. Abstract
. Sexual selection is a major force shaping morphological and behavioral diversity. Existing theory focuses on courtship display traits such as morphological ornaments whose costs and benefits are assumed be to fixed across individuals’ lifetimes. In contrast, empirically observed displays are often inherently dynamic, as vividly illustrated by the acrobatic dances, loud vocalizations, and vigorous motor displays involved in courtship behavior across a broad range of taxa. One empirically observed form of display flexibility occurs when signalers adjust their courtship investment based on the number of rival signalers. The predictions of established sexual selection theory cannot readily be extended to such displays because display expression varies between courtship events, such that any given display may not reliably reflect signaler quality. We thus lack an understanding of how dynamic displays coevolve with sexual preferences and how signalers should tactically adjust their display investment across multiple courtship opportunities. To address these questions, we extended an established model of the coevolution of a female sexual preference and a male display trait to allow for flexible, dynamic displays. We find that such a display can coevolve with a sexual preference away from their naturally selected optima, though display intensity is a weaker signal of male quality than for non-flexible displays. Furthermore, we find that males evolve to decrease their display investment when displaying alongside more rivals. This research represents a first step towards generalizing the findings of sexual selection theory to account for the ubiquitous dynamism of animal courtship.
.
. Significance statement
. Animal courtship displays are typically costly for survival: songs attract predators; dances are exhausting; extravagant plumage is cumbersome. Because of the trade-off between mating benefits and survival costs, displaying individuals often vary their displays across time, courting more intensely when the potential benefit is higher or the cost is lower. Despite the ubiquity of such adjustment in nature, existing theory cannot account for how this flexibility might affect the coevolution of displays with sexual preferences, nor for the patterns of tactical display adjustment that might result, because those models treat displays as static, with fixed costs and benefits. Generalizing a well-studied model of sexual selection, we find that a static display and a flexible display can evolve under similar conditions. Our model predicts that courtship should be less intense when more competitors are present.
.

In group-living vertebrates, dominance status often covaries with physiological measurements (e.g. glucocorticoid levels), but it is unclear how dominance is linked to dynamic changes in physiological state over a shorter, behavioural timescale. In this observational study, we recorded spontaneous aggression among captive juvenile pheasants (Phasianus colchicus) alongside infrared thermographic measurements of their external temperature, a non-invasive technique previously used to examine stress responses in non-social contexts, where peripheral blood is redirected towards the body core. We found low but highly significant repeatability in maximum head temperature, suggesting individually consistent thermal profiles, and some indication of lower head temperatures in more active behavioural states (e.g. walking compared to resting). These individual differences were partly associated with sex, females being cooler on average than males, but unrelated to body size. During pairwise aggressive encounters, we observed a non-monotonic temperature change, with head temperature dropping rapidly immediately prior to an attack and increasing rapidly afterwards, before returning to baseline levels. This nonlinear pattern was similar for birds in aggressor and recipient roles, but aggressors were slightly hotter on average. Our findings show that aggressive interactions induce rapid temperature changes in dominants and subordinates alike, and highlight infrared thermography as a promising tool for investigating the physiological basis of pecking orders in galliforms.This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’.

Sexual signals are often structured in bouts, which can be adjusted in response to changes in the signaller’s physical and social environment. For example, we might expect individuals to adjust their own signalling behaviour in response to changes in the signalling behaviour of rivals, because this can affect their relative attractiveness to potential mates. In this study, we used a biomimetic robot to experimentally manipulate rival waving behaviour in a wild population of fiddler crabs (Afruca tangeri), and investigated whether this leads to changes in the activity and waving behaviour of a focal male. Analysing the focal male’s behaviour using hidden Markov models and linear hurdle models, we found no evidence that the focal male’s waving rate changed in response to changes in the behaviour of the robotic rival. However, bouts of waving lasted longer when the robotic rival was waving at a fast rate. Focal males were also less likely to enter their burrow when the robotic rival was waving, and spent less time in their burrow if they did enter. These results reveal tactical adjustment of behaviour by competing signallers, and highlight the flexible nature of bout-structured sexual displays.

The volunteer’s dilemma, in which a single individual is required to produce a public good, predicts that individuals in larger groups will cooperate less frequently. Mechanistically, this could result from trade-offs between costs associated with volunteering and costs incurred if the public good is not produced (nobody volunteers). During predator inspection, one major contributor to the cost of volunteering is likely increased probability of predation; however, a predator also poses a risk to all individuals if nobody inspects. We tested the prediction that guppies in larger groups will inspect a predator less than those in smaller groups. We also predicted that individuals in larger groups would perceive less threat from the predator stimulus because of the protective benefits of larger groups (e.g. dilution). Contrary to prediction, we found that individuals in large groups inspected more frequently than those in smaller groups, but (as predicted) spent less time in refuges. There was evidence that individuals in intermediate-sized groups made fewest inspections and spent most time in refuges, suggesting that any link between group size, risk and cooperation is not driven by simple dilution. Extensions of theoretical models that capture these dynamics will likely be broadly applicable to risky cooperative behaviour.

Studies into the effective use of accelerometers in the automated assessment of sheep behaviour to improve welfare has increased exponentially with promising preliminary results. Previous research has focused primarily on explicit behaviour classification, for example, parturition and urination events, with a view to create a commercial tool that will provide health warnings for farmers. Yet the majority of trials have not been conducted in a farm environment. This study aims to provide essential primary research investigating environmental variables that may influence the behavioural patterns of a commercial flock. This vital information has been largely overlooked and crucial when considering tools that provide health warnings, due to the many factors that influence sheep behaviour such as weather, vegetation, soil type, land typography and breed (Hinch, 2017).

The primary aim of this study was to assess the most appropriate model to predict the behaviours of commercial ewes. This was achieved by deploying accelerometers on a commercial flock and simultaneously collecting manual observations and video recordings of flock’s individual activity. The raw acceleration data was processed to create 6 variables. Behaviour classification was also evaluated using three ethograms, each with two mutually exclusive behavioural/postural states: 1. Head Position (head up/down), 2. Posture (standing/lying), 3. Activity (resting/grazing). Three Window setting (3, 5 and 7 seconds) and five machine learning algorithms
(Linear Discriminate Analysis (LDA), Classification and Regression Trees (CART), K Nearest Neighbour (KNN), Support Vector Machines (SVM) and Random Forest (RF)) were evaluated. Results indicated a RF with a 7 second window the optimal model across all ethograms. (Accuracy by ethogram; 1) 91.5%, 2) 91.0% and 3) 99.3%).

The secondary aim of this study was to use a Linear Mixed Model (LMM) to investigate the influence of temperature and rainfall on grazing and resting behaviours. This was accomplished by using the initially developed model (RF) on data collected from an unsupervised commercial flock, recorded in a second trial. Results indicated that there was a significant positive relationship between grazing durations and rainfall (p.001), this finding conflicts with previous research observations and is yet unpublished. In addition, prior sheep behaviour research has suggested ‘foraging’ as the dominant activity, results from this trial indicate the dominant daily activity was resting (67% of daily activity).
In conclusion this study highlights the difficultly of defining what ‘normal’ sheep behaviour is and that it is not viable to implement a ‘one-size fits all’ approach. Further research is required in the behavioural assessment for this particularly malleable species.

Males that employ dynamic courtship displays to attract females may tactically adjust their courtship in response to their social environment. However, we know little about how sexual signals are adjusted in complex natural settings, where individuals are competing for attention against a backdrop of signals from nearby and distant rivals. We investigated this using data from the WildCrickets project, a wild population of field crickets, Gryllus campestris, continuously monitored via CCTV cameras. We used over a million scan samples from 129 males across 51 days to explore how the singing and proximity of other males influenced male singing behaviour. We first quantified the spatial network of the males to understand how the extent of singing overlap is affected by the distance between them, and found a moderate overlap across the whole population, regardless of distance. We then used a finer-grained analysis controlling for the effect of environmental variables. At distances greater than 1 m, we found a stimulatory effect of singing by other males on a focal male's singing behaviour, leading to males singing in the same time intervals. The overlap in singing became weaker as the distance between males increased. Conversely, we found that males were less likely to call when another male was singing very close by (within 1 m), suggesting an inhibitory effect. These findings reveal how, in a dynamic social network in a wild population, males perform fine-scale adjustments to their signalling behaviour in response to signalling by other males both nearby and far away.

. Abstract
. Sexual selection is a major force shaping morphological and behavioral diversity. Existing theory focuses on courtship display traits such as morphological ornaments whose costs and benefits are assumed be to fixed across individuals’ lifetimes. In contrast, empirically observed displays are often inherently dynamic, as vividly illustrated by the acrobatic dances, loud vocalizations, and vigorous motor displays involved in courtship behavior across a broad range of taxa. One empirically observed form of display flexibility occurs when signalers adjust their courtship investment based on the number of rival signalers. The predictions of established sexual selection theory cannot readily be extended to such displays because display expression varies between courtship events, such that any given display may not reliably reflect signaler quality. We thus lack an understanding of how dynamic displays coevolve with sexual preferences and how signalers should tactically adjust their display investment across multiple courtship opportunities. To address these questions, we extended an established model of the coevolution of a female sexual preference and a male display trait to allow for flexible, dynamic displays. We find that such a display can coevolve with a sexual preference away from their naturally selected optima, though display intensity is a weaker signal of male quality than for non-flexible displays. Furthermore, we find that males evolve to decrease their display investment when displaying alongside more rivals. This research represents a first step towards generalizing the findings of sexual selection theory to account for the ubiquitous dynamism of animal courtship.
.
. Significance statement
. Animal courtship displays are typically costly for survival: songs attract predators; dances are exhausting; extravagant plumage is cumbersome. Because of the trade-off between mating benefits and survival costs, displaying individuals often vary their displays across time, courting more intensely when the potential benefit is higher or the cost is lower. Despite the ubiquity of such adjustment in nature, existing theory cannot account for how this flexibility might affect the coevolution of displays with sexual preferences, nor for the patterns of tactical display adjustment that might result, because those models treat displays as static, with fixed costs and benefits. Generalizing a well-studied model of sexual selection, we find that a static display and a flexible display can evolve under similar conditions. Our model predicts that courtship should be less intense when more competitors are present.
.

The behaviour of sheep has large applications to the UK sheep industry to improve productivity to boost profits and meet global demand. This can be achieved by ensuring maximum reproductive output each year by maximising pregnancy rates, increasing lamb crop sizes and ensuring efficient lamb growth. The advancement in bio-logging technology has facilitated significant advancements in the measurement of animal behaviour and has made the continuous monitoring of the behaviour of farm animals in a commercial setting feasible. A growing body of work has begun to validate this technology in extensive grazing systems and there have been an increasing number of studies linking behaviour measurement to a range of production outcomes. However, evidence is scarce in 3 key areas, including (1) aging, (2) the detection of oestrous and (3) lamb growth and maternal ability which this thesis aimed to explore. Firstly, this thesis aimed to validate the use of bio-loggers in an extensive grazing system, using accelerometers and proximity sensors attached to sheep for 14-day periods at various points in the farm production cycle to collect behavioural data on a commercial sheep flock. Behavioural data was then combined with production records on a pedigree, performance-recorded sheep population and environmental data collected on-farm, to determine links with production traits to investigate how the sheep industry can improve production through maximising reproductive success. This thesis was able to bridge the gap between research and the UK sheep industry, by demonstrating the feasibility of continuously monitoring the behaviour of an entire commercial sheep flock at multiple stages of the production cycle using bio-loggers. Links between behavioural data and production revealed, (i) the presence of age effects on behaviour but no effects on long-term production, (ii) the feasibility of using bio-loggers for the automatic detection of oestrous either indirectly, from ewe-ram social behaviour or directly from ewe behaviour and (iii) lamb and maternal behavioural predictors of lamb growth. As a secondary aim, environmental effects on behaviour were also described, which may prove useful for quantifying the resilience of animals. Advancing our understanding of the measurement of behaviour in a commercial setting and uncovering links with production traits is key to facilitating commercial uptake by the UK sheep industry for real-time monitoring of behaviour and health of sheep flocks to improve performance.

In group-living vertebrates, dominance status often covaries with physiological measurements (e.g. glucocorticoid levels), but it is unclear how dominance is linked to dynamic changes in physiological state over a shorter, behavioural timescale. In this observational study, we recorded spontaneous aggression among captive juvenile pheasants (Phasianus colchicus) alongside infrared thermographic measurements of their external temperature, a non-invasive technique previously used to examine stress responses in non-social contexts, where peripheral blood is redirected towards the body core. We found low but highly significant repeatability in maximum head temperature, suggesting individually consistent thermal profiles, and some indication of lower head temperatures in more active behavioural states (e.g. walking compared to resting). These individual differences were partly associated with sex, females being cooler on average than males, but unrelated to body size. During pairwise aggressive encounters, we observed a non-monotonic temperature change, with head temperature dropping rapidly immediately prior to an attack and increasing rapidly afterwards, before returning to baseline levels. This nonlinear pattern was similar for birds in aggressor and recipient roles, but aggressors were slightly hotter on average. Our findings show that aggressive interactions induce rapid temperature changes in dominants and subordinates alike, and highlight infrared thermography as a promising tool for investigating the physiological basis of pecking orders in galliforms.This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’.

Rapid population growth and the urbanization of modern environments are markedly increasing human-wildlife conflict. Wild animals in urban landscapes can benefit from exploiting human resources, but are also exposed to increased risk of human-caused injury, which should favor the ability to perceive and respond to human cues. Although it is well known that domesticated animals use human cues that may indicate threats, less is known about wild animals living in urban environments. Herring gulls (Larus argentatus) in urban landscapes have adapted kleptoparasitic behaviors to obtain human food, often resulting in negative interactions with humans. Here we quantified both the behavioral and physiological responses of free-living urban herring gulls to human shouting. We presented urban gulls with a fake human food item and played back recordings of either a man shouting, a natural stressor (i.e. conspecific alarm call), or a neutral stimulus (i.e. robin song). We recorded behavioral responses and used non-invasive infrared thermography to measure eye-region surface temperature changes associated with the avian physiological stress response. We found that gulls exposed to shouting and to conspecific alarm calls showed similar changes in behavior (indicating high levels of vigilance) and eye-region surface temperature (indicating physiological stress). Both responses were significantly stronger than the responses to robin song. Additionally, the behavioral and physiological responses were positively correlated across individuals. Our results demonstrate that urban-dwelling gulls respond to human shouting and conspecific alarm calls in a similar way, and suggest that infrared thermography is a viable technique to monitor stress responses in free-living birds.

This thesis explores engagement between autistic children and donkeys during Equid Assisted Activity (EAA) sessions. I present the blurred position of EAA in Human-Animal Research that results in unreliable methodology and understanding about the equids’ perceived abilities. I argue that ‘benefits of EAA’ explored in other research is a problematic concept, because of the heterogeneous nature of autism and the individual character differences between donkeys. Using narrative analysis and narrative ethology showed that autistic children and their donkey partners demonstrate diverse and complex engagement behaviours that cannot be reduced to an entity of benefits that applies to all individuals. Qualitative stories about autistic children and donkey interactions offered a broader understanding of who each participant was, resulting in their caretakers forming new accountabilities and making informed decisions about their participants’ wellbeing.
I questioned the quality of engagement in 15 reported studies on EAA and the methodological preference of only measuring and reporting human responses. In order to measure the quality of engagement between autistic children and donkeys I designed and tested a Quality of Engagement Tool (QET) that was reliable enough to be used in a number of research designs.
The QET identified that engagement behaviour of one partner was correlated with that of the other partner in the same session. Individuals (children or donkeys) engaged differently when interacting with a conspecific as opposed to a heterospecific. The stories presented through narrative analysis and narrative ethology, coupled with the findings from the QET are important for future research. Measuring outcomes for children would be highly dependent on their relationship with their equid partner or indeed if they had the same partner for the duration of the research therefore; equids and humans should be considered as equal participants. The thesis concludes with a summary of findings from this project and signposts future research directions.

To date, very little is known about the African turquoise killifish and its social behaviour. It is emerging as a model organism in gerontological research due to its exceptionally short lifespan (approximately 6-8 months), yet its social behaviour is unknown. In this study, I investigate the grouping tendencies of juveniles using different methodologies to determine which best suits the species. Secondly, using the most suitable methodology, I investigate the grouping preferences of both juveniles and adults and observe whether they are capable of familiar and kin recognition. To my knowledge, this is the first study to investigate the grouping preferences and recognition capabilities of the African turquoise killifish. Using 7-week-old juveniles I compared a standard binary choice and Y-maze test arena and determined that the Y-maze was not only a more suitable test arena for my study species, but that at this age juveniles grouped. Using the Y-maze for further testing I investigated differences in juvenile and adult behaviour. I observed that at 5 weeks old juveniles displayed no preference for grouping, kin or familiar individuals. In contrast, adult killifish showed a preference for grouping and males demonstrated a preference for familiar male individuals. Similar to juveniles, adult killifish showed no preference for kin, nor did females show any preference for other familiar females. This work provides a framework for future studies to investigate this species further and increase our knowledge on both the African turquoise killifish and, more generally, on ontogenetic shifts in social behaviour.

Statistical analysis of a data set of number of equations and number of citations of papers published in volumes 94 and 104 of the journal Physical Review Letters. This analysis is referred to by the paper Equation-dense papers receive fewer citations—in physics as well as biology in the New Journal of Physics (vol. 18, article 118003) by Andrew D Higginson and Tim W Fawcett. http://iopscience.iop.org/article/10.1088/1367-2630/18/11/118003

BACKGROUND AND OBJECTIVES: Depression is a major medical problem diagnosed in an increasing proportion of people and for which commonly prescribed psychoactive drugs are frequently ineffective. Development of treatment options may be facilitated by an evolutionary perspective; several adaptive reasons for proneness to depression have been proposed. A common feature of many explanations is that depressive behaviour is a way to avoid costly effort where benefits are small and/or unlikely. However, this viewpoint fails to explain why low mood persists when the situation improves. We investigate whether a behavioural rule that is adapted to a stochastically changing world can cause inactivity which appears similar to the effect of depression, in that it persists after the situation has improved. METHODOLOGY: We develop an adaptive learning model in which an individual has repeated choices of whether to invest costly effort that may result in a net benefit. Investing effort also provides information about the current conditions and rates of change of the conditions. RESULTS: an individual following the optimal behavioural strategy may sometimes remain inactive when conditions are favourable (i.e. when it would be better to invest effort) when it is poorly informed about the current environmental state. Initially benign conditions can predispose an individual to inactivity after a relatively brief period of negative experiences. CONCLUSIONS AND IMPLICATIONS: Our approach suggests that the antecedent factors causing depressed behaviour could go much further back in an individual s history than is currently appreciated. The insights from our approach have implications for the ongoing debate about best treatment options for patients with depressive symptoms.

Models of adaptive behaviour typically assume that animals behave as though they have highly complex, detailed strategies for making decisions. In reality, selection favours the optimal balance between the costs and benefits of complexity. Here we investigate this trade-off for an animal that has to decide whether or not to forage for food - and so how much energy reserves to store - depending on the food availability in its environment. We evolve a decision rule that controls the target reserve level for different ranges of food availability, but where increasing complexity is costly in that metabolic rate increases with the sensitivity of the rule. The evolved rule tends to be much less complex than the optimal strategy but performs almost as well, while being less costly to implement. It achieves this by being highly sensitive to changing food availability at low food abun-dance - where it provides a close fit to the optimal strategy - but insensitive when food is plentiful. When food availability is high, the target reserve level that evolves is much higher than under the optimal strategy, which has implications for our under-standing of obesity. Our work highlights the important principle of generalisability of simple decision-making mechanisms, which enables animals to respond reasonably well to conditions not directly experienced by themselves or their ancestors.

When given a choice between options with uncertain outcomes, people tend to be loss averse and risk averse regarding potential gains and risk prone regarding potential losses. These features of human decision making are captured by prospect theory (PT)-a hugely influential descriptive model of choice, but one which lacks any unifying principle that might explain why such preferences exist. Recently there have been several attempts to connect PT with risk-sensitive foraging theory (RSFT), a normative framework developed by evolutionary biologists to explain how animals should choose optimally when faced with uncertain foraging options. Although this seems a promising direction, here we show that current approaches are overly simplistic, and, despite their claims, they leave key features of PT unaccounted for. A common problem is the failure to appreciate the central concept of reproductive value in RSFT, which depends on the decision maker's current state and the particular situation it faces. Reproductive value provides a common currency in which decisions can be compared in a logical way. In contrast, existing models provide no rational justification for the reference state in PT. Evolutionary approaches to understanding PT preferences must confront this basic problem.

Conflict between groups (intergroup conflict) is common in many social species [1-4] and is widely discussed as an evolutionary driver of within-group dynamics and social structure [2, 5]. However, empirical studies investigating the impacts of intergroup conflict have focused on the immediate aftermath [6-9], when behavioral changes may be the direct result of elevated stress levels [7] or territorial exclusions [9]. Demonstrations of longer-term effects, with behavioral changes persisting once increases in stress have diminished and full access to resources is again possible, would support proposed links to individual fitness and social evolution. Here we show that conflicts between neighboring groups of cooperatively breeding green woodhoopoes (Phoeniculus purpureus) have a lasting influence on decisions concerning roost cavities, a limiting resource vital for survival and breeding. Groups involved in extended conflicts in the morning were more likely to return to the zone of conflict that evening, roosting closer to territorial borders, than when intergroup interactions were short or did not occur. Extended morning conflicts also increased the likelihood that groupmates roosted together and preened one another at the roost, suggesting that intergroup conflict promotes consensus decision-making, social bonding, and group cohesion. Border roost use and allopreening increased more following conflicts that were lost rather than won. By demonstrating that both the intensity and outcome of intergroup interactions affect resource defense and associated within-group behavior many hours later, our results begin to bridge the gap between the immediate impacts of intergroup conflict and its role in social evolution.

Behavioral ecologists have long been comfortable assuming that genetic architecture does not constrain which phenotypescan evolve (the "phenotypic gambit"). For flexible behavioral traits, however, solutions to adaptive problems are reached not only by genetic evolution but also by behavioral changes within an individual's lifetime, via psychological mechanisms such as learning. Standard optimality approaches ignore these mechanisms, implicitly assuming that they do not constrain the expression of adaptive behavior. This assumption, which we dub the behavioral gambit, is sometimes wrong: evolved psychological mechanisms can prevent animals from behaving optimally in specific situations. To understand the functional basis of behavior, we would do better by considering the underlying mechanisms, rather than the behavioral outcomes they produce, as the target of selection. This change of focus yields new, testable predictions about evolutionary equilibria, the development of behavior, and the properties of cognitive systems. Studies on the evolution of learning rules hint at the potential insights to be gained, but such mechanism-based approaches are underexploited. We highlight three future research priorities: (1) systematic theoretical analysis of the evolutionary properties of learning rules; (2) detailed empirical study of how animals learn in nonforaging contexts;and (3) analysis of individual differences in learning rules and their associated fitness consequences. © 2012 the Author.

In human societies, parents often have a strong influence on the mate choice of their offspring. Moreover, empirical studies show that conflict over mate choice between parents and offspring is widespread across human cultures. Here we provide the first theoretical investigation into this conflict, showing that it may result from an underlying evolutionary conflict over parental resource distribution. We present a series of evolutionary simulations in which we gradually expand a standard model of sexual selection by the stepwise addition of elements of parental involvement. In our model, females obtain resources enhancing their fecundity from both their chosen mate and their parents. Potential mates differ in their ability to provide resources and may signal this ability. Both females and their parents can develop a preference for the signal, with both preferences influencing the realized mate choice of the female. Parents may differentially allocate resources among their daughters depending on the resource-provisioning abilities of their sons-in-law. When fecundity returns on investment are diminishing, we find that parents invest most in daughters whose mates provide few resources. Subsequently, the daughters evolve to exploit this allocation rule through their mate choice, which is not in the parents' best interests. This results in a conflict over mate choice between parents and their offspring, manifested as an on-going divergence of offspring and parental preferences. We predict that the conflict should be most pronounced when fathers, as opposed to mothers, control resource allocation. © 2013 Elsevier Inc.

Sexual selection theory posits that females should choose mates in a way that maximizes their reproductive success. But what exactly is the optimal choice? Most empirical research is based on the assumption that females seek a male of the highest possible quality (in terms of the genes or resources he can provide), and hence show directional preferences for indicators of male quality. This implies that attractiveness and quality should be highly correlated. However, females frequently differ in what they find attractive. New theoretical and empirical insights provide mounting evidence that a female's own quality biases her judgement of male attractiveness, such that male quality and attractiveness do not always coincide. A recent experiment in songbirds demonstrated for the first time that manipulation of female condition can lead to divergent female preferences, with low-quality females actively preferring low-quality males over high-quality males. This result is in line with theory on state-dependent mate choice and is reminiscent of assortative mating preferences in humans. Here we discuss the implications of this work for the study of mate preferences. © 2010 Landes Bioscience.

It is often argued that females with attractive partners should produce more sons because these sons will inherit their father's attractiveness. Numerous field and laboratory studies have addressed this hypothesis, with inconsistent results, but there is surprisingly little theoretical work on the topic. Here, we present an extensive investigation of the link between male attractiveness and offspring sex ratios, using evolutionary, individual-based computer simulations. In situations where sexual selection leads to the stable exaggeration of a costly male trait and a costly female preference, we find that females with attractive partners produce more sons than females with unattractive partners. This same qualitative pattern is seen for a wide range of different models, with discrete or continuous variation in the male trait, under Fisherian or good-genes sexual selection and for abrupt or gradual sex ratio adjustment. However, in all simulations, it takes a huge number of generations to evolve, suggesting that selection acting on sex ratio adjustment is weak. Our models ignore many potential costs and constraints associated with manipulation, which implies that selection may be weaker still in natural populations. These results may explain why published evidence for sex ratio bias in relation to male attractiveness is mixed. © the Author 2006. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.

In a wide range of contexts from mate choice to foraging, animals are required to discriminate between alternative options on the basis of multiple cues. How should they best assess such complex multicomponent stimuli? Here, we construct a model to investigate this problem, focusing on a simple case where a 'chooser' faces a discrimination task involving two cues. These cues vary in their accuracy and in how costly they are to assess. As an example, we consider a mate-choice situation where females choose between males of differing quality. Our model predicts the following: (i) females should become less choosy as the cost of finding new males increases; (ii) females should prioritize cues differently depending on how choosy they are; (iii) females may sometimes prioritize less accurate cues; and (iv) which cues are most important depends on the abundance of desirable mates. These predictions are testable in mate-choice experiments where the costs of choice can be manipulated. Our findings are applicable to other discrimination tasks besides mate choice, for example a predator's choice between palatable and unpalatable prey, or an altruist's choice between kin and non-kin.

Imitative learning, in which an individual learns to reproduce the behaviour pattern of another, has attracted considerable attention as a potentially powerful form of social learning. Despite extensive research, however, it has proved difficult to demonstrate in nonhuman animals. We investigated the ability of European starlings, Sturnus vulgaris, to imitate the behaviour of a conspecific. Subjects watched a trained conspecific manipulating a plug for access to a food reward, using either a pushing or a pulling action. When later tested with the same apparatus these birds completed the task using the same action they had previously observed. In a second experiment, a separate group of starlings saw the plug move upwards or downwards automatically and a nearby conspecific obtain a food reward. When given access to the task these starlings failed to move the plug in the direction they had seen. Our experiment is an improvement on previous bidirectional control designs and provides strong evidence that starlings are capable of imitation. We advocate further use of this experimental design in attempts to demonstrate imitative learning. © 2002 the Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

1. Conservation issues and a potential role in disease transmission generate the continued need to census Eurasian badgers Meles meles, but direct counts and sett counts present difficulties. The feasibility of estimating social group size and population density of badgers by quantifying their use of latrines was evaluated. 2. The number of latrines, or preferably the number of separate dung pits, which were known from bait-marking to be used by members of a social group, was positively correlated with adult group size estimated from mark-recapture studies at Woodchester Park and North Nibley (south-west England). In the latter study area both latrine-use measures were also significantly associated with total group size (i.e. including cubs and adults). 3. In spring 1997 and 1998, we quantified latrine use along strip transects, following linear features across four and five areas, respectively, in England, where badger density in summer was known from mark-recapture/resight studies. 4. Seven latrine-use measures were evaluated with regard to their potential to predict badger density. Each measure separately explained between 62% and 91% of the variation in population density in a given year. The simplest measures (latrines km-1 and pits km-1) were most stable between years. 5. For these two simple latrine-use measures, a linear model without an intercept term explained the highest proportion of variation in population density. A stepwise procedure to produce the best model selected only one (latrines km-1) of the two measures as an explanatory variable, indicating that pits km-1 is colinear with the former variable. 6. A badger census technique based on simple measurements of latrine use has great promise but needs to be validated across a wider range of badger populations, habitats, years, seasons and weather conditions.