The study of emotion is rife with debate over issues as fundamental as how to define emotion, and such disputes are particularly common in the nonhuman animal emotion literature. Here, we seek to address some of these issues, especially in terms of how they relate to animal research. Definitional issues are prevalent; clear definitions are often not given of crucial terms, including 'emotion,' and even where provided, such terms may be used inconsistently throughout a single paper. Further disagreement over the structure of emotions, and the nature of conscious experiences involved, leads to consistent differences in authors' criteria for emotions. We concur with those who believe that animals experience emotions and believe that animal emotions should be studied in their own right, not only as they compare to those of humans. We also propose several avenues for future research that we believe will further our understanding of animal emotions. First, the use of multiple measurement methods to assess emotional responses is most likely to provide the information necessary to distinguish between various states and opens the field to more research in harder-to-study species, such as marine mammals. Second, researchers should also endeavor to increase the range of emotions studied, particularly positive ones, in order to move toward a more balanced range of studied states. Finally, we believe that several aspects of personality research would prove beneficial to the study of animal emotions, particularly the distinction between trait and state emotion and the use of the rating method. WIREs Cogn Sci 2016, 7:354-362. doi: 10.1002/wcs.1399 For further resources related to this article, please visit the WIREs website.

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Personality has now been studied in species as diverse as chimpanzees and cuttlefish, but marine mammals remain vastly underrepresented in this area. A broad range of traits have been assessed only once in each of bottlenose dolphins and California sea lions, while consistent individual differences in a few specific behaviors have been identified in grey seals. Furthermore, the context component of definitions of personality is not often assessed, despite evidence that animals may show individual patterns of behavioral consistency across contexts. The current study therefore aimed to use behavioral coding to assess underlying personality factors and consistency across contexts in two marine mammal species: California sea lions and harbor seals. In both species, two personality factors were extracted using exploratory factor analysis. Both were broadly similar across species; the first, Boldness, resembled human Extraversion, and to some extent Openness, with sea lions exhibiting a greater social component. The second factor was labeled Routine Activity, and may contain some Conscientiousness-like traits. Species-specific patterns were also identified for interactive behaviors across two contexts. However, there was substantial individual variation in the frequency of these behaviors, as well as some animals who did not conform to group-level trends. This study therefore provides novel evidence for broad personality factors and both group- and individual-level patterns of contextual consistency in two pinniped species.

The effects of visitor presence on zoo and aquarium animals have become increasingly well studied, using measures such as behavioral responses and exhibit usage. Many taxa remain underrepresented in this literature; this is the case for marine mammals, despite widespread public concern for their welfare in managed care settings. The current study therefore used behavioral activity budgets and exhibit usage to assess the responses of California sea lions (Zalophus californianus) and harbor seals (Phoca vitulina) to visitors at the Seal Cove exhibit at Six Flags Discovery Kingdom, Vallejo CA. Data was collected via focal follow video recordings over the summer season of 2016, and analyzed using MANCOVAs, discriminant analyses, and modified Spread of Participation Indices. The sea lions showed no significant changes in behavior when visitors were present, but did show greater preference for the water bordering visitor viewing areas during these times. Two sea lions gave birth during the study period, and showed greater preference for land areas both adjacent to and out of sight of visitors when nursing compared to while pregnant. In contrast, the harbor seals showed significant behavioral changes in the presence of visitors, including increased vigilance and feeding. This was associated with increased preferential use of water areas adjacent to the visitor viewing area. Visitors were able to purchase fish to throw to the animals, which likely contributed to the differences observed. Overall, this study found little evidence for negative visitor impacts on two pinniped species in a zoo setting.

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