To better understand seasonal and spatial distribution of bats offshore, the Department of Energy (DOE) funded an acoustic survey of bat activity on islands, offshore structures, and coastal sites in the New England Gulf of Maine, mid-Atlantic coast, and Great Lakes regions from 2012 – 2014 (Award Number DE-EE005378). The primary purpose of the study was to enhance understanding of when and where bats occur offshore (here defined as waters beyond 3 nautical miles from land), with the underlying objective of assessing potential impacts to bats from offshore wind energy development. This effort built upon a pilot acoustic study conducted by Stantec Consulting Services Inc. (Stantec) in the Gulf of Maine between 2009 and 2011, and supported an expanded survey effort in the Gulf of Maine, mid-Atlantic coast, and Great Lakes regions. This report combines data from the 2009 – 2011 Gulf of Maine pilot study as well as the 2012 – 2014 expanded study.
Although our ultimate goal was to assess bat activity offshore, current logistical constraints on long-term acoustic monitoring require that we base inferences regarding bat presence and activity over large expanses of open water on the results of surveys conducted at islands, coastal sites, and offshore structures where equipment can be more readily and reliably deployed. In some cases, remote offshore structures such as isolated weather buoys and ships provided a unique opportunity to directly measure bat activity above open water. However, monitoring bat activity at remote islands is still informative, as bats must travel considerable distances offshore to reach the islands. The broad spectrum of coastal sites, islands, and offshore structures included in this study, combined with the long-term nature of the project, allow for analysis of bat activity patterns across a number of spatial and temporal gradients.