# A Collection of Best Practices for the Collection and Analysis of Bioacoustic Data
## 8 Discussion  
Bioacousticians benefit from adopting best practices in study design and data collection to rise to a variety of challenges in interpreting animal acoustic communication. In the preceding sections we have discussed six different studies that focused on a variety of questions that can be investigated using acoustic data. While the studies we have included address a range of questions using a range of methodologies, some commonalities emerge as best practices which should be adhered to as best as possible in data collection, processing, and interpretation of bioacoustic data (Figure 3). Several important themes emerged related to the sampling design and data collection phases of an acoustic study. In each of our case studies, we have pointed out the importance of collecting data that adequately captures variability in the acoustic behaviour of species of interest. Some species produce different types of sounds in different behavioural states [6; 142; 143; 144], at different times of the day or year [145; 146], or in different locations [147; 38]. If these differences are not taken into account, results of acoustic analyses can be misinterpreted. For example, as we pointed out in Section 3, Ecosystem Biodiversity, failure to account for differences in calls produced by a single species at different times could lead to over-estimates of species diversity. Sample sizes should also be carefully  
Figure 3: Summary of target best practices in the collection and analysis of bioacoustic data. considered at this stage. This is particularly important for acoustic repertoires with high variability, such as the whistle repertoires of short- and long-beaked common dolphins, which are comprised of hundreds of different whistle types [149]. Sample sizes should be large enough to capture as much variability as possible, and to represent the different signal types adequately. Statistical analyses such as discovery curves can be useful tools in determining whether a given sample is sufficiently large to capture the variability in a target population [150, 151]. Barriers to collecting sufficient acoustic data include challenges and logistics of carrying out field work (especially for expensive sampling protocols such as making recordings in remote locations or field work involving large ships), limitations on battery life of recording equipment, data storage space, and resources for analyzing large datasets. One strategy for overcoming these challenges is to use duty-cycling when making recordings; that is, to record for only certain periods during a given time window. For example, a duty-cycled recording regime could record for 1 min every 5 min, for 10 min every hour, or for 1 h every 4 h. However, such an approach can compromise the final sample in several ways including missed detections of rare sounds and incomplete representation of sound occurrence patterns. In addition, the effects of using duty cycles can vary by species due to differences in acoustic behavior, characteristics of the signals being produced, and propagation characteristics of the environment. Therefore, it is not always appropriate to use the same duty cycle for different species, in different habitats, or to answer different questions [152, 153, 154, 155], a point that should be considered especially if a given recording sample will be used to examine multiple questions spanning multiple species. Before selecting a duty cycle it is advisable to examine a dataset of continuous recordings to evaluate the effect that different duty cycles will have on the detection of vocalizations of interest and thus the questions that can be answered using duty cycled data. Placement of microphones or hydrophones (transducers) is another important consideration. For example, if conducting a small-scale study of a targeted population [156, 157, 158], transducers should be placed in locations where they can adequately capture sounds produced by a representative sample of the population, and at appropriate times.