphlet says that the device is an effective tool to resolve problems created when a dam is built at a critical location but not problems caused by beavers elsewhere. This pamphlet recommends that "in most beaver flooding situations, the most effective way to reduce flooding is to remove beaver and then the dam or culvert plug."