Acoustic Disturbance Risk Estimates and Mitigation Strategies: An Animal-Centric Approach

Implication of Altered Acoustic Active Space for Cetacean Species That Result from Soundscape Changes and Noise Additions

“…Call function may be interpreted from the season, group association and proximity, or behavioral, emotional, or physiological state concomitant to the vocalization. However, it is the estimation of the active space which allows us to better understand how an animal associates with its habitat and makes sense of its surroundings from the whale's perspective [4,23,78].…”

“…An understanding of active space and signal masking could be incorporated as a metric of impact to estimate the effectiveness of management measures designed to reduce disturbance. A masking metric, calculated by expressing the active space or range that an individual can maintain communication or use echolocation under different noise scenarios as a proportion of the extent of the same signals under ideal soundscape conditions, has been suggested as such a tool (see [4,21,89]). Other metrics, such as the level of noise exposure that results in either temporary or permanent changes in hearing sensitivity or physiological stress of an organism can be a means to assess impact also but only speak to the potential changes in signal reception and processing that occur at the receiver.…”

“…Active space calculations are a means to assess the potential acoustic disturbance from noise additions to the soundscape (e.g., see [4]). They may also support an estimate of acoustic stress on an individual when changes in behavior are not observable, for example when whales are willing to withstand disturbance to continue to exploit prey reserves.…”

“…Using a framework that incorporates the concept of active space gives a speciescentric approach to understanding the potential disturbance, and efficacy of mitigation measures. Even when calculated in a rudimentary way, the application of active space or range, centered around an individual, demonstrates their place in an ecosystem, and how things might be impacted by a source of disturbance (see [4]).…”

“…Active space is a 'time-space-organism' conception of the environment, whereby the extent responds to both temporal and spatial variables, and it is centered around an individual. If defined by the acoustic sense, it could be described as the 'dynamic spatio-spectral-temporal acoustic habitat' [16] or as the operational ambisonic niche of an individual [4]. The active space extent reflects the variability in the transmission of signals given properties of the air or water the sounds are emitted in and traits of the signal itself.…”