David L. Sinn

Development of shy/bold behaviour in squid: context-specific phenotypes associated with developmental plasticity

Animals often differ from one another in their willingness to take risks in a number of functional contexts related to fitness (e.g. mating, dispersal, and foraging behaviour). Although several studies have reported life history correlates and selective consequences of this variation in shy/bold behaviour, little attention has been paid to developmental processes resulting in shy/bold phenotypes. Here, we present a lifetime developmental study of shy/bold behaviour in dumpling squid, Euprymna tasmanica. Behaviour was measured in two test contexts, a threat and a feeding test, at five times across the entire life span. Across test contexts, shy/bold behaviour was not correlated at any age; while within a test context, individual shy/ bold phenotypes were consistent both before and after sexual maturity. During sexual maturity, different phenotypes displayed different amounts of developmental variation; shyer animals were more plastic in feeding tests, while bolder animals were more plastic in threat ones. Our results suggest that for some animals shy/bold behaviour throughout development is uncorrelated across different contexts related to risk, while within a context, there may still be developmental constraints to changing shy/bold behaviour. This constraint within a functional context, however, may be phenotype-specific, with some phenotypes able to change more than others. These results indicate that a greater understanding of developmental pathways is needed to determine whether shy/bold phenotypes per se are the sole focus of selection. Differences in developmental plasticity between shy/bold phenotypes may also confer differential fitness in fluctuating environments.

Heritability and fitness-related consequences of squid personality traits

Dumpling squid, Euprymna tasmanica, show consistent individual differences in behaviour that can be classified according to indices reflecting shy–bold, activity and reactivity responses. Using crosses of wild‐caught single males to multiple females with known behavioural phenotypes, this study estimated patterns of additive genetic and residual variance in these behavioural traits from offspring of squid in two contexts, a threat (antipredator) and feeding (foraging) test. Genetic contributions to behavioural expression were dependent on test context. Behaviours in antipredator contexts had significant heritabilities (h2 = 0.2–0.8) while behaviours from foraging contexts had lesser additive genetic and greater residual components (h2 = 0.05–0.08). Personality trait variation in females was not related to her fecundity. Female boldness in foraging situations, which co‐varied with body size, explained small but significant variation (∼21%) in brood hatching success, while successful fertilization was determined by positive assortion of mate pairs according to their shy–bold phenotype. These results are discussed in terms of the ecological and evolutionary significance of animal ‘personality’ traits in wild populations of animals.

Personality Traits in Dumpling Squid (Euprymna tasmanica): Context-Specific Traits and Their Correlation With Biological Characteristics

Personality traits are a major class of behavioral variation often observed within populations of animals. However, little is known of the integration between personality and an individuals underlying biology. To address this, the authors measured personality traits in squid (Euprymna tasmanica) in 2 contexts while also describing trait correlates with biological parameters. Four traits (shy avoidance- bold aggression, activity, bury persistence, and reactivity) were reliably measured; however, trait expression between contexts was not correlated and thus was context-specific. Trait variation was not a function of gender or of somatic or reproductive condition but was explained partially by a squids sexual maturity and its size. Results are discussed in terms of the interplay between personality variation and resulting life history strategies in animals.

Ethical and welfare considerations when using cephalopods as experimental animals

When using cephalopods as experimental animals, a number of factors, including morality, quality of information derived from experiments, and public perception, drives the motivation to consider welfare issues. Refinement of methods and techniques is a major step in ensuring protection of cephalopod welfare in both laboratory and field studies. To this end, existing literature that provides details of methods used in the collection, handling, maintenance, and culture of a range of cephalopods is a useful starting point when refining and justifying decisions about animal welfare. This review collates recent literature in which authors have used cephalopods as experimental animals, revealing the extent of use and diversity of cephalopod species and techniques. It also highlights several major issues when considering cephalopod welfare; how little is known about disease in cephalopods and its relationship to senescence and also how to define objective endpoints when animals are stressed or dying as a result of the experiment.

Climate effects on offspring sex ratio in a viviparous lizard

1. Understanding individual and population responses to climate change is emerging as an important challenge. Because many phenotypic traits are sensitive to environmental conditions, directional climate change could significantly alter trait distribution within populations and may generate an evolutionary response. 2. In species with environment-dependent sex determination, climate change may lead to skewed sex ratios at hatching or birth. However, there are virtually no empirical data on the putative link between climatic parameters and sex ratios from natural populations. 3. We monitored a natural population of viviparous lizards with temperature-dependent sex determination (Niveoscincus ocellatus) over seven field seasons. Sex ratios at birth fluctuated significantly among years and closely tracked thermal conditions in the field, with the proportion of male offspring increasing in colder years. 4. This is the first study to demonstrate the effect of local climatic conditions (e.g. temperature) on offspring sex ratio fluctuations in a free-living population of a viviparous ectotherm. A succession of warmer-than-usual years (as predicted under many climate-change scenarios) likely would generate female-biased sex ratios at birth, while an increase in interannual variation (as also predicted under climate change scenarios) could lead to significant fluctuations in cohort sex ratios. If cohort sex ratio bias at birth leads to adult sex ratio bias, long-term directional changes in thermal conditions may have important effects on population dynamics in this species.

Personality Consistency in Dogs: A Meta-Analysis

Personality, or consistent individual differences in behavior, is well established in studies of dogs. Such consistency implies predictability of behavior, but some recent research suggests that predictability cannot be assumed. In addition, anecdotally, many dog experts believe that ‘puppy tests’ measuring behavior during the first year of a dogs life are not accurate indicators of subsequent adult behavior. Personality consistency in dogs is an important aspect of human-dog relationships (e.g., when selecting dogs suitable for substance-detection work or placement in a family). Here we perform the first comprehensive meta-analysis of studies reporting estimates of temporal consistency of dog personality. A thorough literature search identified 31 studies suitable for inclusion in our meta-analysis. Overall, we found evidence to suggest substantial consistency (r = 0.43). Furthermore, personality consistency was higher in older dogs, when behavioral assessment intervals were shorter, and when the measurement tool was exactly the same in both assessments. In puppies, aggression and submissiveness were the most consistent dimensions, while responsiveness to training, fearfulness, and sociability were the least consistent dimensions. In adult dogs, there were no dimension-based differences in consistency. There was no difference in personality consistency in dogs tested first as puppies and later as adults (e.g., ‘puppy tests’) versus dogs tested first as puppies and later again as puppies. Finally, there were no differences in consistency between working versus non-working dogs, between behavioral codings versus behavioral ratings, and between aggregate versus single measures. Implications for theory, practice, and future research are discussed.

Early temperamental traits in an octopus (Octopus bimaculoides).

During their 3rd week of life, 73 Octopus bimaculoides were observed to test whether discrete behaviors could be grouped reliably to reflect dimensions of temperament. Frequencies of behaviors during Week 3 were subjected to principal-components analysis (PCA), resulting in 4 components (active engagement, arousal/readiness, aggression, and avoidance/disinterest) that explain 53% of the variance. Levels of temperamental traits were then evaluated for 37 octopuses using composite scores at 3 time points across the first 9 weeks of life. Profile analysis revealed significant change for the testing group as a whole in trait expression levels from Week 3 to Week 6. Results also suggest a significant effect of relatedness on developing temperamental profiles of octopuses. Discussion focuses on how results apply to the life history of O. bimaculoides and what temperament can reveal about adaptive individuality in a protostome.

The World from a Dog’s Point of View: A Review and Synthesis of Dog Cognition Research

Driven by both applied and theoretical goals, scientific interest in canine cognition has experienced a rapid surge in popularity, especially over the last 15 years. Here we provide the most comprehensive review to date of dog cognition research, capturing all the articles (285) we could find on the subject going back to 1911. We begin by summarizing the general research trends, first documenting the rapid recent growth in dog cognition research (particularly in the domain of social cognition), and then identifying a number of trends in terms of the cognition topics and dog populations studied. Next, we summarize and synthesize the substantive conclusions emerging from research on nonsocial (discrimination learning, object permanence, object learning, categorization, object manipulation, quantitative understanding, spatial cognition, and memory) and social (responses to human cues, perspective taking, dog-human communication, and social learning) cognition. In light of the burgeoning research on individual differences in cognition and on the biological organization of cognitive domains, we highlight the potential impact of these topics on the dog cognition field. Finally, based on our syntheses, we outline some ideas for future research, including recommendations that studies focus on: (1) incorporating multiple sensory modalities (most notably olfaction); (2) using more diverse populations of subjects; (3) replicating studies where current knowledge is based on small study sets or on small samples; (4) identifying fundamental developmental patterns of cognitive development; (5) identifying individual differences in cognitive ability; and (6) identifying potential cognitive constraints (e.g. cognitive abilities that are nonindependent due to pleiotropic biological organization).

Female aggression predicts mode of paternity acquisition in a social lizard

Individual differences in behaviour are ubiquitous in nature. Despite the likely role of selection in maintaining these differences, there are few demonstrations of their fitness consequences in wild populations and, consequently, the mechanisms that link behavioural variation to variation in fitness are poorly understood. Specifically, the consequences of consistent individual differences in behaviour for the evolution of social and mating strategies have rarely been considered. We examined the functional links between variation in female aggression and her social and mating strategies in a wild population of the social lizard Egernia whitii. We show that female Egernia exhibit temporally consistent aggressive phenotypes, which are unrelated to body size, territory size or social density. A females aggressive phenotype, however, has strong links to her mode of paternity acquisition (within- versus extra-pair paternity), with more aggressive females having more offspring sired by extra-pair males than less aggressive females. We discuss the potential mechanisms by which female aggression could underpin mating strategies, such as the pursuit/acceptance of extra-pair copulations. We propose that a deeper understanding of the evolution and maintenance of social and mating systems may result from an explicit focus on individual-level female behavioural phenotypes and their relationship with key reproductive strategies.

Are behavioral syndromes invariant? Spatiotemporal variation in shy/bold behavior in squid

Behavioral syndromes are correlated suites of behavior, analogous to human personality traits. Most work to date has been taken from limited “snapshots” in space and time, with the implicit assumption that a behavioral syndrome is an invariant property, fixed by evolutionary constraints or adaptations. However, directional selection on two mechanistically independent traits (selective covariance) could also result in correlated behaviors. Previously, we have shown that shy/bold behavior in Southern dumpling squid (Euprymna tasmanica) across predator encounter and feeding risk contexts is genetically and phenotypically uncoupled, and hence potentially free to vary independently. Here, we collected data on shy/bold behaviors from two independent wild populations of squid in two different years to test whether behavioral correlations across these same two functional contexts vary through time and space. We detected significant influences of population, sex, and body size on the expression of boldness in squid within each functional context, and this was coupled with significant differences in relative population density and adult sex ratio. Despite these changes in behavior and demographic parameters, we found that correlations between boldness scores across the two functional contexts were largely absent in both wild populations of squid in both years. Our work suggests that some animal groups may be largely characterized by context-specific behavioral expression. A theoretical framework which conceptualizes behavioral syndromes resulting from context-specific behavioral rules may be needed to fully understand why behaviors are sometimes correlated, and why sometimes they are not.