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New Directions in Marine Mammal Behavioral Noise Exposure Criteria8Marine Research of the National Academy of Marine ResearchDOI: 10.29677/MR.202406_4(1).00013 NEW DIRECTIONS We've seen tremendous advances in science, technology, and analytical methods for evaluating the effectsof noise on marine mammals in the past several decades. In terms of behavioral responses, the most significant steps have been the extension of early efforts in captive and contextually-simulated settings to more realistic field, full-scale contexts using well-designed observational studies and increasingly experimentally controlled contexts. While additional data on key species and for new and evolving noise disturbances are clearly needed, the evidence supporting a probabilistic and highly contextually-dependent probability of response within and between individuals and species is now overwhelming. Consequently, simplistic received level-only stepfunction 'thresholds' indicating a binary lack or presence of response for any sound type are outdated and Assessments highlighted study design and analytical approach, data collection platform, whether the unitof analysis was individuals or groups, and associated limitations (Bejder & Samuels 2003; Senigaglia et al., 2016; Booth et al. 2020). For whale watching studies, a description of the history of the industry in the study area was included, given that they can have variable levels of regulatory oversight and vary in fleet size and number of vessels allowed per encounter, type of tour offered, with or without an in-water component, and other factors. In cases of resident populations or those with high site fidelity, the duration since implementation of the industry was assumed to be a proxy for the potential magnitude of an effect. Differences in the life history characteristics of mysticetes and odontocete cetaceans were also considered. Mysticetes are capital breeders, accumulating energy on feeding grounds and transferring energy to calves in breeding grounds, whereas most odontocetes are income breeders with less discrete feeding and breeding periods (McHuron et al., 2018). Anthropogenic disturbance studies thus generally focus on specific habitats within home ranges as this may affect their ability to compensate for disturbances. The assessments of long-term, chronic impact studies, primarily related to cetacean watching activities, made in Southall et al. (2021), which were based on the approaches developed by Bejder and Samuels (2003), provide general and specific conclusions. Longitudinal studies of marine mammals over their entire home range are of particular importance in order to quantify the ability of the targeted animal to compensate for disturbance and the associated impact(s). Animals living in degraded habitats or that rely on patchy resources may be less resilient, the impacts of disturbance may be higher, and population level consequences are more likely to be mediated by individual responses (Lusseau, 2014), highlighting the importance of considering individual exposure, response, and environmental covariates (Pirotta et al., 2021). Furthermore, key differences are likely to occur in impacts of chronic nature between capital and income breeders, likely because of variabilities in their compensatory opportunities. Mysticetes as capital breeders may be more able to compensate for short-term effects, although the threatened or endangered status of many species are also important considerations. Conversely, odontocetes in many contexts may experience a higher cumulative exposure to whale watching disturbance due to their localized and coastal home range, and in some cases greater predation risk (Senigaglia et al., 2012, 2016; Lusseau, 2014; Pirotta et al., 2015). Neither Southall et al. (2021) nor this paper presumes to have fully developed a kind of systematic newparadigm for integrating well-conducted long-term population studies within a regulatory-applicable criteria assessment akin to the acute response severity assessment and probabilistic function. Both are highlighting the need for such an approach and underscoring some progress and ideas for key considerations and new directions, clearly building from some of the ongoing work in evaluating population disturbances of multiple stressors. The development of such an assessment paradigm will require a dedicated, multi-sectoral collaboration of scientists from different disciplines interacting with policy managers. It is critically important in this process that a diversity of perspectives from both the scientific community as well as regulatory perspectives from different jurisdictions be considered.