BackgroundUltrasonic vocalizations (USVs) emitted by muroid rodents, including laboratory mice and rats, are used as phenotypic markers in behavioral assays and biomedical research. Interpretation of these USVs depends on understanding the significance of USV production by rodents in the wild. However, there has never been a study of muroid rodent ultrasound function in the wild and comparisons of USVs produced by wild and laboratory rodents are lacking to date. Here, we report the first comparison of wild and captive rodent USVs recorded from the same species, Peromyscus californicus.Methodology and Principal FindingsWe used standard ultrasound recording techniques to measure USVs from California mice in the laboratory (Peromyscus Genetic Stock Center, SC, USA) and the wild (Hastings Natural History Reserve, CA, USA). To determine which California mouse in the wild was vocalizing, we used a remote sensing method that used a 12-microphone acoustic localization array coupled with automated radio telemetry of all resident Peromyscus californicus in the area of the acoustic localization array. California mice in the laboratory and the wild produced the same types of USV motifs. However, wild California mice produced USVs that were 2–8 kHz higher in median frequency and significantly more variable in frequency than laboratory California mice.SignificanceThe similarity in overall form of USVs from wild and laboratory California mice demonstrates that production of USVs by captive Peromyscus is not an artifact of captivity. Our study validates the widespread use of USVs in laboratory rodents as behavioral indicators but highlights that particular characteristics of laboratory USVs may not reflect natural conditions.

We examined the individual context of ultrasonic vocalizations (USVs) produced by free-living wild male and female adult brush mice (Peromyscus boylii). We tested the hypothesis that USV production is dependent on behavioral context, and is important during both adult male and female interactions. Our methods included a 12-channel microphone array, radio-telemetry and thermal imaging that allowed us to determine: (1) who produced USVs, (2) characteristics of USVs, (3) type of USVs, (4) behavioral context of USVs and (5) the identity of the second mouse if an individual was not alone when a USV was produced. Females vocalized as much as males and produced the same types of USVs as males. There were no differences between spectral characteristics of male and female USVs. Females and males vocalized in the presence of one another. Importantly, when females were together they vocalized more than expected based on the proportion of time they spent together. Our results suggest that, in addition to facilitating courtship and mating, USVs are general territorial calls for neighbors because females vocalized in the presence of their neighbors. Despite a large literature on laboratory mouse (Mus musculus) USVs, studies are heavily biased towards males. Our results on brush mice, a species with a similar breeding system to the lab mouse and other rodents, suggest that female–female communication is an important and underappreciated component of the evolution and maintenance of mouse USVs.

High levels of bat activity have been reported at forest edges worldwide, but few studies have examined the ecological function of edges as a linear landscape feature. Patterns of association of bats at edges between old and young forest stands (hard edges) could be a result of edges acting as either a semi‐permeable barrier or a filter to movement into the forest between different‐aged forest stands for bats (or their insect prey), causing an accumulation of bat activity along the edge. Alternatively, edges may be a linear landscape feature similar to roads and riparian corridors that bats use as flight conduits as they move from one place to another. Using ultrasound microphone arrays and recording equipment, we were able to determine flight patterns of bats at hard edges within a landscape of intensively managed loblolly pine (Pinus taeda) plantation in eastern North Carolina, USA, during 2009. Across edges and species sampled, bats consistently flew parallel to edges, suggesting that edges act as conduits for bats. Feeding rates of bats at edges were low, further supporting use of edges as conduits for bats that are either flying along edges to move to and from roosting and foraging habitat patches or moving among foraging patches. Continuous edges should be maintained between linear and nonlinear landscape features, especially where known roosting and foraging areas are being connected by an edge. © 2013 The Wildlife Society.

In the urban environment, wildlife faces novel human disturbances in unique temporal patterns. The weekend effect describes that human activities on weekends trigger changes in the environment and impact wildlife negatively. Reduced occurrence, altered behaviors, and/or reduced fitness have been found in birds, ungulates, and meso-carnivores due to the weekend effect. We aimed to investigate if urban bat activity would differ on weekends from weekdays. We analyzed year-round bat acoustic monitoring data collected from two sites near the city center and two sites in the residential area/park complex in the city periphery. We constructed generalized linear models and found that bat activity was significantly lower on weekends as compared to weekdays during spring and summer at the site in the open space near the city center. In contrast, during the same seasons, the sites in the city periphery showed increased bat activity on weekends. Hourly bat activity overnight suggested that bats might move from the city center to the periphery on weekends. We demonstrated the behavioral adaptability in urban wildlife for co-existing with human. We recommend that urban planning should implement practices such as adding new greenspaces and/or preserving old-growth vegetation to form continuous greenways from the city center to the city periphery as corridors to facilitate bat movements and reduce possible human-wildlife conflict.

Proactive artificial wetland constructions have been implemented to mitigate the loss of wetlands and their ecosystem services. As wetlands are habitats for bats, short-term (one or two years) studies find that constructed wetlands can immediately increase local bat activity and diversity. However, it is not clear how constructed wetlands affect bats through time while the wetlands are aging. We collected four years of continuous bat acoustic monitoring data at two constructed wetlands in an urban park in Greensboro, NC, USA. We examined bat activity and community composition patterns at these wetlands and compared them with reference sites in the city. With four years of data, we found that the effects of constructed wetlands were both habitat- and species-specific. The wetland in forests significantly increased bat activity, while the wetland in the open grass altered bat community composition. Specifically, in terms of species, we found that over time, constructed wetlands no longer attracted more big brown, silver-haired, or evening bats than control sites while the wetlands aged, highlighting the need to study broadly how each bat species uses natural and artificial wetlands. We emphasize the importance of long-term monitoring and the periodical evaluation of wildlife conservation actions.