Bat use of created and natural wetlands.

摘要

Compensatory wetland mitigation is a common practice to account for wetland losses due to dredging and filling under the Clean Water Act, but successful replacement of function is rarely achieved. Small, isolated wetlands also receive no federal protection, and are usually not included in accounts of losses. Although latest reports show an increase in wetlands for the first time, this is due in large part to voluntary construction of open water ponds, while the loss of freshwater emergent wetlands continues to decline. Research on the wildlife functions of wetlands has focused on plants, invertebrates, avian or amphibian species. But wetlands also are important for bat foraging habitat because most insects depend on water for some part of their life cycle. Bats could serve as a mammalian indicator of constructed wetland function due to their size, mobility, and ease of acoustic monitoring. Despite this connection, there is a lack of studies focusing on bats and wetlands in the Mid-Atlantic and Midwest, and few have occurred elsewhere.I examined 79 constructed and natural wetlands in western Pennsylvania and eastern Ohio for the presence of bats using acoustical monitoring. The recent use of acoustical monitoring has garnered habitat level comparisons, and can be used as an index of bat activity and to determine presence and absence. I used an information theoretic approach to model the response of bats to wetland design and landscape based on the following: wetland origin, age, size, pH, distance to highway, and areas within the surrounding landscape of forest, urban, open water, barren, wetland, and edge density.For all species except for eastern pipistrelles (Pipistrellus subflavus), landscape characteristics influenced both presence and relative activity of observed bat species. The Combo model incorporated wetland size as well as landscape parameters, and received support for most species, with differences among species based on wing morphology and habitats. Within supported models, surrounding wetlands in the landscape had the greatest influence on most bat species. Big brown bats (Eptesicus fuscus) were influenced by barren and open areas, while eastern red bats (Lasiuris borealis) were influenced by agriculture. Wetlands created in a landscape with an overall lack of wetlands and less edge may be particularly important for all species of bats, regardless of wing morphology. My results also showed that wetlands of all sizes, even small ones not afforded federal protection, can be vital foraging areas for bat species. The wetland origin and abiotic characteristics received no support, suggesting that placement within the landscape may be the most important consideration for bats. The origin of the wetland only influenced activity for eastern pipistrelles, which may be due to the closed canopy associated with natural wetlands. With the latest research in developing indices of biotic integrity for various groups of wildlife such as birds, amphibians, and plants, a mammalian indicator group should also be considered. Because of the association of bats with wetlands, relative ease of acoustical monitoring, and importance of wetlands to mammals in general, bats may be good candidates to develop as a mammalian indicator for wetland function.