Climate change is now known to be affecting the oceans. It is widely anticipated that impacts on marine mammals will be mediated primarily via changes in prey distribution and abundance and that the more mobile (or otherwise adaptable) species may be able to respond to this to some extent. However, the extent of this adaptability is largely unknown. Meanwhile, within the last few years direct observations have been made of several marine mammal populations that illustrate reactions to climate change. These observations indicate that certain species and populations may be especially vulnerable, including those with a limited habitat range, such as the vaquita Phocoena sinus, or those for which sea ice provides an important part of their habitat, such as narwhals Monodon monoceros, bowhead Balaena mysticetus and beluga Delphinapterus leucas whales and polar bears Ursus maritimus. Similarly, there are concerns about those species that migrate to feeding grounds in polar regions because of rapidly changing conditions there, and this includes many baleen whale populations. This review highlights the need to take projected impacts into account in future conservation and management plans, including species assessments. How this should be done in an adequately precautionary manner offers a significant challenge to those involved in such processes, although it is possible to identify at this time at least some species and populations that may be regarded as especially vulnerable. Marine ecosystems modellers and marine mammal experts will need to work together to make such assessments and conservation plans as robust as possible.
This review highlights significant gaps in our knowledge of the effects of seismic air gun noise on marine mammals. Although the characteristics of the seismic signal at different ranges and depths and at higher frequencies are poorly understood, and there are often insufficient data to identify the appropriate acoustic propagation models to apply in particular conditions, these uncertainties are modest compared with those associated with biological factors. Potential biological effects of air gun noise include physical/physiological effects, behavioral disruption, and indirect effects associated with altered prey availability. Physical/physiological effects could include hearing threshold shifts and auditory damage as well as non-auditory disruption, and can be directly caused by sound exposure or the result of behavioral changes in response to sounds, e.g. recent observations suggesting that exposure to loud noise may result in decompression sickness. Direct information on the extent to which seismic pulses could damage hearing are difficult to obtain and as a consequence the impacts on hearing remain poorly known. Behavioral data have been collected for a few species in a limited range of conditions. Responses, including startle and fright, avoidance, and changes in behavior and vocalization patterns, have been observed in baleen whales, odontocetes, and pinnipeds and in some case these have occurred at ranges of tens or hundreds of kilometers. However, behavioral observations are typically variable, some findings are contradictory, and the biological significance of these effects has not been measured. Where feeding, orientation, hazard avoidance, migration or social behavior are altered, it is possible that populations could be adversely affected. There may also be serious long-term consequences due to chronic exposure, and sound could affect marine mammals indirectly by changing the accessibility of their prey species. A precautionary approach to management and regulation must be recommended. While such large degrees of uncertainty remain, this may result in restrictions to operational practices but these could be relaxed if key uncertainties are clarified by appropriate research.
Animal culture, defined as "information or behavior-shared within a community-which is acquired from conspecifics through some form of social learning" (1), can have important consequences for the survival and reproduction of individuals, social groups, and potentially, entire populations (1, 2). Yet, until recently, conservation strategies and policies have focused primarily on broad demographic responses and the preservation of genetically defined, evolutionarily significant units. A burgeoning body of evidence on cultural transmission and other aspects of sociality (3) is now affording critical insights into what should be conserved (going beyond the protection of genetic diversity, to consider adaptive aspects of phenotypic variation), and why specific conservation programs succeed (e.g., through facilitating the resilience of cultural diversity) while others fail (e.g., by neglecting key repositories of socially transmitted knowledge). Here, we highlight how international legal instruments, such as the Convention on the Conservation of Migratory Species of Wild Animals (CMS), can facilitate smart, targeted conservation of a wide range of taxa, by explicitly considering aspects of their sociality and cultures. CONSEQUENCES OF SOCIAL KNOWLEDGE An important aspect of social learning is the speed with which new behaviors can potentially spread through populations, with effects that may be positive (e.g., adaptive exploitation of a new food source) or negative (e.g., increasing conflict with humans, such as when sperm whales learn to remove fish from longlines) (2). Transmission can be mediated by an inherent propensity to adopt innovations (e.g., "lobtail" feeding in humpback whales (1)), or curbed by cultural conservatism (e.g., southern resident killer whales' persistent foraging specialization on Chinook salmon (2)). Social learning can result in the emergence of subpopulations with distinctive behavioral profiles, erecting social barriers, as observed in distinct vocal clans of sperm whales (see the Figure). Culturally mediated population structure has important implications for conservation efforts (4), as it can influence species-wide phenotypic diversity and adaptability to changing conditions (5). In some cases, such as humpback or blue whale song, cultural variation can reflect demography and facilitate more efficient, or less invasive, assays of contemporary genetic population structure (1, 4). Most profoundly, culture can play a causal role in establishing and maintaining distinct evolutionary trajectories (6). Another consequence of social learning can be the increased importance of key individuals as repositories of accumulated knowledge, making their targeted protection particularly important for the persistence of social units. For example, the experience of African elephant matriarchs (see
A key goal of conservation is to protect biodiversity by supporting the long-term persistence of viable, natural populations of wild species. Conservation practice has long been guided by genetic, ecological and demographic indicators of risk. Emerging evidence of animal culture across diverse taxa and its role as a driver of evolutionary diversification, population structure and demographic processes may be essential for augmenting these conventional conservation approaches and decision-making. Animal culture was the focus of a ground-breaking resolution under the Convention on the Conservation of Migratory Species of Wild Animals (CMS), an international treaty operating under the UN Environment Programme. Here, we synthesize existing evidence to demonstrate how social learning and animal culture interact with processes important to conservation management. Specifically, we explore how social learning might influence population viability and be an important resource in response to anthropogenic change, and provide examples of how it can result in phenotypically distinct units with different, socially learnt behavioural strategies. While identifying culture and social learning can be challenging, indirect identification and parsimonious inferences may be informative. Finally, we identify relevant methodologies and provide a framework for viewing behavioural data through a cultural lens which might provide new insights for conservation management.
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