DOI: 10.5061/dryad.vmcvdncp9
title: Data from: Vocal characteristics of prairie dog alarm calls across an urban noise gradient

description: Increasing anthropogenic noise is having a global impact on wildlife,
 particularly due to the masking of crucial acoustical communication.
 However, there have been few studies examining the impacts of noise
 exposure on communication in free-ranging terrestrial mammals. We studied
 alarm calls of black-tailed prairie dogs (Cynomys ludovicianus) across an
 urban gradient to explore vocal adjustment relative to different levels of
 noise exposure. There was no change in the frequency 5%, peak frequency or
 duration of the alarm calls across the noise gradient. However, the
 minimum frequency – a commonly used, yet potentially compromised metric –
 did indeed show a positive relationship with noise exposure. We suspect
 this is a result of masking of observable call properties by noise, rather
 than behavioural adjustment. In addition, the proximity of conspecifics
 and the distance to the perceived threat (observer) did affect the
 frequency 5% of alarm calls. These results reveal that prairie dogs do not
 appear to be adjusting their alarm calls in noisy environments but likely
 do in relation to their social context and the proximity of a predatory
 threat. Anthropogenic noise can elicit a range of behavioural and
 physiological responses across taxa, but elucidating the specific
 mechanisms driving these responses can be challenging, particularly as
 these are not necessarily mutually exclusive. Our research sheds light on
 how prairie dogs appear to respond to noise as a source of increased risk,
 rather than as a distraction or through acoustical masking as shown in
 other commonly studied species (e.g. fish, songbirds, marine mammals).
description: Prairie dog alarm calls were recorded across an urban gradient at
 three distinct colonies from 28 August to 6 December 2014. Alarm calls
 were elicited by the observer approaching a randomly selected prairie dog.
 Once the prairie dog began alarm calling the observer remained stationary
 and recorded 30 seconds of vocalization while the animal was in situ. A
 band-limited automated detector was used in Raven Pro v1.5 to select each
 of the individual barks in the 30-second calling bouts and to optimize
 extraction of call parameters. Before measurements were extracted on the
 individual barks, all detections were examined manually for accuracy and
 adjusted to maximize the detection of all barks within a recording period
 and to ensure the entire bandwidth and duration of calls were selected.
 Random selections of half of the barks in a calling bout (n = 4516) were
 then measured. Four acoustic metrics were calculated for each bark: (1)
 minimum frequency (Hz) – the lower frequency limit of the call, a commonly
 used metric in previous studies; (2) frequency 5% (Hz) – the frequency
 where the summed energy equals 5% of the total, a measure of lower
 frequency properties; (3) peak
 frequency (Hz) – the frequency with the highest concentration of energy;
 and (4) bark duration (milliseconds). Ambient sound levels were measured
 using a calibrated Larson-Davis 831 sound level meter (frequency weighting
 = A) over a 2-minute period as soon as the vocalization recording was
 completed. Sound pressure levels were measured as 1-second frequency
 weighted (12.5Hz - 20kHz) equivalent continuous levels (L<sub>Aeq,
 1s</sub>). 
description: Spreadsheet columns: Colony: 1 = Pineridge, 2
 = Coyote Ridge & 3 = The Coterie BeginTime
 & EndTime: Specific start and end time of each bark on the
 recorder MinFreq, Freq5, PeakFreq &
 BarkDuration: Response variables - details of these provided in methods
 section above Individual: ID for each individual that
 was recorded Laeq: Ambient sound level recorded over a
 two minute period Dist_Rec: Distance to the focal
 animal Dist_NPD: Distance from the focal animal to
 nearest neighbour Windspeed & Julian Day:
 Additional explanatory variables Normalized values are
 provided for all explanatory variables - these are given the 'n'
 prefix