Developing a winter population survey protocol for Acadia National Park’s beaver population

Smith, Erickson

From the abstract: "Rising out of extirpation after reintroductions in the early 1920s, North American beavers (Castor canadensis) have quickly repopulated Acadia National Park and Mount Desert Island, Hancock County, Maine. As beavers have a great capacity for modifying landscapes (those with and without humans), their presence in dynamic landscapes such as national parks can create problems for park management. Many independent researchers and park employees have recommended the formulation of a population management plan to keep park management and human-beaver conflicts to a minimum. Accurate information on the population status and reproductive dynamics of the park and area beaver population is necessary for park managers to construct an ecologically sound management plan. To address this need, I designed and developed this study as one approach to providing the park with a population survey protocol (combination of survey methods) tailored to the park’s landscape and seasonal changes. The objective was to develop a tested population survey protocol that park and Maine wildlife managers could use in tracking beaver populations (i.e., numbers, distribution, etc.) for management planning. This winter protocol, when used in conjunction with other survey protocols, would then be able to serve as the baseline in managing and conserving beavers and other wetland communities. Between January and May 2015, I visited 50 beaver lodges in 13 different watersheds a total of 158 times, resulting in 183 man-hours of field observation. The fieldwork produced a winter survey protocol that is 96% effective at predicting the occupancy of a given beaver lodge. The protocol uses a tiered hierarchy of 13-18 beaver signs to determine the occupancy of a lodge, while minimizing the likelihood of false positives and negatives in the data. The protocol is designed to allow the surveyor to make a determination on a lodge after one visit, which would make visiting every lodge in Acadia in one season possible. This survey method, as a ground survey, may be more effective for large-scale surveys in Acadia than an aerial survey, given Acadia’s steep topography and largely wooded watersheds. The timing and nature of the survey would also minimize disturbance to park wildlife and visitors by using non-invasive, quiet survey and transportation methods in the park’s off-season. If the survey methods tested in this study are used in conjunction with a known or tested average beaver colony size, this protocol could be a powerful tool for assessing the park’s beaver population. and having information to make informed management decisions. This survey protocol should enable park managers to produce a population estimate that would be the starting point and catalyst for an ecologically sound beaver management plan."