Relationships between two northeastern bats, Myotis lucifugus and Eptesicus fuscus, and landscape structure

Background/Question/Methods

Bats are an important part of temperate ecosystems, providing valuable services as regulators of insect populations.  However, northeastern US bat populations face a number of threats (e.g., land use change, and white nose syndrome) that affect their abundance and distribution.  Consequently, estimates of population size, habitat use, and knowledge about current distributions are uncertain.  This study evaluated the response of two bat species, Myotis lucifugus and Eptesicus fuscus, to landscape structure. These species are considered common in New England, inhabit and utilize forest, and produce sufficiently loud echolocation calls that can be reliably recorded by monitoring devices. Bats were sampled with Autonomous Recording Units (ARUs) at twenty interior forest sites throughout Connecticut. Sites were located at least 10 km from each other. Each ARU recorded for 4 hours each night after sunset between 6/1/12 and 6/14/12.  Bat activity was estimated at each site as the total number of echolocation pulses per species during the sample period.  Echolocation pulses were identified using species-specific recognizers in Songscope software. Each site was characterized by a suite of compositional and configurational landscape metrics calculated at circular focal scales of 3 km and 5 km radius from a 2010 state land cover map. 

Results/Conclusions

Relationships between bat activity and landscape characteristics were assessed using hierarchical partitioning. In general, relationships between activity of M. lucifugus, and E. fuscus and landscape characteristics were similar and scale-dependent.  Only the spatial arrangement of wetland habitat was significantly related to bat activity at both 3km and 5km focal scales.  Although other metrics significantly related to bat activity differed among scales, they were similar in that they all characterized aspects of the landscape other than forest (i.e., open areas and edge habitats). Like many insectivorous bats, E. fuscus and M. lucifugus are known to cover large distances and usually forage throughout the night in good weather. These species in particular and potentially temperate insectivorous bats in general, likely require a mix of habitat types in addition to forest. This may include open spaces, which could be used as more efficient flyways between prime feeding locations and roosting sites as well as water sources that may also serve as source locations and breeding grounds for insect prey.  Consequently, effective management strategies should incorporate protection for a mix of habitats, but in general it may be the case that separate plans for each species will be unnecessary.