Characteristics of wild moose (Alces alces) vocalizations.

Moose are a popular species with recreationists but understudied acoustically. We used publicly available videos to characterize and quantify the vocalizations of moose in New Hampshire separated by age/sex class. We found significant differences in peak frequency, center frequency, bandwidth, and duration across the groups. Our results provide quantification of wild moose vocalizations across age/sex classes, which is a key step for passive acoustic detection of this species and highlights public videos as a potential resource for bioacoustics research of hard-to-capture and understudied species.

Graded alarm call behavior in wild fox squirrels (Sciurus niger).

Distress or alarm calls are vocalizations made when animals are in stressful situations or faced with a predator. Squirrels (Sciuridae) are known for being very vocal; however, most studies on alarm vocalizations are limited to ground squirrels. We investigated the acoustic behavior of the arboreal fox squirrel (Sciurus niger) under different conditions. Specifically, we tested the hypothesis that fox squirrels modify acoustic alarm behavior in response to different perceived threat levels and that this response is affected by sex and individual experience. Squirrels were trapped, and acoustic data were collected during periods in which the squirrels were alone, approached by humans, manipulated in traps, and handled by humans. Calls were categorized based on acoustic features, and we quantified the call rate (calls/s) across conditions. Threat level significantly affected vocal rate, with squirrels producing more calls overall when alone but shifting the proportion of emitted call types as threat level increased. Sex, capture history, and individual had no effect on call rate. These results suggest that fox squirrels use a graded alarm call response system to respond to threatening situations.

Acoustic behavior in the northern short-tailed shrew (Blarina brevicauda): Ultrasonic click production in a novel environment.

Although echolocation is classically associated with bats and dolphins, many animals produce ultrasonic and/or click-like signals to potentially navigate their environment. Shrews (Soricidae) are thought to rely on ultrasonic signals for echo-orientation, producing both ultrasonic click-like signals and tonal twittering signals. Recently, the role of ultrasonic clicks in shrew echo-orientation has been questioned, as these clicks have been proposed to be artifacts of shrews moving throughout their environment. By combining infrared video and ultrasonic audio recordings, we investigated the acoustic signals made by shrews (Blarina brevicauda) during different periods of locomotion. We hypothesized that if shrews are using ultrasonic vocalizations as a sensory mechanism, they will display head scanning behavior while emitting clicks that share key characteristics with other known echolocating animals. Our results show that B. brevicauda predominantly emit ultrasonic clicks rather than ultrasonic twittering calls while exploring a new environment, with clicks having the following characteristics: less than 120 µs in duration, median peak frequency of 26.9 kHz, and median bandwidth of 22.9 kHz. Across individuals we found no significant difference in peak frequency. Our results indicate that shrews emit ultrasonic clicks in novel environments which further supports the hypothesis of echo-orientation or echolocation in shrews.

BatCount: A software program to count moving animals.

One of the biggest challenges with species conservation is collecting accurate and efficient information on population sizes, especially from species that are difficult to count. Bats worldwide are declining due to disease, habitat destruction, and climate change, and many species lack reliable population information to guide management decisions. Current approaches for estimating population sizes of bats in densely occupied colonies are time-intensive, may negatively impact the population due to disturbance, and/or have low accuracy. Research-based video tracking options are rarely used by conservation or management agencies for animal counting due to the perceived training and elevated operating costs. In this paper, we present BatCount, a free software program created in direct consultation with end-users designed to automatically count bats emerging from cave roosts (historical populations 20,000-250,000) with a streamlined and user-friendly interface. We report on the software package and provide performance metrics for different recording habitat conditions. Our analysis demonstrates that BatCount is an efficient and reliable option for counting bats in flight, with performance hundreds of times faster than manual counting, and has important implications for range- and species-wide population monitoring. Furthermore, this software can be extended to count any organisms moving across a camera including birds, mammals, fish or insects.